Wes Carter
EF5
I never gave heat island too much credit, until I recently found out that there was a 2 degree F difference in average temperature between the metro area and Rochester to the south. Who knows how that factors in, but I think another factor is the glacial ridge.
Disclaimer - this is a rough composite I put together to show people what I'm working on. It's a map of tornado frequency by county, with topography overlaid. Maybe one day I'll build out my theory and have some real science behind it
You can see the glacial ridge (the white area) cutting a swath through the state. The periphery of the ridge seems to be a focus point for tornadic activity - and I started thinking about this when realizing that the metro area never has tornadoes, and the corridor between Wilmar and Alexandria always gets nailed. Even though the close proximity of KMPX, large number of Skywarn spotters, and well-populated area would lead you to believe the metro area would be statistically over-represented, it doesn't seem to skew the data.
Robert, that is a very interesting map you put together. We had a meteorologist at the NWS in Nashville, Dr Jerry Orchanian, who was a firm believer that topography played a major role in tornadogenesis, whether it be by orographic lifting, evapotranspiration, or even the albedo affecting the instability locally. I also think it would be interesting to play with your map just a bit more and compensate for the great difference in land areas for the counties, then compare the numbers to the terrain.
