P74 Prediction of convective morphology in near-cloud permitting WRF model simulations

Gallus, William A., Jr., and Darren Snively, Iowa State University

Classification of convective morphology was performed using 3-km horizontal grid spacing WRF-ARW simulations for 37 events during the warm season from 2006 to 2010. Ten classifications were used. An objective scoring method, based on normalized time and the type of mode exhibited, was developed to measure the accuracy of the modeled morphologies when compared to radar observations. Trends in the simulated evolution were noted, as well as common discrepancies between the model and observed events. Environmental conditions before convective initiation were obtained from RUC analyses, and statistically significant associations between the parameters and the model accuracy scores were found.

Overall, simulations entailed more cellular modes and fewer linear modes than observed. Bow echoes and linear systems with trailing stratiform rain regions were especially poorly forecast. Cellular modes were forecast better, as 75% of the forecast comparisons with an observed cellular mode also featured a modeled cellular mode. Simulations usually portrayed convective evolution more accurately when the synoptic environment included strong deep-layer shear and cool potential temperatures at the level of maximum theta-E. Major timing errors for initiation or dissipation usually occurred when 0-6 km shear was weak, and surface potential temperatures were cool and quickly warmed with height.