000
WTNT45 KNHC 071452
TCDAT5

Hurricane Dorian Discussion Number  57
NWS National Hurricane Center Miami FL       AL052019
1100 AM AST Sat Sep 07 2019

Satellite imagery this morning indicates that Dorian is starting
extratropical transition, with cold air clouds entraining into the
southwestern side of the cyclone and a developing warm front to the
north and east.  However, the cyclone still has persistent
convection just north and northeast of the center, so it remains a
hurricane on this advisory.  NOAA buoy 44011 reported a minimum
pressure of 955.3 mb as the center passed just to the west, so the
initial central pressure is lowered to 953 mb.  The initial
intensity remains 75 kt based partly on recently-received WindSat
data showing hurricane-force winds southwest of the center.

Dorian continues to move rapidly northeastward with an initial
motion of 040/25 kt.  The current motion should bring the center
of Dorian over central and eastern Nova Scotia in about 12 h and
near or over Prince Edward Island shortly thereafter.  Subsequently,
Dorian is forecast to move near or through northern Newfoundland
and southeastern Labrador before turning east-northeastward over the
far north Atlantic.  There are no significant changes to the
previous forecast, and the new forecast is again close to the
various consensus aids.

Dorian is expected to complete extratropical transition during the
next 24 h as it merges with a strong mid- to upper-level trough and
associated surface frontal zone.  The global models agree on a
gradual decay of the winds after transition is complete.  However,
the cyclone will likely still be producing hurricane-force winds as
it moves through portions of eastern Canada.  The global models also
agree that the post-tropical cyclone should become absorbed by
another extratropical low in 2-3 days.  The NHC intensity forecast
again leans towards the GFS and ECMWF models, which typically handle
large extratropical lows better that than the intensity models that
are made for tropical cyclones.


Key Messages:

1. Regardless of whether it is a hurricane or a post-tropical
cyclone, Dorian is expected to have a significant impact in portions
of eastern Canada beginning during the next several hours. Dangerous
storm surge impacts are likely in portions of the Gulf of St.
Lawrence, southwestern Newfoundland and eastern Nova Scotia.
Hurricane-force winds are also likely in Nova Scotia, Prince Edward
Island and Newfoundland later today and tonight. Refer to
information from the Canadian Hurricane Centre for more information
on these hazards.


FORECAST POSITIONS AND MAX WINDS

INIT  07/1500Z 42.0N  66.0W   75 KT  85 MPH
 12H  08/0000Z 45.1N  63.0W   70 KT  80 MPH...OVER NOVA SCOTIA
 24H  08/1200Z 48.9N  59.7W   65 KT  75 MPH...POST-TROP/EXTRATROP
 36H  09/0000Z 51.7N  54.6W   55 KT  65 MPH...POST-TROP/EXTRATROP
 48H  09/1200Z 54.2N  47.8W   45 KT  50 MPH...POST-TROP/EXTRATROP
 72H  10/1200Z...DISSIPATED

$$
Forecaster Beven