656 
 WTNT41 KNHC 301458
 TCDAT1
 
 HURRICANE JOAQUIN DISCUSSION NUMBER  11
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL112015
 1100 AM EDT WED SEP 30 2015
 
 Joaquin has continued to strengthen overnight.  Satellite imagery
 shows that the convection has become more symmetric, and recent
 visible images show what might be an eye trying to form.  An Air
 Force Reserve Hurricane Hunter aircraft reported 700-mb flight-
 level winds of 83 kt and estimated 70 kt surface winds from the
 Stepped Frequency Microwave Radiometer, with a central pressure of
 971 mb estimated from the aircraft data.  Based on these, the
 initial intensity is increased to 70 kt.
 
 Joaquin has moved a little south of the previous track with an
 initial motion of 230/5.  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.
 This is expected to cause the hurricane to turn northward by 72
 hours.  There is disagreement in the track guidance between the
 ECMWF and the other dynamical models.  The majority of the guidance
 forecasts Joaquin to turn west of north after 48-72 hours, with the
 storm moving inland over the mid-Atlantic states and merging with
 the trough. On the other hand, the ECMWF forecast the hurricane to
 move out to sea between North America and Bermuda.  The ECMWF
 forecasts Joaquin to move more to the south during the first 24-48
 hours than the other models.  In addition, it shows the hurricane
 interacting with an upper-level low to its northeast that results in
 a more eastward motion after 48 hours.  The new forecast track,
 which is similar to the previous track, leans more toward the
 non-ECMWF guidance.  However, out of deference to the ECMWF, it
 lies to the east of the center of the guidance envelope and the
 consensus models.  The NOAA G-IV jet is scheduled to fly a synoptic
 surveillance mission this afternoon, which, along with special
 rawinsonde launches over the eastern U. S., hopefully will reduce
 the spread of the guidance.
 
 Joaquin is expected to remain in an environment of moderate
 northeasterly vertical shear for the next 24-36 hours.  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 72 hours.  Based on this, the intensity forecast calls for
 Joaquin to peak as a major hurricane in about 72 hours, and it is
 possible it could be stronger than currently forecast.  After 72
 hours, increasing shear and cold air intrusion should cause
 weakening and the start of extratropical transition.
 
 
 KEY MESSAGES:
 
 1. Confidence in the details of the track forecast late in the
 period remains low, since the environmental steering currents are
 complex and the model guidance is inconsistent.  A wide range of
 outcomes is possible, from a direct impact of a major hurricane
 along the U.S. east coast to a track of Joaquin out to sea away from
 the coast.  It is therefore way too soon to talk about specific
 wind, rain, or surge impacts from Joaquin in the U.S.
 
 2. Should the threat to the U.S. increase, any further adjustments
 of the forecast to the west would likely be accompanied by an
 increase in the forecast forward speed, with impacts along the coast
 occurring sooner than currently forecast. A hurricane watch could
 be required for portions of the U.S. coast as early as Thursday
 evening.
 
 3. 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.
 
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  30/1500Z 24.7N  72.6W   70 KT  80 MPH
  12H  01/0000Z 24.3N  73.2W   80 KT  90 MPH
  24H  01/1200Z 24.1N  74.0W   85 KT 100 MPH
  36H  02/0000Z 24.4N  74.4W   90 KT 105 MPH
  48H  02/1200Z 25.3N  74.5W   95 KT 110 MPH
  72H  03/1200Z 28.5N  73.5W  100 KT 115 MPH
  96H  04/1200Z 34.0N  73.0W   90 KT 105 MPH
 120H  05/1200Z 38.5N  74.0W   75 KT  85 MPH
 
 $$
 Forecaster Beven