Clare Lane: You're listening to WBEZ. It's time for our weekly climate conversation. Here in the Midwest, we're far from the tragic destruction left in the wake of hurricanes like Ian. But hurricanes do have an impact on our weather.

Joining us to explain how is Dr. Scott Collis, an atmospheric scientist at nearby Argonne National Laboratory. Welcome.

Scott Collis: Good afternoon Clare.

Clare Lane: So Scott, Hurricane Ian was devastating along the Southeast coast while we've had very pleasant weather in Chicagoland. Is there a connection?

Scott Collis: There is. First of all, Hurricane Ian, an absolutely devastating and potentially historic storm that has uprooted the lives of so many in Florida. These storms are so large and they interact with our weather systems. So not only has Ian influenced the weather over our region, bringing in cooler northerly air, but the weather over our region has also influenced Ian with the storm systems and high pressure systems actually creating a lot of uncertainty in the path of Ian's trajectory influencing the uncertainty in the forecast.

Clare Lane: The predicted path kept changing. Why is that?

Scott Collis: It did. But I will point out, the National Hurricane Center knew about the uncertainty. When you look at the cone they produced - that cone did take into account both paths. A hurricane and its particular impacts are very difficult to predict, because depending on where you are, where the hurricane makes landfall, can make a big difference on the type of weather you get.

The weather systems over the center of the continent. Were really influencing the path of IAN's central Eye or the center of the storm. So not only did the simulation to the National Weather Service, users have to get the track of Ian right. They had to get those weather systems right as well. So with two degrees of freedom, there is increased uncertainty in the prediction.

Clare Lane: Now, are there times when hurricanes have had more of an impact on Illinois?

Scott Collis: Absolutely. Once Ian hit Florida and headed over the Carolinas, its weather really influenced Washington D. C. But, often when we get hurricanes that make landfall in Texas and go up into the interior of the country across the Great Plains, they can inject a lot of moisture into our region, leading to some soaking rains in the fall season.

Clare Lane: And while we have an expert here, I'm curious how is the category of a hurricane determined. Ian was a category four storm, so not the highest, but it seems like it's not always the highest numbers that cause the most damage.

Scott Collis: That's right. One of the challenges we have right now is the communication of the impact of these storms. The only thing that determines the category of a storm (the Saffir-Simpson scale) is the winds in the hurricane. Ian was a category four hurricane. It had 150 mile per hour winds just as it made landfall. If it was just 6 mile per hour faster, it would have been a category five: our most destructive, in terms of wind speed hurricane.

But there are a couple of things the category does not take into account. It doesn't take into account the size of the hurricane, or the rainfall in the hurricane. There is historic flooding ongoing in central Florida, with the Peace River hitting its highest ever level because of the over one foot of rainfall from Ian. Rainfall is not a part of the category system we use - at all.

Clare Lane: Dr. Scott Collis is an atmospheric scientist at Argonne National Laboratory. Thanks for joining us.

Scott Collis: My pleasure Clare.

WBEZ transcripts are generated by an automatic speech recognition service. We do our best to edit for misspellings and typos, but mistakes do come through.