Tuesday, 31 July 2001
Evaluation of Local-Scale Forecasts for Severe Weather of July 20, 2000
The Local Analysis and Prediction System (LAPS) performs a real time analysis of three-dimensional winds along with other state variables each hour over a multi-state domain centered on Colorado. These analyses routinely initialize local-scale high-resolution models such as the Colorado State University's Regional Atmospheric Modeling System (RAMS) and NCAR's MM5 (mesoscale model, version 5). The LAPS system has been integrated into the AWIPS system as part of the National Weather Service modernization. Research to expand LAPS capabilities is one avenue toward providing advanced technologies and new innovations to the operational forecaster.
This paper presents the results of a case study in which various LAPS initialization techniques were tested including the new LAPS balance scheme which allows for model "hot start". A 4-h MM5 model hot-start forecast running with 10km resolution was able to accurately locate a developing storm core on the severe weather day of 20 July 2000 on Colorado's Eastern Plains. Two tornadoes, several hail reports, and one flooding report are seen to validate the area identified by the model as having a high radar reflectivity value. Forecast storm-active regions in KS and WY were also confirmed by severe reports. This paper will contrast various initialization strategies.