P1.15

Observations of the Z_dr column during two severe weather events

Cynthia A. Whittier, National Weather Center REU, Winthrop Harbor, IL

The Z_dr column signature was studied using data collected by KOUN, the prototype polarimetric WSR-88D at the National Severe Storms Laboratory in Norman, Oklahoma. Eight storms from two severe weather events during the Joint Polarization Experiment (JPOLE), 8 May 2003 and 9-10 May 2003, were chosen for detailed study. The height above the 0°C level, width, location, maximum values of Z_dr within the column, and time of appearance were recorded for each of these storms. There were differences in the height of the Z_dr column from storm-to-storm, but when beamwidth error was considered the differences were not identifiable. The width of the Z_dr column also varied from storm-to-storm, with the widest column nearly 6.3 km across and the narrowest 2.2 km across. When a bounded weak echo region was present, the Z_dr column was usually co-located with it. Z_dr values within the column ranged from 0.9 dB to 5 dB. Comparisons were made between the time of the first Z_dr column appearance and the first National Weather Service-issued severe thunderstorm warnings and severe weather reports. The appearance of the Z_dr column preceded the first warning by an average of 15 minutes and the first severe weather report by an average of 39 minutes.

Poster Session 1, Student Conference Poster Session
Sunday, 9 January 2005, 5:30 PM-5:30 PM

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