000 WTNT44 KNHC 052040 TCDAT4 HURRICANE MATTHEW DISCUSSION NUMBER 31 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 500 PM EDT WED OCT 05 2016 Data from an Air Force Hurricane Hunter plane a couple of hours ago indicated that the structure of Matthew had not changed very much, and the initial intensity remains at 105 kt. Another Hurricane Hunter plane will be in the eye soon. The environment continues to be favorable for Matthew to restrengthen while it approaches the the east coast of Florida during the next day or so. After that time, the shear is forecast to increase significantly, resulting in gradual weakening of the hurricane. Satellite images indicate that Matthew is moving toward the northwest or 325 degrees at about 10 kt. The subtropical ridge over the western Atlantic is still strong, and the flow pattern around this ridge should continue to steer the hurricane toward the northwest during the next day or two with no significant change in forward speed. After that time, the ridge will shift eastward, allowing Matthew to move northward very near or over the north Florida east coast, and then near or to the east of the Georgia and South Carolina coasts. By the end of the forecast period, models diverge considerably, with the GFS moving the cyclone southwestward toward land, and the ECMWF keeping Matthew over the Atlantic a good distance from the coast. The NHC forecast keeps Matthew over water in the middle of these two model solutions. KEY MESSAGES: 1. Matthew is likely to produce devastating impacts from storm surge, extreme winds, and heavy rains in the Bahamas. Please consult statements from the meteorological service and other government officials in that country. 2. 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. For example, 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. However, a small deviation to the right could keep the hurricane- force winds offshore. Similarly large variations in impacts are possible in the hurricane watch area in northern Florida and Georgia. 3. Tropical storm or hurricane conditions could affect South Carolina and North Carolina later this week or this weekend, even if the center of Matthew remains offshore. It is too soon to determine what, if any, land areas might be directly affected by Matthew next week. At a minimum, dangerous beach and boating conditions are likely along much of the U.S. east coast during the next several days. 4. 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 05/2100Z 22.5N 75.7W 105 KT 120 MPH 12H 06/0600Z 24.0N 76.9W 110 KT 125 MPH 24H 06/1800Z 25.6N 78.5W 115 KT 130 MPH 36H 07/0600Z 27.2N 79.8W 115 KT 130 MPH 48H 07/1800Z 29.0N 80.8W 115 KT 130 MPH 72H 08/1800Z 32.0N 79.5W 90 KT 105 MPH 96H 09/1800Z 32.6N 76.4W 80 KT 90 MPH 120H 10/1800Z 30.0N 74.0W 65 KT 75 MPH $$ Forecaster Avila