000 WTNT44 KNHC 080858 TCDAT4 HURRICANE MATTHEW DISCUSSION NUMBER 41 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 500 AM EDT SAT OCT 08 2016 Coastal Doppler weather radars this morning continue to depict a 40-nmi wide eye with a band of intense convection located in the northwestern quadrant along the coasts of extreme eastern Georgia and South Carolina from Tybee Island northeast to near the entrance of Charleston Harbor. Air Force Reserve and NOAA reconnaissance wind data, along with Doppler radar velocity data and surface observations, indicate that hurricane-force wind gusts in excess of 80 kt are occuring along the aforementioned coastal areas. Based on 700-mb maximum flight-level winds of 108 kt, peak SFMR surface winds of 83 kt, and Doppler velocities of 100-102 kt between 8000-11000 ft, the initial intensity will remain at 90 kt for this advisory. The initial motion estimate is 015/10 kt. Matthew made a northward jog since the previous advisory, but now appears to moving north-northeastward based on the latest radar and recon fixes. However, the more northward motion earlier has increased the possibility that the center of Matthew's eye will move onshore the coast of South Carolina later this morning or early afternoon as the cyclone turns northeastward ahead of a strong shortwave trough. Regardless of whether or not the center makes landfall, hurricane-force winds in the northern eyewall will lash much of the coast of South Carolina today as the center moves to a position just east of Charleston Harbor in about 12 hours. After that, the models are in fair agreement on Matthew turning eastward through 36 hours as the cyclone briefly gets captured by the aforementioned shortwave trough. However, by 48 hours and beyond, Matthew is expected to turn southeastward and southward as the cyclone moves around the eastern periphery of an amplifying ridge located east of Florida. In the 48-72 hours time period, some erratic motion could occur as Matthew and Tropical Storm Nicole briefly undergo some binary interaction before separating by 96 hours. The official forecast track closely follows a blend of the GFS and ECMWF solutions. The vertical wind shear is forecast to increase to more than 30 kt by 12 hours, which should induce steady weakening. At 48 hours and beyond, the SHIPS model is forecasting the shear to increase to more than 40 kt, resulting in rapid weakening to remnant low status by 120 hours. However, the shear forecast appears to be overdone since both the GFS and ECMWF models indicate that Matthew and Nicole will both be moving underneath a narrow 200 mb ridge axis, which should act to reduce the shear across the two cyclones in the 48-96 hour period. The official intensity forecast closely follows the consensus model IVCN, and maintains Matthew as a tropical cyclone throughout the forecast period. KEY MESSAGES: 1. The western eyewall of Matthew, which contains hurricane-force winds, is now moving over the northern coast of Georgia and the southern coast of South Carolina and should spread up the coast during the day. 2. Hurricane winds increase very rapidly with height, and occupants of high-rise buildings along the coast 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. 3. The water hazards remain, even if the core of Matthew remains offshore. These include the danger of life-threatening inundation from storm surge, as well as inland flooding from heavy rains from Florida to North Carolina. 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. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 32.0N 80.5W 90 KT 105 MPH 12H 08/1800Z 32.9N 79.4W 80 KT 90 MPH 24H 09/0600Z 33.7N 77.1W 70 KT 80 MPH 36H 09/1800Z 33.4N 75.1W 60 KT 70 MPH 48H 10/0600Z 32.6N 73.5W 50 KT 60 MPH 72H 11/0600Z 29.0N 73.5W 40 KT 45 MPH 96H 12/0600Z 26.0N 75.3W 30 KT 35 MPH 120H 13/0600Z 25.0N 76.2W 30 KT 35 MPH $$ Forecaster Stewart