Tropical Cyclone Discussion
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WTNT41 KNHC 060837

500 AM AST TUE OCT 06 2015

There has been little change in the structure of Joaquin during
the past few hours.  An eye has occasionally appeared in microwave
imagery, and recent AMSR-2 and GPM data continue to hint at the
presence of concentric eyewalls.  The initial intensity remains 75
kt based on a satellite intensity estimate from TAFB and continuity
from the previous advisory.  The 34 and 50 kt wind radii were
adjusted slightly based on recent ASCAT data.

The initial motion is now 050/15.  Joaquin is entering the
westerlies, and the track guidance is in good agreement that the
cyclone should move rapidly east-northeastward for the next three
days or so.  After that time, the guidance agrees on a slower
motion, but there there is some spread between the GFS/UKMET which
call for a northward turn and the ECMWF which turns the system
southeastward.  This part of the forecast lies a little north of the
previous forecast near the average of the GFS and ECMWF models.

The forecast track carries Joaquin over colder sea surface
temperatures and close to a baroclinic zone in about 24 hours.
This combination should cause the cyclone to weaken and begin
extratropical transition.  Transition should be complete between 36
and 48 hours, with Joaquin expected to weaken below hurricane
strength by that time.  The global models are in good agreement
that Joaquin will produce gale- to storm-force winds as an
extratropical low during the 48-120 hour period.  The new intensity
forecast is an update of the previous forecast, with the
extratropical portion based on guidance from the Ocean Prediction


INIT  06/0900Z 37.5N  61.0W   75 KT  85 MPH
 12H  06/1800Z 38.8N  57.7W   75 KT  85 MPH
 24H  07/0600Z 40.2N  51.5W   70 KT  80 MPH
 36H  07/1800Z 41.6N  43.8W   65 KT  75 MPH
 48H  08/0600Z 42.8N  35.7W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  09/0600Z 45.5N  23.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 96H  10/0600Z 47.5N  16.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  11/0600Z 51.0N  12.5W   45 KT  50 MPH...POST-TROP/EXTRATROP

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