Lessons from the wreckage: How Alabama could help tornado preparedness
Meteorologists are combing through the damage from last week's historic tornado outbreak in Alabama, hoping to find clues about how to save more lives in the future.
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Many of last week's tornadoes moved through rural areas with houses built before communities began adopting codes aimed at improving a home's ability to withstand high winds, says John Ferree, who heads the severe-storms division of the NWS Office of Climate, Water, and Weather Service in Norman, Okla.Skip to next paragraph
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Had more of those homes been built to today's highest storm-resistance standards, the death toll might have been lower, he adds.
Still, he says, better forecasting, improved communications that allow people to see what's happening as it happens, and a deeper understanding of tornado-generating storms helped to reduce storm fatalities. The average lead time for warnings around the country during the outbreak was 24 minutes, according to initial NWS data.
"The general public knows more, so they take shelter" more often than they once did, he says.
Post-storm surveys – a kind of CSI: Tornado – provide a foundation for these improvements, he says.
"If we're issuing 30 tornado warnings and not verifying any of them, or only two tornadoes are occurring, people can become complacent," he says. "When big events like this one occur and we issue warnings, they may not take them very seriously. It's important we put some meat to the bone."
Still, he adds, the work "is physically hard and emotionally hard" as teams of at least two forecasters – often joined by civil engineers or meteorology professors from nearby universities, or forecasters and other specialists from forecast offices outside the affected region – spread out to record a tornado's aftermath.
From the air, field surveys try to map the start-to-finish path a twister takes and the damage it inflicts. Patterns in the orientation of debris on the ground –especially in forested areas – help distinguish between damage from the tornado itself and damage from intense downdrafts that can appear off to one side of a tornado. From the ground, the damage can look the same.
As happened last week, some of the more powerful funnel clouds spawned their own smaller twisters. Each of these siblings also leaves a distinctive signature along the main funnel cloud's path, although for reporting purposes, the collection still counts as one tornado.
In some cases, the evidence even from the ground is unambiguous. The twisters took out 90 tall, high-tension electrical towers in northern Alabama. These towers were designed to withstand winds of up to 150 miles per hour.
"I saw many of those taken all the way to the ground, some wrapped up like pretzels," Darden says. In other places, large oak trees had been flattened, their bark stripped, and the wood left sandpaper-smooth after scouring by the tornado-borne debris, he adds.
Investigators also try to track debris lofted from populated areas – from personal checks and other documents to full-size sedans.
Tracking light-weight debris – which can travel more than 200 miles – gives investigators an idea of the wind movement within the larger storm system.