000
WTNT45 KNHC 300837
TCDAT5

Tropical Storm Maria Discussion Number  57
NWS National Hurricane Center Miami FL       AL152017
500 AM AST Sat Sep 30 2017

Despite now being over sea surface temperatures of around 25
degrees Celsius, Maria is producing a persistent cluster of deep
convection that is displaced to the east of the center due to 15 kt
of west-northwesterly shear.  Satellite imagery shows cold
advection occurring within the western part of the cyclone's
circulation behind an approaching cold front, heralding the
beginning of Maria's extratropical transition.  Based on global
model guidance, this transition should be complete within 24 hours,
and Maria's intensity is unlikely to change much up until that time
due to baroclinic forcing.  The extratropical low is likely to
gradually weaken after 24 hours and become absorbed within a
frontal zone by day 3, if not sooner.

Maria is accelerating east-northeastward in the flow ahead of a
positively tilted trough moving off the northeastern coast of North
America, and the initial motion estimate is 070/28 kt.  The trough
should continue steering Maria even faster toward the east-northeast
for the next couple of days.  The GFS is significantly faster than
the ECMWF, UKMET, and Canadian models since it shows Maria becoming
absorbed by the front much sooner.  The NHC track forecast remains
close to the latter models and is relatively unchanged from the
previous forecast.

Guidance from the NOAA Ocean Prediction Center was used for the
track, intensity, and wind radii forecasts during Maria's
post-tropical stages.

FORECAST POSITIONS AND MAX WINDS

INIT  30/0900Z 39.6N  50.5W   50 KT  60 MPH
 12H  30/1800Z 41.3N  45.4W   50 KT  60 MPH
 24H  01/0600Z 43.8N  38.3W   50 KT  60 MPH...POST-TROP/EXTRATROP
 36H  01/1800Z 46.6N  30.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 48H  02/0600Z 48.9N  20.5W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  03/0600Z...ABSORBED WITHIN A FRONTAL ZONE

$$
Forecaster Berg