[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 071436
TCDAT5

TROPICAL STORM NICOLE DISCUSSION NUMBER  14
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152016
1100 AM AST FRI OCT 07 2016

Strong shear has taken its toll on Nicole overnight.   The cyclone's
cloud pattern has rapidly deteriorated, with the low-level center
now exposed to the northwest of a greatly reduced area of deep
convection. Dvorak Final T-numbers have decreased quickly to T3.5
from SAB and TAFB, and a blend of these and CI-numbers was used to
set the initial intensity to 65 kt at 1200 UTC. Since the cloud
pattern has degraded even further since that time, the advisory
intensity is lowered to 60 kt, which could prove to be generous.

Nicole has barely been moving, and the initial motion estimate
is nearly stationary.  Although Nicole remains in a region of weak
steering at the moment, a blocking mid-level high should build
north of the cyclone soon, and impart a slow motion generally
toward the south for the next couple of days.  Around 48 hours, a
mid-level ridge is forecast to develop to the east of Nicole, which
should result in the cyclone gradually turning northward with
some increase in forward speed through the remainder of the
forecast period.  Most of the model guidance is in better agreement
than yesterday on this scenario, which increases the overall
confidence of the track forecast.  The new track forecast is based
on a consensus of the regional and global models minus the GFDL.

A potent mid- to upper-level shortwave trough digging to the east
of Nicole should cause deep-layer northerly shear over the cyclone
to increase further today.  In the wake of the shortwave, the shear
should veer to the north-northeast but remain just as strong
through about 72 hours. Nicole is also shown interacting with a lobe
of vorticity that fractures from the shortwave, but it remains
unclear how this interaction would affect the cyclone's intensity or
structure. Regardless, the overall hostile environment should cause
weakening, perhaps even more than indicated in this forecast.
Indications are that late in the forecast period the large- scale
environment should become more conducive for Nicole to re-intensify,
but to what extent is in doubt.  As a result of developments
overnight, the new intensity forecast is substantially lower than
the previous one and is below all of the intensity guidance through
72 hours.  It is near the multi-model consensus after that time,
although this part of the forecast is of low confidence.


FORECAST POSITIONS AND MAX WINDS

INIT  07/1500Z 27.5N  65.3W   60 KT  70 MPH
 12H  08/0000Z 27.0N  65.1W   50 KT  60 MPH
 24H  08/1200Z 26.1N  64.8W   45 KT  50 MPH
 36H  09/0000Z 25.4N  64.7W   40 KT  45 MPH
 48H  09/1200Z 25.3N  65.1W   40 KT  45 MPH
 72H  10/1200Z 26.6N  65.7W   35 KT  40 MPH
 96H  11/1200Z 28.8N  66.1W   40 KT  45 MPH
120H  12/1200Z 32.0N  65.6W   50 KT  60 MPH

$$
Forecaster Kimberlain
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