Down in Miami, near the southern tip of Florida, is the National Hurricane Center. Here, in a large room, filled with computer screens and television monitors, six hurricane specialists fill shifts around the clock, standing guard and watching the oceans between Africa and Hawaii.

This place is wired. Every 30 minutes, they receive new pictures from satellites orbiting the Earth. They are also part of a global network, called the World Meteorological Organization, which collects data and observations from meteorologists working around the world and makes it available for forecasting.

"We have computers, and we get new satellite pictures every half hour," says Dr. Lixion Avila. "If I see some suspicious cloud area, I say, okay, lets watch how this area will evolve. I can zoom into the area and gather more information. I can get higher resolution pictures, and I can run tests; and then I gather more satellites pictures and more observations."

Suspicious clouds, for Dr. Avila, may mean a thunderstorm, full of wind and rain, forming in the tropics. Any one of a hundred clues, such as the way the clouds are defined or the intensity of a thunderstorm, might hint that a weather system contains the seeds of a major tropical storm, according to Dr. Avila. Tropical oceans are breading grounds for hurricanes. The tropics receive a great deal of sunlight, which warms the oceans and causes air and moisture to rise. This rising air can generate fierce thunderstorms, which may grow into even larger storms.

Thunderstorms can band together and grow into a proto-hurricane known as a tropical depression. If the storm begins to spiral around a low pressure center, and the winds exceed 40 miles per hour, it is known as a tropical storm. If winds gust faster than 73 miles per hour, it becomes a hurricane. Each year, 60 odd hurricanes form over tropical oceans. Most never strike land, but the few that do can be deadly and cause an estimated five billion dollars in property damage each year in the United States. In 1992, Hurricane Andrew did $26 billion dollars in damage, and killed over 60 people.

If a major storm is developing, Dr. Avila can call out the Hurricane Hunters, an airforce unit based in Biloxi, Mississippi. The 53rd Weather Reconnaissance Squadron regularly flies into storms to obtain atmospheric measurements like wind speed, moisture levels, and pressure readings. They can also detect the center of the storm's low pressure system. This data is then transmitted to the meteorologists in Miami every 30 seconds and greatly increases their ability to predict when and where a storm might hit land.

"Our mission is to save lives and property," says Dr. Avila. Timely and accurate hurricane warnings can alert local emergency managers to begin the evacuations of coastal areas in the path of the storm. "When a hurricane is coming," he says, "they have to move people away from the coastline and the barrier islands. Nine out of ten people who are killed in hurricanes are killed by the storm surge."

The National Hurricane Center issues weather bulletins every six hours. Each bulletin contains a 72 hour forecast and can predict the behavior of a hurricane within 200 nautical miles. "Our forecasts are improving," says Dr. Avila. Fifty years ago, meteorologists could only issue 24 hour forecasts. And a decade ago, forecasts could be done only within 300 nautical miles. Someday soon, he says, an accurate five day forecast may become possible.


Although precise long-term forecasts remain beyond reach, the National Weather Service began issuing hurricane season predictions three years ago. They predict that the coming hurricane season, which runs from June 1 to November 30, 2000, is going to see "above average" hurricane activity. They estimate that there will be at least 11 tropical storms, of which seven will become hurricanes, and three or more will develop into major hurricanes.

How do they know?

"We take the pulse of the planet," says Dr. Ants Leetmaa, the director of the Climate Prediction Center in Camp Springs, Maryland, which produces the annual hurricane prediction. The center uses enormously powerful supercomputers to analyze millions of data points drawn from around the Earth.

"It's only in the last few years," says Dr. Jerry Bell, a research meteorologist at the Climate Prediction Center, "that we realized that there is a coherent global system of atmospheric patterns." One of the major keys to this system, he says, is rainfall in the tropics, which determines the atmospheric wind and pressure patterns for most of Africa, Asia, and the Americas, from Mexico to Brazil.

The break through came when meteorologists identified long-term weather patterns that have a profound and comprehensible influence on global climate. Long lasting shifts in water temperature of the Indian and Pacific oceans, known as El Niño and La Niña, for example, have a predictable influence on global rainfall, which in turn influences global wind patterns, which then creates conditions that give birth to hurricanes in the south Atlantic Ocean.

The ability to model these patterns of cause and effect has encouraged researchers to begin making long-term predictions about seasonal storm behavior. "This is a really big deal," says Dr. Bell, "for the first time we are beginning to understand how the atmosphere is structured. We've identified the factors that tie the larger global patterns together."

"We are refining our models now," says Dr. Bell, "trying to build accurate models that can lead to specific computer forecasts about local weather conditions that can be made months ahead. Five years ago, I could never have imagined we could say something about the Spring hurricane season, and now we are doing it with confidence."