JARRELL -- The tornado that obliterated a subdivision and killed 27 people was one of only four storms in the United States to be rated an "F5" in the past decade, according to weather experts who on Friday defended their efforts to warn the public.

People in Jarrell had no more than 15 minutes to find shelter after the initial warnings were issued about 3:30 p.m. on Tuesday, said Al Dreumont, a National Weather Service meteorologist in charge of the Austin-San Antonio forecast office at New Braunfels.

"I've been in the weather service 34 years and this is the first time I've seen an F5. Indeed, it's something awesome to behold," Dreumont said after touring the devastation.

Jim Henderson of Kansas City, Mo., the weather service's assessment team leader who visits major storm sites, also attested to the tornado's might.

"In this particular case, there has been asphalt stripped right off the roadways. The houses have been cleaned down to the slab. Trees have been snatched out of the ground. This is every indication of an F5," he said. "Those are very rare. We've only had three nationwide in the last 10 years. It's certainly very rare in the central part of Texas.

"Tornadoes are rare events to start with and this is rarer than rare," he added.

The most recent F5 was the 1995 twister that hit near Pampa, he said.

Based on examination of the Jarrell area, both from the air and ground, and a preliminary check of instrument readings, the weather service experts theorized that the tornado took from five to 10 minutes to lay waste to the area.

The funnel cloud developed in southern Bell County and entered Williamson County on a path from north-northwest to south-southeast, Dreumont said. But soon after crossing the county line, the twister veered south-southwest and plowed into the Double Creek Estates subdivision after raking farms, crops and a few scattered structures.

"It looks like there was an F2-F3 variety in Bell County. The tornado weakened somewhat and then the tornado began to grow again once it got into Williamson County and then became an F5 once it got into this area here," Dreumont said.

Surface markings indicate the tornado, whose funnel was sprawled about half-mile wide and wobbled as it careened through the area, was on the ground from 6 to 6.5 miles, the experts said.

Some of the debris, and perhaps victims, were carried a mile or two by the ferocious winds, which pushed objects both upward and horizontally.

The Jarrell tornado was one of eight separate twisters verified that day, prompting a total of 49 official warnings, Dreumont said. The first warning, which involved the Jarrell tornado, was prompted by sightings near Belton.

"With the new Doppler radar that we have, we were able to do as good a job as we did," said Dreumont. But if the weather service had been relying on equipment it used until five years ago, "no way," he said.

Henderson agreed that "the equipment worked real well. The warnings were out. It's unfortunate that there were lives lost and one of the things we'll have to look at is, in terms of the safety, what are some changes we might suggest."

But Henderson added that experts aren't sure much can be done to hold off the forces of an F5, with winds from 261-318 mph. The Tornado Project based in St. Johnsbury, Vt., describes F5s as capable of "incredible" damage: "Strong frame houses lifted off foundations and carried considerable distances to disintegrate; automobile-sized missiles fly through the air in excess of 100 meters; trees debarked; steel-reinforced concrete structures badly damaged."

All those phenomena were recorded in Jarrell.

"It's very similar to Hurricane Andrew, where they had 200-mph winds. It took everything down to the slab in that area, too," Henderson said.

Because storms can move swiftly and erratically, even the most modern devices can't prevent all casualties, the officials said. Old-fashioned spotters who eyeball the skies continue to play a key role in Texas, they said.

"We have not advanced that much in our science that we can do away with the spotters. As a matter of fact, we had a spotter training exercise in this county in April to teach people what to look for, to save their own lives," Dreumont said.

"We still need the human eye ... but the radar is doing a fantastic job. Fifteen minutes' lead time, 20 minutes' lead time -- that's become quite the average," he said.

"But this is like watching a pot of water boil. Where is that first boil going to occur?" he said. "We know it's going to boil, but we don't know where."

Jim Robinson, K5PNV

Webmaster

SKYWARN Texas

http://www.skywarn-texas.org