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TROPICAL STORM IVETTE DISCUSSION NUMBER  14
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP102016
800 PM PDT FRI AUG 05 2016

The convective structure of Ivette has not changed substantially
this evening with most of the convection limited to the northeastern
semicircle.  A blend of the TAFB/SAB Dvorak, CIMSS Advanced Dvorak,
and AMSU intensity estimates indicate about 50 kt at the initial
time, unchanged from the previous advisory.  Ivette remains small in
size, as indicated by the limited central dense overcast and
tropical-storm-force wind radii from CIRA/AMSU.

While Ivette remains over 28C water, the vertical shear appears to
still be disrupting the convection, as the center - like yesterday -
is occasionally showing up just west of the cirrus canopy. Even
though the shear is quite low (5 to 10 kt from the CIMSS and SHIPS
analyses), Ivette's small size and moderate intensity isn't enough
to overcome the shear's detrimental effects.  The tropical storm has
about 12-24 hours of time left to intensify before the combination
of cool SSTs, dry stable air, and strong southwesterly vertical
shear kicks in.  Once that combination begins, Ivette should
steadily weaken and become a remnant low in about four days and
dissipate shortly afterwards.  The NHC intensity forecast, based
upon the IVCN intensity consensus technique, indicates a slight
intensification shortly before weakening commences in a couple days.
 It is of note that the only model to show significant strengthening
- COAMPS, boosting Ivette to about 60 kt - has been the best
performing guidance during the cyclone's lifetime.

There have been several helpful microwave images of Ivette providing
an accurate assessment of the system's center.  These indicate that
the tropical storm has not yet turned west-northwestward, as Ivette
continues moving westward at 9 kt, due the steering influence of a
mid-level subtropical ridge to its north.  Despite the current
motion, Ivette should turn toward the west-northwestward shortly, as
it begins to round the western periphery of the ridge.  However, in
about three days, the tropical cyclone should bend back toward west
as it is advected along in the easterly trade winds.  The NHC track
forecast is based upon the tightly clustered members of
the multi-model ensemble (TVCN) and is somewhat south of the track
from the previous advisory at 12 and 24 hours because of the
unexpected continuation of westward motion.


FORECAST POSITIONS AND MAX WINDS

INIT  06/0300Z 15.4N 132.6W   50 KT  60 MPH
 12H  06/1200Z 15.8N 134.0W   55 KT  65 MPH
 24H  07/0000Z 16.6N 135.8W   55 KT  65 MPH
 36H  07/1200Z 17.4N 137.5W   50 KT  60 MPH
 48H  08/0000Z 18.2N 138.9W   40 KT  45 MPH
 72H  09/0000Z 18.8N 141.8W   30 KT  35 MPH
 96H  10/0000Z 18.5N 145.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  11/0000Z...DISSIPATED

$$
Forecaster Landsea

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