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Wanted for Test: A Tornado for Weather Forecasters

May 31, 1987|LEE DYE | Times Science Writer

BOULDER, Colo. — Modern computer technology has been wedded with sophisticated new tools to create a storm-warning system here that will tell meteorologists what the weather is doing far overhead at the very moment it is doing it.

It was created to give the earliest warning possible of explosive weather systems like the tornado that destroyed Saragosa, Tex., on May 22, killing at least 29 people and injuring more than 100 others.

The new system is still in the experimental stage at the National Oceanic and Atmospheric Administration's environmental research laboratories here, where chase crews are being sent out into the field in pursuit of foul weather to see if storms develop the way the data suggests.

The new tools include Doppler radar systems, called "profilers," pointed nearly straight up that give instantaneous readings of which way and how fast the wind is blowing at every elevation up to 50,000 feet over northeastern Colorado. That information, coupled with computer terminals that overlay data from various sources to provide sort of a motion picture of high-level weather patterns, gives researchers in Boulder the best chance they have ever had to predict storms.

Nationwide System Planned

And although the system is still being tested and is not yet operational, parts of it will be expanded into a nationwide system over the next few years, and the heart of this program will be extended to cover the entire Tornado Belt through the central United States, which is ripped by more than 800 tornadoes each year.

"There's no question we'll get a big improvement in our forecasting," said Sandy MacDonald, director of the program.

The system should allow forecasters to issue a warning at least 20 minutes before the tornado hits, giving residents more of an opportunity to take cover.

But even though the new system may be a giant leap forward in forecasting, success will still depend largely on the interpretation of the data by meteorologists who must find order in the chaotic weather patterns that can change dramatically in just a few minutes here, where the great Rocky Mountains plunge into the rich farmlands of eastern Colorado.

The best tools, MacDonald acknowledged, are no better than the men and women who use them.

"We've been doing this for almost 100 years, but it still comes down to a tough call," he said as he sat behind an array of computer consoles.

That was demonstrated last week when The Times accompanied a chase crew in hot pursuit of storms that looked beautiful to researchers, but threatening to anyone else.

Flush With Excitement

The people of Boulder had awakened one recent morning to an uncommonly beautiful day for a season normally marked by fierce thunderstorms and occasional tornadoes. A few clouds hovered over the Rockies to the west, and more could be seen over the plains to the east, but overhead the sun was in full command.

But as he twisted the dials of a series of computers inside his laboratory here, MacDonald was flush with excitement.

"The ingredients for good storms are here today," he said. It helps to remember that for a storm chaser, good weather is the kind of stuff that produces storms that send others running for cover.

MacDonald flipped one switch and a computer terminal turned into a movie screen, rapidly displaying satellite photos taken 30 minutes apart to re-create the past few hours, showing the movement of cloud systems over North America. He hit a switch and zoomed in to the area between Denver and the Wyoming border, and the clouds danced across the screen, showing that the winds above were anything but stable.

He hit another switch and the terminal displayed a series of short lines that looked a little like a badly worn, hand-woven rug. Each line on the screen represented the direction the wind was blowing at every elevation up to 50,000 feet. That "profiler" display was made possible by the newest tool in the program, Doppler radar antennas pointed nearly straight up. The profiler is one of two Doppler radar systems used in the program.

The Center for Atmospheric Research, a Boulder facility run by a consortium of 57 universities and research institutions, has experimented with Doppler radar of a more conventional sort for years. The Doppler effect, familiar to anyone who has listened to the change in pitch of a train whistle as it approaches and recedes, results from the change in the wavelength emitted by the moving object.

Sound waves from a moving train are compressed as the train approaches and stretched as the train recedes, thus altering the pitch. Radar waves do the same thing, and by measuring the change in wavelength, it is possible to determine if the object is moving closer or farther away, and how fast. The information is fed into a computer that measures the change and presents it automatically in a color-coded image of the area.

Measure of Moisture Content

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