[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 102035
TCDAT5

TROPICAL STORM NICOLE DISCUSSION NUMBER  27
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152016
500 PM AST MON OCT 10 2016

While Nicole's convective organization has not changed much over
the last several hours, satellite data indicate that the cyclone is
maintaining a well-defined inner-core structure. Several bands have
also developed over the eastern half of the circulation.  An ASCAT
pass received after the previous advisory's issuance indicated a
couple of reliable 50-kt wind vectors, and the initial intensity
estimate is set to this value in basic agreement with satellite
classifications.

Nicole appears to have turned slightly west of due north, and the
initial motion estimate is 355/05.  This general motion is expected
to continue through tonight or early Tuesday while a shortwave
trough treks across Atlantic Canada and bypasses the storm to the
north.  In the wake of this weather system, a weak low- to mid-level
ridge is forecast to build north and west of Nicole for a short
time, allowing the track to bend more toward the left. The ECMWF
continues to predict a greater westerly component motion than the
other guidance for the next 3 days, with still about half of the
the 0000 UTC ensemble members left of the current forecast.  Before
Nicole reaches 30N, it should encounter a stronger mid-latitude flow
and recurve into the westerlies with increasing forward speed over
the next few days. The new track forecast continues to place greater
weight on the ECMWF guidance suite, which results in the track being
adjusted slightly left of the previous one through the forecast
period.  It is in the middle of the 0000 UTC ECMWF ensemble output
and to the left of the latest multi-model consensus.

Nicole is still struggling partially from mid- to upper-level dry
air associated with a lobe of vorticity from a mid-latitude
shortwave trough that has been wrapping around the cyclone's
circulation.  In addition, oceanic upwelling beneath the cyclone
has also likely contributed to the cyclone's lack of convective
vigor.  Once Nicole starts to move farther west over untapped waters
and its interaction with the above-mentioned feature ends, the
strong northerly shear affecting Nicole for days will have decreased
significantly. With the tropical cyclone moving over near-record
warm SSTs at that time, in a reasonably moist large-scale
environment, and under a diffluent flow at upper levels, a
significant intensification is likely. Global models maintain the
theme of showing substantial deepening over the next few days.  By
72 hours, or shortly thereafter, strong southwesterly shear could
bring the predicted intensification to a close unless baroclinic
processes counteract the shear enough to allow for some further
increase in strength.  Extratropical transition in shown by day 5.
The new intensity forecast is an update of the previous one and
generally near or just above the model consensus aids.



FORECAST POSITIONS AND MAX WINDS

INIT  10/2100Z 26.3N  65.4W   50 KT  60 MPH
 12H  11/0600Z 26.9N  65.7W   55 KT  65 MPH
 24H  11/1800Z 27.5N  66.3W   65 KT  75 MPH
 36H  12/0600Z 28.2N  66.7W   70 KT  80 MPH
 48H  12/1800Z 29.5N  66.7W   80 KT  90 MPH
 72H  13/1800Z 33.2N  64.3W   80 KT  90 MPH
 96H  14/1800Z 38.1N  58.3W   80 KT  90 MPH
120H  15/1800Z 42.0N  54.2W   70 KT  80 MPH...POST-TROP/EXTRATROP

$$
Forecaster Kimberlain

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