648 
 WTNT41 KNHC 070255
 TCDAT1
 
 HURRICANE JOAQUIN DISCUSSION NUMBER  38
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL112015
 1100 PM AST TUE OCT 06 2015
 
 Until just a couple of hours ago, Joaquin continued to display
 a tight inner core, with deep convection surrounding a 20
 n mi diameter eye.  The most recent geostationary infrared imagery
 is finally showing that the convection is becoming asymmetric with
 the 25 kt of tropospheric vertical shear adversely affecting the
 cyclone.  The intensity remains 70 kt, since both the SAB and TAFB
 Dvorak Current Intensity values are unchanged.
 
 The hurricane is about to cross over the north wall of the Gulf
 Stream and will be traversing very chilly 21-22C waters by tomorrow.
 The combination of cold SSTs, dry air, and strong vertical shear
 should cause the deep convection to either completely dislocate or
 cease and the forecast calls for Joaquin to become a strong
 post-tropical cyclone in about a day.  The FSU Cyclone Phase Space
 diagrams, based upon the global and regional models, suggest that
 Joaquin will gradually become more frontal and extratropical
 transition is anticipated by Thursday.  Baroclinic forcing should
 allow for only a gradual winding down as depicted by the models, and
 dissipation is anticipated in about five days.
 
 Joaquin is moving toward the east-northeast at a rather quick pace
 of 25 kt, as it is being advected along by the mid-latitude
 westerlies.  The system should accelerate east-northeastward for
 about 36 hours, before slowing down in the eastern north Atlantic.
 The track forecast is based upon the tightly clustered global and
 regional models through 72 hours.  By day four, the guidance becomes
 divergent with some solutions turning northeastward toward
 Ireland and Great Britain, but most turning east-southeastward
 toward Portugal and Spain.  This latter scenario is the basis for
 the track forecast at day 4.
 
 The track, intensity, and wind radii forecasts from 36 hours and
 beyond are based upon guidance provided by the Ocean Prediction
 Center.
 
 A last-minute-arriving ASCAT scatterometer pass indicated that
 Joaquin continues to expand in size.  The 34- and 50-kt wind radii
 analyses and forecasts were adjusted accordingly.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  07/0300Z 40.0N  53.1W   70 KT  80 MPH
  12H  07/1200Z 41.0N  47.7W   65 KT  75 MPH
  24H  08/0000Z 42.1N  39.3W   60 KT  70 MPH...POST-TROPICAL
  36H  08/1200Z 43.4N  31.2W   60 KT  70 MPH...POST-TROP/EXTRATROP
  48H  09/0000Z 44.7N  25.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
  72H  10/0000Z 44.0N  17.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
  96H  11/0000Z 43.0N  13.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
 120H  12/0000Z...POST-TROP/EXTRATROP
 
 $$
 Forecaster Landsea