P4.10
The "Owl Horn" radar signature in developing supercells
Matthew R. Kramar, University of Oklahoma, Norman, OK; and H. B. Bluestein, A. Pazmany, and J. D. Tuttle
Using a mobile 3 cm-wavelength radar built by the University of Massachusetts, we have been able to survey supercell thunderstorms with a much finer spatial and temporal resolution than using the standard WSR-88D radar. Consequently we are able to see features of supercell thunderstorms that might otherwise go unobserved by other methods. In the course of the 2001 severe storm season in the Central Plains, we observed a curious, recurring reflectivity signature on our radar display which we have called the "Owl Horn" signature. (See attached image) The feature was apparent from various viewing angles with respect to the storms exhibiting the signature, thus eliminating the possibility of the feature being an artifact of the radar.
We have undertaken a study of the "Owl Horn" signature using NCAR's TREC technique. TREC is used to derive an estimate of the horizontal wind field from radar reflectivity data by tracking and correlating discrete reflectivity structures in sequential scans of a radar. We have found nothing in the literature which discusses the "Owl Horn" signature. Although TREC has previously been applied to clear air and hurricane environments (Tuttle and Foote, 1990; Tuttle and Gall, 1995), also absent from the literature is an application of TREC to severe storms and supercell storms in the interest of studying supercell evolution. Through the application of TREC to our radar data (Doppler wind data were not available in 2001) from May and June, 2001, we find an estimate of the horizontal wind field around and in the "Owl Horn" signature in four different storms. In this paper we will summarize the characteristics of the signature and identify the conditions under which it occurs and why. It appears that the signature may be a hallmark of some supercells early in their development.
Poster Session 4, Radar Applications
Tuesday, 13 August 2002, 3:00 PM-4:30 PM
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Extended Abstract (596K)