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TROPICAL STORM OTTO DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL162016
1000 PM EST MON NOV 21 2016

Deep convection continues to burst over the low-level center of
Otto.  A 2329 UTC WindSat microwave overpass shows that the
inner-core structure of the small tropical cyclone has become
better organized with a low-level ring feature now evident.
Dvorak data T-numbers from SAB and TAFB have increased to 3.0
and 3.5, respectively, and objective T-numbers from UW/CIMSS are
3.2. These data support an initial wind speed of 50 kt, which
could be somewhat conservative.

The upper-level outflow remains well established over the western
and northern portions of the circulation but it remains restricted
to the southeast due to southeasterly shear of 15 to 20 kt.  The
shear is forecast to abate a little during the next couple of days
while Otto traverses SSTs of around 29C.  These conditions favor
intensification and the NHC forecast is near a consensus of the
SHIPS and LGEM models, and brings Otto to hurricane strength within
36 hours.  Although the NHC forecast does not indicate strengthening
between 48 and 72 hours, Otto could become a little stronger after
48 hours and before it moves inland over Central America in about
3 days. After that time, uncertainty remains as to whether the
tropical cyclone will survive its crossing of Central America. The
NHC forecast continues to show the system as a remnant low over the
eastern Pacific, which is supported by most of the global models.

Center fixes from the microwave imagery indicate that Otto has
been drifting southward this evening.  The cyclone is not expected
to move much overnight while it remains within an area of weak
steering currents.  On Tuesday, a mid-level ridge is forecast to
begin building to the north of the storm and Otto is forecast to
start moving slowly westward.  The ridge is expected to remain in
place during the remainder of the week and Otto should continue to
move generally westward at a slightly faster pace.  The new NHC
track forecast is similar to the previous advisory, and lies between
the latest GFS and ECMWF solutions, which is also near the most
recent GFS ensemble mean.


FORECAST POSITIONS AND MAX WINDS

INIT  22/0300Z 10.9N  79.1W   50 KT  60 MPH
 12H  22/1200Z 10.8N  79.3W   55 KT  65 MPH
 24H  23/0000Z 10.9N  79.8W   60 KT  70 MPH
 36H  23/1200Z 11.1N  80.7W   65 KT  75 MPH
 48H  24/0000Z 11.3N  81.5W   70 KT  80 MPH
 72H  25/0000Z 11.3N  84.0W   70 KT  80 MPH...INLAND
 96H  26/0000Z 11.3N  87.2W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  27/0000Z 10.8N  90.5W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Brown

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