Why so many tornadoes?

First North Carolina, then Alabama, now Missouri.  The devastation and loss of life is absolutely horrifying.  Yesterday's CSM has the best explanation I have yet seen as to why we are having so many tornadoes this year.  Two key factors: (1) La Niña trade winds in the equatorial Pacific ocean have sharply diminished, resulting in the jet stream being much further south than normal this time of year and (2) a collision between colder than usual air north of the jet stream (last winter's heavy snows) and warmer than usual air in the Gulf of Mexico (La Niña, again, with perhaps some global warming to boot). 

The article also reports that some human factors have been at play behind the record number of tornadoes reported this year: there are more of us, we have more electronic gadgets to capture images of tornadoes, and more of us live in places that were totally isolated in 1953 (when we had a comparable number of reported storms).  This means that any tornado has a much greater odds of being observed and reported today and makes historical comparisons problematic. 

"Just because we've seen an increase in the number of tornadoes doesn't mean there has actually been an increase in the number of tornadoes," said Greg Carbin, the warning coordination meteorologist with the Storm Prediction Center in Norman, Okla.

Always make a point of understanding how statistics are collected before putting too much faith in the numbers themselves. This applies to economic statistics as well.