Severe Storms Leave Damage Across Wisconsin, Sparing Northern Michigan
What Leads to a Severe Storm?
The Doppler 9&10 Weather Team issued a Weather Alert Day for Central Lower Peninsula Wednesday. Overnight storms were forecast to impact Wisconsin and Michigan, with the highest threat across Wisconsin and southwest lower Michigan. Before we dive into what went right or wrong in the forecast, you need to know how severe storms develop. Severe storms need a few ingredients to form and maintain strength.
Shear: Winds changing speed and direction from the surface to 30,00 feet. The quicker the change from the surface to 3,000 feet, the more rotation a storm will have.
Lift: You need something to lift air. Usually, we look for a cold front or stationary front for a lift. Warm fronts may also be a good source of lift, depending on other atmospheric conditions.
Instability: The more unstable the atmosphere, the quicker storms can develop, especially with a lifting mechanism. Instability is measured by integrating a parcel from the surface to the cloud top. The quantity is known as Convective Available Potential Energy or CAPE.
Surface Moisture: The muggier it feels, the more moisture there is in the atmosphere. The best way to measure moisture quickly is through the dew point. When the dew point temperature is in the 60s or 70s, the moisture is plentiful for severe storms.
Here is a quick checklist next time you are watching us. You can walk through the severe weather potential with us.
Shear – 20 to 40 knots or greater (do not use quantity on tv)
Lift – Cold Front/Stationary Front
Instability – 1000 j/kg or greater
Moisture – 65 F or greater
Wednesday’s Event – Expecting a High-End Wind Event
Shear – 40 to 60 knots +
Lift – Cold Front
Instability – 1000 to 1500 joules/kilogram
Moisture – Dew Points 65 F to 75 F
Extra Help – Low Level Jet, Winds at 3,000 feet feeding into storms at 40 to 50 mph.
Upper-level jet is an atmospheric wind flow at 30,000 feet that storm systems usually follow. Based on the wind direction from 3,000 to 30,000 feet, the storm motion was estimated as a southeast projection once they developed across northern Wisconsin.
Models were CONSISTANT bringing in strong to severe storms into Wisconsin and Southwestern Lower Michigan for a few days in advance.
A Few Strong to Severe storms moving through south of U.S. 10. The models agreed with our thinking, a southeast progression into southwestern Michigan, clipping southwestern portions of Central Lower Peninsula.
Storms developed as expected across northern Wisconsin and had an initial movement toward the east, southeast. Once these storms got “tall enough”, we expected the atmospheric flow to take over, tracking these storms off to the east.
Instead, the storms had a mind of their own. The storms chased the areas of highest cape or instability, rather than flowing with the upper levels of the atmosphere. When storm complexes develop that are so large scale, sometimes they will behave in very unexpected ways – something meteorologists can’t always predict.
Think of the storms as a car on a freeway. It decided to get off on exit 150 instead of exit 170. The car is taking a shortcut because it is running low on gas. Southern Wisconsin was exit 150, Michigan was exit 170. Instead of getting off at exit 170 and refueling to make it to exit 170, the car took exit 150 and eventually ran out of gas. This lead to the storm falling apart eventually early Thursday.
For more information check out the video from Doppler 9&10 Meteorologist Madison Ryke and her breakdown at Noon.