639 
 WTNT41 KNHC 291445
 TCDAT1
 
 TROPICAL STORM JOAQUIN DISCUSSION NUMBER   7
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL112015
 ISSUED BY THE NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
 1100 AM EDT TUE SEP 29 2015
 
 Visible satellite imagery this morning shows that the cloud pattern
 of the tropical cyclone is somewhat better organized than it was 24
 hours ago.  The low-level center is situated near the northern side
 of the main area of deep convection due to northerly shear.  The
 upper level outflow is well defined over the southern semicircle of
 the system, and restricted over the northern part of the
 circulation.  The current intensity is conservatively set at 45 kt,
 which is a little below the latest Dvorak estimates.  An Air Force
 plane will be investigating Joaquin in a few hours, and should
 provide a better estimate of intensity.
 
 Based on the satellite center fixes, the initial motion continues
 to be slowly westward, or 260/04 kt.  The forecast track in
 this advisory attempts to reconcile large model spread with an
 overall shift toward the southwest of the previous track through 72
 hours.  Joaquin is currently in a relatively weak steering pattern,
 but a building shortwave ridge in the northwestern Atlantic should
 allow the cyclone to drift west and then west-southwestward.  This
 pushes the storm in the direction of the Bahamas, but the
 deterministic and ensemble model consensus still shows a good
 likelihood that Joaquin will stop fairly well short of the Bahamas,
 and then begin accelerating to either the north or northeast.  The
 00Z ECMWF made a closer approach to the Bahamas, but it too turns
 the storm sharply and accelerates it back into the Atlantic beyond
 72 hours.  The official forecast is to the left of the previous
 forecast through 72 hours, and significantly slower at 4 and 5
 days.  It should be repeated that the confidence in the track
 forecast is very low.
 
 The vertical shear is predicted by the dynamical models to decrease
 in 1 to 2 days.  This should allow for additional strengthening,
 which is reflected in the official forecast.  The NHC wind speed
 predictions may be conservative, since some of the guidance suggests
 that Joaquin could become a hurricane in a few days.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  29/1500Z 26.5N  70.8W   40 KT  45 MPH
  12H  30/0000Z 26.4N  71.5W   45 KT  50 MPH
  24H  30/1200Z 26.3N  72.4W   45 KT  50 MPH
  36H  01/0000Z 26.2N  73.1W   50 KT  60 MPH
  48H  01/1200Z 26.1N  73.7W   55 KT  65 MPH
  72H  02/1200Z 26.0N  74.0W   60 KT  70 MPH
  96H  03/1200Z 29.0N  73.5W   60 KT  70 MPH
 120H  04/1200Z 34.0N  72.0W   60 KT  70 MPH
 
 $$
 Forecaster Pasch