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Hurricane Irma intensifies to Category 4

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A Growing Threat for U.S.; Hurricane Warnings Issued for Leeward Islands, Hurricane Watch Hoisted in Puerto Rico

From the Weather Channel

Irma has strengthened to a Category 4 hurricane, and additional strengthening is forecast during the next day or two.

Hurricane warnings have been issued for portions of the Leeward Islands, and a hurricane watch is in effect for Puerto Rico and the Virgin Islands.

Irma will move close to the Leeward Islands and Puerto Rico into midweek, and then near Hispaniola, the Turks and Caicos, Cuba and the Bahamas late week into this weekend.

This weekend into early next week, Irma will turn north and likely impact a portion of the U.S. coastline.

It's too soon to know exactly what impacts to expect in the U.S. and where they will occur, but the chances of Irma impacting Florida are increasing.

Hurricane Irma is a growing threat to the continental United States, with impacts possibly beginning in Florida later this week. Before that, Irma will bring dangerous conditions to the Leeward Islands, Puerto Rico, Hispaniola, the Bahamas and Cuba.

Below is everything we know about Irma right now, including its latest status, along with potential forecast impacts in the U.S. and the Caribbean Islands.

Irma's Latest Status, Timing

The center of Irma is located about 450 miles east of the Leeward Islands and is moving westward at about 13 mph.

Irma has strengthened to a Category 4 hurricane, and satellite imagery shows that it has become better organized in the past day with an eye now clearly evident. Additional strengthening is forecast during the next 48 hours.

Low wind shear, increased mid-level moisture and ample oceanic-heat content favor that Irma will remain a major hurricane (Category 3 or stronger) for the next several days, though some intensity fluctuations are likely at times.

(LATEST NEWS: Florida Governor Declares State of Emergency Ahead of Possible Hurricane Irma Strike)

One potential inhibitor of Irma maintaining its intensity would be if the hurricane's core interacts with land as it cruises westward near the Greater Antilles later this week.

Current Storm Status

The highest cloud tops, corresponding to the most vigorous convection, are shown in the brightest red colors. Clustering, deep convection around the center is a sign of a healthy tropical cyclone.

Hurricane warnings have been issued for portions of the Leeward Islands. This includes Antigua, Barbuda, Anguilla, Montserrat, St. Kitts, Nevis, Saba, St. Eustatius, Sint Maarten, St. Martin and St. Barthelemy.

A hurricane watch is in effect for Puerto Rico, Vieques, Culebra, the Virgin Islands and Guadeloupe.

In addition, a tropical storm warning has been issued for Guadeloupe, and a tropical storm watch is in effect for Dominica.

Watches and Warnings

A watch means hurricane or tropical storm conditions are possible within 48 hours. A warning means those conditions are expected within 36 hours.

For the next five days, Irma will move west, then west-northwest on the south side of a ridge of high pressure called the Bermuda high, centered in the central Atlantic.

(INTERACTIVE MAP: Track Irma)

By this weekend, Irma will begin to turn north in the direction of a departing southward dip in the jet stream that will set up in the eastern United States. Where that northward turn occurs will be critical for what impacts Irma may bring to parts of the southeastern United States.

Here's a general overview of the timing for impacts from Irma into this weekend.

Potential Impact Timing

Leeward Islands: Late Tuesday-Wednesday

Puerto Rico/Virgin Islands: Wednesday-Thursday

Dominican Republic/Haiti: Thursday-Friday

Turks and Caicos: Thursday-Friday

Bahamas: Friday-this weekend

Cuba: Friday-this weekend

Southeast United States: This weekend into early next week (possibly as early as Friday in South Florida)

Projected Path

The red-shaded area denotes the potential path of the center of the tropical cyclone. Note that impacts (particularly heavy rain, high surf, coastal flooding) with any tropical cyclone may spread beyond its forecast path.

U.S. Forecast: Watching Florida, Southeast Closely

It is too soon to speculate on the specifics surrounding the U.S. threat from Irma, but the hurricane is forecast to remain powerful as it draws closer to Florida later this week.

