MAY 30-31, 1998 DERECHO

"The Southern Great Lakes Derecho of 1998"

Figure 1. Area affected by the May 30-31, 1998 derecho event (outlined in blue). Curved purple lines represent the approximate locations of the "gust front" at three hourly intervals. "+" symbols indicate the locations of wind damage or wind gusts above severe limits (measured or estimated at 58 mph or greater). Red dots and paths indicate tornado events.

On Saturday May 30, 1998 a low pressure system moving towards the northern Plains and Great Lakes region posed a threat for severe storms. By late Saturday afternoon supercell thunderstorms developed over eastern South Dakota and some began producing tornadoes. One violent tornado hit Spencer, South Dakota causing devastating damage and killing 6 people. However, this localized tornado outbreak in South Dakota would not be the only significant severe weather episode associated with this low pressure system. The storm system would also produce a major derecho event in the Upper Mississippi Valley and southern Great Lakes region during the evening and overnight hours of May 30th and May 31st (Fig. 1). And then, on Sunday May 31st, it would produce a third severe weather episode in the northeastern United States including strong tornadoes associated with supercells and damaging winds associated with bow echoes. The following paragraphs, images, and links focus on the second significant severe weather episode, the major derecho event shown in Fig. 1.

Figure 2. Composite radar reflectivity imagery for portions of the northern Plains at 7 PM CDT May 30, 1998 (A) and at 10 PM CDT May 30, 1998 (B). (Imagery provided by NWS meteorologist Randy Graham)

During the early evening hours on Saturday May 30, 1998, the tornado-producing supercells over eastern South Dakota (Fig. 2A) merged and became a squall line that moved eastward into southern Minnesota (Fig. 2B). As the squall line crossed southern Minnesota it evolved into a bow echo system which would expand in scale and race eastward across the southern Great Lakes region finally dissipating over central New York after sunrise on Sunday morning May 31st. This bow echo system would produce one of the most dangerous and costly derecho events in the history of the Great Lakes region. Thus, "The Southern Great Lakes Region Derecho of 1998" would prove to be a very scary weekend event for millions of people in the area. There would be many casualties and record amounts of damage.

An animated radar loop of the bow echo system as it moves from southern Minnesota into Lower Michigan and grows in scale can be observed by clicking here.

...MINNESOTA AND IOWA...

The bow echo system began to produce significant wind damage over south central Minnesota about 10 PM CDT on Saturday evening (Figs. 1 and 2B). As the system moved eastward it grew southward into northern Iowa and caused damaging winds over most of southeast Minnesota and northeastern Iowa as it moved rapidly eastward. Many trees and power lines were blown down and several farm buildings were damaged or destroyed.

Figure 3. Minnesota counties (in black) and some of the towns and cities (in blue) that were the most severely affected by the derecho of May 30-31, 1998. The red numbers are measured wind gusts in mph.

However, the most intense damage occurred near the northern end of the bow echo system in Minnesota, from Sibley and McLeod Counties eastward across the southern portions of the Minneapolis/St. Paul metropolitan area (Fig. 3). Along this band, winds of greater than 80 mph were measured and in some areas were estimated to have reached 100 mph. Tens of thousands of trees were blown down, 500,000 customers lost power, 2 semi-trailer trucks were overturned, 2 apartment roofs were blown off, and 100 boats were destroyed. In addition, over 100 homes were destroyed or very badly damaged, and over 2000 others received some damage. Twenty-two people were injured and the damage to property was estimated to be about 48 million in 1998 U.S. dollars...with 35 million dollars of that damage occurring in Dakota County alone!

In summary, while crossing southern Minnesota and northeastern Iowa, the derecho event caused about $50 million in 1998 U.S. dollars of damage, left about 600,000 customers without power, and injured 22 people. In some areas customers would not get power back until 5 or 6 days after the event.

Additional information about what happened in Minnesota with the May 30-31, 1998 derecho event can be found on the Minneapolis NWS Forecast Office web site by clicking here.

...WISCONSIN...

The derecho was in full force as it entered west central Wisconsin just before midnight CDT. It raced across the southern two-thirds of the state at a speed near 60 mph reaching Lake Michigan in about 3 hours and exiting the southeastern corner of the state by 4 AM CDT on Sunday morning, May 31st.

Figure 4. Maximum wind gusts in mph associated with the May 30-31 derecho in Wisconsin. Measured gust values are red and estimated gust values are black [Modified version of a map prepared by NWS Warning Coordination Meteorologists Rusty Kapela (Sullivan/Milwaukee, WI), Jeff Last (Green Bay, WI) and Todd Shea (LaCrosse, WI)].

As the derecho crossed central and southern Wisconsin almost every point experienced winds above severe limits (58 mph or greater) (Fig. 4). Measured and estimated wind gusts from 70 to 100 mph were common in the southern half of the state. Extremely strong measured winds gusts from 100 to 128 mph were recorded in a band from northeast of Madison to the northern part of the Milwaukee metropolitan area. The strong winds knocked down hundreds of power poles and thousands of trees. About 250,000 customers lost electrical power. Some residences and businesses remained without power for 5 or 6 days. Affected utilities companies and some emergency managers stated that this was the most damaging and widespread straight-line thunderstorm wind event to affect southern Wisconsin in the past 100 years! Over 5000 homes, businesses, and farm buildings were damaged and about two dozen homes and businesses were destroyed. Total damage estimates for Wisconsin exceeded 60 million in 1998 U.S. dollars. In Washington County a person was killed when a tree fell through the roof of her home and onto the bed where she was sleeping. Thirty seven other people were injured as the derecho roared through Wisconsin.

