[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 092040
TCDAT5

TROPICAL STORM NICOLE DISCUSSION NUMBER  23
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152016
500 PM AST SUN OCT 09 2016

Nicole's cloud pattern has become better organized this afternoon.
Deep convection has been pulsing but, unlike yesterday, it has not
diminished.  The cyclone's maintenance of deep convection suggests
that the vertical shear has decreased, which is supported by the
SHIPS analyses. In addition, the low-level center is underneath but
on the northwestern side of a formative and expanding central dense
overcast, consisting of cold cloud tops. Dvorak classifications are
T3.5 from TAFB and SAB, and the initial intensity estimate is
therefore raised to 55 kt.

Nicole has been nearly stationary during the last several hours.  A
slow motion generally toward the north or north-northwest is
expected to commence soon, now that the blocking high north of it
has slid to the northeast of Nicole. A shortwave trough currently
over the northeastern United States is shown in global model
solutions bypassing Nicole in about 2 days.  The ECMWF has stronger
ridging in the wake of this feature than the GFS, and thus carries
Nicole farther to the west as did the 0000 UTC ECMWF ensembles.  A
turn toward the north and northeast is likely after 72 hours once
Nicole reaches a belt of stronger mid-latitude southwesterly flow.
The new track forecast is adjusted slightly to the left of the
previous one and is slower, and it is shifted again toward the
ECMWF. The NHC track is close to an average of the ECMWF and GFS
models and to the west of the other model consensus aids.

Northerly vertical shear of 20 to 25 kt over Nicole will continue
for about another 24 hours, which should prevent significant
intensification from occurring.  After that time, the shear is
forecast to gradually diminish and remain relatively low until
about 3 days. The reduction of shear, in combination with
near-record warm SSTs, a relatively moist environment, and an
increasingly diffluent flow aloft, suggest that intensification is
likely.  The only caveat involves much a cooler and drier air mass
in the wake of Post-Tropical Cyclone Matthew would affect Nicole.
The new intensity forecast is increased again, much more than in the
previous advisory, and is near the high end of the guidance in
closest agreement with the SHIPS model.  It is worth mentioning that
global models continue to show significant deepening in 2 to 3 days,
still more than indicated in the current forecast. The guidance
shows a sharp increase in shear by 96 hours, which ordinarily would
curb any further intensification.  However, baroclinic forcing could
offset the negative effects of the shear and Nicole should at a
minimum maintain its intensity if not intensify a bit further.

FORECAST POSITIONS AND MAX WINDS

INIT  09/2100Z 24.2N  65.3W   55 KT  65 MPH
 12H  10/0600Z 25.0N  65.2W   60 KT  70 MPH
 24H  10/1800Z 25.9N  65.3W   65 KT  75 MPH
 36H  11/0600Z 26.6N  65.5W   70 KT  80 MPH
 48H  11/1800Z 27.2N  65.9W   75 KT  85 MPH
 72H  12/1800Z 28.4N  66.4W   80 KT  90 MPH
 96H  13/1800Z 31.3N  65.0W   80 KT  90 MPH
120H  14/1800Z 35.4N  59.0W   75 KT  85 MPH

$$
Forecaster Kimberlain
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