[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 050256
TCDAT4

HURRICANE MATTHEW DISCUSSION NUMBER  28
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142016
1100 PM EDT TUE OCT 04 2016

Hurricane Matthew made landfall along the extreme eastern coast of
Cuba near Juaco around 0000 UTC this evening, and the eye is just
now moving off of the northeastern coast of Cuba. Some weakening has
occurred due to interaction with the mountains of eastern Cuba and
western Haiti. However, latest reports from an Air Force Reserve
reconnaissance aircraft indicate that the central pressure hasn't
risen much and that the maximum winds have only decreased to an
estimated 115 kt, keeping Matthew a dangerous category four
hurricane.

Radar and recon fixes indicate that Matthew is moving slightly west
of due north, or 350/07 kt. Matthew is expected to begin turning
toward the north-northwest during the next 12 hours or so, followed
by a northwestward motion in 24-48 hours as the large ridge to the
north of the powerful hurricane begins to build westward across the
southeastern United States in response to a broad trough over the
central U.S. weakening and lifting out to the northeast. The next
upstream weather system that will affect the steering currents
surrrounding Matthew is a large trough currently approaching the
northwestern U.S. and southwestern Canada. That system is forecast
to dig southeastward and amplify over the central U.S. during next
several days, resulting in significant ridging downstream over the
northeastern United States. As the next ridge builds and lifts
northward, Matthew is expected to turn northward as well by 72
hours, and turn northeastward after that as the aforementioned
trough moves eastward into the eastern United States by 96-120
hours.  The official forecast track remains close to a blend of the
GFS and ECMWF models.

The current 10-15 kt of northwesterly vertical wind shear is
forecast to weaken to around 5 kt by 36-48 hours while Matthew is
moving over the warm waters of the Gulf Stream, where SSTs are
expected to be near 30 deg C.  That combination, along with high
mid-level humidity, should enable Matthew to maintain category four
status, although eyewall replacement cycles, which can not be
forecast with any skill, could result in fluctuations in the
intensity not shown by the official forecast. By 72 hours and
beyond, steadily increasing vertical wind shear is expected to
induce gradual weakening. The official intensity forecast is close
to but slightly above the consensus model IVCN.

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  05/0300Z 20.4N  74.4W  115 KT 130 MPH
 12H  05/1200Z 21.7N  74.8W  115 KT 130 MPH
 24H  06/0000Z 23.3N  76.0W  115 KT 130 MPH
 36H  06/1200Z 25.0N  77.6W  115 KT 130 MPH
 48H  07/0000Z 26.7N  79.0W  115 KT 130 MPH
 72H  08/0000Z 30.3N  80.8W  100 KT 115 MPH
 96H  09/0000Z 33.2N  78.1W   85 KT 100 MPH
120H  10/0000Z 37.0N  72.0W   70 KT  80 MPH

$$
Forecaster Stewart
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