000
WTNT41 KNHC 291441
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

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