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TROPICAL DEPRESSION SIX DISCUSSION NUMBER 2
NWS NATIONAL HURRICANE CENTER MIAMI FL AL062016
500 AM AST WED AUG 17 2016
The depression's cloud pattern is gradually becoming better
organized. It consists of a central mass of deep convection and a
newly formed band over the northern half of the circulation. The
low-level center appears to still be located near the northeastern
edge of the main convective mass, likely due to some northeasterly
shear. Satellite classifications are T2.0 from TAFB and SAB, and
support maintaining the initial intensity estimate of 30 kt.
The northeasterly shear is forecast to decrease while the cyclone
moves over marginally warm waters during the next 24 to 36 hours.
These two factors should favor some intensification during this time
frame. However, the global models, and the ECMWF in particular,
show the cyclone moving into a much drier environment after 48 hours
and encountering strong southwesterly shear in association with a
mid- to upper-level trough. Thus weakening is forecast to begin by
day 3 despite the cyclone's trek over warmer waters, and there is
the possibility that the system could degenerate into a remnant low
by day 4 or 5 as depicted in the ECMWF. The new NHC intensity
forecast is somewhat higher than the previous one and the multi-
model consensus in the short term but lower later in the forecast
period and a little below most of the guidance.
The depression has been responding to a weakness in the subtropical
ridge between 40w and 50w by moving on a northwesterly track, and
the initial motion estimate is 305/13. The track guidance remains
split into two distinct camps, with GFS-based deterministic models
and GFS ensemble members showing a deeper system moving more
poleward. The ECMWF and its ensemble solutions are much farther to
the south as a result of the model's forecast of a weaker, shallower
system moving on a more westerly course. Based on the assumption
of a weaker system, the NHC track forecast is adjusted toward the
ECMWF solution, and is well south of the previous one and a little
to the left of the multi-model consensus.
FORECAST POSITIONS AND MAX WINDS
INIT 17/0900Z 13.2N 35.2W 30 KT 35 MPH
12H 17/1800Z 14.3N 36.8W 40 KT 45 MPH
24H 18/0600Z 15.5N 38.3W 45 KT 50 MPH
36H 18/1800Z 16.8N 39.9W 50 KT 60 MPH
48H 19/0600Z 17.8N 41.4W 50 KT 60 MPH
72H 20/0600Z 19.2N 44.7W 45 KT 50 MPH
96H 21/0600Z 21.6N 48.9W 40 KT 45 MPH
120H 22/0600Z 23.6N 52.3W 35 KT 40 MPH
$$
Forecaster Kimberlain
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