A Climatology of Dryline Convection in the Southern Great Plains

Synoptic-scale processes regulate dryline formation and intensity and provide a favorable environment for deep, moist convection. However, how these processes lead to convection initiation is not well understood. For instance, is synoptic-scale ascent required to allow the mesoscale dryline circulation to initiate convection? Are certain synoptic environments more conducive to dryline convection? Furthermore, does synoptic forcing regulate the convective mode? These questions highlight the need for a climatology as the first step in improving our understanding of dryline convection.

We present a climatology of dryline convection within the southern Great Plains for April, May and June 2006­­­–15. Drylines were documented using archived Weather Prediction Center surface analyses, and Doppler radar, visible and infrared satellite imagery were used to identify convective drylines. A dryline was considered convective if an identifiable cell that formed along the dryline had a reflectivity of at least 40 dBZ for a continuous period of one hour or more.

Dryline convection occurred on 20 days per season on average, which is about 60% of the total number of drylines and 22% of all days examined. Of these convective drylines, the primary mode of convection was discrete in more than half of cases one hour after initiation. However, the proportion of discrete convection reduced over time. After six hours only one fifth of convective drylines had a mode that was discrete.

The question arises as to whether convection initiation is primarily controlled by local-scale processes. Furthermore, is the reduction in discrete modes with time related to an increase in synoptic forcing such as that which may occur with the arrival of an upper-level trough? Or is the reduction in discrete modes primarily due to storm interactions? We believe these questions warrant further investigation.