[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 072046
TCDAT4

HURRICANE MATTHEW DISCUSSION NUMBER  39
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142016
500 PM EDT FRI OCT 07 2016

Data from a NOAA Hurricane Hunter plane and satellite intensity
estimates indicate that Matthew has weakened a little bit and the
maximum winds are 95 kt.  The hurricane is heading toward an area of
increasing shear, and this should result in gradual weakening.  The
shear is forecast to continue during the next 5 days, so additional
weakening is anticipated and Matthew is expected to be a tropical
depression by the end of the forecast period.

Matthew has begun to move northward at about 10 kt. In about 12
hours, the hurricane will encounter the mid-latitude westerlies, and
this flow pattern should induce a northeastward and then eastward
motion during the next 2 days. During that time the core of the
hurricane is expected to hug the coast from Georgia through
southeastern North Carolina.  The confidence in this portion of the
track forecast is high.  After that time, the steering flow becomes
very complex, and both the GFS and ECMWF models turn the cyclone
southward and southwestward embedded within the flow on the west
side of a mid-level trough. The NHC track follows these two models,
but the confidence is portion of the forecast is low.


KEY MESSAGES:

1.  We have been very fortunate that Matthew's strongest winds have
remained a short distance offshore of the Florida Coast thus far,
but this should not be a reason to let down our guard.  Only a
small deviation to the left of the forecast track could bring these
winds onshore.  The western eyewall of Matthew, which contains
hurricane-force winds, is expected to move over or very near the
coast of northeastern Florida and Georgia through tonight.

2.  Hurricane winds increase very rapidly with height, and occupants
of high-rise buildings in the Jacksonville area are at particular
risk of strong winds.  Winds at the top of a 30-story building will
average one Saffir-Simpson category higher than the winds near the
surface.

3.  The water hazards remain, even if the core of Matthew remains
offshore.  These include the danger of life-threatening inundation
from storm surge, as well as inland flooding from heavy rains from
Florida to North Carolina.

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.

FORECAST POSITIONS AND MAX WINDS

INIT  07/2100Z 30.2N  80.7W   95 KT 110 MPH
 12H  08/0600Z 31.7N  80.7W   90 KT 105 MPH
 24H  08/1800Z 33.0N  79.0W   80 KT  90 MPH
 36H  09/0600Z 33.8N  76.7W   65 KT  75 MPH
 48H  09/1800Z 33.5N  75.0W   60 KT  70 MPH
 72H  10/1800Z 30.0N  74.5W   40 KT  45 MPH
 96H  11/1800Z 27.0N  76.0W   35 KT  40 MPH
120H  12/1800Z 26.0N  77.0W   30 KT  35 MPH

$$
Forecaster Avila
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