- The Washington Times - Thursday, June 6, 2002

When Clay Stamp began his job as director of emergency services for Ocean City, Md., back in 1984, the main tools of his trade were a grease pencil, a compass, a tracking map and a ruler.
He still uses them, but these days, when bad summertime weather threatens, he's more likely to turn to his buddies Hurritrack and Hurrevac, two computer software programs that have revolutionized the world of hurricane prediction and tracking.
"With Hurritrack, you can download the entire [National Hurricane Center] forecast package when there's a hurricane out there and graphically represent it," Mr. Stamp says.
"And Hurrevac does the same thing for evacuation purposes. It shows you where storms are likely to hit land and what the various evacuation times from those points will be based on how big the storm is and how fast it's moving. It really helps us make decisions on what to tell the public and when."
The hurricane season, which runs from June 1 until the end of November, promises to be a busy one this year. Predictions call for a "normal to slightly above normal" level of activity in the Atlantic Ocean, with nine to 13 tropical storms though meteorologists say it's too early to know which specific areas of the Eastern United States will be hit.
One thing is clear: Grease pencils and compasses are no longer on the cutting edge.
Any casual observer of the local nightly newscasts probably has been able to see how powerfully technology has permeated weather forecasting. First there was radar. Then there was Doppler radar, a technique for measuring not just how far away a storm is, but also how fast it's traveling. Then came digital Doppler radar. Now local TV meteorologists can boast of their ability to tell you where thunderstorms are heading, often down to a particular street at a particular second.
Though many of us may grumble that all that technology still can't produce a dependable forecast for the next day, at places such as the National Hurricane Center in Miami and the Climate Prediction Center in Camp Springs both part of the National Oceanic and Atmospheric Administration's National Weather Service the experts swear by it.
"It's amazing the amount of technology we've increased just in the last five years," says Gerry Bell, a meteorologist with the Climate Prediction Center. "It's vastly improved our ability to analyze data and diagnose the climate and all the improved understanding that goes with that. We wouldn't be able to make any long-range predictions without it."

