Effects of climate change on Central United States severe weather environments

This study examines the severe weather environment of the Central United States simulated by the Weather Research and Forecasting regional climate model under a climate change scenario. The observed severe weather climate of the Central United States is characterized by the seasonal migration of Mesoscale Convective Systems and their accompanying severe wind reports. We compare the observed seasonal migration of convection with the models precipitation systems (PS) sorted into 6 size groups. In general the smallest and largest groups have little seasonal migration but the mid-range of the groups have a seasonal trend that is similar to the observations. Overall decreases to the south of the PS frequency maximum indicated a northward shift, but without substantial increases in the number of PSs.

These changes may be explained in part by the increase in surface temperature and moisture. These changes lead to increased CAPE and when coupled with increasing vertical wind shear imply potential positive changes to severe storms. Combining the CAPE and shear for use as a severe weather environment proxy more clearly indicate a change in the seasonal migration in the future climate.

The Low Level Jet (LLJ) appears to play a role as well, at least in terms of providing the moisture to the northern plains, but the increased frequency of occurrence appears locked to the terrain and does not expand northward. Rather the LLJ frequencies increase to the immediate west of the maximum suggesting only a small position change.