Automated Identification of Cold Pools in a Convection-permitting model

Automated techniques for identifying cold pools in high resolution ensemble forecasts were developed. Cold pools arise from evaporative cooling underneath a convective storm or rain-induced drag pulling air parcels down to the surface. The leading edge of cold pools can be responsible for the development of new convection and for the sustained propagation of mesoscale convective systems (MCSs). During the Spring 2013 NOAA/Hazardous Weather Testbed Spring Forecasting Experiment, the Center for Analysis and Prediction of Storms produced a convection-permitting 4-km grid-spacing storm-scale ensemble forecast (SSEF) system using the Advanced Research WRF. By identifying areas of convection, theta E perturbations were used to initially determine cold pool locations within the storm. This area was grown until the entire perturbation area was enclosed, even if it was outside the area of convection. These cold pools were tracked over time to determine cold pool strength over time and to look for upscale growth, which could reflect MCS formation. The algorithm was then used to determine the differences in cold pool characteristics among the different microphysics parameterizations used in the SSEF and how these differences were related to associated MCSs among the various ensemble members. Future work includes using the cold pool detection algorithm in conjunction with low level convergence and 925 or 850 hPa vertical velocity to identify gust fronts, which could initiate further convection and are thus useful to track automatically.