[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 042059
TCDAT4

HURRICANE MATTHEW DISCUSSION NUMBER  27
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142016
500 PM EDT TUE OCT 04 2016

The eye of Hurricane Matthew is not as distinct as it was earlier
today, and the change in the overall pattern suggests that the
cyclone is a little weaker due to the interaction with the nearby
high terrain. The initial intensity has been lowered to 120 kt and
some slight additional weakening could occur tonight while Matthew's
circulation continues to interact with Cuba and Hispaniola. Once
Matthew moves into the Bahamas, the environment is favorable for the
hurricane to maintain category 4 status for the next 2 days. Some
weakening is anticipated beyond 3 days due to an increase of the
wind shear.

Earlier reconnaissance aircraft fixes, satellite and radar data from
Cuba indicate that Matthew is moving toward the north or 360 degrees
at about 8 kt.  The hurricane continues to be steered by the flow
around the western edge of a subtropical ridge. Most of the global
models build the ridge westward, and this pattern should force the
hurricane to turn toward the northwest across the Bahamas and to the
waters just east of Florida. The most interesting change this
afternoon is that the ECMWF has forecast a stronger western Atlantic
ridge than in previous runs. This evolution resulted in an
additional leftward shift of the ECMWF track and consequently, the
NHC forecast has also been adjusted to the left, necessitating the
southward extension of the hurricane watch in Florida. Beyond 3
days, the ridge is forecast to move eastward, allowing Matthew to
turn northward and then northeastward.


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 portions of
Florida north of the current Hurricane Watch area, 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, very dangerous beach and boating conditions are likely
along much of the U.S. east coast later this week and weekend.


FORECAST POSITIONS AND MAX WINDS

INIT  04/2100Z 19.8N  74.3W  120 KT 140 MPH
 12H  05/0600Z 21.1N  74.5W  115 KT 130 MPH
 24H  05/1800Z 22.5N  75.3W  115 KT 130 MPH
 36H  06/0600Z 24.0N  76.6W  115 KT 130 MPH
 48H  06/1800Z 25.9N  78.2W  115 KT 130 MPH
 72H  07/1800Z 29.5N  80.3W  100 KT 115 MPH
 96H  08/1800Z 33.5N  78.0W   85 KT 100 MPH
120H  09/1800Z 40.0N  71.0W   70 KT  80 MPH

$$
Forecaster Avila
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