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Tropical Depression FOUR-E


Tropical Depression Four-E Discussion Number   1
NWS National Hurricane Center Miami FL       EP042017
1000 PM CDT Sat Jun 24 2017

Satellite images indicate that the low pressure system south of
Mexico has a well-defined circulation with convective banding
features developing near the center.  The convection appears to
have enough organization to classify the system as a tropical
cyclone, and the initial intensity is set at 25 kt based on Dvorak
estimates of T2.0 from TAFB and T1.5 from SAB.

The depression is located to the southwest of a closed mid-/
upper-level low located over the western Gulf of Mexico, and to the
southeast of a large mid-tropospheric high centered over Arizona.
The initial motion is west-northwestward, or 300/9 kt, and this
general motion should continue for the next three days as the
depression is increasingly steered by the strong high pressure to
its north.  Some decrease in speed is likely by days 4 and 5 once
the cyclone weakens and is steered by lower-level winds.  The track
models are showing relatively little cross-track spread, but there
are some speed differences, with the ECMWF most notably being slower
than the other guidance.  The NHC official track forecast is
relatively close to the multi-model consensus TVCN, and there is
high confidence that the cyclone will move parallel to the coast of
Mexico, keeping the tropical-storm-force winds well offshore.

Water vapor imagery shows the depression's outflow expanding in
nearly all directions, and deep-layer shear is forecast to be very
low for the entire forecast period.  Therefore, strengthening is
expected for the next 48 hours before the cyclone reaches colder
water.  The NHC intensity forecast closely follows HCCA during the
first 36 hours but then diverges from HCCA and indicates a peak
intensity occurring at 48 hours, which is closer in timing to the
peak intensities shown by SHIPS, the GFS, and the ECMWF models.
Cold water should cause the cyclone to degenerate to a remnant low
by day 4 or 5.


INIT  25/0300Z 14.3N 100.0W   25 KT  30 MPH
 12H  25/1200Z 15.1N 101.6W   35 KT  40 MPH
 24H  26/0000Z 15.9N 103.4W   45 KT  50 MPH
 36H  26/1200Z 16.8N 105.2W   55 KT  65 MPH
 48H  27/0000Z 17.9N 106.9W   60 KT  70 MPH
 72H  28/0000Z 19.5N 110.5W   45 KT  50 MPH
 96H  29/0000Z 20.5N 113.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  30/0000Z 21.0N 116.0W   20 KT  25 MPH...POST-TROP/REMNT LOW

Forecaster Berg