CANCELLED: Weekly Meeting - March 25: Chasing Tornadoes In A Rental Car: What Could Possibly Go Wrong?


Speaker: Perry Samson is Arthur F. Thurnau Professor of Atmospheric Science in the Climate and Space Sciences and Engineering Department at the University of Michigan. He co-founded The Weather Undergound. Its mission is to make relevant, local weather data widely available. Its more than 250,000 members collect and send in real-time data from their own personal weather stations; its team of meteorologists then uses a proprietary forecast model to refine that data into reliable forecasts. Its team of meteorologists and climatologists fleshes out those forecasts with insight into the science behind that data as well as the relationship between weather and climate change. Our speaker earned his Ph.D. in Meterology from the University of Wisconsin (Madison) in 1979 and holds M.S. (1974) and B.S. (1972) degrees from the University at Albany.

Learning in the field is essential to Perry Samson’s teaching. Groups of his students regularly participate in meteorological research trips. Last summer, he took them to Greenland to study climate change. In past years, though, he has led them around the Midwest seeking out tornadoes as they form.

In today’s presentration, you will see some amazing videos made by students during our extreme weather expeditions. This will include a (way too) close encounter with a large tornado in Kansas and camping in polar bear country of western Greenland. The goal of these expeditions is to offer experiential learning opportunities for aspiring climate and weather students

Four basic conditions must coalesce for a tornado to form. Convective instability, a layer of cold dry air overlaying a hot moist layer, must be present. So must wind shear; differing wind speeds and wind directions as altitude increases combine to induce rotation. The jet stream must be in play so that suddenly faster winds create low-pressure pockets at high altitude. And a “trigger,” often hot dry air originating in Arizona or New Mexico, needs to create a “dryline” where the heavier hot, dry air meets lighter hot, moist air and forces it aloft. Our speaker’s students utilize an array of vehicle-mounted instruments, as well as real-time links to other weather services, to track the confluence of these four conditions. Once they are just right, a tornado-generating storm can grow explosively.

The typical three car team has two instrument vehicles  driven by students trying to get as close as possible to the forming storm. A third car, standing back a bit, coordinates their activity and analyzes the data which they collect.

It can’t be overemphasized how important it is to be a tornado chaser rather than a tornado chasee. These storms generally move in a southwest to northeast direction. Tornadoes usually form in the southwest quadrant of the storm; storms have to be tracked from that direction if a person is interested in participating in more than one such research project. The most dangerous part of chasing tornadoes is the reckless driving of amateur storm chasers. Unlike Dorothy and her dog Toto, such amateurs are not likely to be transported to the Magical Land of Oz by the tornadoes that snatch them up. “We weather chasers are different than normal people,” our speaker told the University Record in June 2008. “We want to be there. It should not be taken lightly or considered a spectator sport.”

Our speaker has developed a website ( that shows where tornadoes hit the United States each day. This website integrates data from the National Oceanic and Atmospheric Administration, Google Maps, and Google Earth, updating automatically every 10 minutes. Visitors can zoom in to see a city or zoom out to see the entire country. If nothing appears on the screen, that means no tornadoes hit on that particular day. “As tornado chasers,” our speaker has noted, “it’s interesting for us to know where the storms have been and have a record of them. This …  is another way for those interested in weather to get a sense for what’s going on.”

We will learn more about these weather pursuits this afternoon.