With the hurricane season starting today, can South Florida expect a return of the high-pressure ridge that steered all those storms away last year?

Maybe, but don't count on it, forecasters say.

"These weather patterns are very transient," Robert Molleda, warning coordination meteorologist for the National Weather Service's Miami office, told a monthly meeting of emergency managers Tuesday at the Palm Beach County Emergency Operations Center.

"And all you need is one small break in a prevailing pattern that could mean something totally different," Molleda said.

The area of high pressure is often called the "Bermuda High" because, for most of the summer, it's centered over the island chain.

Over the course of the season, parts of its eastern or western edges soften, allowing tropical systems to slide around them and turn north. Or the high pressure allows systems to strengthen and steers them west.

If the mass is stronger to the east, storms make their big northward arc harmlessly at sea.

If the mass is positioned farther west, storms still turn. But instead of doing so in the Atlantic, they might do it somewhere over Lake Okeechobee .

"Last year, during the meat of the season, it was east," Frank Marks, director of the National Oceanic and Atmospheric Administration's Hurricane Research Division, said Tuesday. "In '04-'05, during the meat of the season it was west."

And, he said, "seasonally, we don't know why some years it sets up strong to the west. We know even during a season it can switch. Early last year, it was farther to the east. As we got into the summer, it slid west."

The fortunate part for Florida was that at the height of the season, in August and September, an "alley" opened between the high-pressure system and a trough of low pressure over the western part of North America. That steered the great midsummer monsters north and kept them offshore.

One was Earl, which put a scare into the East Coast in early September and ended up ripping through far eastern Canada.

If there had been a 200-mile shift in the high-pressure system, National Hurricane Center spokesman Dennis Feltgen said, "most of the (U.S.) East Coast would have been devastated."

Marks said the high-pressure system is " a little west. Just a little." That would be bad for Florida. But, he said, "in the next month or two, it could move to the east again."