A correlation of synoptic features and upper level flow patterns with 16 crop-hail insurance claim areas in the mid-western United States is made. This study indicates that the following two parameters are present in each case, and may play a significant role in the establishment of an air mass structure which sustains wide-spread hail activity:

  • (a) A 30–40 knot band of maximum wind flow at 16,000 feet through, or just north of, the hail area.

  • (b) A closed anticyclonic circulation extending from the gradient level up to the 8,000–10,000 ft level, and occasionally higher.

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* Published with permission of Commander, Air Weather Service.