Aspects of a Tornadic Left-Moving Thunderstorm of 25 May 1999

Abstract

A severe left-moving thunderstorm occurred on 25 May 1999 between the cities of Lubbock and Amarillo, Texas. Over its 3.5-h lifetime, the storm was responsible for flash flooding, reports of hail of up to 7 cm in diameter, and two weak tornadoes. Satellite imagery reveals that it was traveling along the northward-moving outflow boundary of the storm from which it formed. The left mover displayed anticyclonic rotation, as was seen in storm-relative radial velocity imagery from the Weather Surveillance Radar-1988 Doppler (WSR-88D) located at Lubbock. The tornadoes developed west of Canyon, Texas, near the intersection of the left mover and a southward-moving boundary. The occurrence of tornadoes with a left mover is a particularly noteworthy event; to the authors' knowledge, only four other tornadic left movers have been reported in the meteorological literature.