@article{jung_lackmann_2023, title={Changes in Tropical Cyclones Undergoing Extratropical Transition in a Warming Climate: Quasi-Idealized Numerical Experiments of North Atlantic Landfalling Events}, volume={50}, ISSN={["1944-8007"]}, DOI={10.1029/2022GL101963}, abstractNote={The current study extends earlier work that demonstrated future extratropical transition (ET) events will feature greater intensity and heavier precipitation to specifically consider potential changes in the impacts of landfalling ET events in a warming climate. A quasi-idealized modeling framework allows comparison of highly similar present-day and future event simulations; the model initial conditions are based on observational composites, increasing representativeness of the results. The future composite ET event features substantially more impactful weather conditions in coastal areas, with heavier precipitation and greater storm intensity. Specifically, a Category 2 present-day storm attained Category 4 Saffir-Simpson intensity in the future simulation and maintained greater intensity throughout the entire life cycle, although the storm undergoes less reintensification during the post-ET process, a result of reduced baroclinic conversion. These findings suggest increased potential for coastal hazards due to stronger tropical cyclone winds and heavier rainfall, leading to more severe coastal flooding and storm surge.}, number={8}, journal={GEOPHYSICAL RESEARCH LETTERS}, author={Jung, Chunyong and Lackmann, Gary M. M.}, year={2023}, month={Apr} }
 @article{chase_harrison_burke_lackmann_mcgovern_2022, title={A Machine Learning Tutorial for Operational Meteorology. Part I: Traditional Machine Learning}, volume={37}, ISSN={["1520-0434"]}, DOI={10.1175/WAF-D-22-0070.1}, abstractNote={Abstract Recently, the use of machine learning in meteorology has increased greatly. While many machine learning methods are not new, university classes on machine learning are largely unavailable to meteorology students and are not required to become a meteorologist. The lack of formal instruction has contributed to perception that machine learning methods are “black boxes” and thus end-users are hesitant to apply the machine learning methods in their everyday workflow. To reduce the opaqueness of machine learning methods and lower hesitancy toward machine learning in meteorology, this paper provides a survey of some of the most common machine learning methods. A familiar meteorological example is used to contextualize the machine learning methods while also discussing machine learning topics using plain language. The following machine learning methods are demonstrated: linear regression, logistic regression, decision trees, random forest, gradient boosted decision trees, naïve Bayes, and support vector machines. Beyond discussing the different methods, the paper also contains discussions on the general machine learning process as well as best practices to enable readers to apply machine learning to their own datasets. Furthermore, all code (in the form of Jupyter notebooks and Google Colaboratory notebooks) used to make the examples in the paper is provided in an effort to catalyze the use of machine learning in meteorology.}, number={8}, journal={WEATHER AND FORECASTING}, author={Chase, Randy J. and Harrison, David R. and Burke, Amanda and Lackmann, Gary M. and McGovern, Amy}, year={2022}, month={Aug}, pages={1509–1529} }
 @article{zick_matyas_lackmann_tang_bennett_2022, title={Illustration of an object-based approach to identify structural differences in tropical cyclone wind fields}, volume={7}, ISSN={["1477-870X"]}, DOI={10.1002/qj.4326}, abstractNote={The meteorology community primarily assesses tropical cyclone (TC) forecast skill using track and intensity errors. These metrics are frequently uncorrelated and can offer conflicting information about model performance. Continued improvements in intensity forecasting require improved representation of physical processes over multiple scales, and model verification of TC spatial structure can contribute to these improvements. To date, there are limited studies into forecast model representation of wind fields. More work is needed to better understand model deficiencies in skillfully predicting TC size metrics. In this study, we demonstrate an object-based approach that can reveal structural differences in TC wind fields. Object-based methods have been underutilized, and these methods, along with spatial metrics, can serve as additional verification methods for assessing storm structure in both observations and model simulations. Specifically, we illustrate this approach by examining a major difference between the Tiedtke and Kain–Fritsch cumulus parametrization schemes: The Tiedtke scheme includes convective momentum transport while the Kain–Fritsch scheme does not. We create three experiments of Hurricane Isabel (2003) using the Weather Research and Forecasting model using the Kain–Fritsch and Tiedtke cumulus parametrization schemes and an altered Tiedtke scheme with convective momentum transport turned off. Within the three experiments, we generate a small ensemble of four simulations to avoid drawing erroneous conclusions due to growth of numerical noise. Then, we use object-based methods to measure and compare spatial attributes of the low-level wind fields to confirm the dominant influence of momentum transport in influencing the TC spatial structure. Our spatial metric approach offers an objective suite of structural attributes that could be useful in diverse applications. A future goal is to use spatial metrics in systematic verification studies of TCs in operational model forecasts and climate model simulations, which may offer great benefit to operational forecasters and numerical model developers.}, journal={QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY}, author={Zick, Stephanie and Matyas, Corene and Lackmann, Gary and Tang, Jingyin and Bennett, Brian}, year={2022}, month={Jul} }
 @article{turnau_robinson_lackmann_michaelis_2022, title={Model Projections of Increased Severity of Heat Waves in Eastern Europe}, volume={49}, ISSN={["1944-8007"]}, url={https://doi.org/10.1029/2022GL100183}, DOI={10.1029/2022GL100183}, abstractNote={Extreme heat is investigated in a series of high-resolution time-slice global simulations comparing the current and late-21st century climates. An increase in climate-relative extreme heat is found in the region surrounding the Black Sea. Similarities between the synoptic-scale flows in current and future heat events combined with a decrease in future summer precipitation suggests that the increased future severity stems from strengthened land-atmosphere feedbacks driven primarily by the changes in precipitation. The resulting intensification of heat events beyond the mean warming driven by climate change could generate significant future heat hazards in vulnerable regions. Given the continental cool bias in the present-day simulations, the resulting estimates of future extreme heat are likely to be conservative.}, number={22}, journal={GEOPHYSICAL RESEARCH LETTERS}, author={Turnau, Roger and Robinson, Walter A. A. and Lackmann, Gary M. M. and Michaelis, Allison C. C.}, year={2022}, month={Nov} }
 @article{stuart_hartfield_schultz_wilson_west_hoffman_lackmann_brooks_roebber_bals-elsholz_et al._2022, title={The Evolving Role of Humans in Weather Prediction and Communication}, volume={103}, ISSN={["1520-0477"]}, DOI={10.1175/BAMS-D-20-0326.1}, abstractNote={Abstract A series of webinars and panel discussions were conducted on the topic of the evolving role of humans in weather prediction and communication, in recognition of the 100th anniversary of the founding of the AMS. One main theme that arose was the inevitability that new tools using artificial intelligence will improve data analysis, forecasting, and communication. We discussed what tools are being created, how they are being created, and how the tools will potentially affect various duties for operational meteorologists in multiple sectors of the profession. Even as artificial intelligence increases automation, humans will remain a vital part of the forecast process as that process changes over time. Additionally, both university training and professional development must be revised to accommodate the evolving forecasting process, including addressing the need for computing and data skills (including artificial intelligence and visualization), probabilistic and ensemble forecasting, decision support, and communication skills. These changing skill sets necessitate that both the U.S. Government’s Meteorologist General Schedule 1340 requirements and the AMS standards for a bachelor’s degree need to be revised. Seven recommendations are presented for student and forecaster preparation and career planning, highlighting the need for students and operational meteorologists to be flexible lifelong learners, acquire new skills, and be engaged in the changes to forecast technology in order to best serve the user community throughout their careers. The article closes with our vision for the ways that humans can maintain an essential role in weather prediction and communication, highlighting the interdependent relationship between computers and humans.}, number={8}, journal={BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY}, author={Stuart, Neil A. and Hartfield, Gail and Schultz, David M. and Wilson, Katie and West, Gregory and Hoffman, Robert and Lackmann, Gary and Brooks, Harold and Roebber, Paul and Bals-Elsholz, Teresa and et al.}, year={2022}, month={Aug}, pages={E1720–E1746} }
 @article{lackmann_miller_robinson_michaelis_2021, title={Persistent Anomaly Changes in High-Resolution Climate Simulations}, volume={34}, ISSN={["1520-0442"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85106939084&partnerID=MN8TOARS}, DOI={10.1175/JCLI-D-20-0465.1}, abstractNote={Abstract Persistent anomalies (PAs) are associated with a variety of impactful weather extremes, prompting research into how their characteristics will respond to climate change. Previous studies, however, have not provided conclusive results, owing to the complexity of the phenomenon and to difficulties in general circulation model (GCM) representations of PAs. Here, we diagnose PA activity in ten years of current and projected future output from global, high-resolution (15-km mesh) time-slice simulations performed with the Model for Prediction Across Scales-Atmosphere (MPAS-A). These time slices span a range of ENSO states. They include high-resolution representations of sea-surface temperatures and GCM-based sea ice for present and future climates. Future projections, based on the RCP8.5 scenario, exhibit strong Arctic amplification and tropical upper warming, providing a valuable experiment with which to assess the impact of climate change on PA frequency. The MPAS-A present-climate simulations reproduce the main centers of observed PA activity, but with an eastward shift in the North Pacific and reduced amplitude in the North Atlantic. The overall frequency of positive PAs in the future simulations is similar to that in the present-day simulations, while negative PAs become less frequent. Although some regional changes emerge, the small, generally negative changes in PA frequency and meridional circulation index indicate that climate change does not lead to increased persistence of midlatitude flow anomalies or increased waviness in these simulations.}, number={13}, journal={JOURNAL OF CLIMATE}, author={Lackmann, Gary M. and Miller, Rebecca L. and Robinson, Walter A. and Michaelis, Allison C.}, year={2021}, month={Jul}, pages={5425–5442} }
 @article{michaelis_lackmann_2021, title={Storm-Scale Dynamical Changes of Extratropical Transition Events in Present-Day and Future High-Resolution Global Simulations}, volume={34}, ISSN={["1520-0442"]}, DOI={10.1175/JCLI-D-20-0472.1}, abstractNote={Abstract Tropical cyclones (TCs) propagating into baroclinic midlatitude environments can transform into extratropical cyclones, in some cases resulting in high-impact weather conditions far from the tropics. This study extends analysis of extratropical transition (ET) changes in multi-seasonal global simulations using the Model for Prediction Across Scales-Atmosphere (MPAS-A) under present-day and projected future conditions. High-resolution (15 km) covers the Northern Hemisphere; TCs and ET events are tracked based on sea-level pressure minima accompanied by a warm core and use of a cyclone phase space method. Previous analysis of these simulations showed large changes in ET over the North Atlantic (NATL) basin, with ET events exhibiting a 4–5° northward latitudinal shift and a ~6 hPa strengthening of the post-transition extratropical cyclone. Storm-relative composites, primarily representing post-transformation cold-core events, indicate that this increase in post-transition storm intensity is associated with an intensification of the neighboring upper-level trough and downstream ridge, and a poleward shift in the storm center, conducive to enhanced trough-TC interactions after ET completion. Additionally, the future composite ET event is located in the right-jet entrance of an outflow jet that is strengthened relative to its present-day counterpart. Localized impacts associated with ET events, such as heavy precipitation and strong near-surface winds, are significantly enhanced in the future-climate simulations; 6-hourly precipitation for NATL events increases at a super-Clausius-Clapeyron rate with area-average precipitation increasing over 30%. Furthermore, intensified precipitation contributes to enhanced lower-tropospheric potential vorticity and stronger upper-tropospheric outflow, implying the potential for more extreme downstream impacts under the future climate scenario.}, number={12}, journal={JOURNAL OF CLIMATE}, author={Michaelis, Allison C. and Lackmann, Gary M.}, year={2021}, month={Jun}, pages={5037–5062} }
