918 
 WTNT44 KNHC 070857
 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