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Tropical Depression EIGHTEEN-E (Text)

ZCZC MIATCDEP3 ALL
TTAA00 KNHC DDHHMM

TROPICAL DEPRESSION EIGHTEEN-E DISCUSSION NUMBER   1
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP182014
800 AM PDT WED SEP 24 2014

Convection associated with the area of low pressure located south of
Mexico has increased and persisted overnight.  The convection is not
extremely well organized due to strong northeasterly shear, however
Dvorak T-numbers of 2.0 from both SAB and TAFB suggest that the
system has enough organization to be classified as a tropical
depression.  The shear is causing the convection to be displaced to
the south and southwest of the low-level center.  The initial
intensity is set at 30 kt, which is in agreement with the latest
Dvorak classifications and earlier ASCAT data.  Strong upper-level
winds over the cyclone are expected to continue during the next 24
hours or so.  After that time, the depression is forecast to move
into an area of decreasing shear and some gradually strengthening is
predicted.  Late in the period, the cyclone will move into a less
favorable thermodynamic environment and weakening should commence.
The NHC intensity forecast is close to the SHIPS guidance.

The initial motion estimate is 285/12 kt.  The depression should
move west-northwestward to the south of a mid-level ridge over
Mexico during the next several days.  After 72 hours, the cyclone
will approach a weakness in the ridge caused by a mid-latitude
trough that will be moving into California.  This should cause the
cyclone to slow down and turn northwestward by days 4 and 5. The
track guidance is in good agreement with this scenario and the NHC
track is a blend of the latest ECMWF and GFS model solutions.

FORECAST POSITIONS AND MAX WINDS

INIT  24/1500Z 15.0N 105.5W   30 KT  35 MPH
 12H  25/0000Z 15.7N 107.0W   30 KT  35 MPH
 24H  25/1200Z 16.7N 109.0W   30 KT  35 MPH
 36H  26/0000Z 17.7N 110.9W   35 KT  40 MPH
 48H  26/1200Z 18.6N 112.7W   40 KT  45 MPH
 72H  27/1200Z 20.0N 115.0W   45 KT  50 MPH
 96H  28/1200Z 21.0N 116.0W   45 KT  50 MPH
120H  29/1200Z 22.0N 116.5W   40 KT  45 MPH

$$
Forecaster Brown

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