Additional information concerning the May 30-31, 1998 derecho event in Wisconsin can be found on the following web page:

"Southern and Central Wisconsin's Hurricane Force Downburst Wind Event on May 30-31, 1998".............Sullivan/Milwaukee, Wisconsin National Weather Service Forecast Office.

...LOWER MICHIGAN...

The leading edge of the derecho reached the eastern shores of Lake Michigan about 4:45 AM EDT Sunday morning and blasted across Lower Michigan at a speed of about 70 mph reaching the "Thumb area" in a little over 2 hours (Fig. 1). Winds from 60 to 90 mph were common and in some areas the winds were estimated to have reached 130 mph (Fig 5). Of all the regions affected by this major derecho event, the greatest damage and the greatest number of casualties would occur in Lower Michigan. In this region 4 people were killed and 146 were injured. Total damage was estimated to be 172 million in 1998 U.S. dollars. Approximately 250 homes and 34 businesses were destroyed and over 12,000 homes and 800 businesses were damaged. About 860,000 customers in Michigan lost electrical power which is a new historical record, slightly exceeding the number of customers that lost power during the Southern Great Lakes Derecho of 1991. Some would not get power back for 10 days. For Consumers Energy utility company, which serves much of western and middle Lower Michigan, this derecho event would be its most destructive weather event in history. Besides the loss of hundreds of power poles and lines, five of the company's 345-kilovolt transmission towers were blown down between Ludington and Grand Rapids. These massive towers were designed to withstand continuous winds up to 90 mph, and gusts to 110 mph.

Figure 5. Area of Lower Michigan affected by the worst damage from the May 30-31, 1998 derecho. Red numbers are maximum measured wind gusts in mph. Orange numbers are estimated maximum gusts in mph based on a damage survey by Grand Rapids NWS Forecast Office meteorologists. Thirteen Michigan counties (noted in black lettering and within light blue border) were declared a Federal Disaster Area by the Federal Emergency Managers Association (FEMA). The purple "S" represents where a "seiche" took place on the eastern shore of Lake Michigan.

The most devastated counties were in central Lower Michigan and 13 of them were declared a Federal Disaster Area by the Federal Emergency Managers Association (FEMA) (outlined in blue on Fig. 5). Some of the towns and communities within the Federal Disaster Area that received the greatest damage included Spring Lake in Ottawa County and Walker, which is a western suburb of Grand Rapids, in Kent County. Damage surveys suggested that winds in these towns likely reached speeds from 120 to 130 mph. The damage near Cody Lake and Stanton in Montcalm County suggested that the derecho winds in that area reached 100 mph.

Derechos crossing Lake Michigan occasionally produce what is called a "seiche" (pronounced as "say-sh") where the water slouches back and forth across the lake, sometimes changing the water level by as much as 10 feet at a particular point. The May 30-31, 1998 derecho produced a seiche as the water level rose on the east shore of the lake because of the intense westerly winds. At the time the derecho hit the east shore, the Stephen M. Asher tug boat was traveling through a channel between Lake Michigan and White Lake north of Muskegon (the purple "S" on Fig. 5). The sailors noticed the surge and rise in the water level as the strong winds passed through the area. However, after the winds let up and the derecho had passed, the boat received an even higher surge from the opposite direction as the water in White Lake tried to return back into Lake Michigan. It was this return surge that overturned the boat and it sank. Fortunately, the sailors on board were able to reach the bank of the channel and no one drowned.

Radar images and damage pictures from southeastern Lower Michigan provided by the Detroit/Pontiac NWS Forecast Office can be viewed by clicking here.

...ONTARIO AND NEW YORK..

The derecho entered southern Ontario after daybreak on Sunday morning May 31st and the severe damage and casualties continued to occur as the bow echo system raced across the province during the morning. Winds up to 120 kph (75 mph) knocked down many trees, damaged many buildings, and destroyed some barns. Some of the most intense damage occurred in the Dufferin, southern Simcoe, and northern York regions. Over 300,000 in 1998 Canadian dollars of damage was done to crops alone. Windows were blown out of some office buildings in downtown Toronto and about 200,000 Ontario-Hydro customers lost electrical power. During the morning, some teenagers began boating on a lake along the Severn River just east of Georgian Bay. As the gust front hit them about 9:30 AM EDT, their boat was overturned and one of them was unable to make it to shore and drowned. Several additional people were injured over southern Ontario by the severe winds.

The derecho entered western New York about 11 AM EDT and although it was weakening, it would produce about 300,000 in 1998 U. S. dollars of damage in western and central New York before diminishing just after midday.

An animated loop from Environment Canada's King City, Ontario radar showing the bow echo system progressing across southern Ontario and western New York can be observed by clicking here.

...SUMMARY...

The "Southern Great Lakes Derecho of 1998" traveled 975 miles from southern Minnesota to north central New York in 15 hours with an average speed of 65 mph! It became one of the most damaging North American derecho events in history, destroying over 400 homes and businesses and damaging almost 20,000 others. Total damage estimates were close to 300 million in 1998 U.S. dollars. Almost 2 million customers were left without power, some for many days. For some electrical power companies in Wisconsin and Lower Michigan this event was the most damaging weather event in their history. Six people were killed and over 200 were injured during this major derecho event on that last fateful weekend in May of 1998.

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Scientific data and other information concerning May 30-31, 1998 derecho in Ontario were provided by Environment Canada meteorologists Phil Chadwick, Michael Leduc, and Peter Rodriquez.

Information about this derecho event was also provided by NWS meteorologists Randy Graham, Rusty Kapela, Jeff Last, and Todd Shea.

References...Storm Data for May 1998.

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