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HURRICANE JOAQUIN DISCUSSION NUMBER  32
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL112015
1100 AM AST MON OCT 05 2015

Joaquin's cloud pattern and overall structure has remained intact
based on conventional and microwave satellite data. Recent SSMIS
and SSMI microwave passes showed a well-defined small eye still
exists, which is also indicated in reflectivity data from the
Bermuda Doppler radar. As a result, the intensity of Joaquin is
being maintained at 75 kt, which is supported by Dvorak satellite
current intensity estimates of T4.5/77 kt from both TAFB and SAB.

The initial motion estimate is 030/11 kt. The forecast track and
reasoning basically remain unchanged. Joaquin is expected to turn
northeastward today and begin moving at a slightly faster forward
speed tonight and Tuesday as the hurricane rounds the northwestern
periphery of a weakening ridge and begins to feel the effects of the
faster flow in the mid-latitude westerlies. By 36 hours, Joaquin
should begin to accelerate east-northeastward at a faster forward
speed of more than 25 kt. The official forecast track is essentially
just an extension of the previous advisory track guidance and lies
close to the consensus models TCVA and GFEX through 48 hours. After
that time, the extratropical forecast track is based on guidance
provided by the NOAA Ocean Prediction Center.

Deep convection has persisted and even expanded somewhat since the
previous advisory, with a small area of cloud tops colder than -70C
having developed just west of the center. With the vertical wind
shear expected to remain between 10 to 15 kt for the next 24 hours
or so, only slight weakening is forecast. By 48 hours and beyond,
however, westerly vertical wind shear is forecast to increase to
more than 30 kt when the cyclone will be moving over SSTs less than
23C. The result should be steady weakening and a transition to a
large and expanding extratropical low pressure system over the north
Atlantic. Extratropical transition could occur sooner if Joaquin
interacts or merges with a frontal system currently located a few
hundred n mi north of the hurricane. The NHC intensity forecast is
similar to the previous advisory and follows the intensity consensus
model IVCN through 48 hours, and is based on guidance provided by
the Ocean Prediction Center for days 3-5.

The tropical storm force wind radii were expanded outward slightly
in the southwestern quadrant based on surface observation and radar
data from Bermuda.

FORECAST POSITIONS AND MAX WINDS

INIT  05/1500Z 35.0N  64.6W   75 KT  85 MPH
 12H  06/0000Z 36.3N  63.0W   70 KT  80 MPH
 24H  06/1200Z 38.0N  59.6W   70 KT  80 MPH
 36H  07/0000Z 39.3N  54.1W   65 KT  75 MPH
 48H  07/1200Z 40.5N  47.2W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  08/1200Z 42.5N  32.6W   55 KT  65 MPH...POST-TROP/EXTRATROP
 96H  09/1200Z 44.0N  21.4W   50 KT  60 MPH...POST-TROP/EXTRATROP
120H  10/1200Z 45.1N  15.9W   45 KT  50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Stewart

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