| Additional watches issued. NHC Track: http://www.nhc.noaa.gov/refresh/graphics_at1+shtml/?cone#contents Floater: http://www.ssd.noaa.gov/PS/TROP/floaters/11L/11L_floater.html Wider Atlantic views: http://www.ssd.noaa.gov/PS/TROP/trop-atl.html Hurricane Irma Advisory Number 21 NWS National Hurricane Center Miami FL AL112017 1100 AM AST Mon Sep 04 2017 ...HURRICANE WARNINGS ISSUED FOR PORTIONS OF THE LEEWARD ISLANDS... ...HURRICANE WATCHES ISSUED FOR THE BRITISH AND U.S. VIRGIN ISLANDS AND PUERTO RICO... SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION ----------------------------------------------- LOCATION...16.8N 53.3W ABOUT 560 MI...905 KM E OF THE LEEWARD ISLANDS MAXIMUM SUSTAINED WINDS...120 MPH...195 KM/H PRESENT MOVEMENT...WSW OR 255 DEGREES AT 14 MPH...22 KM/H MINIMUM CENTRAL PRESSURE...944 MB...27.88 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: The government of Antigua has issued a Hurricane Warning for the islands of Antigua, Barbuda, Anguilla, Montserrat, St. Kitts, and Nevis. A Hurricane Watch has been issued for the British Virgin Islands. The government of the Netherlands has issued a Hurricane Warning for the islands of Saba, St. Eustatius, and Sint Maarten. The government of France has issued a Hurricane Warning for St. Martin and Saint Barthelemy. A Hurricane Watch has been issued for Guadeloupe. A Hurricane Watch has been issued for the U.S. Virgin Islands, Puerto Rico, Vieques, and Culebra. The government of Barbados has issued a Tropical Storm Watch for Dominica. 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 A Hurricane Watch is in effect for... * Guadeloupe * British Virgin Islands * U.S. Virgin Islands * Puerto Rico, Vieques, and Culebra 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 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, and the southeastern 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 AM AST (1500 UTC), the eye of Hurricane Irma was located near latitude 16.8 North, longitude 53.3 West. Irma is moving toward the west-southwest near 14 mph (22 km/h). A turn toward the west is expected later today, followed by a west-northwestward turn 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 120 mph (195 km/h) with higher gusts. Irma is a category 3 hurricane on the Saffir-Simpson Hurricane Wind Scale. Additional strengthening is forecast through Tuesday night. Hurricane-force winds extend outward up to 35 miles (55 km) from the center and tropical-storm-force winds extend outward up to 140 miles (220 km). The estimated minimum central pressure based on data from a NOAA Hurricane Hunter aircraft is 944 mb (27.88 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. 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 by late Wednesday, with tropical storm conditions possible by early Wednesday. RAINFALL: Irma is expected to produce total rainfall accumulations of 3 to 6 inches across the Leeward Islands, with isolated maximum amounts of 10 inches across the northern Leeward Islands. These rainfall amounts may cause life-threatening flash floods and mudslides. SURF: Swells generated by Irma will affect the northern Leeward 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 ADVISORY ------------- Next intermediate advisory at 200 PM AST. Next complete advisory at 500 PM AST. $$ Forecaster Brown Hurricane Irma Discussion Number 21 NWS National Hurricane Center Miami FL AL112017 1100 AM AST Mon Sep 04 2017 The satellite presentation of Irma has improved markedly over the past 24 hours, with the eye becoming larger and much more distinct. A NOAA Hurricane Hunter aircraft has reported peak 700-mb flight level winds of 117 kt, SFMR winds of 107 kt, and dropsonde data that support a minimum pressure of around 944 mb. These data support an initial intensity of 105 kt. The aircraft also reported concentric eyewalls and a double wind maximum during the last couple of passes through the center, indicating that an eyewall replacement cycle has likely begun. Irma is expected to remain within a very favorable environment for strengthening during the next several days and additional intensification appears likely. However, eyewall replacement cycles are likely to cause some fluctuations in intensity during that time. The NHC forecast brings the hurricane to category 4 strength within the next 24 hours, and then maintains Irma as a powerful hurricane during the next 5 days, assuming that the core of the cyclone does not move over any of the Greater Antilles. Irma has been moving west-southwestward or 255/11 kt to the south of a strong mid-level ridge over the central Atlantic. The hurricane should turn westward later today or tonight, then west-northwestward Tuesday as it reaches the southwestern portion of the ridge. As mentioned in the previous NHC discussion, a large mid-latitude trough is expected to amplify over the eastern United States during the next few days. The global models are unanimous in lifting the trough out to the northeast by late in the week, allowing the Atlantic ridge to build westward on days 3 through 5. The track guidance has again shifted westward and southwestward at days 4 and 5, but the models remain in very good agreement through the forecast period. The updated NHC track forecast has been adjusted southwestward late in the period, and lies very near the consensus of the ECMWF, GFS, and HWRF models. Six hourly upper-air soundings will begin at 1800 UTC today over the central United States to better sample the upstream mid-latitude trough. In addition, the NOAA G-IV aircraft will begin sampling the environment around Irma this afternoon and evening, and these data will be included in tonight's 0000 UTC model runs. Users are reminded to not focus on the exact forecast track since strong winds and heavy rainfall extend well away from the center. In addition, average NHC track errors are about 175 and 225 statute miles at days 4 and 5, respectively. KEY MESSAGES: 1. Irma is expected to affect the northeastern Leeward Islands as a dangerous major hurricane, accompanied by life-threatening wind, storm surge, and rainfall impacts, along with rough surf and rip currents. Hurricane warnings have been issued for portions of the Leeward Islands. Preparations should be rushed to completion, as tropical-storm force winds are expected to first arrive in the hurricane warning area by late Tuesday. 2. Irma could directly affect the British and U.S. Virgin Islands and Puerto Rico as a dangerous major hurricane later this week. Hurricane watches have been issued for these areas, and tropical- storm-force winds could arrive in these areas by early Wednesday. 3. Irma could directly affect Hispaniola, the Turks and Caicos, the Bahamas, and Cuba as a dangerous major hurricane later this week. Residents in these areas should monitor the progress of Irma and listen to advice given by officials. 4. There is an increasing chance of seeing some impacts from Irma in the Florida Peninsula and the Florida Keys later this week and this weekend. In addition, rough surf and dangerous marine conditions will begin to affect the southeastern U.S. coast by later this week. Otherwise, it is still too early to determine what direct impacts Irma might have on the continental United States. However, 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 POSITIONS AND MAX WINDS INIT 04/1500Z 16.8N 53.3W 105 KT 120 MPH 12H 05/0000Z 16.5N 54.8W 115 KT 130 MPH 24H 05/1200Z 16.7N 57.1W 120 KT 140 MPH 36H 06/0000Z 17.3N 59.6W 120 KT 140 MPH 48H 06/1200Z 18.2N 62.4W 125 KT 145 MPH 72H 07/1200Z 19.9N 68.0W 120 KT 140 MPH 96H 08/1200Z 21.2N 73.3W 115 KT 130 MPH 120H 09/1200Z 22.0N 77.8W 115 KT 130 MPH...NEAR THE COAST OF CUBA $$ Forecaster Brown |