The Effect of Elevated Thunderstorms on Mesoscale/Synoptic Scale Boundaries

The University of Missouri’s Program for Research on Elevated Convection with Intense Precipitation (PRECIP) sampled eight cases of heavy rainfall associated with elevated convection during the summers of 2014 and 2015. Determination of deployment timing and location were forecasted using both operational deterministic and probabilistic model forecasts. It was found that these model forecasts struggled with handling the mesoscale details of frontal and thunderstorm interaction which often led to an incorrect forecast of location and intensity of heavy rainfall. Furthermore, it was observed that the frontal motion and location was very often displaced by elevated convection compared to what forecasters and operational models were anticipating.  The cause for the displacement was the expansion of cold pools from significant long lasting elevated convection events. Events where elevated convection was isolated or embedded within stratiform precipitation did not show an alteration of frontal motion. It will be shown that unified cold pools from elevated convection disrupted frontal motion and location. Exploration of both Petterssen frontogenesis and a twelve-term frontogenesis will show how and where (both at what level and horizontal location) frontogenesis changes as the cold pool expands and how this corresponds to (re)developing convection.   Analysis will come from the highest verified solution (via Model Evaluation Tool (MET) and Method for Object-Based Diagnostic Evaluation tool) of a 3 km 48 member Weather Research and Forecasting (WRF) based dynamic ensemble forecast (see the abstract titled Dynamic Ensemble Model Evaluation of Elevated Thunderstorms sampled by PRECIP via MET and MODE for more details on the model).