1197 Differentiating Convective Cases with Upscale Growth into MCSs and Those without Upscale Growth during PECAN

Wednesday, 15 January 2020
Hall B (Boston Convention and Exhibition Center)
Zachary A. Hiris, Iowa State Univ., Ames, IA; and W. A. Gallus Jr.

Nocturnal convection contributes to a significant portion of summertime precipitation in the Great Plains. Much of this precipitation is associated with mesoscale convective systems (MCSs), which can traverse hundreds of kilometers. In the past two decades, a large number of researchers have contributed to an increased understanding of the “ideal” synoptic and mesoscale environments of MCSs. However, forecasting the upscale growth phase of MCS development remains a significant challenge.

This study focuses on cold pool, low level wind shear, and other thermodynamic and kinematic variables from six intensive operation periods (IOPs) during the Plains Elevated Convection at Night project. Using the Weather Research and Forecasting model (WRF), simulations are completed at 3 km horizontal grid spacing using both a local and a non-local planetary boundary layer scheme. Preliminary results suggest that initial deep cold pool development originating from cellular convection and ample line-normal vertical wind shear is critical for upscale growth into an organized MCS, especially in the absence of large scale linear forcing. Additionally, the ratios of line normal to line parallel shear and cold pool/line normal shear also reveal potential causes for a lack of upscale growth. Further cross section and sounding analysis will also be presented.

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