I'm currently a student at GMU. I decided to go back for a second degree in environmental science. Last semester, I took a class in severe weather and the focus of my study was in tornado genesis and why we get the most tornadoes here in the US---on the average of 1,000 per year. The 2nd country with the most occurrences--Canada at only 100 tornadoes. So we get 10 times more tornadoes here then the second closest country and it all has to do with the rockies and gulf of mexico.
Incase anyone is interested in how they work, here's the presentation I made. Currently, the best we can forecast a tornado warning is 15-30 minutes in ideal conditions. However, in 2015, NASA will launch the GOES-R satellite, which is expected to at least double that warning time.
If you like detailed information, just let me know. I'd be happy to share.
Best of luck to those affected and dearest condolences to the lives lost.