Category 4 Hurricane Irma Strengthens; 11pm Advisory 9/4/17

From The National Hurricane Center:

...HURRICANE WARNINGS ISSUED FOR PUERTO RICO AND THE VIRGIN ISLANDS...

SUMMARY OF 1100 PM AST...0300 UTC...

INFORMATION -----------------------------------------------

LOCATION...16.7N 55.6W ABOUT 410 MI...660 KM E OF THE LEEWARD ISLANDS MAXIMUM SUSTAINED WINDS...140 MPH...220 KM/H PRESENT MOVEMENT...W OR 270 DEGREES AT 13 MPH...20 KM/H

MINIMUM CENTRAL PRESSURE...943 MB...27.85 INCHES

WARNINGS -------------------- CHANGES WITH THIS ADVISORY: The Hurricane Watch for the U.S. Virgin Islands, Puerto Rico, Vieques, and Culebra has been changed to a Hurricane Warning. The government of Antigua has changed the Hurricane Watch for the British Virgin Islands to a Hurricane Warning.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Hurricane Warning is in effect for... * Antigua, Barbuda, Anguilla, Montserrat, St. Kitts, and Nevis * Saba, St. Eustatius, and Sint Maarten * Saint Martin and Saint Barthelemy * British Virgin Islands * U.S. Virgin Islands * Puerto Rico, Vieques, and Culebra A Hurricane Watch is in effect for... * Guadeloupe

A Tropical Storm Warning is in effect for... * Guadeloupe

A Tropical Storm Watch is in effect for... * Dominica

A Hurricane Warning means that hurricane conditions are expected somewhere within the warning area.  A warning is typically issued 36 hours before the anticipated first occurrence of tropical-storm- force winds, conditions that make outside preparations difficult or dangerous.  Preparations to protect life and property should be rushed to completion.

A Hurricane Watch means that hurricane conditions are possible within the watch area.  A watch is typically issued 48 hours before the anticipated first occurrence of tropical-storm-force winds, conditions that make outside preparations difficult or dangerous.

A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area within 36 hours.

A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours.

Interests in the Dominican Republic, Haiti, the Turks and Caicos Islands, Cuba, and the southeastern and central Bahamas should monitor the progress of Irma. For storm information specific to your area in the United States, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office. For storm information specific to your area outside the United States, please monitor products issued by your national meteorological service.

DISCUSSION AND 48-HOUR OUTLOOK ------------------------------

At 1100 PM AST (0300 UTC), the eye of Hurricane Irma was located by an Air Force Hurricane Hunter aircraft near latitude 16.7 North, longitude 55.6 West.  Irma is moving toward the west near 13 mph (20 km/h) and this general motion is expected to continue into Tuesday, followed by a turn toward the west-northwest late Tuesday.  On the forecast track, the center of Irma will move near or over portions of the northern Leeward Islands Tuesday night and early Wednesday. Maximum sustained winds are near 140 mph (220 km/h) with higher gusts.  Irma is a category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale.  Additional strengthening is forecast during the next 48 hours. Hurricane-force winds extend outward up to 45 miles (75 km) from the center and tropical-storm-force winds extend outward up to 140 miles (220 km). The minimum central pressure estimated from Hurricane Hunter observations is 943 mb (27.85 inches).

HAZARDS AFFECTING LAND ----------------------

STORM SURGE:  The combination of a dangerous storm surge and large breaking waves will raise water levels by as much as 6 to 9 feet above normal tide levels along the coasts of the extreme northern Leeward Islands within the hurricane warning area near and to the north of the center of Irma.  Near the coast, the surge will be accompanied by large and destructive waves. The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline.  The water is expected to reach the following heights above ground if the peak surge occurs at the time of high tide... British and U.S. Virgin Islands except St. Croix...4 to 6 ft Northern coast of Puerto Rico...2 to 4 ft Southern coast of Puerto Rico and St. Croix...1 to 2 ft The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large and destructive waves.  Surge-related flooding depends on the relative timing of the surge and the tidal cycle, and can vary greatly over short distances.  For information specific to your area, please see products issued by your local National Weather Service forecast office.

WIND:  Hurricane conditions are expected within the hurricane warning area by Tuesday night, with tropical storm conditions expected by late Tuesday.  Hurricane conditions are possible within the hurricane watch area in the Virgin Islands and Puerto Rico by late Wednesday, with tropical storm conditions possible by early Wednesday.  Tropical Storm conditions are expected within the tropical storm warning area by late Tuesday.

RAINFALL:  Irma is expected to produce total rainfall accumulations of 3 to 6 inches with isolated maximum amounts of 10 inches across the northern Leeward Islands, the British and U.S. Virgin Islands, and Puerto Rico.  These rainfall amounts may cause life-threatening flash floods and mudslides. SURF:  Swells generated by Irma will affect the northern Leeward Islands, Puerto Rico, and the U.S. and British Virgin Islands during the next several days.  These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.  

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Forecast track through Saturday