 @article{green_leins_lackmann_morrow_blaes_2021, title={The National Weather Service-North Carolina State University Internship Course Impacts and Success over a Generation}, volume={102}, ISSN={["1520-0477"]}, DOI={10.1175/BAMS-D-20-0260.1}, abstractNote={Abstract Nearly 100 North Carolina State University students have participated in a unique, highly structured internship course conducted by the National Weather Service Forecast Office in Raleigh, NC. Here, we explore the impact that this course has had on their professional development and career trajectories. The course has now been running for 17 years, and this paper provides an update on how the course has changed over time, including an evolution of the interview process to participate in the course, the number of students enrolled each semester has systematically been lowered to allow for more individual attention, and additional experiences outside of the WFO have been added. There are benefits for the students, with about half of the students now employed by the NWS, and nearly universal praise for how the course impacted their career progression. The university benefits from the course because the course serves as a compelling selling point for the MEAS department when recruiting students and the department also ensures that the curriculum is adequately preparing potential students for the job market. Finally, the NWS gains by creating a pool of potential employees that will require less spin-up time if hired, and graduates of the NCSU program have gone on to be involved with similar student volunteer programs at their respective offices once hired.}, number={11}, journal={BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY}, author={Green, Thomas A., Jr. and Leins, Daniel and Lackmann, Gary M. and Morrow, James and Blaes, Jonathan}, year={2021}, month={Nov}, pages={E2079–E2085} }
 @article{jung_lackmann_2021, title={The Response of Extratropical Transition of Tropical Cyclones to Climate Change: Quasi-Idealized Numerical Experiments}, volume={34}, ISSN={["1520-0442"]}, DOI={10.1175/JCLI-D-20-0543.1}, abstractNote={Abstract This study uses small ensembles of convection-allowing, quasi-idealized simulations to examine the response of North Atlantic tropical cyclones (TCs) undergoing extratropical transition (ET) to climate change. Using HURDAT2 and ERA5 data over a 40-yr period from 1979 to 2018, we developed storm-relative composite fields for past North Atlantic recurving, oceanic ET events. The quasi-idealized present-day simulations are initialized from these composites and run in an aquaplanet domain. A pseudo–global warming approach is used for future simulations: Thermodynamic changes between late twenty-first century and twentieth century, derived from an ensemble of 20 CMIP5 GCMs under the RCP8.5 scenario, are added to the present-day initial and lateral boundary conditions. The composite-initialized present-day simulations exhibit realistic ET characteristics. Future simulations show greater intensity, heavier precipitation, and stronger downstream midlatitude wave train development relative to the present-day case. Specifically, the future ET event is substantially stronger before ET completion, though the system undergoes less reintensification after ET completion. Reductions in lower-tropospheric baroclinicity associated with Arctic amplification could contribute to this result. The future simulation exhibits 3-hourly ensemble-mean precipitation rate increases ranging from ~23% to ~50%, depending on ET phase and averaging radius. In addition, larger eddy kinetic energy accompanies the future storm, partly created by increased baroclinic conversion, resulting in stronger amplification of downstream energy maxima via intensified ageostrophic geopotential flux convergence and divergence. These results suggest that future TCs undergoing ET could have greater potential to cause high-impact weather in western Europe through both direct and remote processes.}, number={11}, journal={JOURNAL OF CLIMATE}, author={Jung, Chunyong and Lackmann, Gary M.}, year={2021}, month={Jun}, pages={4361–4381} }
 @article{tierney_robinson_lackmann_miller_2021, title={The Sensitivity of Persistent Geopotential Anomalies to the Climate of a Moist Channel Model}, volume={34}, ISSN={["1520-0442"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85106894701&partnerID=MN8TOARS}, DOI={10.1175/JCLI-D-20-0254.1}, abstractNote={Abstract High-impact events such as heat waves and droughts are often associated with persistent positive geopotential height anomalies (PAs). Understanding how PA activity will change in a future warmer climate is therefore fundamental to projecting associated changes in weather and climate extremes. This is a complex problem because the dynamics of PAs and their associated blocking activity are still poorly understood. Furthermore, climate-change influences on PA activity may be geographically dependent and encompass competing influences. To expose the salient impacts of climate change, we use an oceanic channel configuration of the Weather Research and Forecasting model (WRF) in a bivariate experiment focused on changes in environmental temperature, moisture, and baroclinicity. The 500-hPa wind speed and flow variability are found to increase with increasing temperature and baroclinicity, driven by increases in latent heat release and a stronger virtual temperature gradient. Changes to 500-hPa sinuosity are negligible. PAs are objectively identified at the 500-hPa level using an anomaly threshold method. When using a fixed threshold, PA trends indicate increased activity and strength with warming, but decreased activity and strength with Arctic amplification. Use of a climate-relative threshold hides these trends and highlights the importance of accurate characterization of the mean flow. Changes in PA activity mirror corresponding changes in 500-hPa flow variability and are found to be attributable to changes in three distinct dynamical mechanisms: baroclinic wave activity, virtual temperature effects, and latent heat release.}, number={12}, journal={JOURNAL OF CLIMATE}, author={Tierney, Gregory and Robinson, Walter A. and Lackmann, Gary and Miller, Rebecca}, year={2021}, month={Jun}, pages={5093–5108} }
 @article{miller_lackmann_robinson_2020, title={A New Variable-Threshold Persistent Anomaly Index: Northern Hemisphere Anomalies in the ERA-Interim Reanalysis}, volume={148}, ISSN={["1520-0493"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85082885384&partnerID=MN8TOARS}, DOI={10.1175/MWR-D-19-0144.1}, abstractNote={Abstract Persistent weather regimes characterized by anomalous temperature or precipitation are often associated with persistent anomalies (PAs) in the tropospheric geopotential height field. To identify PAs throughout the annual cycle, an earlier definition is modified to apply a seasonally varying magnitude threshold, based on a smoothed, daily varying climatological average of daily 500-hPa geopotential height variability. The modified index can be applied to a wide variety of analysis, reanalysis, or model-forecast gridded data. Here, the modified PA index is used to identify positive and negative Northern Hemisphere PAs in all seasons and to compute trends in PA frequency, strength, location, and duration, in the ECMWF ERA-Interim reanalysis dataset (1979–2016). Height data are detrended and anomalies are weighted with an inverse sine-of-latitude function. In addition to maxima in PA frequency identified previously (North Pacific, North Atlantic, and Russia), an additional summertime maximum appears in the Arctic; this feature has not been analyzed extensively. A composite of summertime positive Arctic PA events reveals an equivalent barotropic structure, similar to that documented for midlatitude PAs. Arctic PA frequency is greatest in summer; it exhibits no trend in frequency over the 38-yr ERA-Interim analysis period. In fact, no discernable trends in PA frequency, strength, or duration are evident in the analysis period for the primary PA regions, although there is a suggestion of a northward shift in positive PA activity in the North Pacific.}, number={1}, journal={MONTHLY WEATHER REVIEW}, author={Miller, Rebecca L. and Lackmann, Gary M. and Robinson, Walter A.}, year={2020}, month={Jan}, pages={43–62} }
 @article{radford_lackmann_baxter_2019, title={An Evaluation of Snowband Predictability in the High-Resolution Rapid Refresh}, volume={34}, ISSN={["1520-0434"]}, DOI={10.1175/WAF-D-19-0089.1}, abstractNote={Abstract Narrow regions of intense, banded snowfall present hazardous travel conditions due to rapid onset, high precipitation rates, and lowered visibility. Despite their importance, there are few verification studies of snowbands in operational forecast models. The objective of this study is to evaluate the ability of the High-Resolution Rapid Refresh (HRRR) model to predict snowbands in the United States east of the Rocky Mountains. An automated band-detection algorithm was applied to a 3-yr period of simulated and observed radar reflectivity to compare snowband climatologies. This algorithm uses the distributions of reflectivities in contiguous precipitation regions to determine a band intensity threshold. The predictability of snowbands on a case-by-case basis was also evaluated using an object-oriented approach. The distribution of HRRR forecast banding resembles that of the observations, but with a significant positive frequency bias. This may partially be due to underrepresentation of observed bands in our verification dataset due to limited radar coverage in portions of the central United States. On a case-by-case basis, traditional skill metrics indicate limited predictability, but allowing for small timing discrepancies dramatically improves scores. Object-oriented verification yields mixed results, with 30% of forecasts receiving a score indicative of a well-predicted event. However, 69% of cases have at least one forecast lead demonstrating skill, suggesting the HRRR is successful in depicting environments conducive to band formation. These results suggest adopting a probabilistic, ensemble approach, and indicate that the deterministic HRRR is best suited for the identification of regions of elevated snowband risk and not precise timing or location information.}, number={5}, journal={WEATHER AND FORECASTING}, author={Radford, Jacob T. and Lackmann, Gary M. and Baxter, Martin A.}, year={2019}, month={Oct}, pages={1477–1494} }
 @article{michaelis_lackmann_2019, title={Climatological Changes in the Extratropical Transition of Tropical Cyclones in High-Resolution Global Simulations}, volume={32}, ISSN={["1520-0442"]}, DOI={10.1175/JCLI-D-19-0259.1}, abstractNote={Abstract Tropical cyclones (TCs) undergoing extratropical transition (ET) can develop into intense cyclonic systems accompanied by high-impact weather in areas far removed from the original TC. This study presents an analysis of multiseasonal global simulations representative of present-day and projected future climates using the Model for Prediction Across Scales–Atmosphere (MPAS-A), with high resolution (15-km grid) throughout the Northern Hemisphere. TCs are tracked as minima in sea level pressure (SLP) accompanied by a warm core, and TC tracks are extended into the extratropical phase based on local minima in SLP and use of a cyclone phase space method. The present-day simulations adequately represent observed ET characteristics such as frequency, location, and seasonal cycles throughout the Northern Hemisphere. The most significant changes in future ET events occur in the North Atlantic (NATL) basin. Here, a more favorable background environment, a shift toward stronger TC warm cores in the lower troposphere, and a significant poleward shift in TC location lead to a ~40% increase in the number of NATL ET events and a ~6% increase in the fraction of TCs undergoing ET. This equates to approximately 1–2 additional ET events per year in this region. In the future simulations, ET in the NATL occurs markedly farther north by ~4°–5°N, and the resultant extratropical cyclones are stronger by ~6 hPa. These changes hold potentially important implications for areas directly affected by ET events, such as eastern North America, as well as for regions indirectly impacted by downstream effects, including western Europe.}, number={24}, journal={JOURNAL OF CLIMATE}, author={Michaelis, Allison C. and Lackmann, Gary M.}, year={2019}, month={Dec}, pages={8733–8753} }
 @article{evaluation of a unique approach to high-resolution climate modelling using the model for prediction across scales (mpas) version 5.1_2019, url={http://dx.doi.org/10.5194/gmd-2019-34}, DOI={10.5194/gmd-2019-34}, abstractNote={Abstract. We present multi-seasonal simulations representative of present-day and future thermodynamic environments using the global Model for Prediction Across Scales-Atmosphere (MPAS) version 5.1 with high resolution (15 km) throughout the Northern Hemisphere. We select ten simulation years with varying phases of El Niño-Southern Oscillation (ENSO) and integrate each for 14.5 months. We use analysed sea surface temperature (SST) patterns for present-day simulations. For the future climate simulations, we alter present-day SSTs by applying monthly-averaged temperature changes derived from a 20-member ensemble of Coupled Model Intercomparison Project Phase 5 (CMIP5) general circulation models (GCMs) following the Representative Concentration Pathway (RCP) 8.5 emissions scenario. Daily sea ice fields, obtained from the monthly-averaged CMIP5 ensemble mean sea ice, are used for present-day and future simulations. The present-day simulations provide a reasonable reproduction of large-scale atmospheric features in the Northern Hemisphere such as the wintertime midlatitude storm tracks, upper-tropospheric jets, and maritime sea-level pressure features as well as annual precipitation patterns across the tropics. The simulations also adequately represent tropical cyclone (TC) characteristics such as strength, spatial distribution, and seasonal cycles for most of Northern Hemispheric basins. These results demonstrate the applicability of these model simulations for future studies examining climate change effects on various Northern Hemispheric phenomena, and, more generally, the utility of MPAS for studying climate change at spatial scales generally unachievable in GCMs.}, journal={Geoscientific Model Development Discussions}, year={2019}, month={Apr} }
