Tuesday’s tornadoes and very large hail were caused by weather conditions that came together at just the proper time for severe weather.
When we go down the checklist for severe weather ingredients, we saw yesterday had quite a few of them.
Firstly, we always talk about the time of day being very important for severe weather. Most tornadoes in Michigan have occurred between 3 pm and 8 pm Severe storms like the warmest time of the day. Tuesday’s tornadoes touched down between 5:24 pm and around 8 pm
For tornadoes, we usually have three things. A warm, moist flow of air coming into Michigan from the south is a classic ingredient. Surface winds from the east or northeast make a large amount of wind shear between the surface and aloft. This brings us to a very important severe weather feature- a strong upper-level wind, or what we meteorologists call a jetstream core.
Look at the temperature map and the dew point temperature map. Both temperature maps show the tongue-shaped warm and moist patch coming into southern Michigan.
Temperatures were warmest around Kalamazoo. It’s no coincidence at least one of the tornadoes occurred there.
Probably more important than warmth is a lot of moisture in the air. Notice the dew points were again highest in southwest Michigan.
When surface winds are from the east and aloft winds are blowing from the west there is a lot of “wind shear.” The surface winds were easterly. Now look at the winds aloft up around 30,000 feet in the atmosphere.
Look at the map above. The blue areas have the strongest winds. Notice the jetstream was aimed right at southern Michigan last night. We were also in the stormiest part of the jetstream in an area we call the left-front quadrant. If you draw crosshairs over the jetstream, the northeast quadrant has rising air and can develop severe storms.
The jetstream in a certain spot overhead creates the engine for the rotating thunderstorms that eventually spawn tornadoes.
Wind shear is important to a tornadic storm because it allows the storm to get continuous energy brought into the southeastern part of the storm. In non-tornadic storms the wind flow out of the storm will shut off the warm moist air feed and weaken the storm.
We will be waiting for National Weather Service teams to access the damage and officially confirm the tornadoes.
