Why We Get Tornadoes in Central Minnesota?
A tornado was confirmed to have touched down in rural Benton County near Gilman earlier this week. Meteorologist Megan Moulford from the National Weather Service says severe weather in Central Minnesota can occur as early as April and continue through August or early September. Moulford says the southern states like Alabama and Mississippi typically get tornadoes January - March.
During the winter time in Minnesota Moulford says the fuller jet stream retreats south closer to Texas. She says during the spring time the fuller jet stream starts to retreat back into Canada. Moulford says the retreating of that jet stream is why we see the clash of temperatures this time of year.
Moulford says to get tornadoes we need moisture, instability and lift. She says warm temperatures with dew points in the 60s and 70s are part of the requirement.
Moulford says the heat and humidity is soaked up at the surface and then it rises and condenses into a cloud and certain other aspects are needed for that cloud to rise on its own. She says for severe thunderstorms and tornadoes to form there needs to be bulk shear. Moulford described bulk shear as a change in wind speed and direction with height.
She says the more wind shear you have the more chance you have for the thunderstorm to tilt and that causes an updraft basically to not be cut off by the downdraft. Moulford says the more shear, the more tilt, the longer lift the more severe storms you are going to get especially in super cells. She says another factor includes the spin of the atmosphere. Moulford says if all of these factors combine that can cause a tornado.
Moulford says the strongest probable day part for storms is late afternoon/early evening. She says this is because late afternoon is typically the time for the max heating and that's when storms tend to pop up.
Moulford says tornado alley used to largely include Kansas, Oklahoma, Arkansas and Texas but now that has stretched east to Louisiana, Mississippi and Alabama based on climatology data. She says this has also extended into areas like Illinois, Iowa, Missouri and Minnesota. Moulford says this is because these portions of the country are in the middle of all the air masses.
If you'd like to listen to my entire conversation with Megan Moulford it is available below.