Impacts of tornadic supercells on the central business district of Oklahoma City

Oklahoma City was struck by two significant tornadoes on consecutive days during May 2003. Widespread damage and injuries occurred in the southern (8 May) and northern (9 May) parts of Oklahoma City as a result of each event. Given the immense weather observing capabilities in central Oklahoma, including the Oklahoma Mesonet, the KOUN upper air station, and the KTLX WSR 88-D radar, extensive data was collected during each tornadic event. In addition to synoptic and mesoscale surface observations, over a dozen portable weather information display systems (PWIDS) sites were located in the central business district (CBD) of Oklahoma City. The PWIDS sites continuously measured wind speed and direction, as well as temperature and relative humidity, during both episodes. While these urban instruments were not directly impacted by the tornadoes, they did measure storm-scale variables associated with the parent supercells. Analyses of the PWIDS data were compared with observations both within and outside of the supercell environment. Differences in maximum wind speeds of four meters per second were identified; urban areas had reduced speeds compared with the rural areas. Furthermore, the impact of the forward flank downdraft on the CBD during the 8 May event was quantified. Finally, the temperature observations were compared between the urban and rural areas. The analyses found that temperature at the urban sites decreased approximately ten degrees Celsius while rural sites only dropped five degrees.