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ZCZC MIATCDAT1 ALL TTAA00 KNHC DDHHMM Hurricane Irma Special Discussion Number 25 NWS National Hurricane Center Miami FL AL112017 800 AM AST Tue Sep 05 2017 This special advisory is being issued to increase the initial and forecast intensity of Irma. NOAA and U.S. Air Force Hurricane Hunter aircraft have recently measured peak flight-level winds of around 170 kt and SFMR winds of around 150 kt. Based on these data the initial intensity has been increased to 150 kt, making Irma an extremely dangerous category 5 hurricane. Some additional strengthening is still possible, but fluctuations in intensity are likely during the next couple of days due to eyewall replacement cycles. No change was made to the previous track or wind radii forecast. KEY MESSAGES: 1. Irma is expected to affect the northeastern Leeward Islands as an extremely dangerous category 5 hurricane, accompanied by life-threatening wind, storm surge, and rainfall. Hurricane warnings are in effect 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 later today. 2. Irma is also expected to affect the British and U.S. Virgin Islands and Puerto Rico as a dangerous major hurricane beginning tomorrow, with life-threatening wind, storm surge, and rainfall. Hurricane warnings have been issued for these areas, and tropical- storm-force winds are expected to arrive in these areas by early tomorrow. 3. Irma could directly affect Hispaniola, the Turks and Caicos, the Bahamas, and Cuba as an extremely 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. 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. FORECAST POSITIONS AND MAX WINDS INIT 05/1200Z 16.7N 57.7W 150 KT 175 MPH 12H 05/1800Z 17.0N 58.9W 155 KT 180 MPH 24H 06/0600Z 17.7N 61.5W 150 KT 175 MPH 36H 06/1800Z 18.6N 64.2W 145 KT 165 MPH 48H 07/0600Z 19.6N 67.0W 140 KT 160 MPH 72H 08/0600Z 21.2N 72.5W 135 KT 155 MPH 96H 09/0600Z 22.4N 77.2W 135 KT 155 MPH 120H 10/0600Z 24.0N 81.0W 130 KT 150 MPH $$ Forecaster Brown NNNN