[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 050902
TCDAT4

HURRICANE MATTHEW DISCUSSION NUMBER  29
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142016
500 AM EDT WED OCT 05 2016

The satellite presentation of Matthew has degraded since its
interaction with the mountains terrain of eastern Cuba with the
eye no longer discernible in infrared satellite pictures. Data from
the Air Force Hurricane Hunter aircraft show that Matthew has
weakened slightly.  The aircraft measured peak 700-mb flight-level
winds of 118 kt and SFMR winds of 109 kt to the northeast of the
center. Based on these data the initial wind speed has been lowered
to 110 kt.  Matthew will be moving over sea surface temperatures of
29 to 30 degrees Celsius and the shear is expected to remain low
during the next couple of days.  These conditions should allow some
slight restrengthening while it moves through the Bahamas.
Increasing shear later in the forecast period is likely to cause
gradual weakening.

Matthew is moving northward or 350/8 kt.  A northwestward turn is
expected to occur today as the ridge to the north of Matthew builds
westward.  This should steer the hurricane through the Bahamas and
near the east coast of Florida during the next 48 hours.  After that
time, the global models turn the hurricane northward, then
northeastward when a ridge to the northeast of Matthew shifts
eastward and a mid- to upper-level trough approaches the eastern
United States.  The 0000 UTC GFS has shifted slightly west of the
previous run, and is now close to the UKMET and ECWMF tracks.  The
new NHC forecast is very similar to the previous advisory through
72 hours, and shows a track very close to much of the east coast
of the Florida peninsula.  Only a slight deviation to the west of
forecast track could result in landfall in Florida. The last few
iterations of the global models have been trending toward a solution
in which the trough is not deep enough to completely lift Matthew
northeastward.  As a result, the NHC track has been shifted
significantly southward at day 5, but it remains well north of
the GFS, ECMWF, and UKMET models.


KEY MESSAGES:

1.  Matthew is likely to produce devastating impacts from storm
surge, extreme winds, heavy rains, flash floods, and/or mudslides in
portions of the warning areas in Haiti, Cuba, and the Bahamas.
Please consult statements from the meteorological services and other
government officials in those countries.

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 estimate impacts this
far in advance.  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, while a small deviation to the right could keep
all of the hurricane-force winds offshore.  It will likely take
another day or so for the potential impacts of Matthew in the United
States to clarify.

3.  Tropical storm or hurricane conditions could affect Georgia,
South Carolina, and North Carolina later this week or this weekend,
even if the center of Matthew remains offshore.  It is too soon to
specify what, if any, direct impacts Matthew might have on the
remainder of the U.S. east coast farther to the north.  At a
minimum, dangerous beach and boating conditions are likely
along much of the U.S. east coast later this week and weekend.

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.


FORECAST POSITIONS AND MAX WINDS

INIT  05/0900Z 21.1N  74.6W  110 KT 125 MPH
 12H  05/1800Z 22.3N  75.3W  110 KT 125 MPH
 24H  06/0600Z 23.9N  76.6W  115 KT 130 MPH
 36H  06/1800Z 25.5N  78.2W  115 KT 130 MPH
 48H  07/0600Z 27.2N  79.5W  115 KT 130 MPH
 72H  08/0600Z 30.5N  80.2W   95 KT 110 MPH
 96H  09/0600Z 32.8N  77.0W   85 KT 100 MPH
120H  10/0600Z 33.1N  74.0W   70 KT  80 MPH

$$
Forecaster Brown
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