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Tropical Storm OTIS


Tropical Storm Otis Discussion Number  29
NWS National Hurricane Center Miami FL       EP152017
200 PM PDT Mon Sep 18 2017

Otis has continued to weaken very rapidly.  Without any recent ASCAT
data (or a reliable conceptual model for open-water rapid
weakening), it is tough for me to estimate just how fast the cyclone
is weakening.  Satellite classifications remain constrained, but
given the continued lack of convection over the center, the initial
intensity has been lowered farther, to 40 kt.

Stratocumulus clouds wrap well into the southwest quadrant, evidence
that Otis is embedded within a very stable environment.  Continued
weakening seems inevitable, and the only real question is how soon
Otis will become a remnant low.  The forecast now shows the cyclone
becoming a depression within 12 hours, and a remnant low within 24
hours.  Given current convective trends, Otis could become a remnant
low much sooner than indicated.  The remnant circulation is forecast
to persist for a couple days after that, in agreement with the most
recent ECMWF and GFS model runs.

As expected, Otis is coming to a halt, now that the circulation has
become very shallow.  Within the next 12 to 24 hours, the tropical
storm is still expected to be steered toward the southwest by a
ridge over the central Pacific, and a southwestward motion should
continue until the cyclone dissipates.  The NHC forecast is a little
south of the previous one since Otis appears to have already begun
its turn toward the southwest, and it is close to the various
consensus models.


INIT  18/2100Z 19.1N 127.6W   40 KT  45 MPH
 12H  19/0600Z 19.1N 128.0W   30 KT  35 MPH
 24H  19/1800Z 18.7N 128.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
 36H  20/0600Z 17.8N 129.7W   20 KT  25 MPH...POST-TROP/REMNT LOW
 48H  20/1800Z 16.6N 130.8W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  21/1800Z 14.5N 133.2W   15 KT  15 MPH...POST-TROP/REMNT LOW
 96H  22/1800Z...DISSIPATED

Forecaster Zelinsky