The Day of the Downbursts—May 23, 2017 Sealy and Beeville, TX

During the evening of May 23, 2017 a series of fast moving severe thunderstorms moved across portions of south-central and southeast TX. The strongest storms produced straight-line wind damage, with significant wind damage and large hail near both Sealy and Beeville, TX from separate storms. A downburst near Sealy, TX (just west of the Houston metropolitan area) produced a swath of wind damage nearly 2 miles wide and several miles long which is near the threshold of the micro- or macroburst definition established by Fujita. This event resulted in some of the most significant straight-line (or non-tornadic) wind damage ever surveyed by the authors, with the Damage Assessment Toolkit (DAT) estimating winds in excess of 100+ mph (assuming 3-second gusts). A similar storm developed in central TX and caused extensive damage with 81 mph winds measured at the Beeville Airport Automated Surface Observing System (ASOS). Large hail --larger than golf ball size-- was also reported from both storms, which resulted in several minor injuries in Sealy.

This presentation will examine the environmental factors contributing to such intense downburst winds at multiple locations from multiple storms. In addition, we will discuss the utility and limitations of the EF-scale and the Damage Assessment Toolkit in estimating straight-line wind speeds in events where wind duration may exceed the 3-second estimate in the EF-scale.