 @article{michaelis_lackmann_robinson_2019, title={Evaluation of a unique approach to high-resolution climate modeling using the Model for Prediction Across Scales - Atmosphere (MPAS-A) version 5.1}, volume={12}, ISSN={["1991-9603"]}, url={https://doi.org/10.5194/gmd-12-3725-2019}, DOI={10.5194/gmd-12-3725-2019}, abstractNote={Abstract. We present multi-seasonal simulations representative of present-day and future environments using the global Model for Prediction Across Scales – Atmosphere (MPAS-A) version 5.1 with high resolution (15 km) throughout the Northern Hemisphere. We select 10 simulation years with varying phases of El Niño–Southern Oscillation (ENSO) and integrate each for 14.5 months. We use analyzed sea surface temperature (SST) patterns for present-day simulations. For the future climate simulations, we alter present-day SSTs by applying monthly-averaged temperature changes derived from a 20-member ensemble of Coupled Model Intercomparison Project phase 5 (CMIP5) general circulation models (GCMs) following the Representative Concentration Pathway (RCP) 8.5 emissions scenario. Daily sea ice fields, obtained from the monthly-averaged CMIP5 ensemble mean sea ice, are used for present-day and future simulations. The present-day simulations provide a reasonable reproduction of large-scale atmospheric features in the Northern Hemisphere such as the wintertime midlatitude storm tracks, upper-tropospheric jets, and maritime sea-level pressure features as well as annual precipitation patterns across the tropics. The simulations also adequately represent tropical cyclone (TC) characteristics such as strength, spatial distribution, and seasonal cycles for most Northern Hemisphere basins. These results demonstrate the applicability of these model simulations for future studies examining climate change effects on various Northern Hemisphere phenomena, and, more generally, the utility of MPAS-A for studying climate change at spatial scales generally unachievable in GCMs.}, number={8}, journal={GEOSCIENTIFIC MODEL DEVELOPMENT}, publisher={Copernicus GmbH}, author={Michaelis, Allison C. and Lackmann, Gary M. and Robinson, Walter A.}, year={2019}, month={Aug}, pages={3725–3743} }
 @article{jung_lackmann_2019, title={Extratropical Transition of Hurricane Irene (2011) in a Changing Climate}, volume={32}, ISSN={["1520-0442"]}, DOI={10.1175/JCLI-D-18-0558.1}, abstractNote={Abstract Tropical cyclones (TCs) undergoing strong extratropical transition (ET) can produce adverse societal impacts in areas that rarely experience direct TC impacts. This, in conjunction with projected environmental changes in climatological ET regions, motivates the investigation of possible future changes in ET characteristics. We utilize a small ensemble of numerical model simulations to examine how warming affects the ET of Hurricane Irene. To assess the effects of climate change, we use the pseudo-global warming method in which thermodynamic changes, derived from an ensemble of 20 CMIP5 GCMs, are applied to analyzed initial and lateral boundary conditions of model simulations. We find increased storm intensity in the future simulations, both in reduced minimum sea level pressure and strengthened 10-m wind speed. Storm-centered composites indicate a strengthening of tropospheric potential vorticity near the center of Irene, consistent with enhanced latent heat release. The results also demonstrate that Irene’s precipitation in the warmed simulations increases at a rate that exceeds Clausius–Clapeyron scaling, owing to enhanced moisture flux convergence and an additional contribution from increased surface evaporation. The duration of the transition process increased in the warmed simulations due to a weakened midtropospheric trough and reduced vertical wind shear and meridional SST gradient with a slower northward translation. These results suggest that transitioning storms may exhibit an increased ability to extend TC-like conditions poleward, and motivates additional research.}, number={15}, journal={JOURNAL OF CLIMATE}, author={Jung, Chunyong and Lackmann, Gary M.}, year={2019}, month={Aug}, pages={4847–4871} }
 @article{lackmann_thompson_2019, title={Hydrometeor Lofting and Mesoscale Snowbands}, volume={147}, ISSN={["1520-0493"]}, DOI={10.1175/MWR-D-19-0036.1}, abstractNote={Abstract Environments that accompany mesoscale snowbands in extratropical cyclones feature strong midlevel frontogenesis and weak symmetric stability, conditions conducive to vigorous ascent. Prior observational and numerical studies document the occurrence of upward vertical velocities in excess of 1 m s−1 near the comma head of winter cyclones. These values roughly correspond to the terminal fall velocity of snow; snow lofting has been measured directly with vertically pointing radars. Here, we investigate the occurrence of lower-tropospheric snow lofting near mesoscale bands and its contribution to snowfall heterogeneity. We test the hypothesis that hydrometeor lofting substantially influences snowfall distributions by analyzing the vertical snow flux in case-study simulations, by computing snow trajectories, and by testing sensitivity of simulated snowbands to parameterized snow terminal fall velocity and advection. These experiments confirm the presence of upward snow flux in the lower troposphere upstream of simulated mesoscale snowbands for two events (27 January 2015 and 2 February 2016). The band of lower-tropospheric lofting played a more important role in the January 2015 case relative to the February 2016 event. Lofting enhances the horizontal advection of snow by increasing hydrometeor residence time aloft, influencing the surface snowfall distribution. Experimental simulations illustrate that while lofting and advection influence the snow distribution, these processes reduce snowfall heterogeneity, contrary to our initial hypothesis. Our findings indicate that considerable horizontal displacement can occur between the locations of strongest ascent and heaviest surface snowfall. Numerical forecasts of snowbands are sensitive to formulations of terminal fall velocity of snow in microphysical parameterizations due to this lofting and transport process.}, number={11}, journal={MONTHLY WEATHER REVIEW}, author={Lackmann, Gary M. and Thompson, Gregory}, year={2019}, month={Nov}, pages={3879–3899} }
 @article{wanik_anagnostou_astitha_hartman_lackmann_yang_cerrai_he_frediani_2018, title={A Case Study on Power Outage Impacts from Future Hurricane Sandy Scenarios}, volume={57}, ISSN={["1558-8432"]}, DOI={10.1175/jamc-d-16-0408.1}, abstractNote={Abstract Hurricane Sandy (2012, referred to as Current Sandy) was among the most devastating storms to impact Connecticut’s overhead electric distribution network, resulting in over 15 000 outage locations that affected more than 500 000 customers. In this paper, the severity of tree-caused outages in Connecticut is estimated under future-climate Hurricane Sandy simulations, each exhibiting strengthened winds and heavier rain accumulation over the study area from large-scale thermodynamic changes in the atmosphere and track changes in the year ~2100 (referred to as Future Sandy). Three machine-learning models used five weather simulations and the ensemble mean of Current and Future Sandy, along with land-use and overhead utility infrastructure data, to predict the severity and spatial distribution of outages across the Eversource Energy service territory in Connecticut. To assess the influence of increased precipitation from Future Sandy, two approaches were compared: an outage model fit with a full set of variables accounting for both wind and precipitation, and a reduced set with only wind. Future Sandy displayed an outage increase of 42%–64% when using the ensemble of WRF simulations fit with three different outage prediction models. This study is a proof of concept for the assessment of increased outage risk resulting from potential changes in tropical cyclone intensity associated with late-century thermodynamic changes driven by the IPCC AR4 A2 emissions scenario.}, number={1}, journal={JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY}, author={Wanik, D. W. and Anagnostou, E. N. and Astitha, M. and Hartman, B. M. and Lackmann, G. M. and Yang, J. and Cerrai, D. and He, J. and Frediani, M. E. B.}, year={2018}, month={Jan}, pages={51–79} }
 @article{michaelis_willison_lackmann_robinson_2017, title={Changes in Winter North Atlantic Extratropical Cyclones in High-Resolution Regional Pseudo-Global Warming Simulations}, volume={30}, ISSN={["1520-0442"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85027249354&partnerID=MN8TOARS}, DOI={10.1175/jcli-d-16-0697.1}, abstractNote={The present study investigates changes in the location, frequency, intensity, and dynamical processes of North Atlantic extratropical cyclones with warming consistent with the IPCC Fifth Assessment Report (AR5) representative concentration pathway 8.5 (RCP8.5) scenario. The modeling, analysis, and prediction (MAP) climatology of midlatitude storminess (MCMS) feature-tracking algorithm was utilized to analyze 10 cold-season high-resolution atmospheric simulations over the North Atlantic region in current and future climates. Enhanced extratropical cyclone activity is most evident in the northeast North Atlantic and off the U.S. East Coast. These changes in cyclone activity are offset from changes in eddy kinetic energy and eddy heat flux. Investigation of the minimum SLP reached at each grid point reveals a lack of correspondence between the strongest events in the current and future simulations, indicating the future simulations produced a different population of storms. Examination of the percent change of storms in the storm-track region shows a reduction in the number of strong storms (i.e., those reaching a minimum SLP perturbation of at least −51 hPa). Storm-relative composites of strong and moderate storms show an increase in precipitation, associated with enhanced latent heat release and strengthening of the 900–700-hPa layer-average potential vorticity (PV). Other structural changes found for cyclones in a future climate include weakened upper-level PV for strong storms and a weakened near-surface potential temperature anomaly for moderate storms, demonstrating a change in storm dynamics. Furthermore, the impacts associated with extratropical cyclones, such as strong near-surface winds and heavy precipitation, strengthen and become more frequent with warming.}, number={17}, journal={JOURNAL OF CLIMATE}, author={Michaelis, Allison C. and Willison, Jeff and Lackmann, Gary M. and Robinson, Walter A.}, year={2017}, month={Sep}, pages={6905–6925} }
 @article{king_parker_sherburn_lackmann_2017, title={Rapid Evolution of Cool Season, Low-CAPE Severe Thunderstorm Environments}, volume={32}, ISSN={["1520-0434"]}, DOI={10.1175/waf-d-16-0141.1}, abstractNote={Abstract Low-CAPE (i.e., CAPE ≤ 1000 J kg−1) severe thunderstorms are common in the greater southeastern United States (including the Tennessee and Ohio valleys). These events are often poorly forecasted, and the environments in which they occur may rapidly evolve. Real-data simulations of 11 low-CAPE severe events and 6 low-CAPE nonsevere events were performed at convection-allowing resolution. Some amount of surface-based destabilization occurred during all simulated events over the 3-h period prior to convection. Most simulated severe events experienced comparatively large destabilization relative to the nonsevere events as a result of surface warming, cooling aloft, and surface moistening. The release of potential instability by large-scale forcing for ascent likely influenced the cooling aloft in some cases. Surface warming was attributable primarily to warm advection and appeared to be an important discriminator between severe and nonsevere simulated events. Severe events were also found to have larger low-level wind shear than nonsevere events, particularly during nocturnal cases. Because of the rapid destabilization that occurred within 3 h in the simulated events, it is evident that 3–6-hourly model output may not be adequate for forecasting severe events in high-shear, low-CAPE environments. Monitoring of high-resolution model forecasts and surface observations may be necessary to identify a rapidly changing severe environment.}, number={2}, journal={WEATHER AND FORECASTING}, author={King, Jessica R. and Parker, Matthew D. and Sherburn, Keith D. and Lackmann, Gary M.}, year={2017}, month={Apr}, pages={763–779} }
 @article{sherburn_parker_king_lackmann_2016, title={Composite Environments of Severe and Nonsevere High-Shear, Low-CAPE Convective Events}, volume={31}, ISSN={["1520-0434"]}, DOI={10.1175/waf-d-16-0086.1}, abstractNote={Abstract Severe convection occurring in environments characterized by large amounts of vertical wind shear and limited instability (high-shear, low-CAPE, or “HSLC,” environments) represents a considerable forecasting and nowcasting challenge. Of particular concern, NWS products associated with HSLC convection have low probability of detection and high false alarm rates. Past studies of HSLC convection have examined features associated with single cases; the present work, through composites of numerous cases, illustrates the attributes of “typical” HSLC severe and nonsevere events and identifies features that discriminate between the two. HSLC severe events across the eastern United States typically occur in moist boundary layers within the warm sector or along the cold front of a strong surface cyclone, while those in the western United States have drier boundary layers and more typically occur in the vicinity of a surface triple point or in an upslope regime. The mean HSLC severe event is shown to exhibit stronger forcing for ascent at all levels than its nonsevere counterpart. The majority of EF1 or greater HSLC tornadoes are shown to occur in the southeastern United States, so this region is subjected to the most detailed statistical analysis. Beyond the documented forecasting skill of environmental lapse rates and low-level shear vector magnitude, it is shown that a proxy for the release of potential instability further enhances skill when attempting to identify potentially severe HSLC events. This enhancement is likely associated with the local, in situ CAPE generation provided by this mechanism. Modified forecast parameters including this proxy show considerably improved spatial focusing of the forecast severe threat when compared to existing metrics.}, number={6}, journal={WEATHER AND FORECASTING}, author={Sherburn, Keith D. and Parker, Matthew D. and King, Jessica R. and Lackmann, Gary M.}, year={2016}, month={Dec}, pages={1899–1927} }
