JULY 4, 1969 DERECHO
"The Ohio Fireworks Derecho"
Figure 1. Area affected by the July 4, 1969 derecho (outlined in blue) with the approximate hourly positions of the leading edge of derecho winds (gust front) indicated by the purple curved lines. Arrows indicate the direction of the strong storm winds.
During the afternoon of Friday, July 4, 1969 thunderstorms developed over southeastern Lower Michigan (MI). As these storms moved southeastward a strong derecho developed over extreme southeastern Michigan (MI) and Lake Erie (LE) during the early evening hours. The derecho then roared southeastward across northern and eastern Ohio (OH) and western Pennsylvania (PA) during the next few hours. The hourly positions of the gust front (associated with multiple bow echoes) are shown in Fig. 1 above. Winds gusted to 104 mph in Toledo ("T") and reached 100 mph in the Cleveland ("C") area. In towns and cities near Lake Erie many people were in parks getting ready to watch the Independence Day fireworks. Also, for this occasion small boat owners had anchored their boats just off shore on Lake Erie to watch the fireworks. As the derecho passed through, many thousands of trees were blown down including 5000 in Toledo alone. In the fireworks areas near the south shore of Lake Erie eight people were killed by falling trees and over 100 boats were overturned with three persons drowning. A total of 18 people were killed as a result of the derecho winds in Ohio. Some of the worst damage occurred in Lakewood, Ohio, a suburb of Cleveland. As the derecho moved into Pennsylvania it continued to produce much damage with 5 people being injured in Meadville ("M").
Figure 2. Radar imagery (reflectivity) observed by the DECCA radar near Akron, Ohio at 8:30 PM EDT on July 4, 1969. (From Hamilton 1970)
A radar in Akron, Ohio observed a "bowed" echo about 35 miles northwest of the radar site at 8:30 PM on the evening of July 4th (Fig. 2). This bow echo was associated with the deadly derecho winds in the Cleveland area and was one of the first radar "bow echoes" to be documented.
(Reference......Hamilton, 1970; Storm Data for July 1969).