High Resolution Numerical Weather Prediction for High Impact and Extreme Weather Events in 2014 across Southern California

Operational forecasters now have high resolution numerical weather prediction guidance available to them at multiple times a day for assistance in identifying potential high impact events. The model suite consists of the National Center for Environmental Prediction (NCEP) North American Mesoscale Model at 4 km which includes the Non-hydrostatic Mesoscale Model (NMM) and the Advanced Research (ARW) Weather, Research and Forecasting (WRF) cores, and other region modeling such as the Desert Research Institute's California and Nevada Smoke and Air Committee (DRI-CANSAC) model at 2 km resolution run twice a day out to 72 hours. For short duration lead time the forecaster has hourly updated High Resolution Rapid Refresh (HRRR) guidance available out to 15 hours.

For this study, there were events in extreme southern California chosen that consisted of unusually low snow levels along with significant accumulation and major impact to transportation on December 30-31, 2014, and extreme rainfall (1 in 100 to 500 year return intervals) during summer monsoon thunderstorms in August and September 2014. This presentation will demonstrate that the proper use of high resolution numerical weather prediction guidance, along with ingredients based approaches, can allow the forecaster to make much higher confidence decisions on the magnitude and location of intense precipitation episodes across various types of terrain.