[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 030840
TCDAT1

HURRICANE JOAQUIN DISCUSSION NUMBER  22
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL112015
500 AM EDT SAT OCT 03 2015

The eye of Joaquin has been intermittently seen in infrared
imagery overnight. Overall, the convective pattern is similar
to what it was when the previous aircraft indicated the intensity
was around 110 kt, so that will remain the intensity for this
advisory. Another aircraft will be investigating Joaquin later this
morning. The intensity forecast reasoning remains unchanged, with
the cyclone expected to slowly weaken in the first 24 hours followed
by steadier weakening due to increasing shear and cooler waters.
Late in the period, Joaquin will slowly weaken as it undergoes
extratropical transition. The new NHC intensity forecast is an
update of the previous one and is close to the SHIPS model until
extratropical transition.

The initial motion is 045/11, and Joaquin should continue to
accelerate northeastward today in the deep-layer southwesterly flow
between a deep trough over the southeastern U.S. and the Atlantic
subtropical ridge. The cross-track spread in the guidance increases
on days 2 and 3 due to differences in how much Joaquin is tugged to
the left by an upper-low passing to its north and northwest before
the cyclone accelerates into the westerlies over the north Atlantic.
The ECMWF has shifted left this cycle and is now along the left edge
of the guidance, while the GFS continues to shift east with a track
closer to Bermuda in 36 to 48 hours. The net change in the guidance
envelope and the consensus aids is a slight shift to the east, and
the official forecast has been adjusted in that direction. The NHC
track now lies close to the middle of the guidance envelope. Further
adjustments to the forecast track may be needed later today, and a
Hurricane Watch and Tropical Storm warning continue for Bermuda.

FORECAST POSITIONS AND MAX WINDS

INIT  03/0900Z 25.2N  73.1W  110 KT 125 MPH
 12H  03/1800Z 26.7N  71.4W  105 KT 120 MPH
 24H  04/0600Z 29.2N  69.2W  100 KT 115 MPH
 36H  04/1800Z 31.8N  67.4W   90 KT 105 MPH
 48H  05/0600Z 34.1N  66.4W   80 KT  90 MPH
 72H  06/0600Z 38.0N  62.0W   70 KT  80 MPH
 96H  07/0600Z 42.5N  50.0W   60 KT  70 MPH
120H  08/0600Z 47.0N  32.5W   55 KT  65 MPH...POST-TROP/EXTRATROP

$$
Forecaster Brennan
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