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ZCZC MIATCDAT1 ALL TTAA00 KNHC DDHHMM Hurricane Irma Discussion Number 17 NWS National Hurricane Center Miami FL AL112017 1100 AM AST Sun Sep 03 2017 The eye of Irma is a little less distinct in geostationary satellite images this morning, which suggests that the intensity of the hurricane may be fluctuating yet again. However, the initial wind speed is maintained at 100 kt for this advisory, which is close to a consensus of the various objective and subjective satellite intensity estimates. The first reconnaissance mission, a NOAA P-3 Hurricane Hurricane aircraft, is scheduled to depart Barbados for tail Doppler radar mission into Irma late this afternoon and should provide additional information on Irma's intensity by this evening. A strong high pressure ridge over the central Atlantic is steering Irma west-southwestward or 255/12 kt. This general motion with some reduction in forward speed is expected during the next day or so. After that time, Irma is forecast to turn westward, then west-northwestward in about 72 hours as it approaches the western portion of the ridge. The various consensus aids are generally a little slower than the previous advisory, but there cross-track differences are small. As a result, the updated NHC track is very similar to the previous advisory, and is close to a consensus of the ECMWF, GFS, UKMET, and HWRF, but is not as far south as the latest runs of the UKMET or ECMWF. Irma is forecast to move over slightly warmer SSTs and into a moistening mid-level environment. These conditions, along with a favorable upper-level wind pattern, should allow for gradual strengthening during the next 2 to 3 days. However, eyewall replacement cycles could result in fluctuations in intensity during the next several days. While Irma is currently a small hurricane, the guidance suggests it should grow in size during the next 72 h. This will affect how soon watches may be issued for portions of the Leeward and Virgin Islands, and interests on those islands should continue to monitor Irma's progress. KEY MESSAGES: 1. Irma is expected to be a major hurricane when it moves near or over the northeastern Leeward Islands by the middle of this week, and could cause dangerous wind, storm surge, and rainfall impacts, along with rough surf and rip currents on some islands. Hurricane and tropical storm watches will likely be issued for some of these islands later today or tonight. Residents in these areas should monitor the progress of Irma and listen to advice given by officials. 2. Direct impacts from Irma are also possible in the Virgin Islands and Puerto Rico later this week, and tropical storm or hurricane watches could be issued for these islands by tomorrow. Residents in these areas should monitor the progress of Irma and listen to advice given by officials. 3. The possibility of direct impacts from Irma in Hispaniola, the Turks and Caicos, and the Bahamas later this week is increasing. Residents in these areas should monitor the progress of Irma and listen to advice given by officials. 4. 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 03/1500Z 17.7N 48.4W 100 KT 115 MPH 12H 04/0000Z 17.1N 50.1W 105 KT 120 MPH 24H 04/1200Z 16.6N 52.2W 110 KT 125 MPH 36H 05/0000Z 16.4N 54.3W 115 KT 130 MPH 48H 05/1200Z 16.7N 56.6W 120 KT 140 MPH 72H 06/1200Z 18.2N 61.8W 120 KT 140 MPH 96H 07/1200Z 20.4N 67.1W 115 KT 130 MPH 120H 08/1200Z 22.5N 72.0W 115 KT 130 MPH $$ Forecaster Brown NNNN