[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 080251
TCDAT5

TROPICAL STORM NICOLE DISCUSSION NUMBER  16
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152016
1100 PM AST FRI OCT 07 2016

Strong northerly shear continues to cause all of Nicole's deep
convection to be located in the southern semicircle of the storm.
The deep convection has been going up and down, very typical
for this type of sheared tropical cyclone.  ASCAT showed a sizable
area of winds near 45 kt, and after considering the low bias of
the instrument for a small tropical cyclone, the initial wind speed
is reduced to 50 kt.  This is also consistent with a blend of the
Dvorak T- and CI-numbers from TAFB.

Nicole is moving southward at about 6 kt.  A motion toward the south
or south-southeast is anticipated for the next day or so while the
tropical cyclone is steered on the east side of a mid-level high
between Nicole and Matthew.  The forecast gets very tricky in a
couple of days, with the mid-level high breaking down and Matthew
probably moving toward Nicole.  The possibility of tropical cyclone
binary interaction appears to be increasing, which could cause
Nicole to move toward the north or north-northwest in the 3 to 5 day
period. The details of this interaction, however, are very sketchy,
with models presenting a variety of fairly divergent solutions.  The
new NHC forecast is close to the ensemble means of the UKMET, ECMWF
and GFS, which ends up south of the previous forecast at short
range, and to the east of the previous forecast at long range. These
are relatively small changes since it is probably best not to move
the forecast very much until the models come into better agreement
on the final phase of Matthew.

Northerly shear is forecast to continue near Nicole over the next
two or three days.  Models do not show as much weakening as one
might think, perhaps due to the very warm water that Nicole will be
traversing, or due to Nicole's possible interaction with a shortwave
trough.  After that time, global models generally show a decrease
in shear and a diffluent upper-level pattern, which would support
some restrengthening. The model guidance is slightly higher than the
last cycle, and the latest NHC prediction is nudged in that
direction, although the new forecast is on the low side of the
guidance.

Needless to say, this is a fairly uncertain forecast overall
because Matthew could play a large role in a few days.


FORECAST POSITIONS AND MAX WINDS

INIT  08/0300Z 26.3N  65.3W   50 KT  60 MPH
 12H  08/1200Z 25.5N  65.1W   45 KT  50 MPH
 24H  09/0000Z 24.7N  64.9W   45 KT  50 MPH
 36H  09/1200Z 24.8N  65.2W   45 KT  50 MPH
 48H  10/0000Z 25.5N  65.5W   45 KT  50 MPH
 72H  11/0000Z 27.7N  65.8W   45 KT  50 MPH
 96H  12/0000Z 30.5N  66.0W   50 KT  60 MPH
120H  13/0000Z 33.5N  65.5W   60 KT  70 MPH

$$
Forecaster Blake
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