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Hurricane MATTHEW Forecast Discussion Number 34
2016-10-06 16:56:19| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT THU OCT 06 2016 000 WTNT44 KNHC 061456 TCDAT4 HURRICANE MATTHEW DISCUSSION NUMBER 34 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 1100 AM EDT THU OCT 06 2016 The satellite presentation of the hurricane has continued to improve, with a distinct eye surrounded by very deep convection, and T-numbers are oscillating around 6.0 on the Dvorak scale. Data from an Air Force reconnaissance plane traversing the eye of the hurricane also indicate that Matthew has strengthened. The initial intensity is estimated at 120 kt, based mainly on SFMR data and an eyewall dropsonde. Environmental conditions appear favorable for additional intensification today while Matthew approaches the east coast of Florida. After 24 hours, land interaction is likely to cause some weakening, and later in the period increasing shear should cause a more rapid decrease in winds. The NHC forecast is slightly above most of the guidance during the first 24 hours due to the recent intensification, and follows the weakening trend of the consensus thereafter. Aircraft fixes show that Matthew is moving toward the northwest or 325 degrees at 10 kt. The steering flow has not changed and Matthew is expected to move around the western periphery of the subtropical ridge located over the western Atlantic during the next 24 to 36 hours. After that time, the ridge will shift eastward allowing the hurricane to move northward and then sharply turn eastward while it becomes embedded within the mid-latitude westerlies. By the end of the forecast period the steering pattern is forecast to change again and a weakening cyclone is expected to turn southward. KEY MESSAGES: 1. Matthew is likely to produce devastating impacts from storm surge, extreme winds, and heavy rains in the northwestern Bahamas today, and along extensive portions of the east coast of Florida tonight. 2. Evacuations are not just a coastal event. Strong winds will occur well inland from the coast, and residents of mobile homes under evacuation orders are urged to heed those orders. 3. Hurricane winds increase very rapidly with height, and residents of high-rise buildings are at particular risk of strong winds. Winds at the top of a 30-story building will average one Saffir-Simpson category higher than the winds near the surface. 4. When a hurricane is forecast to take a track roughly parallel to a coastline, as Matthew is forecast to do from Florida through South Carolina, it becomes very difficult to specify impacts at any one location. Only a small deviation of the track to the left of the NHC forecast could bring the core of a major hurricane onshore within the hurricane warning area in Florida and Georgia. Modest deviations to the right could keep much of the hurricane-force winds offshore. Similarly large variations in impacts are possible in the hurricane watch and warning areas in northeast Georgia and South Carolina. 5. The National Hurricane Center is issuing Potential Storm Surge Flooding Maps, and Prototype Storm Surge Watch/Warning Graphics for Matthew. It is important to remember that the Potential Storm Surge Flooding Map does not represent a forecast of expected inundation, but rather depicts a reasonable worst-case scenario - the amount of inundation that has a 10 percent chance of being exceeded. In addition, because the Flooding Map is based on inputs that extend out only to about 72 hours, it best represents the flooding potential in those locations within the watch and warning areas in Florida and Georgia. FORECAST POSITIONS AND MAX WINDS INIT 06/1500Z 25.1N 77.8W 120 KT 140 MPH 12H 07/0000Z 26.4N 79.0W 125 KT 145 MPH 24H 07/1200Z 28.3N 80.4W 125 KT 145 MPH 36H 08/0000Z 30.2N 81.1W 115 KT 130 MPH 48H 08/1200Z 31.7N 80.0W 95 KT 110 MPH 72H 09/1200Z 32.5N 76.5W 75 KT 85 MPH 96H 10/1200Z 30.5N 75.0W 50 KT 60 MPH 120H 11/1200Z 28.5N 76.0W 40 KT 45 MPH $$ Forecaster Avila
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