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Tropical Storm Maria Discussion Number   5
NWS National Hurricane Center Miami FL       AL152017
1100 AM AST Sun Sep 17 2017

The cloud pattern has not changed much since the last advisory.
There appears to be a dry slot working into the western side of
Maria, and the low-level circulation seems to be peaking out from
under the western side of a persistent CDO feature.  Dvorak
estimates are unchanged from six hours ago, so the initial
intensity is held at 55 kt.  An Air Force Reserve Hurricane Hunter
aircraft will be investigating Maria this afternoon.

Maria continues to move west-northwestward, or 290/13 kt, and that
trajectory is expected to continue at least for the next four days
while a mid-level high is centered over the western Atlantic Ocean.
However, the track guidance has generally slowed down since the
high is not very expansive or strong, and the new NHC track
forecast follows that trend, ending up a little slower than the
previous forecast.  The official forecast also continues to hedge
toward the southern side of the track guidance envelope, closest to
the ECMWF and HCCA models, which have been doing very well this
hurricane season.

Until the reconnaissance aircraft investigates Maria, the initial
intensity will be a little uncertain.  Regardless, the storm is
within an environment of very low shear and over sea surface
temperatures around 29 degrees Celsius, so steady strengthening is
expected during the next few days.  Due to this seemingly ideal
environment, the NHC intensity forecast is higher than the
statistical-dynamical guidance and closely follows HCCA and the ICON
intensity consensus through the entire forecast period.  Maria is
likely to become a hurricane later today and could become a major
hurricane in 2 to 3 days.  No major changes to the intensity
forecast were necessary compared with the previous cycle, and I'd
rather wait anyway until we have a better handle on Maria's
intensity and structure.


KEY MESSAGES:

1. Maria is expected to strengthen and affect portions of the
Leeward Islands as a hurricane early this week, bringing dangerous
wind, storm surge and rainfall hazards.  Hurricane and tropical
storm warnings have been issued for portions of the Leeward
Islands, and these warnings will likely be extended northward and
westward later today and tonight.

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  17/1500Z 13.5N  56.2W   55 KT  65 MPH
 12H  18/0000Z 14.1N  57.7W   65 KT  75 MPH
 24H  18/1200Z 14.8N  59.3W   75 KT  85 MPH
 36H  19/0000Z 15.5N  60.7W   85 KT 100 MPH
 48H  19/1200Z 16.1N  62.0W   95 KT 110 MPH
 72H  20/1200Z 17.3N  64.7W  110 KT 125 MPH
 96H  21/1200Z 18.5N  67.5W  105 KT 120 MPH
120H  22/1200Z 20.0N  69.5W  100 KT 115 MPH

$$
Forecaster Berg

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