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Posts Tagged ‘tornado alley’

Tornado Infographic

April 26th, 2011 1 comment

The tornado season this year has been absolutely HUGE so far! So, here’s an infographic dedicated to teaching you more about this amazingly powerful weather phenomenon!

Hook Echo

May 12th, 2010 No comments

I’ve been doing some reading lately on mesocyclones and tornado development, and one of the hallmark signs of a potential tornado forming is a “hook echo” being seen on the weather radar. A hook echo is produced by rain, hail or even debris being wrapped around a supercell, giving the impression of a hook on the radar. Meteorologists consider the presence of a hook echo enough justification to issue a tornado warning for an area. The hook echo has been recognized as a sign of tornado development for most of the history of weather radar. The first hook echo was detected in 1953 by the Illinois State Water Survey during their test to use radar to measure precipitation rates. In the southern US states, hook echos are not always obvious due to the heavier rainfall from the supercell. Instead, the echo will take on a more kidney shape. Here is an example of a classic hook echo – if you see this while checking out the radar, either seek shelter, or head out with your camera!

Classic Hook Echo

Tornado Alley Actually Four Regions?

April 28th, 2010 No comments

When people hear the term “Tornado Alley,” they tend to think of the area from mid-Texas up through the heartland that spawns a greater number of tornadoes annually than any other area of the country. However, recent research by Michael Frates of the University of Akron, reported on MSNBC, suggests that there are actually four regions of active tornado development in the US, and the original Tornado Alley is not the most active!

Michael Frates, a graduate assistant at the University of Akron in Ohio, devised the new boundaries and a more nuanced set of “Tornado Alleys” by analyzing the spatial distribution of F3 to F5 tornadoes with tracks greater than 20 miles in the Central and Eastern U.S. from 1950 to 2006. The output of that work is spread across a grid of more than 3,000 cells across the region.

Each cell was then given a different “frequency value” depending on the frequency of tornadoes with intersected the unit, and out of this process came “major spatial patterns, which served as the basis for delineating new tornado alleys,” as shown on his map, above.

“Results from this analysis indicate that Dixie Alley has the highest frequency of long-track F3 to F5 tornadoes, making it the most active region in the United States,” Frates concluded. Dixie Alley had a frequency value of 2.92, followed by Tornado Alley (2.59), Hoosier Alley (2.37) and Carolina Alley (2.00).

When Frates’ data is presented on a map, it gives the regions indicated below as the four Tornado Alley regions:

Four Tornado Alley Regions

Four Tornado Alley Regions

This new data should help the National Weather Service understand better where to focus tornado predicting technologies, and where to concentrate research efforts. This years spring tornado season, while delayed likely due to the El Nino effect, has been particularly active.