| 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 Discussion Number 19 NWS National Hurricane Center Miami FL AL112017 1100 PM AST Sun Sep 03 2017 Observations from a NOAA Hurricane Hunter aircraft indicated a 25 n mi diameter eye and maximum SFMR-observed surface winds close to 100 kt. That value will be retained for the official intensity. Central core convection is beginning to become a little better organized on satellite imagery and the upper-level outflow is well defined. Given the favorable environment, Irma is likely to strengthen some more over the next day or two. The official intensity forecast follows the model consensus. Based on center fixes from the Hurricane Hunters, Irma has been moving a little south of west or around 255/12 kt. A strong high pressure ridge over the central Atlantic should steer Irma on a west-southward to westward course over the next couple of days. After that time, a turn toward the west-northwest is likely while Irma nears the western portion of the ridge. There continues to be a rather small cross-track spread in most of the track guidance models, but there are some speed differences. The official track forecast is roughly in the middle of the guidance and is just slightly south of the previous NHC prediction. Users are reminded to not focus on the exact forecast track since strong winds and heavy rainfall extend well away from the center. KEY MESSAGES: 1. Irma is expected to affect the northeastern Leeward Islands by the middle of this week as a major hurricane, accompanied by dangerous wind, storm surge, and rainfall impacts, along with rough surf and rip currents. Hurricane watches have been issued for portions of the Leeward Islands and additional hurricane or tropical storm watches or warnings may be required on Monday. Residents in these areas should monitor the progress of Irma and listen to advice given by officials. 2. Irma is expected to remain a dangerous major hurricane through the upcoming week and could directly affect the British and U.S. Virgin Islands, Puerto Rico, Hispaniola, the Turks and Caicos, and the Bahamas. Residents in all of these areas should monitor the progress of Irma and listen to advice given by officials. Tropical storm or hurricane watches could be issued for the British and U.S. Virgin Islands and Puerto Rico on Monday. 3. It is too early to determine what direct impacts Irma might have on the continental United States. Regardless, 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 04/0300Z 17.2N 51.0W 100 KT 115 MPH 12H 04/1200Z 16.7N 52.6W 105 KT 120 MPH 24H 05/0000Z 16.5N 54.8W 110 KT 125 MPH 36H 05/1200Z 16.8N 57.1W 115 KT 130 MPH 48H 06/0000Z 17.4N 59.6W 120 KT 140 MPH 72H 07/0000Z 19.3N 65.0W 120 KT 140 MPH 96H 08/0000Z 21.2N 70.2W 115 KT 130 MPH 120H 09/0000Z 22.8N 74.5W 115 KT 130 MPH $$ Forecaster Pasch Hurricane Irma Advisory Number 19 NWS National Hurricane Center Miami FL AL112017 1100 PM AST Sun Sep 03 2017 ...MAJOR HURRICANE IRMA EXPECTED TO BE NEAR THE NORTHERN LEEWARD ISLANDS TUESDAY NIGHT... SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION ----------------------------------------------- LOCATION...17.2N 51.0W ABOUT 710 MI...1145 KM E OF THE LEEWARD ISLANDS MAXIMUM SUSTAINED WINDS...115 MPH...185 KM/H PRESENT MOVEMENT...WSW OR 255 DEGREES AT 14 MPH...22 KM/H MINIMUM CENTRAL PRESSURE...961 MB...28.38 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: None. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Hurricane Watch is in effect for... * Antigua, Barbuda, Anguilla, Montserrat, St. Kitts, and Nevis * Saba, St. Eustatius, and Sint Maarten * Saint Martin and Saint Barthelemy Interests in the remainder of the Leeward Islands, the British and U.S. Virgin Islands, and Puerto Rico should monitor the progress of Irma. Additional Hurricane and Tropical Storm Watches may be required for portions of this area on Monday. For storm information specific to your area, please monitor products issued by your national meteorological service. DISCUSSION AND 48-HOUR OUTLOOK ------------------------------ At 1100 PM AST (0300 UTC), the center of Hurricane Irma was located near latitude 17.2 North, longitude 51.0 West. Irma is moving toward the west-southwest near 14 mph (22 km/h). A west-southwestward to westward motion is expected through Monday night. On the forecast track, the center of Irma is expected to approach the northern Leeward Islands late Tuesday. Maximum sustained winds are near 115 mph (185 km/h) with higher gusts. Irma is a category 3 hurricane on the Saffir-Simpson Hurricane Wind Scale. Some strengthening is forecast during the next 48 hours. 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). A NOAA Hurricane Hunter aircraft reported a minimum central pressure of 961 mb (28.38 inches). HAZARDS AFFECTING LAND ---------------------- WIND: Hurricane conditions are possible within the watch area by Tuesday night, with tropical storm conditions possible by late Tuesday. SURF: Swells generated by Irma will begin affecting the northern Leeward Islands on Monday. 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 AM AST. Next complete advisory at 500 AM AST. $$ Forecaster Pasch |