Monday, 5 November 2012
Symphony III and Foyer (Loews Vanderbilt Hotel)
This study examined two heat burst events that affected the southeastern Texas Panhandle during the late evening and overnight hours of 14-15 June 2012. A heat burst is characterized by a rapid increase in temperature, decrease in dew point temperature, falling pressure, and the onset of high winds near ground level. The West Texas Mesonet sites near Clarendon and Childress, Texas recorded severe wind gusts in excess of 33.5 m s-1 in conjunction with dry bulb temperature increases in excess of 7˚C and dew point temperature decreases in excess of 10˚C. The magnitude of the wind associated with these phenomena represented a significant threat to life and property and is therefore of interest to the forecast community. Previous studies have shown that heat bursts occur in an environment characterized by nearly dry-adiabatic lapse rates in the low to mid-troposphere, above a shallow stable layer near ground level. This type of environment is most commonly observed in the High Plains during the warm season. The events analyzed here were separated by approximately three hours, and both occurred in the vicinity of a wake low which had developed in the trailing stratiform precipitation region of a decaying mesoscale convective system (as observed by satellite and radar). The wake low was likely generated by subsidence warming brought about by a descending rear-inflow jet, and the heat bursts may have been associated with an enhancement of this descending jet by downdrafts of individual decaying convective cells. The evolution of the associated mesoscale convective system and the mesoscale environment of these heat bursts were investigated using the high-resolution observations from the West Texas Mesonet, radar and radiosonde data, satellite imagery, and data from the West Texas and Oklahoma Lightning Mapping Arrays. The goal of this study was to improve the predictability of the onset and evolution of heat bursts, and provide the operational forecaster with guidance for the decision-making process.
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