Based on preliminary reports, six people were killed in Harrisburg (southeastern Illinois), when a tornado struck late last night. The NWS is surveying the damage today. I will post more information when it becomes available.
Update 9:30 pm, March 1. I have updated the numbers below to reflect the addition of 2011 data.
Update 8:30 am, March 1. The Paducah NWS office has released a preliminary report on the tornado outbreak in southern Illinois, Indiana, and Kentucky.
Update 3:45 pm, February 29. According to a news conference aired on WSIL-TV, the NWS has identified this as an EF-4 tornado with wind speeds up to 170 mph. Wind speeds are estimated from the level of devastation at the scene in Harrisburg. EF-4 tornadoes are relatively rare in Illinois. Out of
2244 2322 tornadoes reported in Illinois between 1950 and 2010 2011, only 40 were in this category. However, they are very deadly. Of the 203 deaths related from tornadoes between 1950- 20102011, 100 of these came from EF-4 tornadoes. That is 49 percent of the data with an average rate of 2.5 deaths per EF-4 event.
Tornadoes are more common in spring and summer, but they can occur in February. A total of
29 39 tornadoes occurred in February from 1950 to 2010 2011, causing 6 deaths and 28 serious injuries. We have a complete analysis of Illinois tornadoes here, including plots and maps. As the map below shows, many of our February tornadoes occur in the southern part of the state.