761 
 WTNT44 KNHC 010847
 TCDAT4
 
 HURRICANE MATTHEW DISCUSSION NUMBER  13
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142016
 500 AM EDT SAT OCT 01 2016
 
 Matthew has changed little in organization since the past advisory,
 with a small eye surrounded by a central dense overcast featuring
 cloud tops colder than -80C.  The eye has become a little less
 distinct, suggesting at least that the hurricane is no longer
 intensifying.  In addition, the raw intensity estimates from the
 CIMSS ADT technique are slightly lower than they were six hours
 ago.  Based on these trends, the initial intensity is reduced to
 135 kt. An Air Force Reserve Hurricane Hunter aircraft is scheduled
 to reach Matthew near 1200 UTC.
 
 The initial motion is now 270/6.  Matthew remains south of a low-
 to mid-level ridge over the western Atlantic.  The dynamical models
 forecast this ridge to weaken over the next 72 hours as a mid- to
 upper-level trough develops over the Gulf of Mexico.  This
 evolution should cause Matthew to turn northwestward after 24 hours
 and northward by 48-72 hours.  The guidance generally agrees with
 this scenario.  However, there is a spread between the GFS forecast
 of landfall in Jamaica and eastern Cuba and the ECMWF forecast
 landfall in southwestern Haiti.  The guidance becomes more divergent
 after 72 hours.  The GFS shows a turn toward the north-northwest,
 which brings the center closer to the northwestern Bahamas and
 Florida. This model is near the western edge of the guidance
 envelope.  The ECMWF is near the eastern edge of the guidance
 envelope and shows the center east of the Bahamas by 120 hours.
 Adding to the uncertainty is the eastward shift of the Canadian
 model since its previous run.  Given the uncertainty, the 96 and 120
 hour forecast points are changed only slightly from the previous
 forecast.  This part of the forecast track lies to the east of the
 GFS, but to the west of the Canadian, ECMWF, and NAVGEM models.  It
 is also a little to the west of the various consensus models.
 
 Matthew should experience significant shear for the next 24 hours or
 so, as water vapor imagery shows westerly flow blowing into the
 hurricane underneath the impressive outflow pattern.  This should
 cause some weakening.  After that time, the dynamical models suggest
 the shear should decrease, which should allow Matthew to at least
 maintain its intensity.  The new intensity forecast shows a
 slightly weaker intensity than the previous advisory through 72
 hours based mainly on current trends.  Subsequently, the hurricane
 is likely to interact with the land masses of Jamaica, Cuba, and
 Hispaniola, leading to some weakening and disruption of the
 structure.  Between this and uncertainty about how much shear
 Matthew will encounter north of Cuba, the new forecast shows only
 modest strengthening after Matthew reaches the Atlantic north of
 Cuba.  There is also the possibility of fluctuations in intensity
 caused by eyewall replacement cycles at any time during the forecast
 period.
 
 It is important to remind users that average NHC track forecast
 errors are around 175 miles at day 4 and 230 miles at day 5.
 Therefore, it is too soon to rule out possible hurricane impacts
 from Matthew in Florida.
 
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  01/0900Z 13.3N  72.8W  135 KT 155 MPH
  12H  01/1800Z 13.3N  73.6W  130 KT 150 MPH
  24H  02/0600Z 13.8N  74.5W  120 KT 140 MPH
  36H  02/1800Z 14.9N  75.1W  110 KT 125 MPH
  48H  03/0600Z 16.2N  75.7W  110 KT 125 MPH
  72H  04/0600Z 19.5N  76.0W  110 KT 125 MPH
  96H  05/0600Z 23.0N  76.0W   90 KT 105 MPH
 120H  06/0600Z 26.0N  76.5W   95 KT 110 MPH
 
 $$
 Forecaster Beven