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TROPICAL STORM HOWARD DISCUSSION NUMBER  10
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092016
200 PM PDT TUE AUG 02 2016

Microwave data indicate that deep convection is displaced a bit to
the north of the low-level center due to moderate southerly shear.
Subjective Dvorak estimates are 3.0/45 kt while objective numbers
have actually increased to between 50-55 kt.  Due to the
conflicting estimates, the initial intensity is being maintained at
50 kt.

Howard is located along the southwestern edge of the subtropical
ridge, and its initial motion remains 295/13 kt.  The ridge is
forecast to build westward and remain situated north of the cyclone
for the entire forecast period, which should maintain Howard on a
west-northwestward or westward heading through day 5.  The track
guidance remains tightly clustered, but there has been a notable
southward shift in the overall model envelope, especially beyond
day 3.  As a result, the NHC official forecast is also shifted a
bit southward and is very close to the TVCN multi-model consensus.

Howard is now moving over sea surface temperatures around 25C and
is forecast to move over even colder waters for the next 2 to 3
days.  Vertical shear, on the other hand, is expected to be less
than 20 kt through 72 hours.  Possibly due to these conflicting
conditions, the intensity forecast is somewhat uncertain.  The
SHIPS and LGEM models indicate that the cyclone will steadily
weaken to a remnant low through day 5, while the HWRF and GFDL
models show a more gradual weakening rate, with even some
re-intensification around days 3 and 4.  These models showed
similar scenarios for Hurricane Darby, which moved through a
similar region, and the SHIPS and LGEM models ended up having a
significant low bias for that storm.  In addition, simulated
infrared satellite imagery derived from the GFS and ECMWF models
shows the cyclone maintaining deep convection through 5 days.  The
NHC official forecast continues to depict the system becoming
post-tropical in 72 hours once the vertical shear increases above 20
kt, but there is low confidence in the time of this transition.  In
addition, the official forecast intensities are a little higher from
36 hours and beyond compared to the previous forecast and are close
to the IVCN intensity consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  02/2100Z 19.3N 130.2W   50 KT  60 MPH
 12H  03/0600Z 20.1N 132.2W   45 KT  50 MPH
 24H  03/1800Z 21.0N 135.0W   45 KT  50 MPH
 36H  04/0600Z 21.7N 137.8W   45 KT  50 MPH
 48H  04/1800Z 22.1N 140.7W   40 KT  45 MPH
 72H  05/1800Z 22.5N 146.6W   40 KT  45 MPH...POST-TROPICAL
 96H  06/1800Z 22.5N 151.5W   35 KT  40 MPH...POST-TROPICAL
120H  07/1800Z 23.0N 156.0W   30 KT  35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Berg

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