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Tropical Storm Tara Discussion Number   5
NWS National Hurricane Center Miami FL       EP222018
1000 AM CDT Mon Oct 15 2018

Tara remains a small, sheared tropical cyclone with convection
continuing to go through bursting phases near the low-level center.
Extremely cold overshooting cloud tops of -90C to -95C have been
occurring just north of the center during the past couple of hours,
and the convective cloud shield has gradually been expanding
southeastward over the center. Satellite intensity estimates are
T3.0/45 kt from TAFB and T2.5/35 kt from SAB, and the most recent
objective ADT estimate from UW-CIMSS was T3.1/47 kt. Based on these
data, the intensity is conservatively raised to 40 kt.

The initial motion estimate is an uncertain 295/01 kt. Tara is
expected to only drift toward the west-northwest or northwest for
the next couple of days while the small cyclone remains embedded in
weak steering currents. The GFS and UKMET models move Tara inland
just west of Manzanillo, Mexico, in 36-48 hours, whereas the ECMWF,
GFS-FV3, HWRF, HMON, COAMPS-TC, and Canadian models keep the center
offshore. For now, the official forecast track follows the consensus
models TVCE, HCCA, and FSSE, keeping the center offshore the
southwestern coast of Mexico since there appears to be no
significant steering mechanism to force the circulation onshore for
the next couple of days. After 48 hours, the ridge to the north of
Tara is forecast to build westward across central Mexico, forcing
the cyclone on a west-northwestward track at a slightly faster
forward speed. However, due to continued large spread in the
guidance, the track forecast is of low confidence.

Moderate easterly to southeasterly shear is forecast by the models
to affect Tara for the next 24 hours or so. By 36 hours, the shear
is forecast to decrease to less than 5 kt and remain low until 72
hours, which should allow for some modest strengthening to occur...
assuming the center remains offshore. The small circulation, low
vertical wind shear conditions, and warm ocean temperatures near 30C
would typically result in more significant strengthening, but
proximity to land and a dry surrounding environment is expected to
temper the intensification process somewhat. By days 4 and 5,
southwesterly shear forecast to increase to around 20 kt should is
expected to induce some slight weakening. The official intensity
forecast is similar to but slightly higher than the consensus models
HCCA, IVCN, and FSSE, and maintains continuity with the previous
forecast.

Regardless of how close Tara comes to southwestern Mexico, heavy
rainfall will be the primary threat along the coast of southwestern
Mexico due to the system's slow motion, and life-threatening flash
flooding will be possible in mountainous areas.

FORECAST POSITIONS AND MAX WINDS

INIT  15/1500Z 17.6N 104.4W   40 KT  45 MPH
 12H  16/0000Z 17.8N 104.6W   45 KT  50 MPH
 24H  16/1200Z 17.9N 104.7W   50 KT  60 MPH
 36H  17/0000Z 17.9N 105.1W   50 KT  60 MPH
 48H  17/1200Z 18.0N 105.7W   55 KT  65 MPH
 72H  18/1200Z 18.4N 107.0W   55 KT  65 MPH
 96H  19/1200Z 18.9N 108.1W   50 KT  60 MPH
120H  20/1200Z 19.0N 108.1W   45 KT  50 MPH

$$
Forecaster Stewart

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