The role that precipitating systems have on the large-scale circulation due to variations in mesoscale divergence is not well understood in the subtropics or midlatitudes. A mesoscale model (MM5) is employed to compare the divergence patterns associated with convective and non-convective precipitating systems arising from different background environments in southeast Texas, a subtropical region affected by both midlatitude (baroclinic) and tropical (barotropic) influences. NCEP Reanalysis temperature and zonal wind fields were analyzed for two years to form three baroclinicity definitions: barotropic, weakly baroclinic, and strongly baroclinic. Well-modeled case studies of varying storm types representative of each classification are used to quantify the relative importance different baroclinic environments have on divergence profiles associated with storms in the subtropics.

Divergence profiles averaged over a nested grid with 3km grid spacing are calculated from the model-derived wind fields for each storm. Rainfall totals and the horizontal and vertical structure of radar reflectivity output by MM5 are also analyzed and checked for consistency with observations. The cumulus and microphysics schemes (including graupel) generating the most realistic representation for each storm are utilized. While most extratropical studies on divergence focus exclusively on mesoscale convective systems, this study attempts to formulate a storm divergence climatology including other common storm types in southeast Texas. After showing that the degree of baroclinicity causes different divergence structures, future work will be able to determine the climatological dynamic response caused by these divergence profiles.