JULY 4, 1977 DERECHO
"The Independence Day Derecho of 1977"
Figure 1. Area affected by the July 4, 1977 derecho event (outlined in blue). Curved blue lines represent the approximate locations of the "gust front" at three hourly intervals. "P" represents the location of Phillips, Wisconsin.
The"Independence Day Derecho of 1977" developed over west central Minnesota (MN) during the morning of Monday, July 4th (Fig. 1). As the derecho moved east southeastward it became very intense near midday over central Minnesota and from that time through the afternoon it would produce winds from 80 to greater than 100 mph and areas of extreme damage from central Minnesota through northern Wisconsin (WI). The derecho storm system continued racing southeastward across portions of Lower Michigan (MI) during the evening hours producing winds up to 70 mph and considerable damage before finally ending over northern Ohio (OH) about 1:30 AM on Tuesday, July 5th.
After this storm event occurred, Dr. T. Theodore Fujita, a meteorology professor at the University of Chicago, became aware of the extreme wind damage in northern Wisconsin and decided to conduct a scientific investigation of the event. By observing the damage pattern from the air, he found that there were three areas where extreme damage and forest blowdowns took place. One extended from central Minnesota into extreme northwestern Wisconsin (shaded area "A" on Fig. 2b) and the other two extended across a long corridor of northern Wisconsin (shaded areas "B" and "C" on Fig. 2b).
Figure 2. (2a) Evolution of radar reflectivity bow echo system on July 4, 1977. Numbers above echoes are the time in CST. (2b) Areas of very intense downburst damage including forest blowdowns (shaded areas) that occurred on July 4, 1977 as determined by an aerial survey by Dr. T. T. Fujita. The orientation of the fallen trees is indicated by the dashed and solid lines within the shaded areas. The solid line indicates the path of the center part of the bow echo system with the small crossed lines indicating one-half hour time increments in CST. (From Fujita 1978).
Dr. Fujita also examined the radar echoes associated with the damage path across eastern Minnesota and northern Wisconsin. He noticed that the radar echoes evolved into a bowed out signature (Fig. 2a). It was from the study of this derecho case that Dr. Fujita coined the term "bow echo" that is widely used today.
Figure 3. Approximate area affected by severe downburst damage in Minnesota and extreme northwestern Wisconsin during the derecho of July 4, 1977 (Enclosed within green line and corresponding with shaded area "A" on Fig. 2b).
The counties affected by the first series of intense downbursts associated with the July 4, 1977 derecho, mostly in Minnesota, are shown on Fig. 3. Estimated wind gust from 80 to 100 mph roared through this area between noon and 2 PM CDT causing hundreds of thousands of dollars worth of damage to personal property. Thousands of trees were blown down extensively damaging cabins and cars. Shortly after the intense winds began, the roof was blown off the Gull Lake Lodge ("G" on Fig. 3) near the Cass/Crow Wing County line. As the derecho winds reached Platte Lake ("P" on Fig. 3), a woman sustained a broken leg when her mobile home was overturned. Some of the worst damage occurred at Milles Lacs Lake ("M" on Fig. 3) where a resort lodge and several boats were totally destroyed. One launch caught on the lake during by the derecho winds had to ride out 8 to 10 foot waves for almost an hour. Farther downstream the storm system's winds stripped and flattened large areas of crops in Kanabec and Pine Counties and downed trees in the forested areas of Burnett County Wisconsin.
Figure 4. Area affected by the severe downburst damage across northern Wisconsin during the derecho of July 4, 1977 (shaded areas "B" and "C" on Fig. 2b). From the damage severity, wind gusts were estimated to have been between 73 and 112 miles per hour in the light red shaded areas and from 113 to 157 mph in the dark red shaded areas. (From Fujita 1978).
As the derecho continued racing across northern Wisconsin during the afternoon hours of Independence Day 1977, a series of intense downburst winds caused major forest blowdowns, widespread severe damage to property, and many casualties. This band of extreme damage, which was 10 to 20 miles wide and over 160 miles long, extended from eastern Burnett County through Washburn, Sawyer, Price, and Oneida Counties (Fig. 4). Approximately 850,000 acres of trees were either destroyed or badly damaged and damage estimates including buildings and vehicles totaled about 24 millions dollars. One person was killed and 35 were injured.
As the bow echo system moved into Sawyer County a gust of 75 mph was recorded at 1:40 PM CDT at the Hayward Airport near the north edge of the storm. Continuing across the county, the downburst winds destroyed many barns and cabins and injured eight people. In the southeastern part of the county derecho winds wrecked havoc in the Flambeau River State Forest where winds were estimated to have reached 135 mph. Within the forest a person was killed at Conner Lake when a tree fell on her camper van. Nearby the "Big Block", one of the only areas of virgin forest in Wisconsin, was completely destroyed.
The derecho then crossed Price County damaging or destroying many homes and injuring 20 people. The gust front reached the county seat of Phillips at 2:55 PM CDT and the severe winds lasted for 25 minutes. The anemometer at the Phillips Airport registered a speed of 100 mph before blowing away. All homes in the Phillips area were damaged and thirty were damaged beyond repair.
After leaving Price County, the bow echo system entered Oneida County and continued to severely damage homes and blow down large areas of forest. Seven people were injured across the county. The gust front entered Rhinelander about 3:30 PM CDT and a gust to 115 mph was recorded at the Rhinelander Airport. After crossing Oneida county the severe derecho winds continued through northeastern Wisconsin and into Lake Michigan (LM) . However, the strength of the winds and the extent of the damage was not as large as it had been farther west.
After crossing Lake Michigan, the bow echo system entered Lower Michigan near the towns of Manistee and Ludington just before 8 PM EDT (Fig. 1). The gust front with winds of 60 to 70 mph moved southeastward across the state during the evening hours blowing over many trees which damaged homes, utility lines, and vehicles. One woman was injured when a tree fell on her car. In addition to the damaging straight-lined winds, the bow echo system had tornadoes associated with it from central Lower Michigan into the southeastern portion of the state. Two people were injured by these tornadoes, one from an overturned mobile home and the other from an overturned camper. As the bow echo system entered northern Ohio during the early morning hours of Tuesday, July 5th, some outbuildings and trees were damaged but the thunderstorm system and the derecho ended shortly thereafter.
In summary, the Independence Day Derecho of 1977 traveled 800 miles in 14 hours from the Upper Mississippi Valley region into the Lower Great Lakes region. One person was killed and 37 were injured. Approximately 1,000,000 acres of forest were badly damaged or destroyed and total damage estimates likely exceeded 30 million in 1977 dollars. It was this derecho case that caught Dr. Fujita's interest and from his research on this case the term "bow echo" was defined.
Additional information concerning the July 4, 1977 case including aerial pictures of the damage in northern Wisconsin can be found on the NWS Green Bay, Wisconsin web site by clicking here.
(References.....Fujita, 1978; Storm Data for July 1978)
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