Multiple Doppler radar and profiler analysis of an intense wake low event

On 13 April 2009 an extensive and intense wake low event occurred over northern MS, northern AL and central GA at the trailing (west) edge of an MCS. Wind gusts near 60 mph were recorded, gusts >50 mph were common, and wind gusts >40 mph persisted at many locations for one hour or more. This was a significant weather event, as many trees were toppled over this large region. The damage assessment is expected to be in the millions of dollars, and about 150,000 Alabama Power customers lost power (in central Alabama alone) during the event.

This paper will focus on the kinematic structure of the stratiform region within which the strong winds were generated. This will be accomplished with WSR-88D radars over this region (KHTX, KGWX, KBMX, and KFFC), with dual Doppler radar analyses using the KHTX and ARMOR radars (70 km baseline), with dual polarization data from the ARMOR radar, with vertical profile data from the MIPS (wind profiles from a 915 MHz wind profiler; and temperature and humidity profiles from a microwave profiling radar), and surface and sounding data. Single Doppler radar data show a 28 m/s low level jet from the southeast centered near 500 m AGL, and a distinct descending 25-30 m/s rear inflow jet from the southwest centered near 3 km. Pressure falls of 8-10 mb were common, and multiple high amplitude oscillations were measured by surface stations. The pressure oscillations were accompanied by waves analyzed in time-height sections of vertical motion, potential temperature, and mixing ratio calculated from MIPS measurements. These data will be used to address the theory of wake lows and to determine their similarity to gravity waves.