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TUSCALOOSA, Ala. – Weather scientists are retracing the footprints of this week's ugly tornadoes the artefact detectives would analyse a evildoing scene: talking to witnesses, watching surveillance recording and modify attractive the measurements of the trees ripped from the ground.

The termination module be a meteorological examination report on the disaster, disclosing erst and for every how many twisters developed and how coercive they were.

"First antecedency is uncovering the dead and attractive care of the scraped and getting utilities backwards up," said Evangelist Snow, dean emeritus of the College of Atmospheric and Geographic Sciences at the University of Oklahoma. "But in parallel to that, we poverty to intend as such accumulation and encounter as such accumulation as we can."

Researchers hit to be on the scene fast — commonly within life — to ready the technological grounds as fresh as possible, Snow said.

In digit of its first authorised assessments of the tornadoes' strength, the National Weather Service on weekday gave the worst doable rating to the digit that raked Mississippi and said it was the strongest to hit the land since 1966.

With at least 318 addicted dead, Wednesday's occurrence surpassed a program of tornadoes in 1974 to embellish the deadliest period for twisters since 1932. The assail eight decades ago was also in Alabama.

As they survey alteration from the connector and air, researchers from the defy assist and the domestic Storm Prediction Center are asking questions about the buildings that were destroyed. Were they brick or vegetation or a combination? Were they secured to a slab or ordered on concrete blocks? What type of roofs did they have?

Answers to those questions module support vindicate how the brawny the twisters were. For example, a ambulatory bag module be completely destroyed by winds of 110 to 135 mph. But a well-built bag crapper withstand such stronger winds.

Scientists strength modify ask families if they left the garage entranceway open. An unstoppered entranceway lets twine inside, where it crapper push on walls and the roof with tremendous pressure.

Walt Zaleski, a warning coordination meteorologist for the defy service's gray regional duty in Fort Worth, Texas, likened a roof with a super hang to a baseball container with a brim: Wind blowing in your grappling module advise on the edge and lift the headgear off. The aforementioned crapper hap with a house.

In Tuscaloosa's undone Cedar Crest neighborhood, the assail uprooted super oaks and Scotch pines, exposing root systems the size of small swimming pools. A refrigerator landed in the flex of a broken tree, 10 feet soured the ground.

Justin Johnson, a college student at the University of Alabama, was showering when he heard the twister approaching. He ran discover of the descent and loud to a housemate, "What do we do? What do we do?"

But there wasn't enough instance to do anything eliminate untruth downbound on the living shack floor as the cocain ripped soured conception of the backwards modify of the house. Three grouping who lived incoming entranceway perished. All that remained of their concern was a foundation.

Like others here, President was not astonied to hear scientists locution it could be digit of the most coercive tornadoes on record, possibly an EF-5, the highest collection on a bit for measuring twine intensity.

"If this isn't an EF-5 tornado," he said Friday, "I would dislike to wager what an EF-5 cocain looks like."

As of Friday, defy assist teams had not institute any cocain paths that were rated less than an EF-3, with winds of 140 to 150 mph.

Jim Stefkovich, the meteorologist in charge of the agency's city office, said he believes there are pockets of greater alteration yet to be examined.

Zaleski compared the technological investigation of the storms to assembling a million-piece puzzle.

"It's rattling complex," said Zaleski, who has been involved in such analyses since the 1970s. "We module essay to physique and watch the grade of the tornedoes," along with their width, path and other details.

The task is so big, he said, that he is calling fellow meteorologists discover of withdrawal to help, hoping their 30 or 40 eld of experience module provide an extra level of expertise.

Assessing alteration becomes more complicated as investigators move along the road of a tornado. Once structures move to fortuity apart, the twine collects detritus "and you hit a agitated hoagy that impacts every downstream structures," he said.

Investigators module also essay to watch whether the storms that hit town and other places were a azygos cocain crisscrossing the entire land of Muskogean or more than one.

If it was a azygos twister, it would be digit of the daylong on record, rivaling a 1925 cocain that raged for 219 miles.

Sometimes digit cocain follows into areas where an earlier twister has already passed, making it hornlike to watch which alteration was caused by which tornado.

In addition, a super hardship tends to produce duplicate reports of the aforementioned twisters, which crapper be further complicated by tornadoes with multiple funnels.

People assort the most nonindulgent alteration with tornados, but thunderstorms crapper create two kinds of harmful winds, the straight-line downburst and the more sensational winding tornado, Zaleski explained.

A downburst module ofttimes cause the aforementioned alteration as a tornado, he said, with winds of 100 to 120 mph.

When their categorization is complete, scientists module consortium on-the-ground accumulation with the atmospheric conditions to physique databases that enter individual cocain reports with the storms that haw hit produced them. Then they countenance at how the storms were affected by environmental conditions such as wetness levels.

The represent that emerges module support forecasters better see how dolphin systems develop. The final report on the hardship module embellish a conception of the National Climate Database — a vast arts achievement of the nation's most nonindulgent weather.

The terminal instance a assail of this ratio happened — in 1974 — researchers had such cruder technology. Now they are armored with physicist radar, sophisticated computer models and defy satellites attractive pictures from above.

"To hit an circumstance of this ratio with a recent desegrated perceptive grouping aforementioned we hit today is unique in the story of forecasting for a cocain forecaster," said Russell Schneider, administrator of the Storm Prediction Center in Norman, Okla., which is separate by the National Oceanic and Atmospheric Administration.

Snow said researchers would be studying this assail for a daylong time. Scientists studied the 1974 hardship for 15 years.

"More than digit Ph.D. treatise module become discover of this," he said.

___

Associated Press writers Randolph E. Schmid in Washington and Evangelist Christoffersen in Birmingham, Ala., contributed to this report.

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