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Tropical Storm Maria Discussion Number  53
NWS National Hurricane Center Miami FL       AL152017
500 AM AST Fri Sep 29 2017

Maria is producing a relatively small cluster of deep convection
that is displaced to the east of the center due to 15 kt of
westerly shear.  Scatterometer data from last evening showed some
45-kt wind vectors south of the center, so Maria's initial
intensity is estimated to be 50 kt, accounting for the low
resolution of the ASCAT instruments.  Maria will continue to move
over waters of at least 26 degrees Celsius for at least the next
24-36 hours, although vertical shear will be increasing over the
cyclone fairly soon.  The first stages of extratropical transition
are likely to begin later today, and baroclinic forcing could allow
Maria to regain a little bit of strength, which is shown by both the
GFS and ECMWF models over the next couple of days.  Maria should be
fully extratropical by 48 hours and then be absorbed within a
frontal zone a little after 72 hours.  Some of the global models,
such as the GFS and UKMET, show this absorption occurring sooner
than that.

Maria is accelerating eastward within the mid-latitude westerlies
with an initial motion of 085/18 kt.  The cyclone should turn
east-northeastward later today, ahead of a mid-latitude trough
moving off the northeastern U.S. and Atlantic Canada coast, with
acceleration continuing up until the time Maria dissipates.
Although the ECMWF model is an outlier and has a slower solution
compared to the other guidance, the NHC track forecast remains
close to the other models and the various consensus aids.

The post-tropical intensity and wind radii forecasts at 48 and 72 h
are based on guidance provided by the NOAA Ocean Prediction Center.

FORECAST POSITIONS AND MAX WINDS

INIT  29/0900Z 37.2N  63.3W   50 KT  60 MPH
 12H  29/1800Z 37.9N  59.0W   55 KT  65 MPH
 24H  30/0600Z 39.8N  52.3W   55 KT  65 MPH
 36H  30/1800Z 42.1N  45.0W   55 KT  65 MPH
 48H  01/0600Z 45.0N  36.8W   50 KT  60 MPH...POST-TROP/EXTRATROP
 72H  02/0600Z 51.4N  16.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
 96H  03/0600Z...ABSORBED WITHIN A FRONTAL ZONE

$$
Forecaster Berg

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