301 
 WTNT44 KNHC 080259
 TCDAT4
 
 HURRICANE MATTHEW DISCUSSION NUMBER  40
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142016
 1100 PM EDT FRI OCT 07 2016
 
 Coastal Doppler radar data this evening indicate that Matthew is
 gradually becoming less organized.  The eyewall has broken open
 with the remaining deep convection in a band just north of the
 center, and there is now little precipitation in the southeastern
 quadrant.  A combination of radar winds and earlier aircraft data
 suggests that the intensity has decreased slightly since the last
 advisory, so the initial intensity is lowered to 90 kt.
 
 The initial motion is now 010/10 kt.  During the next 36 hours,
 Matthew should turn more northeastward as it moves along the
 southern edge of a mid-latitude trough.  The forecast track, which
 lies in the center of the track guidance envelope, has the center
 moving near the coasts of Georgia and South Carolina during the next
 12-18 hours, then near the North Carolina coast from 18-36 hours.
 While this occurs, the cyclone is forecast to encounter strong
 vertical wind shear and to entrain dry air associated with an
 approaching frontal system.  This should result in a steady
 weakening, and Matthew is now forecast to weaken to a tropical storm
 by 36 hours in agreement with the SHIPS model. It is possible that
 Matthew could merge with the frontal system at about 36 hours,
 although none of the available guidance currently forecasts the
 system to become an extratropical low.
 
 The track and intensity forecasts become very low confidence after
 36 hours due to a large diversity of model solutions.  The GFDL and
 HWRF forecast Matthew to turn northeastward and become an
 extratropical low near the Canadian Atlantic provinces.  The UKMET
 moves Matthew eastward and eventually has it absorbed by Tropical
 Storm Nicole.  The ECMWF, NAVGEM, and Canadian models show a
 southwestward turn, with the cyclone or it remnants near the Bahamas
 by 120 hours.  The GFS is between the UKMET and ECMWF, showing
 Matthew moving far enough to the east to interact with Nicole, then
 turning southward.  The new track forecast follows the previous
 advisory in showing a southward/southwestward turn similar to the
 ECMWF, but is east of the previous track due to an overall eastward
 trend in the guidance.  Regarding the intensity, the GFS suggests
 that Matthew could decay to a remnant low by 120 hours, while the
 ECMWF suggests the system could still be a tropical cyclone.  Either
 way, continued weakening is likely due to shear and dry air
 entrainment, and the official forecast calls for Matthew to weaken
 to a depression by 96 hours.
 
 Due to the degradation of the radar signature of Matthew, the
 hourly Tropical Cyclone Updates will no longer be issued.
 
 
 KEY MESSAGES:
 
 1.  We have been very fortunate that Matthew's strongest winds have
 remained a short distance offshore of the Florida and Georgia coasts
 thus far, but this should not be a reason to let down our guard.
 Only a small deviation to the left of the forecast track could bring
 these winds onshore.  The western eyewall of Matthew, which contains
 hurricane-force winds, is expected to move over or very near the
 coasts of Georgia and South Carolina tonight and Friday.
 
 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  08/0300Z 31.2N  80.5W   90 KT 105 MPH
  12H  08/1200Z 32.5N  79.8W   80 KT  90 MPH
  24H  09/0000Z 33.6N  77.8W   70 KT  80 MPH
  36H  09/1200Z 33.9N  75.5W   60 KT  70 MPH
  48H  10/0000Z 33.0N  74.0W   55 KT  65 MPH
  72H  11/0000Z 30.0N  73.5W   40 KT  45 MPH
  96H  12/0000Z 27.5N  74.5W   30 KT  35 MPH
 120H  13/0000Z 26.0N  75.5W   30 KT  35 MPH
 
 $$
 Forecaster Beven