 @article{marciano_lackmann_robinson_2015, title={Changes in US East Coast Cyclone Dynamics with Climate Change}, volume={28}, ISSN={["1520-0442"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84921677491&partnerID=MN8TOARS}, DOI={10.1175/jcli-d-14-00418.1}, abstractNote={Abstract Previous studies investigating the impacts of climate change on extratropical cyclones have primarily focused on changes in the frequency, intensity, and distribution of these events. Fewer studies have directly investigated changes in the storm-scale dynamics of individual cyclones. Precipitation associated with these events is projected to increase with warming owing to increased atmospheric water vapor content. This presents the potential for enhancement of cyclone intensity through increased lower-tropospheric diabatic potential vorticity generation. This hypothesis is tested using the Weather Research and Forecasting Model to simulate individual wintertime extratropical cyclone events along the United States East Coast in present-day and future thermodynamic environments. Thermodynamic changes derived from an ensemble of GCMs for the IPCC Fourth Assessment Report (AR4) A2 emissions scenario are applied to analyzed initial and lateral boundary conditions of observed strongly developing cyclone events, holding relative humidity constant. The perturbed boundary conditions are then used to drive future simulations of these strongly developing events. Present-to-future changes in the storm-scale dynamics are assessed using Earth-relative and storm-relative compositing. Precipitation increases at a rate slightly less than that dictated by the Clausius–Clapeyron relation with warming. Increases in cyclone intensity are seen in the form of minimum sea level pressure decreases and a strengthened 10-m wind field. Amplification of the low-level jet occurs because of the enhancement of latent heating. Storm-relative potential vorticity diagnostics indicate a strengthening of diabatic potential vorticity near the cyclone center, thus supporting the hypothesis that enhanced latent heat release is responsible for this regional increase in future cyclone intensity.}, number={2}, journal={JOURNAL OF CLIMATE}, author={Marciano, Christopher G. and Lackmann, Gary M. and Robinson, Walter A.}, year={2015}, month={Jan}, pages={468–484} }
 @article{lackmann_2015, title={Hurricane Sandy before 1900 and after 2100}, volume={96}, ISSN={["1520-0477"]}, DOI={10.1175/bams-d-14-00123.1}, abstractNote={Abstract To what extent did large-scale thermodynamic climate change contribute to the intensity and unusual track of Hurricane Sandy, which affected the U.S. mid-Atlantic region in late October 2012? How much of an impact would projected future climate change have on a storm such as Sandy? These questions are investigated using an ensemble of high-resolution numerical simulations in conjunction with analyzed and projected changes from a suite of general circulation models (GCMs). Simulations initialized with current analyses from the midpoint of Sandy’s life cycle, while the system was centered near the Bahamas, adequately replicate the observed intensity and track of Sandy. Initial and boundary condition data are then altered with thermodynamic change fields obtained from a five-member GCM ensemble, allowing hypothetical replication of the synoptic weather pattern that accompanied Hurricane Sandy, but for large-scale thermodynamic conditions corresponding to the 1880s and for projections to the twenty-second century. The past ensemble produces a slightly weaker storm that makes landfall south of the observed location. The future ensemble depicts a significantly more intense system that makes landfall farther north, near Long Island, New York. Within the limitations of the methods used, it is suggested that climate change to date exerted only a modest influence on the intensity and track of Sandy. The strengthening in the simulations run with projected future warming is consistent with increased condensational heating; changes in the synoptic steering flow also appear to result from diabatic processes. The questions of how climate change affected Sandy’s genesis and early life cycle, changes in the frequency of this type of synoptic pattern, and changes in impacts related to coastal development and sea level rise are not considered here.}, number={4}, journal={BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY}, author={Lackmann, Gary M.}, year={2015}, month={Apr}, pages={547–560} }
 @article{willison_robinson_lackmann_2015, title={North Atlantic Storm-Track Sensitivity to Warming Increases with Model Resolution}, volume={28}, ISSN={["1520-0442"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84977575720&partnerID=MN8TOARS}, DOI={10.1175/jcli-d-14-00715.1}, abstractNote={Abstract Mesoscale condensational heating can increase the sensitivity of modeled extratropical cyclogenesis to horizontal resolution. Here a pseudo global warming experiment is presented to investigate how this heating-enhanced sensitivity to resolution changes in a warmer and thus moister atmosphere. The Weather Research and Forecasting (WRF) Model with 120- and 20-km grid spacing is used to simulate current and future climates. It is found that the North Atlantic storm-track response to global warming is amplified at the higher model resolution. The most dramatic changes occur over the northeastern Atlantic, where resolution typical of current general circulation models (GCMs) results in a smaller global warming response in comparison with that in the 20-km simulations. These results suggest that caution is warranted when interpreting projections from coarse-resolution GCMs of future cyclone activity over the northeastern Atlantic.}, number={11}, journal={JOURNAL OF CLIMATE}, author={Willison, Jeff and Robinson, Walter A. and Lackmann, Gary M.}, year={2015}, month={Jun}, pages={4513–4524} }
 @article{baxter_lackmann_mahoney_workoff_hamill_2014, title={Verification of Quantitative Precipitation Reforecasts over the Southeastern United States}, volume={29}, ISSN={["1520-0434"]}, DOI={10.1175/waf-d-14-00055.1}, abstractNote={Abstract NOAA’s second-generation reforecasts are approximately consistent with the operational version of the 2012 NOAA Global Ensemble Forecast System (GEFS). The reforecasts allow verification to be performed across a multidecadal time period using a static model, in contrast to verifications performed using an ever-evolving operational modeling system. This contribution examines three commonly used verification metrics for reforecasts of precipitation over the southeastern United States: equitable threat score, bias, and ranked probability skill score. Analysis of the verification metrics highlights the variation in the ability of the GEFS to predict precipitation across amount, season, forecast lead time, and location. Beyond day 5.5, there is little useful skill in quantitative precipitation forecasts (QPFs) or probabilistic QPFs. For lighter precipitation thresholds [e.g., 5 and 10 mm (24 h)−1], use of the ensemble mean adds about 10% to the forecast skill over the deterministic control. QPFs have increased in accuracy from 1985 to 2013, likely due to improvements in observations. Results of this investigation are a first step toward using the reforecast database to distinguish weather regimes that the GEFS typically predicts well from those regimes that the GEFS typically predicts poorly.}, number={5}, journal={WEATHER AND FORECASTING}, author={Baxter, Martin A. and Lackmann, Gary M. and Mahoney, Kelly M. and Workoff, Thomas E. and Hamill, Thomas M.}, year={2014}, month={Oct}, pages={1199–1207} }
 @article{mallard_lackmann_aiyyer_hill_2013, title={Atlantic Hurricanes and Climate Change. Part I: Experimental Design and Isolation of Thermodynamic Effects}, volume={26}, ISSN={["1520-0442"]}, DOI={10.1175/jcli-d-12-00182.1}, abstractNote={Abstract The Weather Research and Forecasting (WRF) model is used in a downscaling experiment to simulate a portion of the Atlantic hurricane season both in present-day conditions and with modifications to include future thermodynamic changes. Temperature and moisture changes are derived from an ensemble of climate simulations from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) A1B scenario and added to analyzed initial and lateral boundary conditions, leaving horizontal temperature gradients and vertical wind shear unaltered. This method of downscaling excludes future changes in shear and incipient disturbances, thereby isolating the thermodynamic component of climate change and its effect on tropical cyclone (TC) activity. The North Atlantic basin is simulated with 18- and 6-km grid spacing, and a four-member physics ensemble is composed by varying microphysical and boundary layer parameterization schemes. This ensemble is used in monthly simulations during an active (2005) and inactive (2009) season, and the simulations are able to capture the change in activity between the different years. TC frequency is better reproduced with use of 6-km grid spacing and explicitly simulated convection, relative to simulations with 18-km grid spacing. A detailed comparison of present-day and future ensemble results is provided in a companion study.}, number={13}, journal={JOURNAL OF CLIMATE}, author={Mallard, Megan S. and Lackmann, Gary M. and Aiyyer, Anantha and Hill, Kevin}, year={2013}, month={Jul}, pages={4876–4893} }
 @article{mallard_lackmann_aiyyer_2013, title={Atlantic Hurricanes and Climate Change. Part II: Role of Thermodynamic Changes in Decreased Hurricane Frequency}, volume={26}, ISSN={["1520-0442"]}, DOI={10.1175/jcli-d-12-00183.1}, abstractNote={Abstract A method of downscaling that isolates the effect of temperature and moisture changes on tropical cyclone (TC) activity was presented in Part I of this study. By applying thermodynamic modifications to analyzed initial and boundary conditions from past TC seasons, initial disturbances and the strength of synoptic-scale vertical wind shear are preserved in future simulations. This experimental design allows comparison of TC genesis events in the same synoptic setting, but in current and future thermodynamic environments. Simulations of both an active (September 2005) and inactive (September 2009) portion of past hurricane seasons are presented. An ensemble of high-resolution simulations projects reductions in ensemble-average TC counts between 18% and 24%, consistent with previous studies. Robust decreases in TC and hurricane counts are simulated with 18- and 6-km grid lengths, for both active and inactive periods. Physical processes responsible for reduced activity are examined through comparison of monthly and spatially averaged genesis-relevant parameters, as well as case studies of development of corresponding initial disturbances in current and future thermodynamic conditions. These case studies show that reductions in TC counts are due to the presence of incipient disturbances in marginal moisture environments, where increases in the moist entropy saturation deficits in future conditions preclude genesis for some disturbances. Increased convective inhibition and reduced vertical velocity are also found in the future environment. It is concluded that a robust decrease in TC frequency can result from thermodynamic changes alone, without modification of vertical wind shear or the number of incipient disturbances.}, number={21}, journal={JOURNAL OF CLIMATE}, author={Mallard, Megan S. and Lackmann, Gary M. and Aiyyer, Anantha}, year={2013}, month={Nov}, pages={8513–8528} }
 @article{tang_xie_lackmann_liu_2013, title={Modeling the Impacts of the Large-Scale Atmospheric Environment on Inland Flooding during the Landfall of Hurricane Floyd (1999)}, volume={2013}, ISSN={["1687-9317"]}, DOI={10.1155/2013/294956}, abstractNote={The contribution of the large-scale atmospheric environment to precipitation and flooding during Hurricane Floyd was investigated in this study. Through the vortex removal technique in the Weather Research and Forecasting (WRF) model, the vortex associated with Hurricane Floyd (1999) was mostly removed in the model initial conditions and subsequent integration. Results show that the environment-induced precipitation can account for as much as 22% of total precipitation in the innermost model domain covering North Carolina coastal area and 7% in the focused hydrological study area. The high-resolution precipitation data from the WRF model was then used for input in a hydrological model to simulate river runoff. Hydrological simulation results demonstrate that without the tropical systems and their interactions with the large-scale synoptic environment the synoptic environment would only contribute 10% to the total discharge at the Tarboro gauge station. This suggests that Hurricane Floyd and Hurricane Dennis preceding it, along with the interactions between these tropical systems and the large-scale environment, have contributed to the bulk (90%) of the record amount of flood water in the Tar-Pamlico River Basin.}, journal={ADVANCES IN METEOROLOGY}, author={Tang, Qianhong and Xie, Lian and Lackmann, Gary M. and Liu, Bin}, year={2013} }
 @article{michaelis_lackmann_2013, title={Numerical modeling of a historic storm: Simulating the Blizzard of 1888}, volume={40}, ISSN={["1944-8007"]}, DOI={10.1002/grl.50750}, abstractNote={[1] The National Oceanic and Atmospheric Administration/Cooperative Institute for Research in Environmental Sciences Twentieth Century Reanalysis (20CR) is used to explore the feasibility of high-resolution simulation of a historic extratropical cyclone event: The New England Blizzard of 1888. Using the 20CR as initial and lateral boundary conditions for the Weather Research and Forecasting model, a reasonable depiction of the cyclone is obtained, albeit displaced significantly to the north of the observed cyclone during the later stages of the event. Despite the position error, the simulated storm produces heavy snowfall over parts of New England and intense offshore cyclogenesis.}, number={15}, journal={GEOPHYSICAL RESEARCH LETTERS}, author={Michaelis, Allison C. and Lackmann, Gary M.}, year={2013}, month={Aug}, pages={4092–4097} }
