000 WTNT44 KNHC 050902 TCDAT4 HURRICANE MATTHEW DISCUSSION NUMBER 29 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 500 AM EDT WED OCT 05 2016 The satellite presentation of Matthew has degraded since its interaction with the mountains terrain of eastern Cuba with the eye no longer discernible in infrared satellite pictures. Data from the Air Force Hurricane Hunter aircraft show that Matthew has weakened slightly. The aircraft measured peak 700-mb flight-level winds of 118 kt and SFMR winds of 109 kt to the northeast of the center. Based on these data the initial wind speed has been lowered to 110 kt. Matthew will be moving over sea surface temperatures of 29 to 30 degrees Celsius and the shear is expected to remain low during the next couple of days. These conditions should allow some slight restrengthening while it moves through the Bahamas. Increasing shear later in the forecast period is likely to cause gradual weakening. Matthew is moving northward or 350/8 kt. A northwestward turn is expected to occur today as the ridge to the north of Matthew builds westward. This should steer the hurricane through the Bahamas and near the east coast of Florida during the next 48 hours. After that time, the global models turn the hurricane northward, then northeastward when a ridge to the northeast of Matthew shifts eastward and a mid- to upper-level trough approaches the eastern United States. The 0000 UTC GFS has shifted slightly west of the previous run, and is now close to the UKMET and ECWMF tracks. The new NHC forecast is very similar to the previous advisory through 72 hours, and shows a track very close to much of the east coast of the Florida peninsula. Only a slight deviation to the west of forecast track could result in landfall in Florida. The last few iterations of the global models have been trending toward a solution in which the trough is not deep enough to completely lift Matthew northeastward. As a result, the NHC track has been shifted significantly southward at day 5, but it remains well north of the GFS, ECMWF, and UKMET models. KEY MESSAGES: 1. Matthew is likely to produce devastating impacts from storm surge, extreme winds, heavy rains, flash floods, and/or mudslides in portions of the warning areas in Haiti, Cuba, and the Bahamas. Please consult statements from the meteorological services and other government officials in those countries. 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 estimate impacts this far in advance. 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, while a small deviation to the right could keep all of the hurricane-force winds offshore. It will likely take another day or so for the potential impacts of Matthew in the United States to clarify. 3. Tropical storm or hurricane conditions could affect Georgia, South Carolina, and North Carolina later this week or this weekend, even if the center of Matthew remains offshore. It is too soon to specify what, if any, direct impacts Matthew might have on the remainder of the U.S. east coast farther to the north. At a minimum, dangerous beach and boating conditions are likely along much of the U.S. east coast later this week and weekend. 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. FORECAST POSITIONS AND MAX WINDS INIT 05/0900Z 21.1N 74.6W 110 KT 125 MPH 12H 05/1800Z 22.3N 75.3W 110 KT 125 MPH 24H 06/0600Z 23.9N 76.6W 115 KT 130 MPH 36H 06/1800Z 25.5N 78.2W 115 KT 130 MPH 48H 07/0600Z 27.2N 79.5W 115 KT 130 MPH 72H 08/0600Z 30.5N 80.2W 95 KT 110 MPH 96H 09/0600Z 32.8N 77.0W 85 KT 100 MPH 120H 10/0600Z 33.1N 74.0W 70 KT 80 MPH $$ Forecaster Brown