Hurricane Irma has begun to devastate the Leeward Islands of the Caribbean as one of the most intense Atlantic cyclones on record, but whether and where it reaches the United States mainland depends on its speed and interactions with two other weather systems.
Irma had maximum sustained winds of 185 mph — the equivalent of an EF-4 tornado — as the eye made its first landfall in the islands of the northeast Caribbean early today, passing over Barbuda around 1:47 a.m., the National Weather Service said.
Residents said over local radio that phone lines went down. Heavy rain and howling winds raked the neighboring island of Antigua, sending debris flying as people huddled in their homes or government shelters. Officials warned people to seek protection from Irma's "onslaught" in a statement that closed with: "May God protect us all."
Irma, which is churning along a path pointing to Puerto Rico, the Dominican Republic, Haiti and Cuba before possibly heading for Florida over the weekend, is the strongest Atlantic hurricane on record outside of the Gulf of Mexico or Caribbean Sea, according to the National Hurricane Center. Its intensity is on par with those of hurricanes Andrew, Katrina and Rita, and behind only Hurricane Allen in 1980, which had 190 mph winds.
The hurricane center called Irma "potentially catastrophic." Carlos Anselmi, a National Weather Service meteorologist in San Juan, Puerto Rico, said the U.S. territory has not seen a storm of Irma's magnitude in a century.
Phil Klotzbach, a meteorologist at Colorado State University, said, "The Leeward Islands are going to get destroyed."
"I just pray that this thing wobbles and misses them," he said. "This is a serious storm."
Forecasters expect Irma will continue to move northwestward toward the Bahamas and Cuba, and eventually Florida. Florida Gov. Rick Scott declared a state of emergency Monday and urged preparations for the worst. Evacuations from Miami Beach and the Keys were expected to begin Wednesday.
Predictions for where the storm might hit the U.S. mainland this weekend remain tentative. Models suggest landfall anywhere from Alabama on the Gulf of Mexico to the Carolinas on the Atlantic Coast.
An area of high pressure that covers the Atlantic from Bermuda to the Azores is expected to steer Irma. Such zones have clockwise circulation, so tropical systems are often pulled around them, up the coast.
If the so-called "Bermuda high" is expansive and strong, it could push Irma into the Gulf of Mexico or up the Atlantic coast, the Weather Channel noted.
A weaker Bermuda high could allow Irma to remain offshore as it curves around the pressure system and into colder Atlantic waters.
Irma could be blocked from moving into the Gulf by a separate system that could itself strengthen to a tropical storm in the coming days.
"That could kind of act as a wall," said Tom Kines, a senior meteorologist with AccuWeather.com.
The hurricane center estimates a 70 percent chance the low-pressure area over Mexico's Bay of Campeche will become Tropical Storm Katia in the next two days. Tropical Storm Jose formed in the middle of the Atlantic on Tuesday, and was expected to become a hurricane Thursday.
If Irma does make landfall in Florida, it likely wouldn't be until Sunday. The National Hurricane Center predicts it will remain a major hurricane until then, potentially making it just the second major storm to strike the U.S. in a dozen years. Hurricane Harvey was the first since Wilma in 2005.
"This hurricane has the potential to be a major event for the East Coast," said Evan Myers, AccuWeather's chief operating officer. "It also has the potential to significantly strain FEMA and other governmental resources occurring so quickly on the heels of Harvey."
Hurricane-force winds extend 60 miles out in all directions from Irma's 30-mile-wide eye, making it a large storm that threatens virtually all of Florida.
If Irma is going to reach Maryland and the Mid-Atlantic, that wouldn't be until some time around next Tuesday — a week away.
The Associated Press contributed to this article.