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of May 3, 1999 Answer to Question 9 |
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Question 9. The Day 1 Convective Outlook issued by the Storm Prediction Center at 3:50 p.m. on May 3
mentioned the possibilty of large hail. Look at the Frederick radar data between 4:30 and 6:30
and the Oklahoma City radar between 7:00 p.m. and midnight and examine the hail threat.
Compare your conclusions with the local storm reports.
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Answer. The May threshold for large hail is 55 kg/m2, from the VIL value chart. Early in the evening, the reflectivity values in the storms in Southwest Oklahoma, exceeded 55 dBZ (hail usually occurs at 57 dBZ and higher) and the VIL values were over 55 kg/m2. These storms produced large hail according to the storms reports from the area. As the storms progressed into central Oklahoma, the reflectivity values remained over 55 dBZ. However, the VIL values diminished and the hail threat lessened. After 7:00 p.m., the storm reports did not have many reports of large hail, as the focus of the reports shifted from large hail to tornadoes. It is possible that areas of central Oklahoma received some hail after 7:00 p.m., but reports of hail may not have been received due to the magnitude of the tornado event in central Oklahoma. | |
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