Here we are at the end of November, and the tropical storm season is officially coming to a close. Along with the lower tropical moisture, for all intents and purposes, the severe thunderstorm season is coming to an end, too!I am breathing a sigh of relief that this year's severe weather season was fairly tame in comparison to 2011. Of course, in the DC Metro area we had the devastating derecho, an event that was basically unheard of in this part of the country before this summer, but the entire country was largely spared from destructive weather in the form of severe storms and tornadoes.
2011 was the 2nd-most tornadic year on record, according to the National Oceanographic and Atmospheric Administration (NOAA). The map below shows all 1,691 confirmed tornadoes, including long-track tornadoes, from last year.
Confirmed tornado reports from 2011,courtesy of NOAA
There's a clear difference from the 1982 map, shown below. 30 years ago, most of the tornadoes were happening in the area we commonly refer to as "Tornado Alley", an area loosely bounded by the Mississippi River to the east and the Rocky Mountains to the west.
Confirmed tornado reports from 1982,courtesy of NOAA
So what's happening here? Is tornadic activity actually shifting eastward into the southeastern United States??
I think one of the factors in play is that there is a heightened awareness of tornadoes throughout the country. There are more trained storm spotters today than ever before, and the general interest in weather has increased through the internet, the Weather Channel, storm chasers, and better weather technology in general.
Another potential factor is population growth. Not only are there more storm spotters and informed weather watchers than before, there are also more people living in the South than ever before! Below is a link to the Census data from 2010:
<iframe src="http://2010.census.gov/2010census/data/embedmap.php" frameborder="0" scrolling="no" marginheight="0" marginwidth="0" width="638" height="405">IFRAMES not supported</iframe>Census map from 2010
Notice thatGeorgia, Tennessee, Virginia, and the Carolinas rankamong the highest in the country for population growth. Meanwhile, the population in major cities like Atlanta, Memphis and our own District of Columbiaremained flat or declined. This means someareas that used to be rural are not as sparsely populated, and again, there are more storm spotters in places that might not have had coverage a generation ago.
Are there more tornadoes in the South than there used to be? Perhaps. Or maybe, we just have a greater awareness of tornadoes now than we did 30 years ago. Either way, we know they happen in the DC Metro area, and we need to be prepared. If you haven't done so yet, now might be a good time to familiarize yourself with the National Weather Service's Severe Weather Preparedness Page. You'll find a bunch of links to valuable information to keep yourself and your family safe!