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TROPICAL DEPRESSION EIGHTEEN-E SPECIAL DISCUSSION NUMBER   1
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP182016
1000 AM PDT SUN SEP 25 2016

Deep convection associated with the low pressure area located well
southwest of the Baja California has become better organized
overnight, and early morning visible satellite imagery indicate
that the circulation has become better defined.  Based on these
observations, and Dvorak classifications of T2.0 and T1.5 from
TAFB and SAB respectively, advisories are being initiated on a
30-kt tropical depression at this time.  The depression is currently
located over warm water and within an area of low vertical wind
shear, which is favorable for some gradual strengthening today.
However, in about 24 hours, the tropical cyclone is forecast to move
into an area of higher southwesterly shear caused by large mid- to
upper-level low and associated trough over northwestern Mexico.  The
global models suggest that the shear will become quite strong in 36
to 48 hours as the cyclone begins moving over cooler waters. This
should result in a rapid spin down, and the system is likely to
become a post-tropical remnant low within 3 days.  The official
intensity foreast is slightly above the SHIPS guidance but is in
good agreement with the intensity consensus.

Since the depression is still in its formative stage, the initial
motion is a somewhat uncertain 360/4 kt.  The cyclone is expected to
be steered slowly northward or north-northeastward during the next
couple of days around the western portion of a weak mid-level ridge
that extends southwestward from southern Mexico.  By 72 hours, the
low should turn northwestward in the low-level steering flow after
it weakens and becomes a vertically shallow system.  Although the
ECMWF and GFS models are on opposite sides of the guidance envelope,
the track models are in general agreement on the overall scenario
and the NHC forecast lies near the multi-model consensus.


FORECAST POSITIONS AND MAX WINDS

INIT  25/1700Z 15.6N 119.7W   30 KT  35 MPH
 12H  26/0000Z 16.2N 119.6W   35 KT  40 MPH
 24H  26/1200Z 16.8N 119.4W   40 KT  45 MPH
 36H  27/0000Z 17.4N 119.1W   40 KT  45 MPH
 48H  27/1200Z 18.5N 118.3W   40 KT  45 MPH
 72H  28/1200Z 21.0N 117.3W   30 KT  35 MPH
 96H  29/1200Z 23.0N 118.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  30/1200Z 24.5N 119.5W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Brown

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