What's with the Weather? The La Niña-Tornado Connection

by Janet Ritz

Cross-posted on The Huffington Post, Reuters

2008 has seen a record outbreak of tornadoes in the United States from California to the Midwest, from the South through the central plains, to the Appalachian states.

In January, THE ENVIRONMENTALIST reported the University of East Anglia's prediction for a strong 2008 La Niña event.

"The assessment for 2008 is that there will be a strong La Niña event in the Pacific, which will limit the warming trend for the year (whilst still being one of the warmest years)."

The La Niña phenomenon is an upwelling of colder waters resulting in a change in ocean temperature that causes a shift in the jet stream, reducing corresponding climate temperature. A NOAA study from October, 1999, still referenced on their site, which uses data from 1950 through 1996, concluded there was no tornadic connection to the El Niño/La Niña event. Since then, however, Joseph Schaefer, Director of NOAA's National Weather Service's Storm Prediction Center, according to this February MSNBC report, has revised his position:

Tornadoes do happen in February, but a study by Schaefer two years ago found that winter tornadoes in parts of the South occur more frequently and are stronger when there is a La Niña.

The La Niña connection was also cited in a Purdue University study reported in Science Daily (also from 1999), this one with data from 1916 to 1996, which offered the intriguing possibility that the La Niña event could be traced to a geographical shift in tornadic activity

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