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Behind the science of tracking storms

The National Oceanic and Atmospheric Administration’s “hurricane hunters” are on the case for Katrina, on the front lines attempting to gain a better understanding of severe storms.

The federal government’s “hurricane hunters” closed the book on Hurricane Katrina on Monday after days of monitoring the monster storm — and breathed a sigh of relief when they saw that New Orleans was spared the heaviest blow.

"That storm wasn't anything you'd wish on your worst enemy," said Capt. Steve Kozak, commanding officer of the National Oceanic and Atmospheric Administration's Aircraft Operations Center at MacDill Air Force Base in Florida.

After Kozak touched down from NOAA's last monitoring flight of the day, he voiced relief that the storm grew less intense as it made landfall. But there was also some "bad news," he said: The airborne observation teams measured hurricane-force winds at surprising distances from the center of the storm.

It's all in a week's work for the weather-watchers who get closest to the hurricane.

In cooperation with NASA and the U.S. Air Force, NOAA's teams supplement satellite imagery and ground radar readings by flying instrument-laden airplanes into the hurricane.

NOAA has outfitted two WP-3D Orion turboprop planes, nicknamed Kermit and Miss Piggy in a tribute to the Muppet characters, with instruments to measure wind speed, barometric pressure and other readings at the center of the storm.

One of the instruments is a stepped-frequency microwave radiometer, or "Smurf," that can peer through the storm to make crucial measurements of wind speeds at the surface, 10,000 feet (3 kilometers) below.

"The instrument picks up disturbances on the surface of the ocean" and translates those data into wind speeds, Kozak explained.

NOAA also has Gulfstream 4 jets that fly around the periphery of the storm and send out capsules known as “dropsondes” to harvest real-time data.

Since 1996, the NOAA has dropped dozens of these parachute-equipped instrument capsules, about the size of a thick rolled-up newspaper, into the heart of each hurricane. The capsules contain sensors to monitor pressure, temperature and humidity, plus a GPS locator device and a radio transmitter.

Kozak said the hunters have been well-trained to handle huge storms, going back to Hurricane Andrew's devastating pass over south Florida in 1992. He voiced concern about the people whose homes and businesses lay within Katrina's path, but he said the airborne crews should be relatively safe.

"It is 10 times better in the air than on the ground," he said.

Computers crunch the numbers
The readings from the NOAA instruments are radioed back to the National Hurricane Center in Miami, where they are combined with data from other sources, then fed into the National Weather Service's modeling software. The computer models create a picture of the storm as it is — and as it's likely to be in the coming hours and days.

Reading the data can be extremely complicated. As with most chaotic systems, a small change in a variable can mushroom into a huge difference in the result. That's what makes hurricane forecasting an inexact science.

Some scientists are looking beyond the issue of tracking hurricanes, focusing instead on what makes a hurricane tick. For example, the Tropical Rainfall Measuring Mission provides satellite-based "CAT scans" of severe storms.

One of the key questions has to do with what happens to a hurricane once it makes landfall.

"There is a misconception," said Josh Wurman, lead scientist for the Colorado-based Center for Severe Weather Research. "The winds that are advertised for the storm over water are never going to be sustained over land."

Wurman said that appeared to be the case with Katrina, based on his reading of the wind-speed reports. However, his research group also has found that hurricanes can whip up "windstreaks," gusts of super-strong wind that may not be reflected in the weather reports but are responsible for the most serious damage.

Understanding future storms
As Katrina came ashore, the storm was monitored from instrument-laden towers spread across the Louisiana and the Mississippi coastline, put up by the Florida Coastal Monitoring Program. Wurman said such monitoring projects provide the "ground truth" to fine-tune the scientific profile of a hurricane — an endeavor that could save lives in future storms.

And during hurricane season, the next storm often seems to be just around the corner. NOAA's Kozak said he and his fellow hurricane hunters would take a day off, but then get back to work.

"There are a couple more disturbances out there," he told "Chances are, by this weekend, we'll be at it again. ... No rest for the weary."