Extended Abstract (1.5M)1.2
Extreme microburst events in the Phoenix metropolitan area
Steven V. Vasiloff, NOAA/NSSL, Norman, OK; and K. Howard, D. P. Jorgensen, C. Dempsey, and G. D. Green
While the frequency of damaging wind reports from microbursts in the Phoenix, AZ metropolitan area has been increasing, there has been little documentation of the details of these storms. In an effort to better understand and document the occurrence of microbursts and their background environments, the National Severe Storms Laboratory, in collaboration with Salt River Project, conducted a second field campaign during the summer of 2008. The goal was to observe a number of microburst events using a Shared Mobile Atmospheric Research and Teaching Radar (SMART-R) in combination with an operational Terminal Doppler Weather Radar and WSR-88D radars. The radar data was used to examine the lifecycle evolution of microbursts and to assess their impact on electrical power transmission infrastructure. On 22 July 2008 a series of microbursts caused severe damage in Mesa including toppling 13 large power poles. This paper documents the structure and evolution of the Mesa storm in an effort to build a climatology of damaging microbursts in the Phoenix area. Much like an event that was observed by the SMART-R on 28 July 2004 near Chandler, the Mesa storm exhibited several pulses during its 1.5 h lifecycle with a peak Doppler radial velocity of 27.5 m/s. The pulses were associated with a series of descending reflectivity cores. In contrast to the 2004 event, the Mesa storm had smaller, weaker and more easily identifiable reflectivity cores. It is hypothesized that the smaller cores resulted in weaker outflow winds than the peak of 31.5 m/s observed in 2004. This paper will also provide information on additional microbursts as they occur subsequent to the AMS abstract deadline.
Session 1, Severe Storms Impacts on the Urban Environment: Modeling and Observations
Tuesday, 13 January 2009, 3:30 PM-5:00 PM, Room 123
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