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TROPICAL STORM FAY DISCUSSION NUMBER  13
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072014
500 AM AST MON OCT 13 2014

A series of microwave images indicate that Fay has begun
extratropical transition.  The cloud pattern has become quite
asymmetric and the remaining central deep convection, situated well
to the northeast of the center of circulation, is decreasing.  An
earlier AMSU-B overpass showed significant erosion of the southern
flank of Fay due to intruding cold, dry, low to mid-level air
associated with an approaching strong baroclinic frontal zone.
Furthermore, the GFS model-forecast cyclone phase diagram shows Fay
completing transition to an asymmetric cold core system in 12 hours
or so.  A compromise of the objective and subjective satellite
intensity estimates keeps the initial intensity at 55 kt for this
advisory.  Although the cyclone is expected to remain generally
in warm water south of the Gulf Stream's north wall, strong,
persistent, vertical shear is forecast to further weaken Fay through
the 72 hr period.  Afterward, the post-tropical cyclone should
continue to decay and open up into a trough of low pressure within
the aforementioned frontal boundary and dissipate over the
northeastern Atlantic.  Based on a consensus of the global models,
an adjustment to the length of the official forecast has been made,
and it now postpones dissipation until day 4.

The tropical storm is gradually accelerating eastward and is now
moving at 23 kt within the mid-latitude westerlies.  Fay is
forecast to slow a bit during the next 24 hours, in response to
interaction with the cold front, and track eastward to
east-southeastward until dissipation.  The NHC forecast is close to
the TVCA multi-model consensus and the post-tropical cyclone
forecast guidance from the Ocean Prediction Center.

FORECAST POSITIONS AND MAX WINDS

INIT  13/0900Z 34.3N  55.3W   55 KT  65 MPH
 12H  13/1800Z 34.3N  51.2W   50 KT  60 MPH...POST-TROP/EXTRATROP
 24H  14/0600Z 33.7N  47.2W   40 KT  45 MPH...POST-TROP/EXTRATROP
 36H  14/1800Z 32.7N  43.2W   35 KT  40 MPH...POST-TROP/EXTRATROP
 48H  15/0600Z 32.1N  39.5W   30 KT  35 MPH...POST-TROP/EXTRATROP
 72H  16/0600Z 32.0N  32.0W   25 KT  30 MPH...POST-TROP/EXTRATROP
 96H  17/0600Z...DISSIPATED

$$
Forecaster Roberts

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