Something is brewing up storm after storm in the Atlantic this autumn, and hurricane experts find themselves at a loss to explain what it is.

Like swallows that fly low before rain, high atmospheric winds sometimes behave in ways that signal stormy hurricane weather ahead.

And while hurricane forecasters use indicators "a little more sophisticated" than low-flying swallows, said Neil Frank, former head of Miami's National Hurricane Center, exact cause-and-effect relationships are notoriously hard to pin down.

Hurricane Roxanne, which sent tourists fleeing from southern Mexico last week, is the 17th named tropical storm this season--the most active year for Atlantic storms since 1933.

Colorado State University meteorologist William Gray predicted such a bonanza season last November. This August, he fine-tuned his estimate, warning that residents of the country's southern and eastern coasts would probably face nine hurricanes this year. Roxanne marks the 10th.

The flurry of storms this year has made this most recent one the first to get as far as the letter "R" in the official storm alphabet. Names are given to storms whenever their winds reach 39 m.p.h. It takes 75-m.p.h. winds to achieve hurricane status.

The hurricanes are back, said meteorologist Gray, not because something different happened this year, but largely because of what \o7 didn't \f7 happen.

That is, the extreme differences in wind speed, called wind sheer, that chop off the heads of potential hurricanes were noticeably absent over the Atlantic this year. So storms seeded in the rains of West Africa were carried unhindered over the ocean and allowed to grow to disastrous proportions.

A hurricane, said climate scientist Nick Graham of the Scripps Institute of Oceanography, is "just like a family. It needs an organized environment to live." The wind sheer slices the growing hurricane in half before it has the time to mature.

The phenomenon of "global warming" does not appear to be linked to the abundance of hurricanes.

But several other conditions are statistically correlated with hurricanes.

The absence of El Nino warming off the coast of Peru seems to be associated with the formation of hurricanes. So does wet weather over West Africa.

But all, Gray said, relate in some way to the winds. "That's the main ingredient."

Other meteorologists are not so sure there is such a cause-and-effect relationship.