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ZCZC MIATCDAT1 ALL TTAA00 KNHC DDHHMM Hurricane Irma Discussion Number 35 NWS National Hurricane Center Miami FL AL112017 500 PM EDT Thu Sep 07 2017 Hurricane Irma continues to have an impressive satellite presentation with a very distinct eye. There is not much more to add about the current intensity except that numerous data from the Air Force reconnaissance plane indicate that the winds remain at 150 kt. The environment along the future track of Irma is favorable for the hurricane to maintain most of its current intensity, although some fluctuations are likely due to eyewall replacement cycles which are difficult to predict. There are no obvious reasons why Irma should not remain a powerful major hurricane for the next 3 days while it is heading for Florida or its adjacent surroundings. Thereafter, an increase in the wind shear and the interaction with land should lead to gradual weakening. The best estimate of the initial motion is toward the west-northwest or 285 degrees at 14 kt. Irma is being steered by the flow around the south side of the subtropical ridge, but in 2 or 3 days the hurricane is expected to be located on the southwestern edge of the aforementioned ridge, and a turn to the northwest and north- northwest should then begin. The forecast track for the first 2 days was adjusted a little bit to the south given that the ridge to the north continues to be strong, and the ECMWF and HFIP corrected consensus (HCCA) models have shifted southward a little bit. These two models have been performing very well during Irma. This adjustment also results in a westward shift of the track near Florida and northward. KEY MESSAGES: 1. Irma is a potentially catastrophic category 5 hurricane and will continue to bring life-threatening wind, storm surge, and rainfall hazards to the northern coast of Hispaniola tonight. These hazards are already spreading across the Turks and Caicos and will affect the Bahamas tonight through Saturday. Hurricane conditions will also spread over portions of the north coast of Cuba, especially over the adjacent Cuban Keys through Saturday. 2. It has become more likely that Irma will make landfall in southern Florida as a dangerous major hurricane, and bring life-threatening storm surge and wind impacts to much of the state. A Hurricane Watch is in effect for South Florida, the Florida Keys, Lake Okeechobee, and Florida Bay, and will likely be expanded northward tonight. 3. A Storm Surge Watch is in effect for portions of South Florida and the Florida Keys. This means there is the possibility of life-threatening inundation from rising water moving inland from the coastline during the next 48 hours in these areas. The Potential Storm Surge Flooding Map depicts a reasonable worst-case scenario - the amount of inundation that has a 10 percent chance of being exceeded. Because the Flooding Map is based on inputs that extend through 72 hours, it best represents the flooding potential in the watch area. 4. There is a chance of direct impacts in portions of Georgia, South Carolina, and North Carolina, but it is too early to specify the magnitude and location of these impacts. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 20.9N 71.1W 150 KT 175 MPH 12H 08/0600Z 21.6N 73.1W 145 KT 165 MPH 24H 08/1800Z 22.2N 75.5W 140 KT 160 MPH 36H 09/0600Z 22.7N 77.6W 135 KT 155 MPH 48H 09/1800Z 23.4N 79.3W 135 KT 155 MPH 72H 10/1800Z 26.2N 80.7W 115 KT 130 MPH...INLAND 96H 11/1800Z 31.5N 82.0W 80 KT 90 MPH...INLAND 120H 12/1800Z 36.0N 84.0W 40 KT 45 MPH...INLAND $$ Forecaster Avila NNNN