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Tropical Storm Maria Discussion Number   4
NWS National Hurricane Center Miami FL       AL152017
500 AM AST Sun Sep 17 2017

Maria's cloud pattern is becoming better organized with developing
convective banding features and a gradually expanding CDO.
Upper-level outflow is only slightly restricted over the southern
portion of the circulation.   The current intensity is set at 55
kt, in agreement with the latest Dvorak estimates from both TAFB and
SAB.  The environment should be conducive for continued
strengthening for the next several days with low shear, a warm
ocean and a fairly moist mid-tropospheric air mass.  The official
intensity forecast follows the model consensus, but a more rapid
intensification than indicated here is certainly possible over the
next couple of days.

Latest center fixes indicate that the tropical cyclone is now
moving west-northwestward, or 285/13 kt.  A mid-level high pressure
area to the north of Maria is forecast to weaken slightly over the
next several days.  This should result in a continued
west-northwestward motion with a slowing of forward speed.  The
official track forecast is a blend of the latest GFS and ECMWF
predictions, and lies on the left side of the guidance envelope.

KEY MESSAGES:

1. Maria is expected to strengthen and affect portions of the
Leeward Islands as a hurricane early next week, bringing dangerous
wind, storm surge and rainfall hazards.  Hurricane or Tropical
Storm Warnings will likely be required for portions of these
islands today.

2. Maria could also affect the British and U.S. Virgin Islands and
Puerto Rico by mid week as a dangerous major hurricane, and
hurricane watches could be issued for these islands as early as
tonight.  Interests in these areas should monitor the progress of
Maria and follow any advice given by local officials.


FORECAST POSITIONS AND MAX WINDS

INIT  17/0900Z 13.0N  54.9W   55 KT  65 MPH
 12H  17/1800Z 13.7N  56.5W   65 KT  75 MPH
 24H  18/0600Z 14.5N  58.3W   75 KT  85 MPH
 36H  18/1800Z 15.2N  60.0W   85 KT 100 MPH
 48H  19/0600Z 15.8N  61.3W   95 KT 110 MPH
 72H  20/0600Z 17.0N  64.0W  110 KT 125 MPH
 96H  21/0600Z 18.4N  67.0W  100 KT 115 MPH...INLAND
120H  22/0600Z 19.5N  69.5W  105 KT 120 MPH...OVER WATER

$$
Forecaster Pasch

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