Comparison of Simulated and Observed Severe Storm Tracks over Alberta Open Access

[摘要] Thunderstorms have the potential to produce severe weather and can result in significant financial and human losses. The province of Alberta is one of Canada’s most active thunderstorm regions, with the record for insured damage due to hail. Therefore, it is crucial that thunderstorm forecasts be as accurate as possible to provide early warning to industry and the public. Numerical Weather Prediction (NWP) models are heavily utilized to provide forecast guidance. Recent advances in computing power and affordability have enabled the use of finer spatial resolutions that allow for the explicit simulation of individual storms, that is, without the use of a cumulus parameterization scheme. There is a need to explore the forecast skill of these high-resolution models as they find their way into forecast operations. This thesis investigates the skill of the widely available Weather Research and Forecasting (WRF) model for predicting the motion of thunderstorms. We use a 4 km resolution, a value that is found to be sufficient for accurately reproducing storm structure and evolution without requiring too many computational resources. Our focus is on a select set of severe summer storms that occurred in Alberta during 2011 and 2012. We compare the WRF simulated and observed radar reflectivity values and present the differences, with an emphasis on the motion and intensity of the storms. We find that storms produced by the WRF model move faster, travel farther, and have more counter clockwise tracks than radar-observed storms. WRF storms are also found to be less intense in terms of reflectivity (dBZ). We also investigate the accuracy of the Traditional Method and Bunkers Method for forecasting storm motion. These methods are frequently used by forecasters because they are relatively easy to employ on an observed or model sounding, and there is no need to rely on the results of a high-resolution model. We find that both methods tend to underestimate storm speed and overestimate storm direction when used on WRF model forecast soundings over Alberta.

[发布机构] University of Alberta

[效力级别] Alberta