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Tropical Depression Eighteen-E Discussion Number   2
NWS National Hurricane Center Miami FL       EP182018
200 PM PDT Sat Sep 08 2018

GOES-16 visible imagery shows the center of the depression on the
edge of a convective mass, with a large part of the eastern part of
the circulation exposed due to shear.   Dvorak estimates are a
little higher than the last advisory, but the evidence is not strong
enough yet to upgrade the system to a tropical storm, so the
winds will stay 30 kt.  Gradual strengthening is anticipated while
the cyclone remains over warm waters within a light-to-moderate
shear environment. After 72 hours, the water temperatures drop off
quite a bit and weakening should begin.  The biggest change is that
the model guidance is considerably lower in this cycle, perhaps due
to easterly shear persisting for a bit longer.  Only a small
decrease was made to the intensity forecast at long range, but
later advisories could be lower if model trends continue.

Visible imagery also helped reposition the depression about a
degree west of the last advisory.  Ironically, the initial motion
estimate is unchanged, still 290/10 kt.  A mid-level ridge over
Mexico should steer the system northwestward for the next day or so,
then the dominant eastern Pacific subtropical ridge is forecast to
turn the system back toward the west-northwest.  Numerical guidance
is a fair distance west of the previous cycle, and the NHC forecast
follows that trend, resulting in a large westward adjustment to the
NHC forecast after absorbing the initial position change.


FORECAST POSITIONS AND MAX WINDS

INIT  08/2100Z 15.8N 116.8W   30 KT  35 MPH
 12H  09/0600Z 16.5N 117.8W   35 KT  40 MPH
 24H  09/1800Z 17.6N 118.8W   40 KT  45 MPH
 36H  10/0600Z 18.9N 119.9W   45 KT  50 MPH
 48H  10/1800Z 19.9N 121.3W   50 KT  60 MPH
 72H  11/1800Z 21.0N 125.0W   60 KT  70 MPH
 96H  12/1800Z 22.3N 129.0W   50 KT  60 MPH
120H  13/1800Z 23.5N 132.0W   35 KT  40 MPH

$$
Forecaster Blake

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