ZCZC MIATCDAT1 ALL TTAA00 KNHC DDHHMM Hurricane Irma Discussion Number 34 NWS National Hurricane Center Miami FL AL112017 1100 AM AST Thu Sep 07 2017 The eye on satellite continues to be quite distinct, and data from an Air Force reconnaissance plane indicate that the initial intensity is 150 kt. The central pressure remains near 921 mb. 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 will not remain a powerful hurricane for the next 3 days while approaching Florida. Thereafter, an increase in the wind shear could lead to gradual weakening, but Irma is expected to remain a major hurricane until landfall occurs. The best estimate of the initial motion is toward the west-northwest or 290 degrees at 14 kt. Irma is being steered by the flow around the south side of the subtropical ridge, but in 2 to 3 days, the hurricane will be located on the southwestern edge of the aforementioned ridge, and a turn to the northwest and north- northwest should then begin. There has been no change in the guidance which is still quite clustered and brings the core of Irma very near the southeast Florida coast in about 3 days. The NHC forecast, which is similar to the previous one, is very close to the multi-model consensus and the HFIP corrected consensus HCCA. The later has been performing very well during Irma. 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 today. These hazards will spread across the Turks and Caicos tonight and the Bahamas tonight through Saturday. 2. A hurricane watch is in effect for much of Cuba. Irma is likely to bring dangerous wind, storm surge, and rainfall to portions of these areas on Friday and Saturday. 3. The threat of dangerous major hurricane impacts in Florida continues to increase. A hurricane watch has been issued for south Florida, the Florida Keys, Lake Okeechobee, and Florida Bay. This watch will likely be expanded northward later today. Residents in these areas should heed any advice given by local officials. 4. A storm surge watch has also been issued 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. 5. The chance of direct impacts is increasing in portions of Georgia, South Carolina, and North Carolina, but it is too early to specify the magnitude and location of the impacts. FORECAST POSITIONS AND MAX WINDS INIT 07/1500Z 20.4N 69.7W 150 KT 175 MPH 12H 08/0000Z 21.1N 71.7W 145 KT 165 MPH 24H 08/1200Z 21.9N 74.2W 140 KT 160 MPH 36H 09/0000Z 22.5N 76.5W 135 KT 155 MPH 48H 09/1200Z 23.1N 78.4W 135 KT 155 MPH 72H 10/1200Z 25.5N 80.0W 125 KT 145 MPH 96H 11/1200Z 30.1N 80.6W 105 KT 120 MPH 120H 12/1200Z 35.0N 82.0W 50 KT 60 MPH...INLAND $$ Forecaster Avila NNNN