The severe weather in Wisconsin last week brought a record-breaking number of tornado warnings: 92 across the state. One touchdown, in Marathon County, damaged at least 75 homes.
The National Weather Service's Green Bay meteorologist-in-chief, Kevin Scharfenberg, talked to WUWM about the high number of tornadoes and what causes them.
This conversation has been edited for length and clarity.
WUWM: Wisconsin gets 23 tornadoes every year on average. That's according to the state climatology office, and most tornadoes occur in June and July. Is it true that the National Weather Service has confirmed 19 tornadoes since April 13 alone?
Kevin Scharfenberg: Well, we are up to 23 tornadoes so far in Wisconsin in April, which would actually match the average number of annual tornadoes in Wisconsin for an entire year. And we still have May, June, and July to go, which are generally our busiest months for severe weather and tornadoes.
My number one question is, what's going on?
Well, we have had an unusually active storm track going from the Northern Rockies into Canada. Those strong storm systems moving from the Northern Rockies into Canada have been bringing up unusually warm and humid air for April. That's the kind of storm track we would usually expect in June or July, bringing severe thunderstorms. It's just happening a lot earlier than usual this year.
What do we know and what don't we know about how climate change is factoring into these formations and these storms?
It's a little hard to pinpoint climate change as the cause for any particular severe thunderstorm or tornado event. What we do know is spring is warming up a little earlier than usual in recent years, with warm temperatures and humid air into Wisconsin in April a little bit more frequently. That means the storm season is getting a little bit longer. The severe storm season is now lasting maybe earlier into April and May instead of just June or July.
Can you give us a short science lesson on the conditions that allow a tornado to be formed, like what happened last week?
To get severe thunderstorms that produce tornadoes, you have to have several ingredients that come together. You need sufficiently warm and humid air. That's the fuel for thunderstorms that they feed off of to become really intense and potentially produce tornadoes. But to get those tornadoes, you also have to have strong wind shear in the atmosphere. So you have to have wind coming from a different direction as you go up into the atmosphere from the surface. And it also has to increase as you go up in the atmosphere. So you put those two ingredients together: strong, unstable air and wind shear in the atmosphere. Any thunderstorm in that environment, you have to watch out for the potential for tornadoes.
In Marathon County there were at least 75 homes that were damaged. The sheriff there said he'd never seen devastation like that. What do you know about what happened there?
The community of Ringle in Marathon County was hit very hard. The degree of damage to some of the homes was really remarkable with all of the exterior walls and roofs blown off some homes, and it was very dangerous to folks who were there who didn't take cover in their basements. So the type of damage we saw in Ringle was very unusual for Wisconsin any time of year. It was a very intense EF3 rated tornado and the folks there really had a lot of damage to contend with.
What should people know about staying as prepared and safe as possible during a tornado warning?
One of the first things you can do to be prepared for tornadoes is to have a plan. Know where you're going to go, if you're at home, if you're at work, or even if you're on the road and a tornado warning is issued and hopefully received on your cell phone — so you'll know what to do when the time comes. Have a plan, know how to get the information, even if it's at night, [and] might you wake up.
One way we really suggest is having a NOAA weather radio or having alerts set up on your phone so you can hear them at night during stormy weather. Have a plan and be ready to enact it as you get those warnings.
