Small Consolation: Tornado Forecasts Are Better

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It is no consolation to those who lost family, friends, homes and livelihoods when tornadoes struck the South and Eastern Seaboard this weekend, but tangible progress is being made by forecasters working to bring down the death tolls from such outbreaks.

Super computers at National Weather Service headquarters are able to identify hot spots across the country where severe thunderstorms that spawn tornadoes are likely to develop any given day, and regional forecast models are getting better at anticipating the formation of specific super-cell storms. These model "runs" are the basis for severe thunderstorm or tornado "watches," which are basically "heads up" alerts that the day's weather could turn ugly.

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When it comes to saving lives, however, the key word is "warning" — a tornado has been detected in your area: take cover! — and the key measure is what forecasters think of as "lead time" — the amount of advance warning they are able to give residents before a tornado touches down.

Thanks to satellites, approaching winter storms and hurricanes can be observed days before they actually arrive, but it is in the nature of these relatively small, sudden, incredibly violent and erratic tornadoes that the time between their detection and their arrival is measured in just a few minutes.

This is where dramatic progress has been made — extending the number of precious minutes of advance warning — from an average of 0-3 minutes in 1978 to a current average of 13 minutes. The biggest single improvement came in the 1990s with the installation of Doppler Radar — a technology that allows forecasters to actually see the "hook" image inside a thunderstorm that signifies a funnel cloud's presence. This improvement alone accounted for a 4.2-minute jump in lead time.

With continuing model improvements, National Weather Service researchers are working on a new approach to the problem — rather than issuing warnings when tornadoes are actually detected, the project calls for issuing warnings when they show up in weather forecast models. Currently only tornado watches are issued at this stage.

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IMAGE: Map shows tornado strikes recorded from 1950 to 2010. CREDIT: NOAA, Storm Prediction Center

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