[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 060901
TCDAT4

HURRICANE MATTHEW DISCUSSION NUMBER  33
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142016
500 AM EDT THU OCT 06 2016

The satellite presentation of Matthew has improved markedly
overnight with eye reappearing and warming within the past couple
of hours.  The eye is also embedded within a very symmetric
central dense overcast with cloud tops colder than -70C.  An Air
Force Reconnaissance Hurricane Hunter that just flew through the
center reported peak 700 mb flight-level winds of 132 kt, SFMR
winds around 103 kt, and a pressure of 944 mb, which is
down about 18 mb from last evening.  Using a blend of the
flight-level and SFMR winds, the initial intensity is set at
110 kt. Environmental conditions appear favorable for continued
strengthening today and Matthew is expected to become an extremely
dangerous category 4 hurricane while it moves over the northwestern
Bahamas and approaches the east coast of Florida.  After 24 hours,
land interaction is likely to cause some weakening, and later in the
period increasing shear should cause a more rapid decrease in
winds. The NHC forecast is above the most of guidance during the
first 24 hours due to the recent increase in organization, but is
close to the consensus thereafter.

Aircraft and satellite fixes show that Matthew is moving
northwestward or 320/10 kt.  Matthew is expected to move around
the western periphery of a subtropical ridge that is forecast to
gradually retreat eastward during the next day or two.  This
pattern should steer Matthew northwestward over the northwestern
Bahamas today, then north-northwestward very near the east coast
of Florida late today through Friday night. The models are tightly
clustered through 48 hours, and the NHC track is near the consensus
of the GFS and ECMWF models through that time.  After 48 hours, the
hurricane should turn northeastward as a broad trough approaches
the Great Lakes region. The trough is expected to pass north of
Matthew in about 72 hours, which is expected to cause the cyclone to
turn eastward, then southeastward late in the forecast period.
There is still significant spread in the long-range guidance so
there is lower than normal confidence in the days 4 and 5 track
prediction.


KEY MESSAGES:

1.  Matthew is likely to produce devastating impacts from storm
surge, extreme winds, and heavy rains in the central and
northwestern Bahamas today, and along portions of the east
coast of Florida tonight.

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 and
Georgia.  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 northeast
Georgia and South Carolina.

3.  Tropical storm or hurricane conditions could affect eastern
North Carolina later this week or this weekend, even if the center
of Matthew remains offshore.

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  06/0900Z 24.2N  77.1W  110 KT 125 MPH
 12H  06/1800Z 25.5N  78.4W  120 KT 140 MPH
 24H  07/0600Z 27.2N  79.9W  125 KT 145 MPH
 36H  07/1800Z 29.0N  80.7W  115 KT 130 MPH
 48H  08/0600Z 30.7N  80.7W   95 KT 110 MPH
 72H  09/0600Z 32.4N  77.6W   80 KT  90 MPH
 96H  10/0600Z 31.0N  75.0W   60 KT  70 MPH
120H  11/0600Z 29.5N  75.0W   50 KT  60 MPH

$$
Forecaster Brown
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