Forecast Skill of the Penn State/NCAR MM5 Mesoscale Model during the heavy precipitation event of 23–24 February 1998 in Southern California

The El Nino of 1997-1998 was the strongest El Nino/Southern Oscillation (ENSO) event in the instrumental record. It caused significant climatic anomalies worldwide especially over North America. Five major storms during that winter season produced individually over 10 inches of rain in Southern California-along with extensive flooding. In each case, existing synoptic model forecasts available from the National Center for Environmental Prediction (NCEP) predicted less than one fifth the rainfall that was actually observed with these storms-inadequate forecasts by any standard. This paper will present high-resolution simulations with the Penn State/National Center for Atmospheric Research (PSU/NCAR) Mesoscale Model 5 Version 3 (MM5-V3). The results indicate that high-resolution mesoscale models can produce greatly improved Quantitative Precipitation Forecasts (QPF) over the complex terrain of Southern California, since much of the rain that falls in the region is produced by orographic lifting.