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TROPICAL STORM OTTO DISCUSSION NUMBER  21
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP222016
900 PM CST FRI NOV 25 2016

Otto is showing the effects of 20-25 kt of easterly vertical wind
shear, as the center is located near the eastern edge of the main
convective area.  Satellite intensity estimates from TAFB and SAB
remain 55 kt, and there is a recent estimate of 47 kt from the
CIMSS satellite consensus technique.  Based on these data, the
initial intensity remains 50 kt.

There are a lot of negative environmental factors in the intensity
forecast.  In the first 12-24 hours, these include moderate to
strong shear and abundant dry air seen in water vapor imagery near
Otto.  At 24-36 hours, the cyclone is likely to move across an area
of cooler sea surface temperatures.  Finally, from 72-120 hours Otto
or its remnants should encounter more dry air and upper-level
convergent flow.  Given these factors, it is not a surprise that the
global models forecast Otto to meet a quick demise.  On the other
hand, the SHIPS and LGEM models forecast a slower decay and suggest
Otto could still be a tropical cyclone at 120 hours.  The new
intensity forecast will lean a little more toward the global models
and show lower intensities than the previous forecast, with the
cyclone forecast to weaken to a depression at 96 hours and to a
remnant low at 120 hours.  However, if the global models are right
both of these events could occur earlier.

The initial motion is 255/14.  The cyclone continues to be south of
a strong deep-layer ridge over Mexico, and this steering pattern
will force Otto to move on a general west-southwestward to westward
track for the next 2-3 days.  After that time, Otto or its remnants
will be located near the southwestern edge of the ridge, which
should result in a turn toward the northwest and a decrease in
forward speed.  The track guidance remains in good agreement with
this scenario, although there is some divergence in how sharply the
system will turn northward at 120 hours.  The new forecast track is
similar to the previous track through 96 hours, then it lies between
the previous track to the west and the consensus models to the east
at 120 hours.


FORECAST POSITIONS AND MAX WINDS

INIT  26/0300Z  9.7N  90.7W   50 KT  60 MPH
 12H  26/1200Z  9.2N  92.7W   45 KT  50 MPH
 24H  27/0000Z  8.9N  95.7W   40 KT  45 MPH
 36H  27/1200Z  8.8N  98.8W   40 KT  45 MPH
 48H  28/0000Z  8.8N 101.7W   35 KT  40 MPH
 72H  29/0000Z 10.0N 106.0W   35 KT  40 MPH
 96H  30/0000Z 11.5N 107.5W   30 KT  35 MPH
120H  01/0000Z 13.0N 108.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Beven

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