[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT44 KNHC 062052
TCDAT4

HURRICANE MATTHEW DISCUSSION NUMBER  35
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142016
500 PM EDT THU OCT 06 2016

A NOAA Hurricane Hunter plane just reached Matthew and measured 121
kt at the 700-mb level and a minimum pressure of of 936 mb. Until
the plane finishes sampling the circulation, the initial intensity
is kept at 120 kt.  There some indications that an outer eyewall is
trying to form, and perhaps an eyewall cycle will occur. If so, some
weakening could occur, but there could also be fluctuations in
intensity while the hurricane moves toward the east coast of Florida
that are not explicitly shown here. After 24 hours, the combination
of land interaction and a significant increase in the shear should
cause weakening. The NHC intensity forecast is very similar to the
SHIPS guidance during the next day or so, and it follows the trend
of the consensus thereafter.

Satellite and aircraft fixes show that Matthew is still moving
toward the northwest or 325 degrees at 11 kt. The steering flow has
not changed, and Matthew should continue to move around the western
periphery of the subtropical ridge located over the western Atlantic
during the next 24 to 36 hours. This portion of the NHC forecast is
very close to the multi-model consensus. After that time, the
hurricane will become embedded within the mid-latitude westerlies
and should turn sharply eastward for a day or so. Then the steering
pattern is forecast to change again, and the track forecast becomes
highly uncertain. Both the GFS and the ECMWF turn a much weaker
Matthew southward and southwestward. The NHC forecast follows the
southwestward trend, and is in the middle of these two global
models.

KEY MESSAGES:

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

2.  Evacuations are not just a coastal event.  Strong winds will
occur well inland from the coast, and residents of mobile
homes under evacuation orders are urged to heed those orders.

3.  Hurricane winds increase very rapidly with height, and residents
of high-rise buildings 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.

4.  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.  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.  Modest deviations to the right could keep much of the
hurricane-force winds offshore.  Similarly large variations in
impacts are possible in the hurricane watch and warning areas in
northeast Georgia and South Carolina.

5.  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  06/2100Z 26.2N  78.6W  120 KT 140 MPH
 12H  07/0600Z 27.6N  79.9W  115 KT 130 MPH
 24H  07/1800Z 29.6N  81.0W  110 KT 125 MPH
 36H  08/0600Z 31.2N  81.0W   95 KT 110 MPH
 48H  08/1800Z 32.1N  80.0W   80 KT  90 MPH
 72H  09/1800Z 31.5N  76.5W   60 KT  70 MPH
 96H  10/1800Z 29.0N  76.5W   50 KT  60 MPH
120H  11/1800Z 27.5N  77.5W   40 KT  45 MPH

$$
Forecaster Avila

This weather bulletin was brought to you by:
www.nashvilleweather.net