 @article{willison_robinson_lackmann_2013, title={The Importance of Resolving Mesoscale Latent Heating in the North Atlantic Storm Track}, volume={70}, ISSN={["1520-0469"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000322125600022&KeyUID=WOS:000322125600022}, DOI={10.1175/jas-d-12-0226.1}, abstractNote={Abstract Theoretical, observational, and modeling studies have established an important role for latent heating in midlatitude cyclone development. Models simulate some contribution from condensational heating to cyclogenesis, even with relatively coarse grid spacing (on the order of 100 km). Our goal is to more accurately assess the diabatic contribution to storm-track dynamics and cyclogenesis while bridging the gap between climate modeling and synoptic dynamics. This study uses Weather Research and Forecasting model (WRF) simulations with 120- and 20-km grid spacing to demonstrate the importance of resolving additional mesoscale features that are associated with intense precipitation and latent heat release within extratropical cyclones. Sensitivity to resolution is demonstrated first with a case study, followed by analyses of 10 simulated winters over the North Atlantic storm track. Potential vorticity diagnostics are employed to isolate the influences of latent heating on storm dynamics, and terms in the Lorenz energy cycle are analyzed to determine the resulting influences on the storm track. The authors find that the intensities of individual storms and their aggregate behavior in the storm track are strongly sensitive to horizontal resolution. An enhanced positive feedback between cyclone intensification and latent heat release is seen at higher resolution, resulting in a systematic increase in eddy intensity and a stronger storm track relative to the coarser simulations. These results have implications for general circulation models and their projections of climate change.}, number={7}, journal={JOURNAL OF THE ATMOSPHERIC SCIENCES}, author={Willison, Jeff and Robinson, Walter A. and Lackmann, Gary M.}, year={2013}, month={Jul}, pages={2234–2250} }
 @article{lackmann_2013, title={The South-Central US Flood of May 2010: Present and Future}, volume={26}, ISSN={["1520-0442"]}, DOI={10.1175/jcli-d-12-00392.1}, abstractNote={Abstract Previous studies have documented a feedback mechanism involving the cyclonic low-level jet (LLJ), poleward moisture flux and flux convergence, and condensational heating. Increased water vapor content and potentially heavier precipitation accompanying climate warming suggest the hypothesis that this feedback could strengthen with warming, contributing to amplification of precipitation extremes beyond what the thermodynamically controlled vapor increase would provide. Here, this hypothesis is tested with numerical simulations of a severe flooding event that took place in early May 2010 in the south-central United States. Control simulations with a mesoscale model capture the main features of the May 2010 flooding event. A pseudo–global warming approach is used to modify the current initial, surface, and boundary conditions by applying thermodynamic changes projected by an ensemble of GCMs for the A2 emission scenario. The observed synoptic pattern of the flooding event is replicated but with modified future thermodynamics, allowing isolation of thermodynamic changes on the moisture feedback. This comparison does not indicate a strengthening of the LLJ in the future simulation. Analysis of the lower-tropospheric potential vorticity evolution reveals that the southern portion of the LLJ over the Gulf of Mexico in this event was strengthened through processes involving the terrain of the Mexican Plateau; this aspect is largely insensitive to climate change. Despite the lack of LLJ strengthening, precipitation in the future simulation increased at a super Clausius–Clapeyron rate because of strengthened convective updrafts.}, number={13}, journal={JOURNAL OF CLIMATE}, author={Lackmann, Gary M.}, year={2013}, month={Jul}, pages={4688–4709} }
 @article{hill_lackmann_2011, title={The Impact of Future Climate Change on TC Intensity and Structure: A Downscaling Approach}, volume={24}, ISSN={["1520-0442"]}, DOI={10.1175/2011jcli3761.1}, abstractNote={A comprehensive analysis of tropical cyclone (TC) intensity change in a warming climate is undertaken with high-resolution (6- and 2-km grid spacing) idealized simulations using the Weather Research and Forecasting (WRF) model. With the goal of isolating the influence of thermodynamic aspects of climate change on maximum hurricane intensity, an idealized TC is placed within a quiescent, horizontally uniform tropical environment computed from averaged reanalysis data for the tropical Atlantic Ocean. The analyzed tropical environment is used for control simulations. Changes between the periods 1990–99 and 2090–99 are computed using output from 13 GCMs from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4), for the A1B, A2, and B1 emissions scenarios. These changes are then added to the reanalysis-derived initial and boundary conditions used in the control simulations. Some processes known to impact TC intensity, such as environmental vertical wind shear and sea surface wake cooling, are not considered in this study. Future TC intensity increased for 75 of 78 future simulations using 6-km grid length, with a 9% (~8 hPa) average increase in central surface-pressure deficit. For the 2-km simulations, the average increase was 14% (~14 hPa). The depth of the TC secondary circulation increases in future simulations, consistent with an increase in the height of the freezing level and tropopause. Inner-core precipitation increases of 10%–30% are found for future simulations, with large sensitivity to the emission scenario. The increase in precipitation is consistent with a stronger potential vorticity tower, a warmer eye, and lower central pressure. Enhanced upper-tropospheric warming in the GCM environment is shown to be an important mitigating influence on TC intensity change but is also shown to exhibit large uncertainty in GCM projections.}, number={17}, journal={JOURNAL OF CLIMATE}, author={Hill, Kevin A. and Lackmann, Gary M.}, year={2011}, month={Sep}, pages={4644–4661} }
 @article{mahoney_lackmann_2011, title={The Sensitivity of Momentum Transport and Severe Surface Winds to Environmental Moisture in Idealized Simulations of a Mesoscale Convective System}, volume={139}, ISSN={["1520-0493"]}, DOI={10.1175/2010mwr3468.1}, abstractNote={Analysis of a pair of three-dimensional simulations of mesoscale convective systems (MCSs) reveals a significant sensitivity of convective momentum transport (CMT), MCS motion, and the generation of severe surface winds to ambient moisture. The Weather Research and Forecasting model is used to simulate an idealized MCS, which is compared with an MCS in a drier midlevel environment. The MCS in the drier environment is smaller, moves slightly faster, and exhibits increased descent and more strongly focused areas of enhanced CMT near the surface in the trailing stratiform region relative to that in the control simulation. A marked increase in the occurrence of severe surface winds is observed between the dry midlevel simulation and the control. It is shown that the enhanced downward motion associated with decreased midlevel relative humidity affects CMT fields and contributes to an increase in the number of grid-cell occurrences of severe surface winds. The role of a descending rear-inflow jet in producing strong surface winds at locations trailing the gust front is also analyzed, and is found to be associated with low-level CMT maxima, particularly in the drier midlevel simulation.}, number={5}, journal={MONTHLY WEATHER REVIEW}, author={Mahoney, Kelly M. and Lackmann, Gary M.}, year={2011}, month={May}, pages={1352–1369} }
 @article{etherton_arms_oolman_lackmann_ramamurthy_2011, title={USING OPERATIONAL AND EXPERIMENTAL OBSERVATIONS IN GEOSCIENCE EDUCATION}, volume={92}, ISSN={["0003-0007"]}, DOI={10.1175/2010bams3045.1}, abstractNote={No Abstract available.}, number={4}, journal={BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY}, author={Etherton, Brian J. and Arms, Sean C. and Oolman, Larry D. and Lackmann, Gary M. and Ramamurthy, Mohan K.}, year={2011}, month={Apr}, pages={477–480} }
 @article{gentry_lackmann_2010, title={Sensitivity of Simulated Tropical Cyclone Structure and Intensity to Horizontal Resolution}, volume={138}, ISSN={["1520-0493"]}, DOI={10.1175/2009mwr2976.1}, abstractNote={Abstract The Weather Research and Forecasting (WRF) model is used to test the sensitivity of simulations of Hurricane Ivan (2004) to changes in horizontal grid spacing for grid lengths from 8 to 1 km. As resolution is increased, minimum central pressure decreases significantly (by 30 hPa from 8- to 1-km grid spacing), although this increase in intensity is not uniform across similar reductions in grid spacing, even when pressure fields are interpolated to a common grid. This implies that the additional strengthening of the simulated tropical cyclone (TC) at higher resolution is not attributable to sampling, but is due to changes in the representation of physical processes important to TC intensity. The most apparent changes in simulated TC structure with resolution occur near a grid length of 4 km. At 4-km grid spacing and below, polygonal eyewall segments appear, suggestive of breaking vortex Rossby waves. With sub-4-km grid lengths, localized, intense updraft cores within the eyewall are numerous and both polygonal and circular eyewall shapes appear regularly. Higher-resolution simulations produce a greater variety of shapes, transitioning more frequently between polygonal and circular eyewalls relative to lower-resolution simulations. It is hypothesized that this is because of the ability to resolve a greater range of wavenumbers in high-resolution simulations. Also, as resolution is increased, a broader range of updraft and downdraft velocities is present in the eyewall. These results suggest that grid spacing of 2 km or less is needed for representation of important physical processes in the TC eyewall. Grid-length and domain size suggestions for operational prediction are provided; for operational prediction, a grid length of 3 km or less is recommended.}, number={3}, journal={MONTHLY WEATHER REVIEW}, author={Gentry, Megan S. and Lackmann, Gary M.}, year={2010}, month={Mar}, pages={688–704} }
 @article{keighton_lee_holloway_hotz_zubrick_hovis_votaw_perry_lackmann_yuter_et al._2009, title={A COLLABORATIVE APPROACH TO STUDY NORTHWEST FLOW SNOW IN THE SOUTHERN APPALACHIANS}, volume={90}, ISSN={["0003-0007"]}, DOI={10.1175/2009BAMS2591.1}, abstractNote={Abstract Upslope-enhanced snowfall events during periods of northwesterly flow in the southern Appalachians have been recognized as a significant winter forecasting problem for some time. However, only in recent years has this problem received noteworthy attention by both the academic and operational communities. The complex meteorology of these events includes significant topographic influences, as well as a linkage between the upstream Great Lakes and resultant southern Appalachian snowfall. A unique collaborative team has recently formed, working toward the goals of improving the physical understanding of the mechanisms at work in these events and developing more accurate forecasts and more detailed climatologies. The literature shows only limited attention to this problem through the 1990s. However, with modernization of the National Weather Service (NWS) in the mid-1990s came opportunities to bring more attention to new or poorly understood forecast problems. These opportunities included the establis...}, number={7}, journal={BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY}, author={Keighton, Steve and Lee, Laurence and Holloway, Blair and Hotz, David and Zubrick, Steven and Hovis, Jeffrey and Votaw, Gary and Perry, L. Baker and Lackmann, Gary and Yuter, Sandra E. and et al.}, year={2009}, month={Jul}, pages={979–991} }
 @article{hill_lackmann_2009, title={Analysis of Idealized Tropical Cyclone Simulations Using the Weather Research and Forecasting Model: Sensitivity to Turbulence Parameterization and Grid Spacing}, volume={137}, ISSN={["1520-0493"]}, DOI={10.1175/2008MWR2220.1}, abstractNote={Abstract The Weather Research and Forecasting Advanced Research Model (WRF-ARW) was used to perform idealized tropical cyclone (TC) simulations, with domains of 36-, 12-, and 4-km horizontal grid spacing. Tests were conducted to determine the sensitivity of TC intensity to the available surface layer (SL) and planetary boundary layer (PBL) parameterizations, including the Yonsei University (YSU) and Mellor–Yamada–Janjic (MYJ) schemes, and to horizontal grid spacing. Simulations were run until a quasi-steady TC intensity was attained. Differences in minimum central pressure (Pmin) of up to 35 hPa and maximum 10-m wind (V10max) differences of up to 30 m s−1 were present between a convection-resolving nested domain with 4-km grid spacing and a parent domain with cumulus parameterization and 36-km grid spacing. Simulations using 4-km grid spacing are the most intense, with the maximum intensity falling close to empirical estimates of maximum TC intensity. Sensitivity to SL and PBL parameterization also exists, most notably in simulations with 4-km grid spacing, where the maximum intensity varied by up to ∼10 m s−1 (V10max) or ∼13 hPa (Pmin). Values of surface latent heat flux (LHFLX) are larger in MYJ than in YSU at the same wind speeds, and the differences increase with wind speed, approaching 1000 W m−2 at wind speeds in excess of 55 m s−1. This difference was traced to a larger exchange coefficient for moisture, CQ, in the MYJ scheme. The exchange coefficients for sensible heat (Cθ) and momentum (CD) varied by <7% between the SL schemes at the same wind speeds. The ratio Cθ/CD varied by <5% between the schemes, whereas CQ/CD was up to 100% larger in MYJ, and the latter is theorized to contribute to the differences in simulated maximum intensity. Differences in PBL scheme mixing also likely played a role in the model sensitivity. Observations of the exchange coefficients, published elsewhere and limited to wind speeds <30 m s−1, suggest that CQ is too large in the MYJ SL scheme, whereas YSU incorporates values more consistent with observations. The exchange coefficient for momentum increases linearly with wind speed in both schemes, whereas observations suggest that the value of CD becomes quasi-steady beyond some critical wind speed (∼30 m s−1).}, number={2}, journal={MONTHLY WEATHER REVIEW}, author={Hill, Kevin A. and Lackmann, Gary M.}, year={2009}, month={Feb}, pages={745–765} }
