Environments of Long-Lived Mesoscale Convective Systems Over the Central United States in Convection Permitting Climate Simulations

TitleEnvironments of Long-Lived Mesoscale Convective Systems Over the Central United States in Convection Permitting Climate Simulations
Publication TypeJournal Article
Year of Publication2018
JournalJournal of Geophysical Research: Atmospheres
Volume122
Number24
Pages13,288-13,307
Date Published04/2018
Abstract / Summary

Continental‐scale convection‐permitting simulations of the warm seasons of 2011 and 2012 using the Weather Research and Forecasting model reproduce realistic structure and frequency distribution of lifetime and event mean precipitation of mesoscale convective systems (MCSs) over the central United States. Analysis is performed to determine the environmental conditions conducive to generating long‐lived MCSs. The simulations show that MCSs systematically form over the central Great Plains ahead of a trough in the westerlies in combination with an enhanced low‐level moist jet from the Gulf of Mexico. These environmental properties at the time of storm initiation are most prominent for the MCSs that persist for the longest times. MCSs reaching lifetimes of 9 h or more occur closer to the approaching trough than shorter‐lived MCSs. These long‐lived MCSs exhibit the strongest feedback to the environment through diabatic heating in the trailing regions of the MCSs. The feedback strengthens the synoptic‐scale trough associated with the MCS by producing an anomaly circulation characterized by a divergent perturbation at high levels over the MCS and a midlevel cyclonic circulation perturbation near the trough line in association with the trailing portion of the MCS. The quasi‐balanced mesoscale vortex may help to maintain the MCS over a long period of time by feeding dry, cool air into the environment at the rear of the MCS region that enhances evaporative cooling and helps maintain the MCS.

URLhttp://dx.doi.org/10.1002/2017jd027033
DOI10.1002/2017jd027033
Journal: Journal of Geophysical Research: Atmospheres
Year of Publication: 2018
Volume: 122
Number: 24
Pages: 13,288-13,307
Date Published: 04/2018

Continental‐scale convection‐permitting simulations of the warm seasons of 2011 and 2012 using the Weather Research and Forecasting model reproduce realistic structure and frequency distribution of lifetime and event mean precipitation of mesoscale convective systems (MCSs) over the central United States. Analysis is performed to determine the environmental conditions conducive to generating long‐lived MCSs. The simulations show that MCSs systematically form over the central Great Plains ahead of a trough in the westerlies in combination with an enhanced low‐level moist jet from the Gulf of Mexico. These environmental properties at the time of storm initiation are most prominent for the MCSs that persist for the longest times. MCSs reaching lifetimes of 9 h or more occur closer to the approaching trough than shorter‐lived MCSs. These long‐lived MCSs exhibit the strongest feedback to the environment through diabatic heating in the trailing regions of the MCSs. The feedback strengthens the synoptic‐scale trough associated with the MCS by producing an anomaly circulation characterized by a divergent perturbation at high levels over the MCS and a midlevel cyclonic circulation perturbation near the trough line in association with the trailing portion of the MCS. The quasi‐balanced mesoscale vortex may help to maintain the MCS over a long period of time by feeding dry, cool air into the environment at the rear of the MCS region that enhances evaporative cooling and helps maintain the MCS.

DOI: 10.1002/2017jd027033
Citation:
Yang, Q, R Houze, L Leung, and Z Feng.  2018.  "Environments of Long-Lived Mesoscale Convective Systems Over the Central United States in Convection Permitting Climate Simulations."  Journal of Geophysical Research: Atmospheres 122(24): 13288-13307.  https://doi.org/10.1002/2017jd027033.