For Release: May 10, 1996

Steve Roy
Office of Media Services
(205) 544-0034
steve.roy@msfc.nasa.gov

RELEASE: 96-35

NASA RESEARCH COULD LEAD TO FASTER SEVERE WEATHER ALERTS

Spring is universally regarded as a season of rebirth. But for many Nebraskans – terrified by tornadoes roaring across their landscape and by twisters screaming in Dolby Sound on the screens of mall cineplexes – spring is an edgy, even white-knuckled time of year.

But NASA scientists may someday be able to help take some of the edge off of Nebraska’s spring.

A satellite – already in orbit – is doing pioneering research that could lead to significantly earlier severe weather alerts, and even shave off crucial minutes for tornado warnings.

What could change chance to science is NASA's Optical Transient Detector, a dual package of optics and electronics, about the size of a two-pound can of coffee and a standard typewriter.

Developed, built and tested on a money-saving fast-track in less than eight months at NASA's Marshall Space Flight Center in Huntsville, Ala., both were squeezed aboard a Microlab satellite and launched by a Pegasus rocket in April 1995.

The information from that optical detector has taken even researchers by surprise.

Passing over a developing severe storm in Oklahoma that would spawn a number of tornadoes as it matured, the sensor detected more than 20 times as many lightning flashes than were spotted by ground-based detectors tracking the same storm.

As the orbiting lightning detector tracked that Oklahoma storm for three minutes, it saw the rate of cloud-to-cloud lightning flashes increase – then drop dramatically.

And, just a minute after the space-borne monitor completed its pass over the storm, ground observers spotted a funnel cloud spinning from it.

Yet when the detector passed over more mature or dissipating storms, it has not seen any similarly sudden decrease in lightning flashes. Nor has it sensed such a large number of lightning flashes between clouds.

Encouraged by this new information coming from the satellite, NASA scientists believe they have discovered a characteristic in the earliest stages of a developing thunderstorm that pinpoints where a tornado is forming.

"What we've found," says Dr. Timothy L. Miller, a NASA scientist and manager with the Global Hydrology and Climate Center in Huntsville, "is that while a storm is still growing – before it develops severe weather such as tornadoes – is when most lightning is occurring in clouds, and not seen from the ground."

That cloud-to-cloud lightning, says Miller, appears to signal the infant stage of violent weather that leads to the birth of tornadoes.

"The current lightning ground-detection network is not able to see all that cloud-to-cloud lightning activity," notes Miller. "For every lightning strike it detects from cloud to ground, there are 20 strikes in the clouds which it does not detect."

"We really don't have a fail-safe observing system to spot tornadoes today," Miller says. "We have lots of tools that show conditions are ripe for a severe storm. But the first warning we get of a tornado is when someone actually spots a funnel cloud – often a matter of luck – or an inconclusive signature is indicated on radar."

For weather forecasters, the new findings from the orbiting detector have great future significance. One day about a half-dozen satellites scanning the globe could spot the identifying characteristic of violent weather early in the formation of a storm, allowing critical additional time for forecasters to make predictions.

Precisely "locking" on an area where a tornado is about to occur, says Miller, "could mean several minutes of crucial additional warning time, or even an hour to those folks downstream of the event. Those are life-saving minutes in weather prediction that we don't have now."

Added to the present forecasting mix of satellite cloud images, radar and weather balloons, a collection of orbiting detectors’ instant snapshots of lightning could take some of the terror out of severe weather reports.

Says Miller: "There could be less crying wolf."

Today, the pioneering optical detector continues its orbit just 450 miles above Earth.

And the future? It's not too distant.

A Japanese rocket will carry a more sophisticated version of the detector – called the Lightning Imaging Sensor – aloft in 1997.

Miller, deputy chief of the Earth Systems Division of the Global climate center, says scientists are proposing that similar devices be placed aboard satellites in geo-stationary orbit.

Eventually, a group of satellites, typically placed 22,000 miles above Earth, could act like orbiting telescopes, searching the globe for storms, following their development, and enabling forecasters to recognize which storms could produce strong winds, damaging hail and even tornadoes.

"Sometime after the year 2000," predicts Miller cautiously, "forecasters in the field could be using data from the optical detector." Then, if the present research result holds up to comparison with other cases, no longer will forecasters "have to totally rely on the chance of observers spotting funnel clouds as we do now," says Miller. "The detector will greatly enhance identifying the development of severe storms."

And even more warning time will be gained when instantaneous information from the orbiting detectors are fed into forecasting computers. "Weather forecasters will be alerted," says Miller. "They'll know, ‘Something's going on there’."

Orbiting lightning detectors won't make severe weather forecasting 100 percent accurate, says Miller. "But we'll do a much better job of nailing down exactly where a severe storm or tornado is developing."

Note To Editors: Additional information and interviews with NASA lightning research scientists are available by contacting Steve Roy at (205) 544-0034. Also, images and motion sequences of lightning detector cloud and lightning observations are available via the World Wide Web at the following URL:

http//wwwghcc.msfc.nasa.gov:5678/otd.html