Hurricane Isabel intensified into a rare and dreaded Category 5 monster last night, packing winds of 160 mph, and continued lumbering west across the Atlantic toward the U.S. mainland.
Although the National Hurricane Center nudged its projected long-range track to the northwest, on a course that would take Isabel north of South Florida, forecasters say that prediction remains tentative. They advised residents to assume the system could easily threaten the region next week.
"So many things can happen in five- to seven days, nobody should be letting their guard down at this point, especially considering this is a very powerful hurricane," said center meteorologist Steve Letro.
If the long-range forecast holds true, Isabel will be well east of the Bahamas on Tuesday on a path toward North Florida or even the Mid-Atlantic states.
However a five-day forecast has an average error of 430 miles on either side of a projected path, meaning the system could arrive on the Florida coast by Wednesday or Thursday.
"Unfortunately, we have little skill in predicting the evolution of steering features at these long ranges," said hurricane specialist Richard Pasch.
"It is still impossible to state with any confidence whether a specific area along the U.S. coast will be impacted by Isabel."
Late yesterday, Isabel was about 450 miles east of the Leeward Islands, or about 1,400 miles from Miami, heading west at 9 mph.
It was expected to maintain Category 5 intensity, with winds of at least 156 mph, for a day or two, then weaken slightly to about 132 mph, which would still be a dangerous Category 4.
Because Isabel's winds and clouds extend hundreds of miles from its core, for the next few days the storm still is expected to generate large ocean swells and dangerous surf conditions in Puerto Rico and the northern Leeward Islands.
Isabel is the first Category 5 hurricane in the Atlantic basin since Hurricane Mitch in 1998. That storm downgraded to a Category 1 by the time it hit Central America, but still was one of the deadliest, killing more than 10,000 people.
Only three Category 5 storms have hit the U.S. coastline, including Andrew, which hit south Miami-Dade County, Fla., in 1992; Camille, which hit Mississippi and Louisiana in 1969, and the Labor Day hurricane of 1935, which hit the Florida Keys.
Letro said a northwest trend is projected because a high-pressure ridge north of Isabel, holding it on a westerly path, is expected to weaken in five to seven days.
"The eventual path of the storm will depend to a large extent on how much that ridge continues to weaken," he said.
The South Florida Sun-Sentinel is a Tribune Publishing newspaper.