 @article{hill_lackmann_2009, title={Influence of Environmental Humidity on Tropical Cyclone Size}, volume={137}, ISSN={["1520-0493"]}, DOI={10.1175/2009MWR2679.1}, abstractNote={Abstract Observations demonstrate that the radius of maximum winds in tropical cyclones (TCs) can vary by an order of magnitude; similar size differences are evident in other spatial measures of the wind field as well as in cloud and precipitation fields. Many TC impacts are related to storm size, yet the physical mechanisms that determine TC size are not well understood and have received limited research attention. Presented here is a hypothesis suggesting that one factor controlling TC size is the environmental relative humidity, to which the intensity and coverage of precipitation occurring outside the TC core is strongly sensitive. From a potential vorticity (PV) perspective, the lateral extent of the TC wind field is linked to the size and strength of the associated cyclonic PV anomalies. Latent heat release in outer rainbands can result in the diabatic lateral expansion of the cyclonic PV distribution and balanced wind field. Results of idealized numerical experiments are consistent with the hypothesized sensitivity of TC size to environmental humidity. Simulated TCs in dry environments exhibit reduced precipitation outside the TC core, a narrower PV distribution, and reduced lateral extension of the wind field relative to storms in more moist environments. The generation of diabatic PV in spiral bands is critical to lateral wind field expansion in the outer portion of numerically simulated tropical cyclones. Breaking vortex Rossby waves in the eyewall lead to an expansion of the eye and the weakening of inner-core PV gradients in the moist environment simulation. Feedback mechanisms involving surface fluxes and the efficiency of diabatic PV production with an expanding cyclonic wind field are discussed.}, number={10}, journal={MONTHLY WEATHER REVIEW}, author={Hill, Kevin A. and Lackmann, Gary M.}, year={2009}, month={Oct}, pages={3294–3315} }
 @article{mahoney_lackmann_parker_2009, title={The Role of Momentum Transport in the Motion of a Quasi-Idealized Mesoscale Convective System}, volume={137}, ISSN={["1520-0493"]}, DOI={10.1175/2009MWR2895.1}, abstractNote={Abstract Momentum transport is examined in a simulated midlatitude mesoscale convective system (MCS) to investigate its contribution to MCS motion. Momentum budgets are computed using model output to quantify the role of specific processes in determining the low-level wind field in the system’s surface-based cold pool. Results show that toward the leading convective line of the MCS and near the leading edge of the cold pool, the momentum field is most strongly determined by the vertical advection of the storm-induced perturbation wind. Across the middle rear of the system, the wind field is largely a product of the pressure gradient acceleration and, to a lesser extent, the vertical advection of the background environmental (i.e., base state) wind. The relative magnitudes of the vertical advection terms in an Eulerian momentum budget suggest that, for gust-front-driven systems, downward momentum transport by the MCS is a significant driver of MCS motion and potentially severe surface winds. Results further illustrate that the contribution of momentum transport to MCS speed occurs mainly via the enhancement of the cold pool propagation speed as higher-momentum air from aloft is transported into the surface-based cold pool.}, number={10}, journal={MONTHLY WEATHER REVIEW}, author={Mahoney, Kelly M. and Lackmann, Gary M. and Parker, Matthew D.}, year={2009}, month={Oct}, pages={3316–3338} }
 @article{brennan_lackmann_mahoney_2008, title={Potential vorticity (PV) thinking in operations: The utility of nonconservation}, volume={23}, ISSN={["0882-8156"]}, DOI={10.1175/2007WAF2006044.1}, abstractNote={Abstract The use of the potential vorticity (PV) framework by operational forecasters is advocated through case examples that demonstrate its utility for interpreting and evaluating numerical weather prediction (NWP) model output for weather systems characterized by strong latent heat release (LHR). The interpretation of the dynamical influence of LHR is straightforward in the PV framework; LHR can lead to the generation of lower-tropospheric cyclonic PV anomalies. These anomalies can be related to meteorological phenomena including extratropical cyclones and low-level jets (LLJs), which can impact lower-tropospheric moisture transport. The nonconservation of PV in the presence of LHR results in a modification of the PV distribution that can be identified in NWP model output and evaluated through a comparison with observations and high-frequency gridded analyses. This methodology, along with the application of PV-based interpretation, can help forecasters identify aspects of NWP model solutions that are driven by LHR; such features are often characterized by increased uncertainty due to difficulties in model representation of precipitation amount and latent heating distributions, particularly for convective systems. Misrepresentation of the intensity and/or distribution of LHR in NWP model forecasts can generate errors that propagate through the model solution with time, potentially degrading the representation of cyclones and LLJs in the model forecast. The PV framework provides human forecasters with a means to evaluate NWP model forecasts in a way that facilitates recognition of when and how value may be added by modifying NWP guidance. This utility is demonstrated in case examples of coastal extratropical cyclogenesis and LLJ enhancement. Information is provided regarding tools developed for applying PV-based techniques in an operational setting.}, number={1}, journal={WEATHER AND FORECASTING}, author={Brennan, Michael J. and Lackmann, Gary M. and Mahoney, Kelly M.}, year={2008}, month={Feb}, pages={168–182} }
 @article{jacobs_raman_lackmann_childs_2008, title={The influence of the Gulf Stream induced SST gradients on the US East Coast winter storm of 24-25 January 2000}, volume={29}, ISSN={["0143-1161"]}, DOI={10.1080/01431160802175561}, abstractNote={This study presents an investigation of the influence of remotely sensed high resolution sea surface temperature (SST) and the SST gradient on the formation and evolution of the 24-25 January 2000 East Coast winter storm. A numerical model was employed for experimental simulation replaced SST analysis with a 1.1 km gridded data set. The most significant improvements were seen in the forecast deepening rate and track. Reduced development of the storm in the control simulation, as compared to the experimental simulation, appears to be due to the coarse grid SST representation, which fails to capture key thermal gradient features of the Gulf Stream. The simulations suggest that the high resolution remotely sensed SST data affect the track by changing the location of lower-tropospheric frontal boundaries through thermally-induced near-surface convergence and differential turbulent heat flux. Enhanced vortex stretching associated with the convergence along the lower frontal boundary appears to contribute to a stronger storm in the experimental simulations.}, number={21}, journal={INTERNATIONAL JOURNAL OF REMOTE SENSING}, author={Jacobs, N. A. and Raman, S. and Lackmann, G. M. and Childs, P. P., Jr.}, year={2008}, pages={6145–6174} }
 @article{orf_lackmann_herbster_krueger_cutrim_whitaker_steenburgh_voss_2007, title={Models as educational tools}, volume={88}, ISSN={["0003-0007"]}, DOI={10.1175/bams-88-7-1101}, number={7}, journal={BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY}, author={Orf, Leigh and Lackmann, Gary and Herbster, Chris and Krueger, Anton and Cutrim, Elen and Whitaker, Tom and Steenburgh, Jim and Voss, Michael}, year={2007}, month={Jul}, pages={1101–1104} }
 @article{mahoney_lackmann_2007, title={The effect of upstream convection on downstream precipitation}, volume={22}, ISSN={["1520-0434"]}, DOI={10.1175/WAF986.1}, abstractNote={Abstract Operational forecasters in the southeast and mid-Atlantic regions of the United States have noted a positive quantitative precipitation forecast (QPF) bias in numerical weather prediction (NWP) model forecasts downstream of some organized, cold-season convective systems. Examination of cold-season cases in which model QPF guidance exhibited large errors allowed identification of two representative cases for detailed analysis. The goals of the case study analyses are to (i) identify physical mechanisms through which the upstream convection (UC) alters downstream precipitation amounts, (ii) determine why operational models are challenged to provide accurate guidance in these situations, and (iii) suggest future research directions that would improve model forecasts in these situations and allow forecasters to better anticipate such events. Two primary scenarios are identified during which downstream precipitation is altered in the presence of UC for the study region: (i) a fast-moving convective (FC) scenario in which organized convective systems oriented parallel to the lower-tropospheric flow are progressive relative to the parent synoptic system, and appear to disrupt poleward moisture transport, and (ii) a situation characterized by slower-moving convection (SC) relative to the parent system. Analysis of a representative FC case indicated that moisture consumption, stabilization via convective overturning, and modification of the low-level flow to a more westerly direction in the postconvective environment all appear to contribute to the reduction of downstream precipitation. In the FC case, operational Eta Model forecasts moved the organized UC too slowly, resulting in an overestimate of downstream moisture transport. A 4-km explicit convection model forecast from the Weather Research and Forecasting model produced a faster-moving upstream convective system and improved downstream QPF. In contrast to the FC event, latent heat release in the primary rainband is shown to enhance the low-level jet ahead of the convection in the SC case, thereby increasing moisture transport into the downstream region. A negative model QPF bias was observed in Eta Model forecasts for the SC event. Suggestions are made for precipitation forecasting in UC situations, and implications for NWP model configuration are discussed.}, number={2}, journal={WEATHER AND FORECASTING}, author={Mahoney, Kelly M. and Lackmann, Gary M.}, year={2007}, month={Apr}, pages={255–277} }
 @article{palmieri_tredway_niyogi_lackmann_2006, title={Development and evaluation of a forecasting system for fungal disease in turfgrass}, volume={13}, ISSN={["1469-8080"]}, DOI={10.1017/S1350482706002428}, abstractNote={A forecasting system for fungal infection of turfgrass using weather-based empirical indices (the ‘Fidanza’ and ‘Schumann’ models) was developed and evaluated for its ability to predict the occurrence of brown patch (Rhizoctonia blight) infection episodes at an experimental site in southeastern USA. Disease observations took place at the Turfgrass Field Laboratory in Raleigh, North Carolina between 8 June and 17 August 2003. Three meteorological data sources were used to generate disease risk indices using the empirical models: an on-site observing station, an observing station at a nearby airport, and the US National Weather Service’s operational Eta weather forecast model. Visual observations of brown patch activity were conducted in the field and used to evaluate the accuracy of the disease prediction models. Results indicate that the Fidanza and Schumann models correctly predicted brown patch activity on 48% and 30% of the days on which disease occurred, respectively. A diagnosis of the model performance of these disease indices was undertaken. Results are dependent on occurrence of high temperatures and rainfall and independent of the source of the meteorological information (on-site, airport and the Eta model); therefore, regional meteorological information can be effectively applied to develop turfgrass disease forecasting systems. Ongoing efforts are directed towards developing new disease indices and modifying existing indices before an operational disease forecasting system can be implemented.}, number={4}, journal={METEOROLOGICAL APPLICATIONS}, author={Palmieri, Richard and Tredway, Lane and Niyogi, Dev and Lackmann, Gary M.}, year={2006}, month={Dec}, pages={405–416} }
 @article{brennan_lackmann_2006, title={Observational diagnosis and model forecast evaluation of unforecasted incipient precipitation during the 24-25 January 2000 East Coast cyclone}, volume={134}, ISSN={["1520-0493"]}, DOI={10.1175/MWR3184.1}, abstractNote={Abstract Previous research has shown that a lower-tropospheric diabatically generated potential vorticity (PV) maximum associated with an area of incipient precipitation (IP) was critical to the moisture transport north of the PV maximum into the Carolinas and Virginia during the 24–25 January 2000 East Coast cyclone. This feature was almost entirely absent in short-term (e.g., 6–12 h) forecasts from the 0000 UTC 24 January 2000 operational runs of the National Centers for Environmental Prediction (NCEP) North American Mesoscale (NAM, formerly Eta) and Global Forecast System (GFS, formerly AVN) models, even though it occurred over land within and downstream of a region of relatively high data density. Observations and model analyses are used to document the forcing for ascent, moisture, and instability (elevated gravitational and/or symmetric) associated with the IP, and the evolution of the IP formation is documented with radar and satellite imagery with the goal of understanding the fundamental nature of this precipitation feature and the models’ inability to predict it. Results show that the IP formed along a zone of lower-tropospheric frontogenesis in a region of strong synoptic-scale forcing for ascent downstream of an approaching upper trough and jet streak. The atmosphere above the frontal inversion was characterized by a mixture of gravitational conditional instability and conditional symmetric instability over a deep layer, and this instability was likely released when air parcels reached saturation as they ascended the frontal surface. The presence of elevated convection is suggested by numerous surface reports of thunder and the cellular nature of radar echoes in the region. Short-term forecasts from the Eta and AVN models failed to capture the magnitude of the frontogenesis, upper forcing, or elevated instability in the region of IP formation. These findings suggest that errors in the initial condition analyses, particularly in the water vapor field, in conjunction with the inability of model physics schemes to generate the precipitation feature, likely played a role in the operational forecast errors related to inland quantitative precipitation forecasts (QPFs) later in the event. A subsequent study will serve to clarify the role of initial conditions and model physics in the representation of the IP by NWP models.}, number={8}, journal={MONTHLY WEATHER REVIEW}, author={Brennan, Michael J. and Lackmann, Gary M.}, year={2006}, month={Aug}, pages={2033–2054} }
