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Hurricane MATTHEW Forecast Discussion Number 35
2016-10-06 22:53:17| National Hurricane Center (Atlantic)
Issued at 500 PM EDT THU OCT 06 2016 000 WTNT44 KNHC 062052 TCDAT4 HURRICANE MATTHEW DISCUSSION NUMBER 35 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 500 PM EDT THU OCT 06 2016 A NOAA Hurricane Hunter plane just reached Matthew and measured 121 kt at the 700-mb level and a minimum pressure of of 936 mb. Until the plane finishes sampling the circulation, the initial intensity is kept at 120 kt. There some indications that an outer eyewall is trying to form, and perhaps an eyewall cycle will occur. If so, some weakening could occur, but there could also be fluctuations in intensity while the hurricane moves toward the east coast of Florida that are not explicitly shown here. After 24 hours, the combination of land interaction and a significant increase in the shear should cause weakening. The NHC intensity forecast is very similar to the SHIPS guidance during the next day or so, and it follows the trend of the consensus thereafter. Satellite and aircraft fixes show that Matthew is still moving toward the northwest or 325 degrees at 11 kt. The steering flow has not changed, and Matthew should continue to move around the western periphery of the subtropical ridge located over the western Atlantic during the next 24 to 36 hours. This portion of the NHC forecast is very close to the multi-model consensus. After that time, the hurricane will become embedded within the mid-latitude westerlies and should turn sharply eastward for a day or so. Then the steering pattern is forecast to change again, and the track forecast becomes highly uncertain. Both the GFS and the ECMWF turn a much weaker Matthew southward and southwestward. The NHC forecast follows the southwestward trend, and is in the middle of these two global models. 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 06/2100Z 26.2N 78.6W 120 KT 140 MPH 12H 07/0600Z 27.6N 79.9W 115 KT 130 MPH 24H 07/1800Z 29.6N 81.0W 110 KT 125 MPH 36H 08/0600Z 31.2N 81.0W 95 KT 110 MPH 48H 08/1800Z 32.1N 80.0W 80 KT 90 MPH 72H 09/1800Z 31.5N 76.5W 60 KT 70 MPH 96H 10/1800Z 29.0N 76.5W 50 KT 60 MPH 120H 11/1800Z 27.5N 77.5W 40 KT 45 MPH $$ Forecaster Avila
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