Bow Echo and Mesovortex Evolution during the 2 May 2007 North Texas Derecho

Abstract

On 2 May 2007, a derecho-producing mesoscale convective system tracked across west-central and north Texas, producing damaging wind speeds up to 40 m s-1 (78 kt). Damage included loss of roofs, overturning of trucks and manufactured homes, and several downed electrical towers. Some of the most intense damage occurred in association with deep mesovortices (≥3 km AGL) along the leading edge of the line of storms. The event began as a cluster of storms in eastern New Mexico and west Texas that evolved into a line-echo wave pattern, and finally transitioned into a larger bow echo as it moved into north Texas. The derecho occurred in a thermodynamic environment characterized as moderately unstable, with weak vertical wind shear and weak synoptic-scale forcing for vertical motions. Some studies suggest that the thermodynamic environment on this day supported a derecho, but other research utilizing numerical simulations indicate that the vertical wind shear was too weak to sustain the elevated rear-inflow jet and deep mesovortices that occurred in this case. Several mesovortices, with average lifetimes of 12 min and depths ≥3 km, were identified within 97 km (60 mi) of the nearest network radar. This event both supports and contradicts various aspects of prior research on derecho evolution and behavior.