The record-setting 2004 Atlantic hurricane season has almost two more months to churn up trouble, but it already reminds veteran tropical storm predictor James J. O'Brien of the Wild West.

"It was like ducking bullets from all directions," said O'Brien, director of the Center for Ocean-Atmosphere Prediction Studies at Florida State University in Tallahassee. "The thing that impresses me is that four hurricanes missed me." Tallahassee, located in the state's panhandle, so far has escaped largely unscathed.

If O'Brien and other hurricane forecasters are right, there will be an unusual number of meteorological bullets like Charley, Ivan, Jeanne and Frances to duck in the future.

They believe that the world has shifted into a cycle of increased hurricane activity that may last more than 20 years.

Authorities are still adding up the damage, but 2004 already may be the costliest hurricane season in U.S. history, claiming more than 130 lives and causing billions in property damage. Jeanne alone killed at least 1,500 people on Haiti, and more than 1,000 others remain missing.

"We are a decade into the active phase of a natural 60-year or so cycle of hurricane activity," said Dr. Hugh E. Willoughby, of the International Hurricane Research Center in Miami. "This season is active, but not dramatically more so than others since 1995."

The last cycle of intense hurricane activity ran from about 1910-1960, peaking from the 1930s through the 1950s. The inactive phase that followed ended in 1995.

Since 1995, the National Oceanic and Atmospheric Administration hurricane index has averaged 139.6, about 50 percent above the 54-year average of 93.2 from 1950 through 2003. The increase occurred despite low indexes in 1997 and 2002. In those years, El Nino events occurred, an unusual warming of the ocean surface off the western coast of South America that suppress hurricane activity.

The increased activity since 1995 is due to an immense flow of Atlantic Ocean water, equal to about 100 Amazon Rivers, which controls the hurricane cycle. The flow is produced by differences in the density of seawater, which depends on temperature [thermal] and saltiness or salinity [haline].

Called the Atlantic "thermohaline" circulation, it transports warm, salty water to the North, where the water cools and sinks into the deep ocean. That water then flows southward, and when there's a lot of it, the circulation system speeds up and spawns more hurricanes.

Most Atlantic hurricanes begin as thunderstorms off the west coast of Africa. The storms move west and intensify as they pick up energy from warm, tropical ocean waters. In a complicated chain of cause-and-effect, a slower thermohaline circulation affects wind patterns in ways that suppress hurricanes. Faster circulation causes winds that favor the formation of more hurricanes.

"That's the pattern we're in now," said Willoughby.