[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 150246
TCDAT5

TROPICAL STORM NICOLE DISCUSSION NUMBER  44
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152016
1100 PM AST FRI OCT 14 2016

Deep convection redeveloped northeast of Nicole's center just after
1800 UTC and has persisted since that time despite nearly 50 kt of
southwesterly shear.  The Dvorak Current Intensity number from TAFB
has decreased to 3.5, and Nicole's initial intensity is therefore
lowered conservatively to 60 kt.

The future classification of Nicole continues to be a quandary,
only because the system will be straddling the nebulous boundary of
what constitutes a tropical and non-tropical cyclone.  Nicole
continues to have a warm core and has not become attached to a
frontal boundary, and phase-space diagrams based off the global
models indicate that the cyclone will only become more symmetric
and develop a deeper warm core from this point forward.  Nicole
will likely become a warm seclusion, with its warm core isolated
from surrounding colder air, and that structure could allow the
cyclone to maintain tropical characteristics even at such a high
latitude.  Simulated infrared satellite imagery from the GFS and
ECMWF models suggests that the cyclone may even develop an eye-like
feature in a day or two.  Given these model trends, it has become
more likely that Nicole will retain tropical or subtropical
characteristics, and the NHC forecast now does not show the system
becoming post-tropical until day 4.  This forecast remains highly
uncertain, however, and does not eliminate the possibility of Nicole
becoming post-tropical during the next day or so.  Regardless of its
classification, Nicole is expected to restrengthen during the next
12-24 hours, mostly due to forcing from an approaching mid-latitude
trough.  If more symmetric deep convection does develop, then the
cyclone should be able to maintain hurricane intensity at least
through day 3.  The NHC intensity forecast closely follows the GFS
and ECMWF models.

The initial motion has increased to 065/19 kt.  However, Nicole is
expected to slow down considerably between 24-48 hours when it
interacts with the approaching shortwave trough and becomes cut off
from the mid-latitude westerlies.  Another mid-latitude trough that
will move across Atlantic Canada on day 3 should cause Nicole to
accelerate north-northeastward on days 4 and 5.  The track guidance
is in very good agreement through the forecast period, and no
significant changes were required from the previous NHC track
forecast.

The radii on the western side of Nicole's circulation have been
increased based on a recent ASCAT-B pass.  Guidance from the NOAA
Ocean Prediction Center was used for the forecast wind radii.

Swells from Nicole will affect Bermuda and portions of the U.S. east
coast and Atlantic Canada during the next couple of days.  By early
next week, wave models suggest that long-period swell from Nicole
will radiate outward and affect much of the North Atlantic basin.

FORECAST POSITIONS AND MAX WINDS

INIT  15/0300Z 37.4N  53.3W   60 KT  70 MPH
 12H  15/1200Z 38.2N  51.0W   70 KT  80 MPH
 24H  16/0000Z 38.6N  48.8W   70 KT  80 MPH
 36H  16/1200Z 38.7N  47.5W   65 KT  75 MPH
 48H  17/0000Z 39.0N  46.6W   65 KT  75 MPH
 72H  18/0000Z 42.1N  43.3W   65 KT  75 MPH
 96H  19/0000Z 50.5N  38.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
120H  20/0000Z 58.0N  34.0W   50 KT  60 MPH...POST-TROP/EXTRATROP

$$
Forecaster Berg
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