 @article{stuart_market_tielfeyan_lackmann_carey_brooks_nietfeld_motta_reeves_2006, title={The future of humans in an increasingly automated forecast process}, volume={87}, ISSN={["1520-0477"]}, DOI={10.1175/BAMS-87-11-1497}, abstractNote={National Weather Service, Wakefield, VirginiaUniversity of Missouri, Columbia, MissouriAir Force Weather Agency, Offutt AFB, NebraskaNorth Carolina State University, Raleigh, North CarolinaMitretek Systems Inc., Falls Church, VirginiaNational Severe Storms Laboratory, Norman, OklahomaNOAA/National Weather Service, Omaha, NebraskaNational Weather Service, Office of Climate, Water and Weather Services, Boulder, ColoradoAccuWeather, Inc., State College, Pennsylvania* CURRENT AFFILIATION: NOAA/National Weather Service, Albany, New YorkCORRESPONDING AUTHOR: Neil A. Stuart, National Weather Service, 251 Fuller Road, Suite B300, Albany, NY 12203-3640, E-mail: neil.stuart@noaa.gov}, number={11}, journal={BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY}, author={Stuart, Neil A. and Market, Partick S. and Tielfeyan, Bruce and Lackmann, Gary M. and Carey, Kenneth and Brooks, Harold E. and Nietfeld, Daniel and Motta, Brian C. and Reeves, Ken}, year={2006}, month={Nov}, pages={1497–1502} }
 @article{mahoney_lackmann_2006, title={The sensitivity of numerical forecasts to convective parameterization: A case study of the 17 February 2004 east coast cyclone}, volume={21}, ISSN={["1520-0434"]}, DOI={10.1175/WAF937.1}, abstractNote={Abstract The sensitivity of numerical model forecasts of coastal cyclogenesis and frontogenesis to the choice of model cumulus parameterization (CP) scheme is examined for the 17 February 2004 southeastern U.S. winter weather event. This event featured a complex synoptic and mesoscale environment, as the presence of cold-air damming, a developing coastal surface cyclone, and an upper-level trough combined to present a daunting winter weather forecast scenario. The operational forecast challenge was further complicated by erratic numerical model predictions. The most poignant area of disagreement between model runs was the treatment of a coastal cyclone and an associated coastal front, features that would affect the location and timing of precipitation and influence the precipitation type. At the time of the event, it was hypothesized that the Betts–Miller–Janjić (BMJ) CP scheme was dictating the location and intensity of the initial coastal cyclone center in operational Eta Model forecasts. For this reason, forecasts for this case were rerun with the workstation Eta Model using the Kain–Fritsch (KF) CP scheme to further examine the sensitivity to this parameterization choice. Results confirm that the model CP scheme played a major role in the forecast for this case, affecting the quantitative precipitation forecast as well as the strength, location, and structure of coastal cyclogenesis and coastal frontogenesis. The Eta Model forecast using the KF CP scheme produced a relatively uniform distribution of convective precipitation oriented along the axis of an inverted trough and strong coastal front. In contrast, the BMJ forecasts resulted in a weaker coastal front and the development of multiple distinct closed cyclonic circulations in association with more localized convective precipitation centers. An additional BMJ forecast in which the shallow mixing component of the scheme was disabled bore a closer semblance to the KF forecasts relative to the original BMJ forecast. Suggestions are provided to facilitate the identification of CP-driven cyclones using standard operational model output parameters.}, number={4}, journal={WEATHER AND FORECASTING}, author={Mahoney, Kelly M. and Lackmann, Gary M.}, year={2006}, month={Aug}, pages={465–488} }
 @article{brennan_keeter_riordan_lackmann_2005, title={Expandng horizons wth an NWS internship course}, volume={86}, ISSN={["1520-0477"]}, DOI={10.1175/BAMS-86-10-1407}, abstractNote={M eteorology students at North Carolina State University (NCSU) participated in an experimental internship course during the spring of 2004 that allowed them to gain an operational perspective on meteorology by experiencing the everyday duties of the staff at the collocated National Weather Service (NWS) Weather Forecast Offi ce (WFO) in Raleigh. Th e course was designed to meet several goals, which included allowing students to contribute to operational forecasting, gain profi ciency with routine NWS duties and soft ware tools, and sample the broad array of work performed by the NWS. Students also were exposed to operational meteorology and NWS careers and received assistance in pursuing such a career. During the semester, fi ve senior undergraduate and fi ve graduate students enrolled in the course. Th ey attended NWS training sessions, “shadowed” NWS staff , performed routine NWS duties, and assisted NWS staff during high-impact weather events. Overall, the students and NWS staff were decidedly positive about the course, which was again off ered during the spring of 2005. As the fi eld of atmospheric science continues to advance and diversify, courses of this type can play an increasingly vital role in education and professional development. In describing the new course, we hope to encourage others who may be contemplating a similar program, especially since many WFOs are located on college campuses, an arrangement that makes this type of experience feasible. Th e internship course was a natural extension of the 17 consecutive years of NOAA-funded collaboration between NCSU and the Raleigh WFO, which moved to the NCSU campus in 1994. Th e course was designed for students interested in an NWS career. Th e hands-on experience should help students decide whether an NWS career is something they might wish to pursue. Secondly, the course provided experience that will be invaluable when they apply for an entry-level NWS position. Students were selected for the course by the evaluation of a written statement of interest by NWS personnel and an interview with the NWS science operations offi cer and other NWS staff . Th e course required students to work at least 16 hours alongside NWS personnel performing routine shift duties and to maintain a journal documenting their experiences. Students initially observed NWS personnel during their shift s and gained experience with manual analysis of surface and upper-air maps, composing the state weather summary, and gathering and disseminating climate and hydrological data. With time, students became independently profi cient with these duties. In addition, the students traveled to NWS equipment sites and attended special sessions for hands-on experience with the Advanced Weather Interactive Processing System (AWIPS), seasonal familiarization with severe and winter weather forecast problems, offi ce safety, and applying for NWS jobs.}, number={10}, journal={BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY}, author={Brennan, MJ and Keeter, K and Riordan, AJ and Lackmann, GM}, year={2005}, month={Oct}, pages={1407–1409} }
 @article{fuentes_chen_davis_lackmann_2005, title={Modeling and predicting complex space-time structures and patterns of coastal wind fields}, volume={16}, ISSN={["1099-095X"]}, DOI={10.1002/env.714}, abstractNote={A statistical technique is developed for wind field mapping that can be used to improve either the assimilation of surface wind observations into a model initial field or the accuracy of post-processing algorithms run on meteorological model output. The observed wind field at any particular location is treated as a function of the true (but unknown) wind and measurement error. The wind field from numerical weather prediction models is treated as a function of a linear and multiplicative bias and a term which represents random deviations with respect to the true wind process. A Bayesian approach is taken to provide information about the true underlying wind field, which is modeled as a stochastic process with a non-stationary and non-separable covariance. The method is applied to forecast wind fields from a widely used mesoscale numerical weather prediction (NWP) model (MM5). The statistical model tests are carried out for the wind speed over the Chesapeake Bay and the surrounding region for 21 July 2002. Coastal wind observations that have not been used in the MM5 initial conditions or forecasts are used in conjunction with the MM5 forecast wind field (valid at the same time that the observations were available) in a post-processing technique that combined these two sources of information to predict the true wind field. Based on the mean square error, this procedure provides a substantial correction to the MM5 wind field forecast over the Chesapeake Bay region. Copyright © 2005 John Wiley & Sons, Ltd.}, number={5}, journal={ENVIRONMETRICS}, author={Fuentes, M and Chen, L and Davis, JM and Lackmann, GM}, year={2005}, month={Aug}, pages={449–464} }
 @article{jacobs_lackmann_raman_2005, title={The combined effects of Gulf Stream-induced baroclinicity and upper-level vorticity on US east coast extratropical cyclogenesis}, volume={133}, ISSN={["1520-0493"]}, DOI={10.1175/MWR2969.1}, abstractNote={Abstract The Atlantic Surface Cyclone Intensification Index (ASCII) is a forecast index that quantifies the strength of low-level baroclinicity in the coastal region of the Carolinas. It is based on the gradient between the coldest 24-h average air temperature at Cape Hatteras and Wilmington, North Carolina, and the temperature at the western boundary of the Gulf Stream. The resulting prestorm baroclinic index (PSBI) is used to forecast the probability that a cyclone in the domain will exhibit rapid cyclogenesis. The initial ASCII study covered the years 1982–90. This dataset was recently expanded to cover the years 1991–2002, which doubled the number of cyclone events in the sample. These additional data provide similar position and slope of the linear regression fits to the previous values, and explain as much as 30% of the variance in cyclone deepening rate. Despite operational value, the neglect of upper-tropospheric forcing as a predictor in the original ASCII formulation precludes explanation of a large fraction of the deepening rate variance. Here, a modified index is derived in which an approximate measure of upper-level forcing is included. The 1991–2002 cyclone events were separated into bins of “strongly forced,” “moderately forced,” and “weakly forced” based on the strength of the nearest upstream maximum of 500-mb absolute vorticity associated with the surface low. This separation method reduced the scatter and further isolated the contributions of surface forcing versus upper-level forcing on extratropical cyclogenesis. Results of the combined upper-level index and surface PSBI demonstrate that as much as 74% of the deepening rate variance can be explained for cases with stronger upper-level forcing.}, number={8}, journal={MONTHLY WEATHER REVIEW}, author={Jacobs, NA and Lackmann, GM and Raman, S}, year={2005}, month={Aug}, pages={2494–2501} }
 @article{brennan_lackmann_2005, title={The influence of incipient latent heat release on the precipitation distribution of the 24-25 January 2000 US East Coast cyclone}, volume={133}, ISSN={["0027-0644"]}, DOI={10.1175/MWR2959.1}, abstractNote={Abstract The role of a diabatically produced lower-tropospheric potential vorticity (PV) maximum in determining the precipitation distribution of the 24–25 January 2000 U.S. East Coast cyclone is investigated. Operational numerical weather prediction (NWP) models performed poorly with this storm, even within 24 h of the event, as they were unable to properly forecast the westward extent of heavy precipitation over the Carolinas and mid-Atlantic. The development of an area of incipient precipitation (IP) around 0600 UTC 24 January over the southeastern United States prior to rapid cyclogenesis was also poorly forecasted by the operational NWP models. It is hypothesized that the lower-tropospheric diabatic PV maximum initially produced by the IP was important to subsequent inland moisture transport over the Carolinas and mid-Atlantic. A PV budget confirms that latent heat release in the midtroposphere associated with the IP led to the initial formation of a PV maximum in the lower troposphere that propagated eastward in association with the IP to the Atlantic coast late on 24 January. The impact of this PV maximum on the westward moisture transport was quantified by piecewise Ertel PV inversion. Results from the inversion show that the balanced flow associated with this evolving cyclonic PV maximum contributed substantially to the onshore moisture flux into the Carolinas and Virginia. The balanced flow associated with the PV anomaly also contributed to quasigeostrophic forcing for ascent in the region. These findings suggest that accurate numerical prediction of the precipitation distribution in this event requires adequate representation of the IP and its associated impacts on the PV distribution.}, number={7}, journal={MONTHLY WEATHER REVIEW}, author={Brennan, MJ and Lackmann, GM}, year={2005}, month={Jul}, pages={1913–1937} }
 @article{reeves_lackmann_2004, title={An investigation of the influence of latent heat release on cold-frontal motion}, volume={132}, ISSN={["1520-0493"]}, DOI={10.1175/MWR2827.1}, abstractNote={Abstract The effects of condensational heating on cold-frontal translation speed are explored through the use of potential vorticity (PV) diagnostics and model sensitivity experiments. It is hypothesized that condensational heating can lead to faster frontal translation speeds in the presence of vertical shear because of the horizontal propagation of the positive PV anomaly associated with the front. A case study of a cold front with an evolving precipitation structure is presented. A positive correlation existed between the position of condensational heating relative to the frontal zone and frontal translation speed, with faster frontal movement occurring when condensational heating was present in the prefrontal zone. This front was numerically simulated to see if the hypothesized mechanism for frontal movement was active. Through the use of a PV budget, it was confirmed that condensational heating did contribute to the forward propagation of the cold-frontal PV band. Numerical experiments were performed...}, number={12}, journal={MONTHLY WEATHER REVIEW}, author={Reeves, HD and Lackmann, GM}, year={2004}, month={Dec}, pages={2864–2881} }
