May 31, 1998 Derecho

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The early morning hours of Sunday, May 31, 1998, brought one of the most memorable storm events to Michigan. A derecho — a long-lived line of intense, fast-moving thunderstorms producing widespread destructive winds — tore through much of the Great Lakes region. The storm complex started in South Dakota around 7 PM CDT May 30, and by 11 AM EDT May 31 it reached upstate New York. The storm crossed the Lower Peninsula of Michigan between 4:45 AM and 8 AM, killing 4 people and injuring 146.

“Straight-line” winds from the storm were commonly in the range of 60 to 90 mph, though winds were estimated as high as 130 mph in a few locations in southern Wisconsin and western Lower Michigan. Several tornadoes developed within this storm complex, including a violent tornado in Spencer, South Dakota. In Michigan, 5 tornadoes were officially discovered embedded in the larger pattern of downburst winds. Most of the tornadoes occurred in northern Lower Michigan on the north end of the storm line. These tornadoes were rather short-lived and developed along the chaotic interface between the thunderstorm outflow “gust front” and the warm & unstable pre-storm air mass. More common, and just as intense, was the west-to-east moving wall of wind that traversed Lower Michigan at an average speed of 70 mph.

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) together were declared a Federal Disaster Area by the Federal Emergency Managers Association. The purple “S” represents where a “seiche” took place on the eastern shore of Lake Michigan.

Above: Radar image from 5:06 AM EDT May 31, 1998. The leading edge of the destructive thunderstorm winds are indicated by the dashed white line labeled “Gust Front.”  The farther the radar beam travels from the origin site in Grand Rapids, the higher above ground the radar beam scans. An intense rear-inflow jet behind the storm line between 3000 and 8000 feet above the ground had winds sampled between 90 and 115 mph. These winds behind the storm line stayed above ground, but closer to the front edge of the storm line, some of that wind momentum was channeled down toward the ground.

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Weather wise we  have cleared out this morning after Alberto put down a little over an inch of rain here in the Otsego-Plainwell area. I have had some trouble with maple seeds getting into my rain gauges. We have had a lot of those this year so I am thinking this may be a precursor to a harder winter coming, we will have to see how the walnut production is in late summer.

The remnants of Alberto will continue to pull away from the region today taking most of the rain with it. Fairly widespread cloud cover will be around to start the day, but those clouds will break up, especially away from Lake Michigan. This will support another day in the 80’s mostly away from the lakeshore. These warmer temperatures will lead to some instability which could trigger an isolated afternoon thunderstorm. The area to the southeast of Grand Rapids stands the highest chance for this to happen. From Muskegon north to Ludington, fog and low clouds may linger into the afternoon, holding back the temperatures considerably.

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