Hurricanes form when three factors are present: warm, humid ocean air; converging winds (winds moving in different directions) at the ocean surface; and a significant difference in air pressure between the ocean surface and high altitude.
Atlantic hurricanes start, usually off the African coast, when warm air from the ocean surface rises to condense and form storm clouds at higher altitudes. The condensation releases heat, which continues to rise as it is replaced by warm air coming from the ocean surface. The heat exchange creates a circular wind pattern (aided by the Earth's rotation) that strengthens as the high- pressure air up high sucks it away from the ocean surface and into the low-pressure storm center. The eye of a hurricane contains the lowest air pressure in the entire storm.
The key to any hurricane's strength, or whether it even forms in the first place, is what meteorologists call "vertical shear," the difference in speed between winds closer to the ocean surface and those 30,000 to 40,000 feet above sea level. If the vertical shear is weak; that is, if the wind speeds are similar, the hurricane can gain ferocious strength quickly, which is what happened to Andrew in 1992.
If the shear is strong, meaning the wind is much greater at one level than another, the storm will rip itself apart before it gains hurricane strength.
"Hurricanes organize vertically, like in a chimney," says Stan Goldenberg, a meteorologist with the Hurricane Research Division in Miami. "It's like if you stand up straight and someone pushes you at your knees and someone else pushes you at your shoulders. If the difference isn't very great, you might lean over a bit, but as soon as they let go, you can straighten up again. If the shear is too strong, it will push the hurricane over, and the hurricane will rip apart and never develop."
Every year since 1998, the National Oceanic and Atmospheric Administration has put out a seasonal hurricane prediction sometime in May, saying how many tropical storms and hurricanes it expects for the upcoming hurricane season, which runs from June through November.
Mr. Bell, who wrote the hurricane outlook report for NOAA this year, says that of the nine to 13 tropical storms NOAA is predicting for the Atlantic this season, it expects six to eight hurricanes. Two or three of those hurricanes are expected to be classified as "major" (category 3 or higher on the Saffir-Simpson Hurricane Scale, on which 1 is the lowest and 5 is the highest and most dangerous).
That prediction is just a starting point, however, Mr. Goldenberg notes. In May and June, meteorologists can see just the most general picture of the season. The view will be updated, he says, sometime in July before the real "meat" of the hurricane season arrives in August.
How can meteorologists make such educated guesses about something as unpredictable as the weather? Increased knowledge and technology, much of it having come about in just the past few years, is the key.
In a press release last month announcing the predictions, NOAA Administrator Conrad C. Lautenbacher Jr. credited improved technology with his organization's ability to predict hurricane activity so precisely.
"Better data from NOAA's environmental satellites, better models, the latest supercomputers and an improved ability to monitor and understand global climate patterns are helping to create better long-term and short-term forecasts," he said.
Mr. Bell says numerous factors go into making NOAA's annual predictions, which are written with the cooperation of the Climate Prediction Center, the National Hurricane Center and the Hurricane Research Division in Miami. The two main factors, he says, are the El Nino/La Nina cycle and what he calls the "global decadal cycle."
"We've known for quite some time that strong El Ninos tend to produce a fairly inactive season and La Ninas favor more activity," he says, referring to the large-scale warming and cooling phenomena in the Pacific Ocean that affect jet streams and other aspects of global weather. Mr. Bell says El Nino conditions are weak this year and shouldn't affect hurricane activity.
As for decadal cycles, he says, "Decadal cycles are things we notice that stay fairly constant for decades, like temperature in the Atlantic, atmospheric wind across the Atlantic, vertical wind shear, those things. In the 1950s and '60s, we had very active hurricane seasons, and from 1970 to 1994 we were very inactive.
"But we've been very active since 1995, and you just don't get low activity for no reason. There are very strong climate signals, and we're back to being in a set of conditions conducive to hurricanes. And we've been that way since 1995. As a result, there's been only one year since 1995 that has not been above normal for hurricane activity."
Mr. Goldenberg says one way to picture the prediction process is to imagine weather experts assigning point values to factors that could affect hurricane activity positively or negatively, then adding them up. For instance, the decadal signals are in an "enhanced period," conducive to hurricanes. "That's a plus factor," he says.
A strong El Nino could subtract points from hurricane probability, but because El Nino conditions are weak this year, he says that would be worth zero points. A strong La Nina effect, such as was the case in hurricane-intensive 1998 and 1999, could add even more points to the forecast.
Adding all the factors, he says, leads experts to make the call this year for normal to above-normal hurricane activity.
Mr. Bell says improved satellite technology has helped meteorologists measure changes in decadal cycles, and a more sophisticated system of weather buoys in the Pacific has helped them track El Nino and La Nina more carefully and accurately.
"Satellites are the biggie," he says. "We use satellites to see climate patterns change in places like tropical rainfall. Tropical rainfall is a big predictor in changes in decadal patterns, and that's absolutely a key in making long-range or short-range predictions."
Mr. Bell says meteorologists don't rely just on current and recent information to make their annual hurricane predictions. NOAA has global atmospheric conditions archived as far back as 1949, but until recently, it lacked the computer ability to analyze all that data. Technology has helped in that area, too. With today's bigger and faster supercomputers, NOAA has been able to analyze the historical record and see how global conditions affected the hurricane seasons over the years.
As a result, he says, NOAA has more than 50 years of data behind it when it makes its annual predictions, which is why he is able to say, with a certain degree of satisfaction, "We've been doing this since 1998, and we haven't missed yet."

Hurricane prediction has become more and more crucial in the past few years, as more and more people have moved to coastal areas or bought rental property there. NOAA's Coastal and Marine Management program estimates that one-fourth of the U.S. population lives in the 285 coastal counties along the Atlantic seaboard from Maine to Florida.
Mr. Stamp says those residents and the millions of vacationers who visit coastal areas during the summer will benefit from NOAA's increased prediction abilities.
"It used to be you couldn't really make long-range forecasts past 48 hours," he says. "Hurricanes and storms could go left or right, forward or backward, they could shrink; you just didn't know. Now we're toying with being able to go to a seven-day forecast with a much lower margin of error.
Mike Black, the field program director for the Hurricane Research Division of NOAA in Miami, says that despite the advances in technology and forecasting, there is still much meteorologists don't know about hurricanes. But he and his colleagues continue to learn more every day.
He talks of inventions such as the SFMR (for Steps Frequency Microwave Radiometer), which weather planes use to measure the brightness of the ocean at the center of a hurricane; and of a program called C-BLAST (for Coupled Boundary Layer Air-Sea Transfer), which should help scientists determine what goes on at the ocean surface in a hurricane. All of it is cutting-edge technology that will help meteorologists unlock more hurricane secrets.
"Hurricanes remain one of nature's mysteries," Mr. Black says. "We don't know how they form. We think we know what moves them along, but even there, we still have a long way to go. We certainly don't have a good idea of how strong they're going to be, although we can usually anticipate when they're going to weaken rapidly. But we're making progress all the time."

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