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Tropical Storm Otis Discussion Number  21
NWS National Hurricane Center Miami FL       EP152017
200 PM PDT Sat Sep 16 2017

The system has been maintaining a small area of deep convection
near the low-level center for the past several hours.  The latest
Dvorak classification from TAFB and ADT values from CIMSS at the
University of Wisconsin have increased, and now support raising the
initial intensity to 35 kt, making the system a tropical storm.

Otis is expected to remain over 27 deg C waters and in a low
wind shear environment for the next couple of days, and this should
allow the cyclone to at least maintain its strength.  Beyond that
time, an increase in shear, drier air, and cooler waters along the
expected track should cause weakening, and Otis is now
forecast to become a remnant low by day 4.  The NHC intensity
forecast is slightly higher than the previous one, based on the
higher initial intensity.

The tropical cyclone continues to drift westward in weak steering
currents.  The models remain in agreement that the storm should
turn slowly northward during the next day or two when it moves
along the west side of a weak mid-level ridge. Once the system
loses convection, a turn back toward the west or west-southwest is
predicted.  The NHC track forecast is a little to the west of the
previous one in the short term to account for the more westward
initial position.

FORECAST POSITIONS AND MAX WINDS

INIT  16/2100Z 15.9N 127.0W   35 KT  40 MPH
 12H  17/0600Z 16.0N 127.2W   35 KT  40 MPH
 24H  17/1800Z 16.4N 127.3W   35 KT  40 MPH
 36H  18/0600Z 17.2N 127.3W   35 KT  40 MPH
 48H  18/1800Z 17.9N 127.3W   35 KT  40 MPH
 72H  19/1800Z 18.0N 128.3W   30 KT  35 MPH
 96H  20/1800Z 17.0N 130.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  21/1800Z 15.8N 133.7W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Cangialosi

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