[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 060254
TCDAT4

HURRICANE MATTHEW DISCUSSION NUMBER  32
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142016
1100 PM EDT WED OCT 05 2016

Data from Air Force Reserve and NOAA Hurricane Hunter aircraft
showed lower winds in Matthew than seen during the previous
mission, with peak 700-mb flight-level winds of 103 kt and estimates
near 95 kt from the SFMR instrument.  Based on these, the initial
intensity is reduced to 100 kt.  However, satellite imagery
indicates that the hurricane is becoming better organized, with the
eye trying to re-appear and cooling cloud tops near the center.  In
addition, the eye has contracted to 15 n mi wide and the central
pressure has fallen to 961 mb.  This suggests that the winds are
about to increase.

The initial motion is 320/9.  There is little change to the
synoptic reasoning or the forecast track through 48 hours.  Matthew
is expected to move around the western side of the subtropical
ridge, which should move slowly eastward during the next couple of
days.  This evolution should steer Matthew generally northwestward
for the next 24 hours or so, followed by a turn toward the
north-northwest.  This forecast track takes the center near Andros
Island and New Providence in about 12 hours, and then very near the
eastern coast of the the Florida peninsula.  This part of the
forecast track is west of the various consensus models, but it lies
near the GFS, ECMWF, and ECMWF ensemble mean.  From 48-72 hours, the
cyclone is expected to recurve northeastward along the southern edge
of the mid-latitude westerlies.  After 72 hours, the track guidance
become very divergent, with solutions ranging from a continued
eastward motion out to sea to a turn back to the southwest.  The new
forecast track shows a slow southeastward motion during this time
in best agreement with the ECMWF.

As mentioned above, Matthew is getting better organized, and during
the next 36 hours or so it should be moving through an area of
light vertical wind shear.  This should allow strengthening, and
the new intensity forecast calls for the system to reach an
intensity near 115 kt in about 36 hours.  This is near the upper
end of the intensity guidance.  After 36 hours, proximity to land
and increasing shear should cause weakening, and the cyclone is now
expected to be down to tropical storm strength by 120 hours.
Overall, the intensity forecast is in best agrement with the SHIPS
model.


KEY MESSAGES:

1.  Matthew is likely to produce devastating impacts from storm
surge, extreme winds, and heavy rains in the Bahamas.  Please
consult statements from the meteorological service and other
government officials in that country.

2.  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.  For example, 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.
However, a small deviation to the right could keep the hurricane-
force winds offshore.  Similarly large variations in impacts are
possible in the hurricane watch area in northern Florida and
Georgia.

3.  Tropical storm or hurricane conditions could affect South
Carolina and North Carolina later this week or this weekend, even if
the center of Matthew remains offshore.  It is too soon to determine
what, if any, land areas might be directly affected by Matthew next
week.  At a minimum, dangerous beach and boating conditions are
likely along much of the U.S. east coast during the next several
days.

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.  In
addition, because the Flooding Map is based on inputs that extend
out only to about 72 hours, it best represents the flooding
potential in those locations within the watch and warning areas in
Florida and Georgia.



FORECAST POSITIONS AND MAX WINDS

INIT  06/0300Z 23.4N  76.4W  100 KT 115 MPH
 12H  06/1200Z 24.6N  77.6W  105 KT 120 MPH
 24H  07/0000Z 26.4N  79.2W  115 KT 130 MPH
 36H  07/1200Z 28.2N  80.4W  115 KT 130 MPH
 48H  08/0000Z 30.1N  81.0W  110 KT 125 MPH
 72H  09/0000Z 32.5N  78.5W   90 KT 105 MPH
 96H  10/0000Z 32.0N  75.5W   70 KT  80 MPH
120H  11/0000Z 30.5N  73.5W   55 KT  65 MPH

$$
Forecaster Beven
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