During the late spring and early summer of 2002, an intensive field campaign known as the International H₂O Project (IHOP) was conducted in the southern plains of the United States. In support of this experiment, the NOAA Forecast Systems Laboratory (FSL) configured a real-time version of the National Center for Atmospheric Research (NCAR)/Pennsylvania State University (PSU) MM5 model to produce 0-12 h forecasts every 3 h on a 12-km grid and a nested 4-km grid. These model runs were initialized using the LAPS diabatic initialization technique with the express purpose of trying to improve short-term, explicit forecasts of convective precipitation by eliminating the model “spin-up” period. Forecasts were made available to the field via FSL’s “FX-Net” application, and were used by forecasters supporting campaign operations.

During the experiment, the forecasts were subjectively evaluated by forecasters and verified objectively using FSL’s Real-Time Verification System (RTVS). This was the first intensive evaluation of the LAPS “hot start” technique over a significant period in a convective weather regime. Objective verification of quantitative precipitation forecasts (QPFs) from the system indicates these forecasts demonstrated an advantage for the 0-6 h period over the operational national models running with the same or similar grid spacing.

Additionally, several lessons were learned about the behavior of the LAPS initialization technique, which led to subsequent improvements. Work to rerun a large number of the cases with the improved technique using both the MM5 and the new Weather Research and Forecast (WRF) model is underway, and preliminary results of this new work will be presented.