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| #877174 (Received by flhurricane at: 5:01 AM 07.Oct.2016) TCDAT4 HURRICANE MATTHEW DISCUSSION NUMBER 37 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142016 500 AM EDT FRI OCT 07 2016 The satellite appearance of Matthew has become rather disheveled looking in infrared satellite imagery since the previous advisory. Land-based Doppler radar data indicate that Matthew has been going through an eyewall replacement cycle for the past 12 hours or so, but the inner eyewall has yet to dissipate within the 35-40 nmi wide outer eyewall. Both Doppler velocity data and recon SFMR surface winds and flight-level winds indicate that hurricane-force winds are and have been occuring within the outer eyewall just 5-10 nmi east of the Florida coastline. Although the central pressure has remained steady between 938-940 mb, the intensity has been lowered to 105 kt based on 700-mb flight-level winds of 118 kt and several patches of Doppler velocities of 120-122 kt between 5000-7500 feet. The initial motion estimate is 330/12 kt. For the next 48 hours, Matthew is expected to move northward and then northeastward around the western periphery of a deep-layer subtropical ridge. After that time, a weakening Matthew is expected to turn slowly southeastward and then southward as the cyclone gets cut off from the influence of the mid-latitude westerlies and becomes embedded within the aforementioned large-scale high pressure ridge. The latest model guidance has shifted to the left of the previous forecast track after 36 hours, and the official forecast has been nudged in that direction, but remains well to the right of the model consensus and close to the GFS-ECMWF consensus. Matthew is expected to slowly weaken some more during the next 12 hours or so while the cyclone completes the eyewall replacement cycle. By 24 hours and beyond, more significant weakening is expected due to the combination of strong southwesterly vertical shear increasing to more than 30 kt and entrainment of very dry mid-level air with humidity values less than 20 percent. The new intensity forecast closely follows the consensus model IVCN. Special thanks to the Air Force Reserve and NOAA Hurricane Hunters for their tireless efforts in having already completed more than 90 center or eye fixes. KEY MESSAGES: 1. Matthew is likely to produce devastating impacts from storm surge, extreme winds, and heavy rains along extensive portions of the east-central and northeast coast of Florida today. 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. FORECAST POSITIONS AND MAX WINDS INIT 07/0900Z 28.2N 80.0W 105 KT 120 MPH 12H 07/1800Z 29.6N 80.6W 100 KT 115 MPH 24H 08/0600Z 31.5N 80.5W 90 KT 105 MPH 36H 08/1800Z 32.6N 79.2W 80 KT 90 MPH 48H 09/0600Z 33.1N 77.7W 65 KT 75 MPH 72H 10/0600Z 31.5N 74.5W 50 KT 60 MPH 96H 11/0600Z 29.0N 75.0W 40 KT 45 MPH 120H 12/0600Z 27.0N 76.5W 35 KT 40 MPH $$ Forecaster Stewart |
