961 
 WTNT41 KNHC 302055
 TCDAT1
 
 HURRICANE JOAQUIN DISCUSSION NUMBER  12
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL112015
 500 PM EDT WED SEP 30 2015
 
 There has been little change in the organization of Joaquin during
 the past several hours.  While the hurricane continues to produce
 cloud tops colder than -80C in the eyewall, the eye has not become
 better defined since the last advisory.  Satellite intensity
 estimates are 77 kt from both TAFB and SAB, so the advisory
 intensity is now 75 kt.
 
 The initial motion is 225/7.  The shortwave ridge causing this
 motion is expected to weaken during the next 24-48 hours as a strong
 deep-layer trough develops over the southeastern United States.
 Thus, a generally southwestward motion is expected for the next 36
 hours or so, followed by a turn toward the north as the trough
 becomes the dominant steering mechanism.  There is an increased
 disagreement between the GFS, UKMET, Canadian, and NAVGEM models
 versus the ECMWF since the last advisory.  The ECMWF has continued
 its forecast of showing a northeastward motion after 72 hours,
 taking Joaquin just west of Bermuda and out to sea.  The other
 models have all shifted their forecasts to the left and now
 call for landfall in the Carolinas and the mid-Atlantic states,
 followed by merger with the baroclinic trough.  Given the shift in
 the non-ECMWF models, a major westward adjustment has been made to
 the forecast track at 96 and 120 hours, bringing the center of
 Joaquin near or over portions of the mid-Atlantic states.  Due to
 the use of the ECMWF in the consensus models, the new track lies
 near the various consensus models.  However, it lies well to the
 east of the GFS and the other similar models.  The NOAA G-IV jet is
 currently flying a synoptic surveillance mission, which, along with
 special rawinsonde launches, hopefully will reduce the spread of the
 guidance.
 
 There is little change to the intensity forecast philosophy since
 the last advisory.  Joaquin is expected to remain in an environment
 of moderate northeasterly vertical shear for the next 24-36 hours,
 possibly including strong winds seen at 400 mb in recent dropsondes
 from the G-IV aircraft.  However, since it has been steadily
 strengthening in such an environment, there is no obvious reason to
 think it will stop doing so.  After 36 hours, the hurricane is
 likely to move into an area of divergent southerly upper-level winds
 associated with the eastern U. S. trough.  While there is
 uncertainty as to how much shear should occur, it is expected that
 additional intensification could occur through at least 48 hours.
 Based on this, the intensity forecast calls for Joaquin to peak as a
 major hurricane in 48-72 hours, and it is possible it could be
 stronger than currently forecast.  After 72 hours, increasing shear,
 cold air intrusion, and land interaction should cause weakening and
 the start of extratropical transition.
 
 
 KEY MESSAGES:
 
 1.  Preparations to protect life and property within the warning
 areas in the Bahamas should be rushed to completion.
 
 2.  A significant adjustment to the forecast has been made this
 afternoon, and this shows an increased threat to the mid-Atlantic
 states and the Carolinas.  However, confidence in the details of the
 forecast after 72 hours remains low, since we have one normally
 excellent model that keeps Joaquin far away from the United States
 east coast.   The range of possible outcomes is still large, and
 includes the possibility of a major hurricane landfall in the
 Carolinas.
 
 3.  Every effort is being made to provide the forecast models with
 as much data as possible.  The NOAA G-IV jet has begun a series of
 missions in the storm environment, and the National Weather Service
 is launching extra balloon soundings.
 
 4.  Because landfall, if it occurs, is still more than three days
 away, it is too early to talk about specific wind, rain, or surge
 impacts from Joaquin in the United States.   Even if Joaquin stays
 well out to sea, strong onshore winds will create minor to moderate
 coastal flooding along the coasts of the mid-Atlantic and
 northeastern states through the weekend.
 
 5.  A hurricane watch for a portion of the U.S. coast could be
 required as early as Thursday evening.
 
 6.  Many areas of the eastern U.S. are currently experiencing heavy
 rains and gusty winds associated with a frontal system.  This
 inclement weather is expected to continue over the next few days,
 which could complicate preparations for Joaquin should it head
 toward the coast, and greatly exacerbate the impacts from the
 hurricane.  Heavy rains are likely to continue over these areas
 even if the center of Joaquin stays out to sea.
 
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  30/2100Z 24.3N  73.1W   75 KT  85 MPH
  12H  01/0600Z 24.0N  73.8W   85 KT 100 MPH
  24H  01/1800Z 23.9N  74.5W   90 KT 105 MPH
  36H  02/0600Z 24.5N  75.0W   95 KT 110 MPH
  48H  02/1800Z 25.8N  75.0W  100 KT 115 MPH
  72H  03/1800Z 30.5N  74.5W  100 KT 115 MPH
  96H  04/1800Z 36.0N  75.5W   85 KT 100 MPH
 120H  05/1800Z 38.5N  76.5W   55 KT  65 MPH
 
 $$
 Forecaster Beven