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Tropical Depression NINE-E


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TROPICAL DEPRESSION NINE-E DISCUSSION NUMBER   2
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092016
200 PM PDT SUN JUL 31 2016

Visible satellite imagery showed a low-level cloud swirl emerge
from the convective canopy after the previous advisory was issued.
However, for now it appears that this was not the primary center of
the cyclone, as it has dissipated and low cloud lines continue to
suggest a center closer to the convection.  Given the somewhat
disorganized nature of the system for now, the initial intensity is
held at 30 kt in agreement with the latest Dvorak estimate from
SAB.

The SHIPS model analysis shows about 10 kt of north-northwesterly
shear over the depression, which is consistent with the convection
being displaced mainly to the south and east of the center.  This
shear is expected to relax a little, but the cyclone will only be
over SSTs above 26C for the next 36 hours or so.  This should allow
for some strengthening, followed by gradual weakening to post-
tropical status over cool waters and in a dry, stable atmospheric
environment in about 3 days.  The new NHC intensity forecast is
similar to the previous one, and close to the IVCN consensus aid.

The uncertainty in the center position leads to an uncertain
initial motion estimate of 295/09, which is based in part on
continuity.  Despite this, the track forecast reasoning remains
relatively straightforward,  as a mid-level ridge is expected to
build westward to the north of the cyclone through the forecast
period.  This should result in a west-northwestward heading and
an increase in forward speed over the next 48 hours.  After that
time, the track should gradually bend back toward the west as the
increasingly shallow cyclone comes under the influence of the
low-level trade winds.  The NHC track forecast is about 40 n mi
north of the previous one due to the adjustment in the initial
position, but is otherwise near the middle of the guidance envelope
and the TVCN multi-model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  31/2100Z 15.4N 121.2W   30 KT  35 MPH
 12H  01/0600Z 15.9N 122.6W   35 KT  40 MPH
 24H  01/1800Z 16.7N 124.8W   40 KT  45 MPH
 36H  02/0600Z 17.8N 127.2W   45 KT  50 MPH
 48H  02/1800Z 19.1N 129.9W   45 KT  50 MPH
 72H  03/1800Z 21.1N 135.5W   35 KT  40 MPH
 96H  04/1800Z 22.4N 140.8W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  05/1800Z 23.0N 146.5W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Brennan

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