What if we could predict tornadoes a month out? Scientists make strides.

Scientists have only a fledging ability now, but a new approach to prediction could eventually allow forecasters to identify portions of states facing high risk for tornadoes in an upcoming month.

Scientists have developed a fledgling ability to predict monthly tornado activity in the US up to one month in advance.

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The technique, which uses existing weather-forecasting tools, is not yet ready for prime time. But in initial tests, the approach showed "statistically significant skill" in predicting regional tornado activity during most months of the year, including the peak of the spring tornado season, the researchers say.

If the approach can be honed sufficiently, eventually it could allow forecasters to identify portions of states facing the highest risk for tornadoes in an upcoming month.

In addition, the technique could help scientists explore a potential direct relationship between global warming and tornado activity. So far, such efforts have focused largely on the relationship between global warming and conditions that can spawn severe thunderstorms, which may or may not trigger tornadoes.

Though the results so far are modest, "this is exciting, because it's a hard problem," says Michael Tippett, a researcher with Columbia University's International Research Institute for Climate and Society, who lead the team.

The effort represents "an important early step" along the road to seasonal forecasts of tornado activity, says Harold Brooks, a researcher at the National Severe Storms Laboratory in Norman, Okla.

One potential audience for such forecasts would be federal and state emergency managers, Dr. Brooks suggests.

"If you were able to say: 'The second half of April is going to be really, really bad,' " it could provide extra lead time to marshal emergency supplies or ratchet up efforts to ensure more people know how to respond to tornado watches and warnings when they are issued, he explains.

Ordinarily, Dr. Tippett spends his time developing or improving ways to make extended-range forecasts of tropical cyclones, or swings in natural climate cycles such as El Ni?o or the Arctic Oscillation.?But that changed last April, when the US experienced its worst tornado outbreak on record. The three-day outbreak from April 25 to 28 spawned 359 tornadoes in 21 states, including four tornadoes that reached EF5, the most destructive category. The outbreak and the thunderstorms that spawned them inflicted at least $11 billion in damage and killed 322 people.

At the time, Tippett says, he noted that forecasters at the Storm Prediction Center in Norman, Okla., "had identified large regions where they thought there was going to be trouble, maybe four or five days in advance."

That implied the presence of large-scale, predictable features in the atmosphere that favor the formation of severe storms.

Researchers have applied the same general concept to produce seasonal hurricane forecasts. Tippett says it dawned on him that key atmospheric features also may encourage tornado-spawning storms to form.

Source: http://rss.csmonitor.com/~r/feeds/csm/~3/rCndxLpet88/What-if-we-could-predict-tornadoes-a-month-out-Scientists-make-strides

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