Investigation of derecho storms in Oklahoma and the causes of highest surface wind speeds

This study was conducted to see how derechos in Oklahoma compare with derecho climatology, and then investigate if the highest wind speeds correspond to the apex of the derecho. The motivation for this study was inspired by a BAMEX case study in which it was found that the highest wind speeds were not always collocated with the apex of the bow echo. This study could have important implications for forecasting and warning decisions with respect to location of the severe winds. Two cases were researched for this study: May 27-28, 2001 and June 16-17, 2005. The data used included surface wind speed, surface theta-e contours, and radar reflectivity and velocity data. The surface data and radar data were analyzed to create a composite map identifying the conditions present at the location of highest measured wind speeds. By analyzing the data in this way, the highest wind speeds could be classified as occurring in either the apex or its associated gust front, embedded supercells, or mesovortices. It was found that most of the time, the highest wind speeds were collocated with the apex of the bow echo and gust front. Other times, the highest wind speeds appeared to be associated with leading edge mesovortices or with embedded supercells. This was important because it showed that the area of greatest concern was indeed the apex, although other areas should not be overlooked. While it was beyond the scope of this study to research more than two cases, it could be found with further research that a methodology could be developed to assist forecast meteorologists in their warning decisions.