GRAND RAPIDS, Mich. (WOOD) — Early Saturday, a line of strong storms pushed across West Michigan. Many people woke the following morning to find that lawn furniture was blown across the yard, leaves were everywhere and trees had toppled.
One area that was hit particularly hard was Jenison. When the National Weather Service surveyed the damage, it concluded that a microburst had occurred. The microburst produced straight-line winds of around 80 mph. That wind caused extensive damage to a house, uprooted large trees and even blew a trampoline into some telephone wires.
Strong storms were in the forecast across the Great Lakes region for Friday evening into early Saturday. There was a certainly a chance of strong to severe storms in West Michigan during that time frame, but the better chance of severe weather was to our north and west. It initially looked as though the worst of the weather would pass to the north.
As the strong storms began to track across Wisconsin, they were heading in an easterly direction. They produced three tornadoes in central Wisconsin, as well as damaging straight-line winds.
Once the storms were roughly halfway across Wisconsin, they took a subtle jog to the south.
This normally wouldn’t make a big difference in the track of the storms, but the air mass over West Michigan was abnormally hot and humid. At one point on Friday afternoon, dew point temperatures had approached 80 degrees. Thunderstorms feed on moisture and instability, so once the line of storms had taken a small turn to the south, there was nothing to stop it. The line of severe storms barreled down to the southeast and went right over West Michigan early in the morning.
Here’s what happens in a microburst: In any thunderstorm, there’s something called an updraft that feeds the storm. The updraft suspends rain droplets and hail at the top of the clouds until the water particles have enough weight to fall to the ground as precipitation. As the rain falls, a downdraft is produced. When you feel gusty winds out ahead of a thunderstorm, you’re feeling the downdraft.
In some cases, the updraft can be very strong. The strong updraft can suspend larger amounts of rain droplets and hailstones high up in the cloud. The updraft eventually weakens and there is no longer anything to keep the water droplets suspended in the top of the cloud. The core of rain and hail plummets back down to the surface and spreads out in all directions. Straight-line winds caused by a microburst can top 100 mph.
Microbursts are normally small with a width less than about 2.5 miles. That means the damage is often fairly localized, but it can be very severe.