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Hurricane Irma Special Advisory Number 25
NWS National Hurricane Center Miami FL AL112017
800 AM AST Tue Sep 05 2017
...IRMA BECOMES AN EXTREMELY DANGEROUS CATEGORY 5 HURRICANE...
...PREPARATIONS SHOULD BE RUSHED TO COMPLETION IN THE HURRICANE
SUMMARY OF 800 AM AST...1200 UTC...INFORMATION
ABOUT 270 MI...440 KM E OF ANTIGUA
ABOUT 280 MI...445 KM ESE OF BARBUDA
MAXIMUM SUSTAINED WINDS...175 MPH...280 KM/H
PRESENT MOVEMENT...W OR 280 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...929 MB...27.44 INCHES
WATCHES AND WARNINGS
CHANGES WITH THIS ADVISORY:
The government of the Dominican Republic has issued a Hurricane
Watch from Cabo Engano to the northern border with Haiti and a
Tropical Storm Watch from south of Cabo Engao to Isla Saona.
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...
* Dominican Republic from Cabo Engano to the northern border with
A Tropical Storm Warning is in effect for...
A Tropical Storm Watch is in effect for...
* Dominican Republic from south of Cabo Engao to Isla Saona
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. In this case, for some of easternmost islands, the
hurricane conditions are expected within the next 24 hours.
Preparations to protect life and property should be rushed to
A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area in this case within 36
A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, generally within 48 hours.
Interests elsewhere in the Dominican Republic, along with 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
DISCUSSION AND 48-HOUR OUTLOOK
At 800 AM AST (1200 UTC), the distinct eye center of Hurricane Irma
was located near latitude 16.7 North, longitude 57.7 West. Irma is
moving toward the west near 14 mph (22 km/h), and this general
motion is expected to continue today, followed by a turn toward the
west-northwest tonight. On the forecast track, the dangerous core of
Irma will move near or over portions of the northern Leeward Islands
tonight and early Wednesday.
Reports from NOAA and U.S. Air Force Hurricane Hunter aircraft
indicate Irma continues to strengthen and maximum sustained winds
have increased to near 175 mph (280 km/h) with higher gusts. Irma
is an extremely dangerous category 5 hurricane on the Saffir-Simpson
Hurricane Wind Scale. Some fluctuations in intensity are likely
during the next day or two, but Irma is forecast to remain a
powerful category 4 or 5 hurricane during the next couple of days.
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
The latest estimated minimum central pressure from aircraft data is
929 mb (27.44 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 7 to 11 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...7 to 11 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
WIND: Hurricane conditions are expected within the hurricane
warning area in the Leeward Islands by tonight, with tropical storm
conditions beginning later today. Tropical storm conditions are
expected within the tropical storm warning area where hurricane
conditions are also possible. Hurricane conditions are expected
to begin within the hurricane warning area in the British and U.S.
Virgin Islands and Puerto Rico on Wednesday, with tropical storm
conditions beginning tonight. Hurricane and tropical storm
conditions are possible within the watch area in the Dominican
Republic by early Thursday.
RAINFALL: Irma is expected to produce total rainfall accumulations
of 4 to 8 inches with isolated maximum amounts of 12 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.
Next intermediate advisory at 800 AM AST.
Next complete advisory at 1100 AM AST.