[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 072036
TCDAT5

TROPICAL STORM NICOLE DISCUSSION NUMBER  15
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152016
500 PM AST FRI OCT 07 2016

Nicole is a heavily sheared tropical cyclone.  The well-defined
low-level center is partially exposed on the northwest side of a
bursting mass of deep convection.  Dvorak Final-T numbers have
continued to decrease to T3.0 from both satellite agencies, and a
blend of those with CI-numbers yields an initial intensity of
55 kt.

Nicole has begun to move southward, and the initial motion estimate
is 185/04.  A blocking high north of Nicole should continue to push
the cyclone slowly southward during the next couple of days.  After
that time, the mid-level ridge is forecast to rebuild east of
Nicole, and there is the potential for a binary interaction with
weakening Matthew to the west in 2 to 3 days.  This should cause
Nicole to do an about-face and begin moving northwestward or
north-northwestward from days 2 to 4.  A turn toward the north is
expected by day 5 once the binary interaction ends and Nicole is on
the cusp of entering a stronger mid-latitude southwesterly flow.
Although the bulk of the model guidance is in basic agreement with
this scenario, there are speed differences amongst the models that
make the track forecast of lower confidence than average.

Global models show no diminution of the northerly shear over
Nicole for the next two days or so.  A further complication is
Nicole's interaction during this same time period with a fractured
lobe of vorticity from a shortwave trough to the east that wraps
around the circulation.  The net result of all of this is that the
cyclone could weaken a bit further or remain steady state as a weak
tropical storm for 2 to 3 days, which is what the official forecast
and SHIPS model output indicates.  After that time, the shear is
forecast to decrease and the flow aloft is likely to become much
more diffluent, both of which support some re-intensification.  This
is shown in the latter part of the forecast period, which likewise
is in good agreement with SHIPS model output.


FORECAST POSITIONS AND MAX WINDS

INIT  07/2100Z 27.0N  65.2W   55 KT  65 MPH
 12H  08/0600Z 26.2N  65.0W   45 KT  50 MPH
 24H  08/1800Z 25.4N  64.8W   40 KT  45 MPH
 36H  09/0600Z 25.1N  64.9W   40 KT  45 MPH
 48H  09/1800Z 25.5N  65.3W   40 KT  45 MPH
 72H  10/1800Z 27.4N  66.0W   45 KT  50 MPH
 96H  11/1800Z 29.7N  66.7W   50 KT  60 MPH
120H  12/1800Z 32.6N  66.4W   60 KT  70 MPH

$$
Forecaster Kimberlain
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