E-Journal of Severe Storms Meteorology

E-Journal of Severe Storms Meteorology, Vol 6, No 4 (2011)

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

Jennifer L Dunn, Ted Best

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.


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E-Journal of Severe Storms Meteorology | ISSN 1559-5404 | Some Rights Reserved