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Tropical Depression Fourteen Discussion Number 3
NWS National Hurricane Center Miami FL AL142017
1100 AM AST Fri Sep 15 2017
The depression hasn't changed much in organization since the last
advisory, with curved bands primarily in the southern semicircle due
to some northerly shear. Dvorak estimates range from 25 to 35 kt,
so the initial wind speed is kept at 30 kt. This is an uncertain
estimate because ASCAT has not sampled the cyclone or its precursor
system in quite some time. While the depression is forecast to be
over warm waters for the 5-day period, westerly shear is likely to
increase by early next week due to a large trough over the east-
central Atlantic. Until day 3, the system should be experiencing
light or moderate shear, which would favor gradual strengthening.
The model guidance has backed off some since the last advisory, so
the wind speed forecast is decreased at long range. However, the
new NHC prediction still lies on the high side of the guidance.
The depression is slowing down, and is now moving west-northwestward
at 9 kt. A west or west-northwest track is anticipated for the
next several days while the system remains south of an increasingly
skinny ridge over the eastern Atlantic. At long range, the system
could turn more to the northwest or north as a trough deepens over
the east-central Atlantic. A weaker cyclone, however, would tend to
feel less influence from the trough, and continue moving west-
northwestward. This is the solution suggested by the ECMWF and its
ensembles plus the HFIP corrected consensus models, and the latest
NHC prediction stays just to the northeast of that guidance.
FORECAST POSITIONS AND MAX WINDS
INIT 15/1500Z 11.4N 28.3W 30 KT 35 MPH
12H 16/0000Z 11.7N 29.6W 35 KT 40 MPH
24H 16/1200Z 11.9N 31.0W 40 KT 45 MPH
36H 17/0000Z 11.9N 32.2W 50 KT 60 MPH
48H 17/1200Z 12.1N 33.4W 55 KT 65 MPH
72H 18/1200Z 13.2N 36.9W 50 KT 60 MPH
96H 19/1200Z 14.7N 41.1W 40 KT 45 MPH
120H 20/1200Z 16.5N 45.2W 35 KT 40 MPH
$$
Forecaster Blake
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