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Tropical Storm Otis Discussion Number  24
NWS National Hurricane Center Miami FL       EP152017
800 AM PDT Sun Sep 17 2017

Otis continues to gradually strengthen.  Satellite images show hints
of an eye starting to form, and convection just outside the
center has been increasing during the past few hours.  A blend of
the TAFB Dvorak classification and ADT values from CIMSS at the
University of Wisconsin supports increasing the winds to 50 kt,
though this could be conservative based on the current structure.

Otis has a little more time to strengthen since the storm is
expected to remain in an environment of low wind shear and over 27
deg C waters.  After 24 hours, however, lower SSTs, drier air, and
an increase in wind shear should cause weakening.  Even though SSTs
warm along the expected path by the end of the forecast period, the
models continue to show Otis decaying due to unfavorable atmospheric
conditions.  The cyclone is forecast to become a remnant low by day
4 based on the global models, but this is a low confidence
prediction at this time.

The tropical storm has now turned to the north, as expected, at a
very slow forward speed.  This slow north to north-northwest motion
is expected during the next 36 hours while Otis moves on the west
side of a weak mid-level ridge.  Thereafter, a faster west
and west-southwest motion is expected when the weakening cyclone
becomes more influenced by the low-level tradewind flow.  Only
minor changes were made to the previous NHC track forecast, and this
one lies close to the various consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  17/1500Z 16.3N 127.3W   50 KT  60 MPH
 12H  18/0000Z 17.1N 127.4W   55 KT  65 MPH
 24H  18/1200Z 18.0N 127.5W   55 KT  65 MPH
 36H  19/0000Z 18.8N 127.7W   50 KT  60 MPH
 48H  19/1200Z 18.9N 128.3W   45 KT  50 MPH
 72H  20/1200Z 18.1N 130.1W   35 KT  40 MPH
 96H  21/1200Z 17.0N 133.1W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  22/1200Z 15.7N 136.6W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Cangialosi

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