Does dry month of May mean hurricanes heading toward Florida?

Jun 10, 2008

South Florida Sun-Sentinel--June 9, 2008

South Florida Sun-Sentinel

It can bedevil or bless us.

Depending on its strength and location, the Bermuda High, an expanse of high pressure over the Atlantic, is one of the major atmospheric factors that can steer tropical systems toward South Florida or push them away.

What will the system do during the peak of this season, in August, September and October?

No one can say because where and how robust it will be cannot be predicted this far out, senior hurricane specialist James Franklin, of the National Hurricane Center in Miami-Dade County, said Monday.

“You can’t predict the location of that feature more than a week or so in advance,” he said. “So most of us folks here at the Hurricane Center don’t spend much time worrying about it.”

As of this week, the Bermuda High was centered in the North Atlantic, a position that normally would allow storm systems to skirt it and move north, avoiding Florida.

But the pressure ridge, so named because it is generally centered over the small island of Bermuda in the Western Atlantic, is constantly changing its position and influence, experts say.

Last year, the system was largely responsible for keeping Hurricanes Dean and Felix south of Florida. Both became Category 5 storms in the Caribbean.

In 2004, it pushed Hurricanes Charley, Frances, Jeanne and Ivan in this general direction, making for a horrific year in Florida.

“People want hints as to what it will do,” Franklin said. “But this is just one of those things where we can’t say.”

One seasoned weather specialist, Jim Lushine, a retired meteorologist for the National Weather Service in Miami, thinks an abnormally dry May is a harbinger of a rough storm season in South Florida — and he bases that on the Bermuda High.

Although many tropical meteorologists say there is no real connection between May rains and the subsequent storm season, Lushine concludes that if little rain falls during May of any given year, the chance of a hurricane hitting this region increases by about 60 percent.

Because 1.71 inches of rain fell in Miami last month, almost 4 inches below normal, Lushine said, “It would not surprise me if we had something to worry about in August or September.”

Lushine, of Pembroke Pines, bases his theory on this: When the Bermuda High is strong in May, it prevents weather fronts, and thus rain, from reaching this region.

Then, for reasons that are still mysterious, the strong pressure tends to resurface in August and September, he said. If so, the Bermuda High would help channel hurricanes that form in the Atlantic onto a westerly track toward us.

That happened in 1992, when Hurricane Andrew ripped through Miami-Dade County, as well as in 1965, when Hurricane Betsy hit South Florida and the Keys.

But Lushine’s hypothesis is far from universally accepted.

Meteorologist Robert Molleda, who succeeded him at the National Weather Service’s Miami office, doesn’t agree that “a dry May equals a South Florida hurricane.” For instance, below-average rains fell in 1993, 1994, 1995, 1998 and 2000, all years in which South Florida escaped hurricanes, he said.

“Looking at the data, the correlation isn’t really that strong,” Molleda said.