ESTIMATED DERECHO CLIMATOLOGY
A few disclaimers:
Given the difficulty of identifying linear or bowed characteristics from the old NMC National Radar Summary charts, it was much more difficult to identify pre-NEXRAD events. The changing procedures and efforts to reporting severe winds over the years, and to a lesser degree, the shifts in population, also likely contributed to this problem. Therefore, is it is likely that I missed some events in these earlier years, which hinders the accuracy of a "true" climatology from this data set. Nonetheless, if one can assume that there is no monthly bias to the events that I missed and stationarity to the "true" annual derecho frequency, we can deduce some useful information to the monthly derecho distributions, as well as the geographical distribution of events from this data set. The geographical distributions are produced by drawing a mesh of 200 km by 200 km squares over the U.S. and counting the number of times at least one report from each event enters each box.
ALL EVENTS:
2-hourly distribution of first wind report, midpoint, & last wind report
GEOGRAPHICAL DISTRIBUTION BY MONTH:
"LOW-END" EVENTS (
criteria):2-hourly distribution of first wind report, midpoint, & last wind report
"MID-END" EVENTS (
criteria):2-hourly distribution of first wind report, midpoint, & last wind report
"HIGH-END" EVENTS (
criteria):2-hourly distribution of first wind report, midpoint, & last wind report
"MID-END" PLUS "HIGH-END" EVENTS:
(These events correspond to those intended to be termed "derechos" by Johns and Hirt 1987)
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