NWC REU 2005
May 30 - August 6



A Five-Year Climatology of Elevated Severe Convective Storms in the United States East of the Rocky Mountains

Katherine Horgan, David Schultz, Robert Johns, Stephen Corfidi, and John Hales



A five-year climatology of elevated severe convective storms was constructed for the calendar years 1983 – 1987 from east of the Rocky Mountains to the Atlantic coast. Of the 1689 surface boundaries examined, 129 (8%) were associated with elevated severe storm events. Of the 1066 severe reports associated with the 129 elevated severe storm events, 624 (58%) were hail reports; 396 (37%) were wind reports, and 46 (4%) were tornado reports. A maximum of elevated severe storm events occurred in May with a secondary maximum in September. Elevated severe storm events vary geographically throughout the year with a maximum on the Gulf coast in winter to a High Plains maximum in spring and summer. The diurnal maximum of elevated severe storm events occurred at 2100 UTC, which coincided with the diurnal maximum of hail reports. The wind reports had no pronounced diurnal maximum. Elevated severe storm wind-only events occur roughly five times a year and are difficult to forecast. To examine the conditions associated with events that produced severe winds only, five cases were examined in more detail. These cases consisted of three environments (Type A, B, and C). Type A events were characterized by strongly forced elevated squall lines. Type B events were elevated isolated cellular events, whereas Type C events were elevated northwest flow events. Several questions remain unanswered about elevated severe storm wind-only events such as: Does the strength or depth of the inversion matter? What factors affect the transfer of momentum down to the surface?

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