[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 290251
TCDAT4

TROPICAL STORM MATTHEW DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142016
1100 PM AST WED SEP 28 2016

Matthew crossed a portion of the Lesser Antilles today, and
tropical-storm-force winds were experienced in various islands for
several hours.  The strongest winds appeared to have occurred in
Martinique which was located in the northeastern quadrant of the
storm.  An Air Force plane currently investigating Matthew measured
a peak wind at 850-mb of 73 kt, while the SFMR instrument measured
54 kt. The minimum central pressure was 1004 mb. There are no signs
of an inner core yet, but the cloud pattern has increased in
organization, and the initial intensity was adjusted upward to 55
kt.

Matthew is forecast to move over warm waters and relatively low
shear during the next few days, and these conditions should lead to
gradual strengthening.  There is a possibility, however, that
Matthew encounters some westerly shear in the central Caribbean well
south of Haiti in a day or two. This is an area climatologically
unfavorable for storms to intensify, and Matthew could reduce its
rate of strengthening there.  After that, most of the models show a
more conducive upper-level environment, and Matthew could intensify
at a faster rate. The NHC forecast is not very different from its
predecessor and follows closely the intensity consensus.

Fixes from an Air Force plane indicate that Matthew is moving
toward the west or 270 degrees at 13 kt.  A strong subtropical
ridge over the Atlantic is steering Matthew westward, and some
models even move the cyclone south of due west. Most of the guidance
is very consistent with this track during the next 48 hours. After
that time, guidance becomes more divergent, but in general, all
models turn the cyclone toward the northwest and north. Of the
historically reliable models, the westernmost track is the ECMWF
ensemble mean while the easternmost is the HWRF. The NHC track
forecast is in the middle of the TVCX and TVCN multi-model
consensus, and does not depart very much from the previous official
forecast.

There will be very interesting days ahead as Matthew moves toward
the central and western Caribbean Sea, and users are reminded that
the average NHC track errors at days 4 and 5 are on the order of 180
and 240 miles, respectively.


FORECAST POSITIONS AND MAX WINDS

INIT  29/0300Z 13.9N  63.1W   55 KT  65 MPH
 12H  29/1200Z 14.3N  65.3W   60 KT  70 MPH
 24H  30/0000Z 14.4N  67.9W   65 KT  75 MPH
 36H  30/1200Z 14.3N  70.0W   70 KT  80 MPH
 48H  01/0000Z 14.1N  71.5W   75 KT  85 MPH
 72H  02/0000Z 14.5N  73.5W   75 KT  85 MPH
 96H  03/0000Z 16.8N  75.0W   90 KT 105 MPH
120H  04/0000Z 20.0N  75.5W   90 KT 105 MPH

$$
Forecaster Avila
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