 @article{brennan_lackmann_koch_2004, title={The impact of a split-front rainband on Appalachian cold-air damming erosion}, volume={85}, ISSN={["1520-0477"]}, DOI={10.1175/BAMS-85-7-935}, abstractNote={AFFILIATIONS: BRENNAN AND LACKMANN—Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina; KOCH—NOAA/Forecast Systems Laboratory, Boulder, Colorado CORRESPONDING AUTHOR: Michael J. Brennan, Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, 1125 Jordan Hall, Box 8208, Raleigh, NC 27695-8208 E-mail: mike_brennan@ncsu.edu}, number={7}, journal={BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY}, author={Brennan, MJ and Lackmann, GM and Koch, SE}, year={2004}, month={Jul}, pages={935–939} }
 @article{lackmann_yablonsky_2004, title={The importance of the precipitation mass sink in tropical cyclones and other heavily precipitating systems}, volume={61}, ISSN={["1520-0469"]}, DOI={10.1175/1520-0469(2004)061<1674:TIOTPM>2.0.CO;2}, abstractNote={When water vapor is converted to cloud and precipitation and subsequently removed to the surface via precipitation, there is a corresponding hydrostatic pressure decrease due to the reduction of mass in the overlying column. Pressure changes resulting from the addition or removal of water vapor are currently neglected in most meteorological applications. However, in heavily precipitating systems such as tropical cyclones, where precipitation rates may exceed 250 mm day−1, the pressure equivalent of the precipitation mass sink is not negligible (∼25 hPa day−1). Pressure decreases due to this mechanism are most pronounced in the lower troposphere, particularly below the melting level. The resulting unbalanced pressure-gradient force can enhance convergence, which precludes full realization of the pressure decrease but may contribute to vorticity generation and moisture convergence. The importance of the precipitation mass sink is investigated for the case of Hurricane Lili (2002) through the computation of mass and potential vorticity (PV) budgets and numerical sensitivity experiments. The precipitation mass reaching the surface within 100 km of the storm center is of the same order as the mass loss needed to explain the area-averaged pressure decrease during the intensification stage of Lili. The PV is altered by precipitation mass flux divergence across isentropic layers. A volume-integrated PV budget reveals that the mass sink term is small in comparison to the latent heating term, although the latter exhibits large cancellation. Comparison of a control simulation from the Eta Model to an experimental simulation in which the precipitation mass sink effect is included demonstrates that the mass sink mechanism contributes to lower pressure, stronger wind speeds, and heavier precipitation. The sea level pressure near the storm center in the mass sink simulation is generally 2–5 hPa deeper relative to the control simulation, with 10-m wind speed differences of 5 to 15 kt. The mass sink simulation exhibits a stronger cyclonic PV tower, especially above the melting level, and a stronger troposphere–deep cyclonic circulation relative to the control simulation. The analysis presented indicates that the precipitation mass sink mechanism, though not dominant, is not negligible for tropical cyclones.}, number={14}, journal={JOURNAL OF THE ATMOSPHERIC SCIENCES}, author={Lackmann, GM and Yablonsky, RM}, year={2004}, month={Jul}, pages={1674–1692} }
 @article{brennan_lackmann_koch_2003, title={An analysis of the impact of a split-front rainband on Appalachian cold-air damming}, volume={18}, ISSN={["1520-0434"]}, DOI={10.1175/1520-0434(2003)018<0712:AAOTIO>2.0.CO;2}, abstractNote={Abstract Appalachian cold-air damming (CAD) is characterized by the development of a cool, stable air mass that is advected southwestward along the eastern slopes of the Appalachian Mountains by low-level ageostrophic flow. Operational forecasters have identified the demise of CAD as a major forecasting challenge, in part because numerical weather prediction models have a tendency to erode the cold air too quickly. Previous studies have considered the role of clouds and precipitation in the initiation and maintenance of CAD; generally, precipitation is thought to reinforce CAD due to the cooling and stabilization resulting from evaporation. Here, the impact of precipitation on CAD during a situation where the lower-tropospheric air mass was near saturation prior to the arrival of precipitation is considered. Previous studies have indicated that the passage of a cold front can bring about CAD demise, as the synoptic-scale flow becomes northwesterly behind the front and low-level stable air is scoured. Addi...}, number={5}, journal={WEATHER AND FORECASTING}, author={Brennan, MJ and Lackmann, GM and Koch, SE}, year={2003}, month={Oct}, pages={712–731} }
 @article{bailey_hartfield_lackmann_keeter_sharp_2003, title={An objective climatology, classification scheme, and assessment of sensible weather impacts for Appalachian cold-air damming}, volume={18}, ISSN={["0882-8156"]}, DOI={10.1175/1520-0434(2003)018<0641:AOCCSA>2.0.CO;2}, abstractNote={Abstract The geostrophic adjustment process for a rotating, stratified atmosphere in the presence of an orographic barrier may be manifest as a phenomenon known as “cold-air damming” (CAD). The degree of blocking by an orographic barrier, and therefore CAD intensity, is related to the static stability of the upstream air mass. When precipitation falls into dry near-surface air, differential evaporational cooling can increase static stability, and strengthen or initiate CAD. The sheltering effect of clouds can also maintain surface-based stability. Therefore, the ability of numerical forecast models to accurately predict CAD requires adequate representation of cloud and precipitation processes. Operational forecasters in the Appalachian damming region have previously developed a subjective classification scheme that distinguishes those CAD events that are heavily influenced by diabatic processes from those that are dominated by synoptic-scale forcing. In this study the subjective scheme is formalized in or...}, number={4}, journal={WEATHER AND FORECASTING}, author={Bailey, CM and Hartfield, G and Lackmann, GM and Keeter, K and Sharp, S}, year={2003}, month={Aug}, pages={641–661} }
 @article{lackmann_2002, title={Cold-frontal potential vorticity maxima, the low-level jet, and moisture transport in extratropical cyclones}, volume={130}, ISSN={["0027-0644"]}, DOI={10.1175/1520-0493(2002)130<0059:CFPVMT>2.0.CO;2}, abstractNote={Abstract An elongated cold-frontal maximum in the lower-tropospheric potential vorticity (PV) field accompanies some midlatitude cyclones. These PV maxima are often of diabatic origin, and are hypothesized to contribute substantially to the strength of the low-level jet (LLJ) and moisture transport in the cyclone warm sector. Diagnosis of a representative cyclone event from the central United States during February 1997 is presented with the goals of (i) elucidating the mechanisms of development and propagation of the cold-frontal PV band, and (ii) clarifying the relation between this PV maximum and the LLJ. A confluent upper trough and modest surface cyclone followed a track from the south-central United States northeastward into southern Ontario between 26 and 28 February 1997, accompanied by flooding and widespread straight-line wind damage. A LLJ, with maximum wind speeds in excess of 35 m s−1, was positioned at the western extremity of the cyclone warm sector, immediately east of an elongated PV maxi...}, number={1}, journal={MONTHLY WEATHER REVIEW}, author={Lackmann, GM}, year={2002}, pages={59–74} }
 @article{lackmann_keeter_lee_ek_2002, title={Model representation of freezing and melting precipitation: Implications for winter weather forecasting}, volume={17}, ISSN={["0882-8156"]}, DOI={10.1175/1520-0434(2003)017<1016:MROFAM>2.0.CO;2}, abstractNote={Abstract During episodes of sustained moderate or heavy precipitation in conjunction with near-freezing temperatures and weak horizontal temperature advection, the latent heat released (absorbed) by the freezing (melting) of falling precipitation may alter thermal profiles sufficiently to affect the type and amount of freezing or frozen precipitation observed at the surface. Representation of these processes by operational numerical weather prediction models is incomplete; forecaster knowledge of these model limitations can therefore be advantageous during winter weather forecasting. The Eta Model employs a sophisticated land surface model (LSM) to represent physical processes at the lower-atmospheric interface. When considering the thermodynamic effect of melting or freezing precipitation at the surface, it is shown that limitations in the current version of the Eta LSM can contribute to biases in lower-tropospheric temperature forecasts. The Eta LSM determines the precipitation type reaching the surface...}, number={5}, journal={WEATHER AND FORECASTING}, author={Lackmann, GM and Keeter, K and Lee, LG and Ek, MB}, year={2002}, month={Oct}, pages={1016–1033} }
 @article{lackmann_ek_keeter_2002, title={NWP biases in freezing rain forecasts}, volume={83}, number={9}, journal={Bulletin of the American Meteorological Society}, author={Lackmann, G. M. and Ek, M. B. and Keeter, K.}, year={2002}, pages={1274–1275} }
 @article{lackmann_2001, title={Analysis of a surprise western New York snowstorm}, volume={16}, ISSN={["0882-8156"]}, DOI={10.1175/1520-0434(2001)016<0099:AOASWN>2.0.CO;2}, abstractNote={Although Rochester, New York (ROC), is not located in a climatogically favored region for extreme [i.e., $30 cm (12 in.) 24 h21] lake-effect snow (LES), significant [i.e., $15 cm (6 in.) 24 h21] LES can occur there under specific synoptic regimes. The purposes of this study are to document synoptic conditions that are associated with significant LES in ROC and to examine a specific event in which the passage of an upper disturbance combined with a lower-tropospheric trough to produce a surprise western New York snowstorm on 26‐27 November 1996. A database of 127 events in which 2-day ROC snowfall exceeded 15 cm (6 in.) was constructed for the years 1963 through 1992, inclusive. Each event was categorized as ‘‘LES’’ or ‘‘non-LES’’ on the basis of air‐lake temperature difference, wind direction, and synoptic setting. Of the 127 events, 32 were classified as LES. Composites based on this 32-case sample reveal a mobile upper trough that moves from the western Great Lakes 48 h prior to the snowfall event to northern Maine 24 h after the event. All 32 cases were accompanied by either a mobile upper trough or a closed low at the 500-hPa level. An unexpected snowstorm on 26‐27 November 1996 resulted in accumulations of up to 30 cm (12 in.) in parts of western New York. Nonclassical LES structures developed in a rapidly changing synoptic environment that was characterized by the passage of an intense upper-tropospheric disturbance. Model forecasts underestimated the strength of this disturbance and also the intensity of lower-tropospheric troughing over and north of Lake Ontario. The upper trough is hypothesized to have increased the inversion altitude and relative humidity in the lower troposphere, and likely contributed to the strength of lower-tropospheric troughing near Lake Ontario. Cyclonic isobaric curvature accompanying the surface trough enhanced lower-tropospheric ascent through Ekman pumping and increased the overwater fetch for boundary layer air parcels traversing Lake Ontario. Comparison of Eta Model forecasts with analyses suggests that problems with model initialization and diabatic boundary layer processes both contributed to forecast errors.}, number={1}, journal={WEATHER AND FORECASTING}, author={Lackmann, GM}, year={2001}, month={Feb}, pages={99–116} }
 @article{lackmann_keyser_bosart_1999, title={Energetics of an intensifying jet streak during the experiment on rapidly intensifying cyclones over the Atlantic (ERICA)}, volume={127}, ISSN={["0027-0644"]}, DOI={10.1175/1520-0493(1999)127<2777:EOAIJS>2.0.CO;2}, abstractNote={Abstract A characteristic life cycle of upper-tropospheric cyclogenetic precursors involves the development of an elongated region of lower dynamic tropopause that forms in association with an intensifying midtropospheric jet/front. Transverse divergent circulations associated with the jet/front steepen and depress the dynamic tropopause prior to the onset of lower-tropospheric cyclogenesis. A representative event that occurred during the second intensive observation period (IOP 2) of the Experiment on Rapidly Intensifying Cyclones over the Atlantic (ERICA, December 1988–February 1989) is analyzed from the perspective of local energetics. The goals of the analysis are (i) to document the evolution of the three-dimensional eddy kinetic energy (EKE) distribution during this event and (ii) to identify the mechanisms leading to EKE growth in the upper-tropospheric jet streak associated with the precursor disturbance prior to cyclogenesis, as well as in the developing lower-tropospheric cyclone. Computation of...}, number={12}, journal={MONTHLY WEATHER REVIEW}, author={Lackmann, GM and Keyser, D and Bosart, LF}, year={1999}, month={Dec}, pages={2777–2795} }
 @article{lackmann_gyakum_1999, title={Heavy cold-season precipitation in the northwestern United States: Synoptic climatology and an analysis of the flood of 17-18 January 1986}, volume={14}, ISSN={["0882-8156"]}, DOI={10.1175/1520-0434(1999)014<0687:hcspit>2.0.co;2}, abstractNote={Abstract Warm, moist southwesterly airflow into the northwestern United States during the cold season can result in rapid snowmelt and flooding. The objectives of this research are to document characteristic synoptic flow patterns accompanying cold-season (November–March) flooding events, and isolate flow anomalies associated with the moisture transport during a representative event. The first objective is accomplished through a 46-case composite spanning the years 1962–88; the second objective is addressed through diagnosis of a flooding event that occurred on 17–18 January 1986. The 46-case composite is constructed for a 6-day period centered at 1200 UTC on the day of heavy precipitation onset (denoted τ0). Composite 500-hPa geopotential height anomaly fields reveal anomalous ridging over the Bering Sea preceding the precipitation event, a negative anomaly over the Gulf of Alaska throughout the composite evolution, and a positive anomaly over the southwestern Unites States and adjacent eastern Pacific O...}, number={5}, journal={WEATHER AND FORECASTING}, author={Lackmann, GM and Gyakum, JR}, year={1999}, month={Oct}, pages={687–700} }