Irma is heading for Florida. We still don't know how bad it will be.

National Hurricane Center

One of the most powerful hurricanes on record continued steaming toward South Florida on Wednesday, with impacts to the state certain even if forecast tracks teeter to the east or west.

In an 11 a.m. discussion, National Hurricane Center forecasters said the latest model runs show Irma heading to north-northwest over the next two to three days toward Florida with a good amount of certainty. But where the storm heads after that still depends on where it is steered by a trough moving across the U.S.

The models have been shifting that turn east. But some reliable models also still track the storm slightly west, and forecasters warned the margin of error after four days remains at at least 175 miles.

“That’s why we say look at the cone. The center could be anywhere in that cone,” hurricane center spokesman Dennis Feltgen said. “South Florida and Central Florida will be impacted. We’re confident with that right now. What we’re not confident with is exactly where that center is going to go. But remember a hurricane is not a dot on the map. They’re large storms that cover a large area.”

In their 2 p.m. advisory, forecasters reported that sustained winds remain at 185 mph, with higher gusts, packing a record amount of wind energy in 24 hours and surpassing 1980’s Hurricane Allen. The storm was located 20 miles east, northeast of St. Thomas and 90 miles east of San Juan. A hurricane hunter plane that passed over the storm early Wednesday recorded winds reaching nearly 175 mph.

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National Hurricane Center

Over the next few hours, Irma will cross the Virgin Islands delivering fierce winds before slamming Puerto Rico this afternoon. Sustained winds have been reported at 106 mph on Buck Island. On Thursday, the hurricane is expected to first pass the Dominican Republic before nearing the Turks and Caicos and southeastern Bahamas later in the day.

Storm surge could reach as high as 20 feet in the Turks and Caicos. Rainfall is expected to reach between eight and 12 inches in the northern Leeward Islands and between four and 12 inches in the Virgin Islands and Puerto Rico, which is vulnerable to flash floods.

Hurricane warnings remain in effect for many of the Leeward Islands, along with the Virgin Islands, Puerto Rico and parts of the Dominican Republic and Haiti. Hurricane watches have been issued for parts of Cuba, from the Matanzas province to Guantanamo and the Central Bahamas. Tropical storm warnings also covered large parts of Hispaniola.

Hurricane center forecasters say Irma is the strongest storm ever recorded in the Atlantic, outside the Gulf of Mexico or Caribbean. It has also set a new all-time high for the amount of wind energy ever recorded over a 24-hour period, said Colorado State meteorologist Phil Klotzbach.

The Category 5 storm is expected to bring strong storm surges. Part of the Bahamas and Turks and Caicos is under a hurricane warning.

Overnight, Irma rolled across the northern end of the Leeward Islands, dealing a direct hit to St. Martin and Anguilla. A NOAA weather station on Barbuda reported a 155 mph gust and sustained winds of 118 mph before failing Wednesday morning, forecasters said. Early reports from the islands, including St. Martin, Barbuda and Barthelemy, included widespread flooding, with roofs ripped off and trees downed. St. Martin’s government headquarters was destroyed, the Associated Press reported.

There were no immediate reports of casualties, but Minister Annick Girardin said officials were fearful “for a certain number of our compatriots who unfortunately didn’t want to listen to the protection measures and go to more secure sites… We’re preparing for the worst.”

In South Florida, Irma’s pending arrival triggered mandatory evacuations in the Florida Keys, beginning today. To the north, Miami-Dade County Mayor Carlos Gimenez held off on evacuation orders at midday Wednesday, but warned they could still be issued. Broward county has asked residents along the coast, in low-lying areas and in mobile homes to leave. Schools will be closed Thursday and Friday, with courts statewide also closed Friday. Tolls across state highways were lifted yesterday as long lines began snaking out of gas stations and supplies including plywood and water, flew off the shelves.

To help with preparations, Gov. Rick Scott ordered another 900 National Guard members to duty on Wednesday. By Friday, all 7,000 of the state’s guardsmen will report to duty. Scott has said that no gas shortages have been reported, but the state is keeping watch on supplies and also tracking the availability of bottled water.

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National Hurricane Center

If Irma hits South Florida, it could deliver the first widespread damage to the region since Hurricane Wilma in 2005. Last year, the state’s 10-year streak without a hurricane ended when Hermine hit the state’s Big Bend. Matthew followed in late September, bouncing up the coast and carving a wide swath of erosion north of Daytona Beach.

Shortly after 8 AM ET Wednesday, NASA SPoRT tweeted "Saint-Martin and Anguilla appear to have taken a direct hit by cat 5 Hurricane #Irma." Hours before, video of Saint Martin showed water flowing through streets.

While Wednesday morning’s track shift to the right could be bad news for South Florida’s densely developed east coast, or good news depending on how far it moves, forecasters generally look for patterns in model runs, and avoid basing projections on a single run.

“I don’t like to get all excited about one run to the next run. I like to look at a lot of models over a lot of runs and look for trends and consistency,” said University of Miami hurricane researcher Brian McNoldy. “If you have a model that hops around from one run to the next to the next, it’s kind of like an eye-rolling moment. It shows it doesn’t really have a grasp on what’s happening.”

Florida could begin feeling tropical storm force winds late Friday or early Saturday, with hurricane conditions moving across the state over the weekend. With hurricane winds extending 50 miles from Irma’s center, and tropical winds reaching 185 miles, Irma is bound to deliver widespread impacts if it tracks across the state. On its current course, hurricane winds could be nearing the middle Keys in four days.

Forecasters are calling for Irma to remain a dangerous Cat 4 or 5 storm in the coming days, although it should begin to weaken slightly if it moves across the Florida peninsula.

And while it poses little threat so far, forecasters are also tracking Tropical Storm Jose, which neared hurricane strength Wednesday morning. In their 11 a.m. advisory, forecaster said the storm was located more than 1,100 miles east of the Lesser Antilles with sustained winds of 70 mph. The storm is moving west at 17 mph, with the early forecast track swinging it east of the islands.

Staff writer Kristen Clark and the Associated Press contributed to this story.

Follow Jenny Staletovich on Twitter @jenstaletovich

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