000 WTNT44 KNHC 042059 TCDAT4 HURRICANE MATTHEW DISCUSSION NUMBER 27 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 500 PM EDT TUE OCT 04 2016 The eye of Hurricane Matthew is not as distinct as it was earlier today, and the change in the overall pattern suggests that the cyclone is a little weaker due to the interaction with the nearby high terrain. The initial intensity has been lowered to 120 kt and some slight additional weakening could occur tonight while Matthew's circulation continues to interact with Cuba and Hispaniola. Once Matthew moves into the Bahamas, the environment is favorable for the hurricane to maintain category 4 status for the next 2 days. Some weakening is anticipated beyond 3 days due to an increase of the wind shear. Earlier reconnaissance aircraft fixes, satellite and radar data from Cuba indicate that Matthew is moving toward the north or 360 degrees at about 8 kt. The hurricane continues to be steered by the flow around the western edge of a subtropical ridge. Most of the global models build the ridge westward, and this pattern should force the hurricane to turn toward the northwest across the Bahamas and to the waters just east of Florida. The most interesting change this afternoon is that the ECMWF has forecast a stronger western Atlantic ridge than in previous runs. This evolution resulted in an additional leftward shift of the ECMWF track and consequently, the NHC forecast has also been adjusted to the left, necessitating the southward extension of the hurricane watch in Florida. Beyond 3 days, the ridge is forecast to move eastward, allowing Matthew to turn northward and then northeastward. 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 portions of Florida north of the current Hurricane Watch area, 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, very dangerous beach and boating conditions are likely along much of the U.S. east coast later this week and weekend. FORECAST POSITIONS AND MAX WINDS INIT 04/2100Z 19.8N 74.3W 120 KT 140 MPH 12H 05/0600Z 21.1N 74.5W 115 KT 130 MPH 24H 05/1800Z 22.5N 75.3W 115 KT 130 MPH 36H 06/0600Z 24.0N 76.6W 115 KT 130 MPH 48H 06/1800Z 25.9N 78.2W 115 KT 130 MPH 72H 07/1800Z 29.5N 80.3W 100 KT 115 MPH 96H 08/1800Z 33.5N 78.0W 85 KT 100 MPH 120H 09/1800Z 40.0N 71.0W 70 KT 80 MPH $$ Forecaster Avila