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Tropical Storm MARIA


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Tropical Storm Maria Discussion Number  49
NWS National Hurricane Center Miami FL       AL152017
500 AM EDT Thu Sep 28 2017

Maria's satellite presentation has not changed much during the past
six hours, with 15-20 kt of northwesterly shear continuing to
displace much of the deep convection to the east of the center.
Despite the discrepancy between aircraft observations and Dvorak
estimates noted yesterday, a pair of ASCAT passes from a few hours
ago showed maximum winds in the 50-55 kt range.  Even with the
assumption that the resolution of the ASCAT data may not have
revealed the highest winds, an analysis suggests that Maria has
weakened back to a 60-kt tropical storm.  Little change in intensity
is anticipated during the next two days while Maria moves over sea
surface temperatures of 26-27 degrees Celsius, and while vertical
shear decreases during the next 24 hours.  After 48 hours, a marked
jump in shear and much colder waters should induce more weakening,
and model guidance indicates that Maria should complete
extratropical transition by day 3.  The extratropical low should
then be absorbed by a larger system over the northeastern Atlantic
by day 4.  This scenario is in agreement with guidance provided by
the NOAA Ocean Prediction Center.

Maria is becoming embedded in the mid-latitude westerlies and is
now moving toward the east-northeast, or 060/7 kt.  The cyclone is
expected to turn eastward very soon, but then turn back toward the
east-northeast in 36 hours as a positively tilted trough moves off
the New England and Atlantic Canada coasts.  The speed differences
among the track models are not as significant as they were
yesterday, although the updated NHC track forecast was nudged
southward for much of the forecast period to follow an overall
modest shift in the guidance envelope.

FORECAST POSITIONS AND MAX WINDS

INIT  28/0900Z 36.8N  71.0W   60 KT  70 MPH
 12H  28/1800Z 36.8N  68.8W   55 KT  65 MPH
 24H  29/0600Z 37.0N  64.9W   55 KT  65 MPH
 36H  29/1800Z 38.0N  59.7W   55 KT  65 MPH
 48H  30/0600Z 40.0N  53.1W   55 KT  65 MPH
 72H  01/0600Z 46.4N  35.5W   45 KT  50 MPH...POST-TROP/EXTRATROP
 96H  02/0600Z...DISSIPATED

$$
Forecaster Berg

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