As mentioned before, the vast majority of the forecast guidance indicates Irma will begin to turn more to the north by this weekend. The strength and expansiveness of the Bermuda-Azores high over the Atlantic Ocean and the timing, depth and location of a southward dip in the jet stream near the eastern U.S. will dictate where that northward turn occurs.

(MORE: Why the U.S. Forecast is Uncertain)

For now, all residents along the Southeast coast and eastern Gulf Coast, including Florida, Georgia and the Carolinas, should monitor the progress of Irma closely.

The National Hurricane Center (NHC) said in its advisory late Monday afternoon that the chances of Irma affecting parts of Florida later this week or this weekend are increasing. In addition, rough surf and dangerous boating conditions will exist throughout the southeastern U.S. coastline by late week.

Destructive winds, storm-surge inundation, pounding surf and heavy rainfall could all be potential threats from Irma in the southeast U.S. Determining where those impacts will occur and how serious they may be is too early to determine.

Irma's Steering Late Week

No matter what the future holds for Irma's path and intensity, the NHC advises, "Everyone in hurricane-prone areas should ensure that they have their hurricane plan in place, as we are now near the peak of the season."

Forecast: Leeward Islands, Puerto Rico, Hispaniola, Cuba, Bahamas

Leeward Islands

Irma is expected to make its closest pass to the Leeward Islands late Tuesday through Wednesday and will likely be an intense hurricane at that time, possibly still a Category 4.

Hurricane-force winds (74-plus mph) are expected within the hurricane warning area of the Leeward Islands by Tuesday night, and tropical-storm-force winds (39-plus mph) are expected by late Tuesday.

Preparations should be rushed to completion in the Leeward Islands at this time.

The exact strength of the winds will be dependent on the path of Irma's circulation center near the Leeward Islands.

Major wind damage can be expected if the eyewall of Irma cruises through the Leeward Islands, including Saint Martin and Anguilla. Storm-surge flooding, high surf and rip currents will also be dangers, and heavy rain could contribute to flooding and mudslides, as well.

The NHC says that a storm surge of 6 to 9 feet above normal tide levels is possible in the extreme northern Leeward Islands near and north of where the center tracks.

Rainfall totals in the Leeward Islands may total 3 to 6 inches, with locally 10 inches in spots.

Tropical-Storm-Force Wind Probabilities

The shaded colors represent the probability of any one location experiencing tropical-storm-force winds from Irma in the next five days.

Puerto Rico and the Virgin Islands

Once again, the exact path of Irma's center will determine the strength of the winds and any storm-surge impacts in Puerto Rico and the Virgin Islands starting Wednesday.

Hurricane-force winds (74-plus mph) are possible in the hurricane watch area by late Wednesday, with tropical-storm-force winds (39-plus mph) possible earlier in the day.

High surf and dangerous rip currents will be impacts no matter where the center of Irma tracks in relation to the islands.

The NHC says that a storm surge of 4 to 6 feet above normal tide levels is possible in the Virgin Islands, except St. Croix.

Additionally, a storm surge of 2 to 4 feet is possible along the northern coast of Puerto Rico, along with a storm surge of 1 to 2 feet along the southern coast of Puerto Rico and St. Croix.

Heavy rain bands are also likely to affect Puerto Rico and the Virgin Islands, which may result in flooding and mudslides.

Rainfall Forecast Through Thursday

Localized higher amounts are possible.

Hispaniola, Turks and Caicos, Bahamas and Cuba

Irma could pass near Hispaniola, the Turks and Caicos, the Bahamas and Cuba late this week into the weekend as a major hurricane.

Residents and visitors in these areas should continue to monitor the progress of Irma and make preparations for a possible direct strike.

It's too early to determine the extent of any impacts at this time. Follow the advice of local officials in the days ahead for instruction.

(MORE: Beware 'I' Hurricanes)

Check back with weather.com for updates on Irma through the week ahead for the very latest. We will be updating our coverage of Irma frequently based on the latest forecast guidance for its future track and intensity.

This is the first time the name Irma has been used for an Atlantic tropical storm or hurricane. Irma replaced the name Irene after it was retired for the damage it caused in the Bahamas and the U.S. during the 2011 hurricane season.

Hurricane Irma, The Weather Channel

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