Sunday, May 06, 2007

Nature's Wrath

Residents of Greensburg, Kansas are beginning the slow process of cleaning up and rebuilding, two days after a killer tornado devastated their town.

Readers of this blog know that I'm something of a weather buff, with a particular interest in tornadoes. After spending much of my life in the Midwest and South, I've developed a healthy respect for these powerful and (sometimes) deadly storms.

The Greensburg twister was the first major tornado of what quickly evolved into a major outbreak. As of Sunday afternoon, the National Weather Service (NWS) had recorded at least 120 tornadoes--across an area stretching from Texas to North Dakota--along with hundreds of of reports of severe thunderstorms, hail and high winds.

But the Greensburg storm will remain the benchmark for this particular outbreak; a powerful, wedge-shaped storm that swept through the Kansas town around 9:45 Friday night, demolishing virtually everything in its path. By most estimates, between 90 and 95% of the homes and businesses in Greensburg were destroyed, or suffered heavy damage. On Sunday afternoon, the NWS announced that the Greensburg storm has been classified as an EF-5 (Enhanced Fujita Scale), with top winds of 205 mph. The Kansas twister is the first to receive an EF-5 rating since the new scale was introduced. Storm chasers from KOTV in Tulsa and KWTV in Oklahoma City photographed the tornado just before it entered the Kansas town.

By most accounts, the residents of Greensburg had up to 20 minutes of warning time before the storm struck--slightly above the NWS average. But, given the strength of the storm, there was only so much that townspeople could do. Residents without a storm shelter or basement were at extreme risk; looking at the utter devastation left along the twister's path, it's amazing that the death toll wasn't higher. By a quirk of geography, the Greensburg tornado (and others reported during the outbreak) have passed through sparsely populated, rural areas. Had the storms struck only 200-300 miles to the east, the death toll might have been higher, given the strenth of some of these tornadoes, and higher population densities.

It will be interesting to see how this particular outbreak compares with the so-called "Super Outbreak" of 1974, which we recounted in early April. While this weekend's outbreak won't match the event of 33 years ago, it may produce a similar number of powerful storms, rated as F-4 or F-5. The 1974 outbreak generated 30 tornadoes that rated as F-4 or F-5 on the original Fujita Scale, including seven in that latter category. The catastrophic results of that event helped drive improvements in the warning system--including Doppler Radar--that helped save lives this weekend.

Our thoughts and prayers go out to the people of Greensburg. Their losses have been horrific, but it could have been much, much worse.


Expert analysis of this event from meteorologist Jesse Farrell of Examining some of the storm warnings from Saturday night, he's amazed at the number of apparently powerful tornadoes--similar to the Greensburg twister--reported in relatively close proximity, another indication of the power of this weather system.

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