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Tropical Storm MATTHEW Forecast Discussion

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WTNT44 KNHC 291455

1100 AM AST THU SEP 29 2016

The center of Matthew is exposed to the southwest of the deep
convection due to moderate southwesterly shear.  Despite the shear,
data from an Air Force Reserve reconnaissance aircraft show that
Matthew is a little stronger this morning.  The aircraft has
measured peak 850 mb flight-level winds of 80 kt, and believable
SFMR winds of around 60 kt, which is the basis for the initial
intensity.  The minimum central pressure reported by the aircraft
is down to 996 mb.

Given the current shear and structure of Matthew, only slight
strengthening is predicted during the next 24 hours.  The shear is
forecast to slowly decrease over the next few days, although there
are some differences in the upper-level wind forecasts between the
ECMWF and GFS models.  The ECMWF keeps a band of southwesterly
upper-level winds near Matthew, while the GFS generally shows lower
shear.  The NHC forecast assumes that there will be a reduction in
shear and calls for intensification similar to the previous
advisory. The official wind speed forecast is between the lower
statistical guidance and the more aggressive HWRF and GFDL models.

Matthew is moving at 275/14 kt.  The tropical storm is expected to
move westward to the south of a mid- to upper-level ridge over the
western Atlantic during the next couple of days. In about 48 hours,
Matthew should turn northwestward when it approaches the western
periphery of the ridge.  After that time, the tropical cyclone is
forecast to turn northward while a mid- to upper-level trough
develops over the Gulf of Mexico.  The GFS is still much faster than
the ECMWF at taking Matthew northward. Although the east/west spread
among the higher quality track models is somewhat smaller this
morning, there is still significant spread among the ECMWF ensembles
beyond 3 days, and the overall confidence in the track forecast is
still low.  The new NHC track forecast is essentially an update of
the previous forecast and is very close to the multi-model


INIT  29/1500Z 14.2N  66.3W   60 KT  70 MPH
 12H  30/0000Z 14.3N  68.0W   60 KT  70 MPH
 24H  30/1200Z 14.1N  70.2W   65 KT  75 MPH
 36H  01/0000Z 13.9N  71.8W   70 KT  80 MPH
 48H  01/1200Z 13.9N  72.8W   75 KT  85 MPH
 72H  02/1200Z 15.3N  74.4W   80 KT  90 MPH
 96H  03/1200Z 18.0N  75.2W   85 KT 100 MPH
120H  04/1200Z 21.5N  75.5W   80 KT  90 MPH

Forecaster Brown