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TROPICAL STORM JOAQUIN DISCUSSION NUMBER   8
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL112015
ISSUED BY THE NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
500 PM EDT TUE SEP 29 2015

The cloud pattern of the storm has become better organized during
the day, with the low level center now embedded inside the northern
edge of the main area of deep convection.  Animation of cirrus
motions suggest that upper-level outflow is becoming a little more
prominent over the northern portion of the circulation, and this is
consistent with decreasing northerly shear.  Flight-level,
dropsonde, and SFMR wind observations from an Air Force
reconnaissance aircraft indicate that Joaquin has strengthened and
the intensity is now estimated to be 55 kt.  With a more favorable
upper-level wind environment now expected to prevail, the official
forecast calls for more strengthening than the previous advisories.
Joaquin is expected to become a hurricane within 24 hours, with
additional intensification likely thereafter.  The NHC intensity
forecast is similar to the latest SHIPS model output.

Fixes from the aircraft show a southward component of motion and
the initial motion estimate is now 240/4 kt.  Joaquin is currently
south of the southwestern periphery of a weak mid-level ridge.  The
ECMWF model shows this ridging to the north of the tropical cyclone
to be more prominent over the next few days than the other dynamical
models.  Consequently, the ECMWF takes Joaquin more to the
west and southwest through 72 hours than any of the other available
guidance.  Later in the forecast period, there is a significant
divergence in the track guidance.  The HWRF and U.K. Met Office
models forecast Joaquin to move over the east coast of the United
States later in the period whereas the ECMWF and GFS keep the system
well offshore.  The official forecast lies between these
possibilities and is similar to the latest Florida State University
Superensemble solution.

Interests in the Bahamas should monitor the progress of this storm.
Watches or warnings may be issued for portions of these islands
later this evening.

FORECAST POSITIONS AND MAX WINDS

INIT  29/2100Z 26.0N  71.0W   55 KT  65 MPH
 12H  30/0600Z 25.8N  71.6W   60 KT  70 MPH
 24H  30/1800Z 25.5N  72.5W   65 KT  75 MPH
 36H  01/0600Z 25.1N  73.3W   70 KT  80 MPH
 48H  01/1800Z 24.8N  73.9W   75 KT  85 MPH
 72H  02/1800Z 25.0N  74.0W   80 KT  90 MPH
 96H  03/1800Z 29.0N  73.0W   80 KT  90 MPH
120H  04/1800Z 34.0N  71.0W   75 KT  85 MPH

$$
Forecaster Pasch

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