[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 152035
TCDAT5

HURRICANE NICOLE DISCUSSION NUMBER  47
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152016
500 PM AST SAT OCT 15 2016

Nicole is currently showing a hybrid structure.  On the larger
scale, the system has the appearance of an extratropical low, with
cold air advection occurring over the southern semicircle and a
developing frontal cloud band east through south of the center.
However, the system has secluded an area of warm air near the
center where a tropical cyclone wind and temperature structure
exists. The earlier scatterometer overpass showed the radius of
maximum winds to be about 75 n mi, and the warm core is strong
enough to produce hurricane-strength AMSU intensity estimates.
Based on little change in the appearance of the cloud pattern since
the last advisory, the intensity is held at 75 kt.

The GFS and the ECMWF continue to forecast organized central
convection for the next 36-48 hours, indicating that Nicole is
likely to maintain tropical cyclone characteristics.  After that
time, the cyclone should move over sea surface temperatures of 16
deg C or less that should cause the central convection to dissipate.
Based on this, the intensity forecast calls for Nicole to become
post-tropical by 72 hours and then fully extratropical by 96 hours.
The latest dynamical model guidance forecasts the cyclone to be
absorbed by another extratropical low by 120 hours, and that is now
reflected in the intensity forecast.  The new forecast is otherwise
an update of the previous forecast.

The initial motion is now 075/10.  A slow easterly motion is
expected during the next 36 hours or so while the cyclone is in an
area of weaker flow in the mid-latitude westerlies.  After that
time, a large mid-latitude trough moving into eastern Canada should
steer Nicole north-northeastward with an increase in forward speed.
The new forecast track is again similar to the previous track and
lies near the various consensus models.

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  15/2100Z 39.4N  49.4W   75 KT  85 MPH
 12H  16/0600Z 39.5N  48.0W   75 KT  85 MPH
 24H  16/1800Z 39.8N  46.7W   70 KT  80 MPH
 36H  17/0600Z 40.6N  45.5W   65 KT  75 MPH
 48H  17/1800Z 42.5N  43.7W   65 KT  75 MPH
 72H  18/1800Z 50.0N  38.0W   60 KT  70 MPH...POST-TROPICAL
 96H  19/1800Z 60.0N  34.5W   55 KT  65 MPH...POST-TROP/EXTRATROP
120H  20/1800Z...ABSORBED BY EXTRATROPICAL LOW

$$
Forecaster Beven
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