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Hurricane Maria Discussion Number   9
NWS National Hurricane Center Miami FL       AL152017
1100 AM AST Mon Sep 18 2017

Reports from an Air Force Reserve Hurricane Hunter aircraft indicate
that Maria is undergoing rapid intensification.  The aircraft
reported 700-mb flight-level winds of 115 kt in the northeastern
eyewall, along with reliable-looking surface wind estimates from the
Stepped Frequency Microwave radiometer as high as 104 kt.  In
addition, the estimated central pressure inside the 10 n mi wide eye
has fallen to 959 mb.  The initial intensity is increased to 100 kt,
making Maria a major category 3 hurricane on the Saffir-Simpson
Hurricane Wind Scale.  The small eye is also apparent in radar data
from Martinique.

The initial motion is 285/9, a little to the left of the previous
motion.  Other than that, there is little change in either the
forecast philosophy or the forecast track.  A high pressure area to
the north of Maria should maintain a general west-northwestward
motion for the next three days or so.  After that, the high weakens,
which should allow the hurricane to turn gradually northwestward and
north-northwestward.  The new forecast track is changed little from
the previous one, and it calls for Maria to move through the Leeward
Islands in 12-24 h, approach the Virgin Islands in about 36 h, then
cross Puerto Rico between 48-72 h.  The new track lies to the left
of the center of the guidance envelope in best agreement with the
ECMWF.

Atmospheric and oceanic conditions appear favorable for additional
rapid strengthening for the next 24 h and possibly longer.
This is reflected in the intensity forecast, which now calls for
Maria to become a category 4 hurricane in 12 h and reach a possibly
conservative peak intensity of 130 kt in about 36 h.  From 72-120 h,
land interaction and less favorable upper-level winds are expected
to cause some weakening.  On top of these general trends, there is
also the possibility that eyewall replacement cycles could occur
that would affect the intensity.  However, Maria is likely to
maintain category 3 to 4 intensity through the forecast period.

KEY MESSAGES:

1. Maria will affect portions of the Leeward Islands and the British
and U.S. Virgin Islands as an extremely dangerous major hurricane
during the next couple of days, and hurricane warnings are in effect
for many of these islands.

2. Maria is likely to affect Puerto Rico as an extremely dangerous
major hurricane, and a hurricane watch is in effect for that island.
A hurricane warning will likely be issued later today.

3. The potential for a life-threatening storm surge, accompanied by
large and destructive waves, has increased for the Leeward Islands,
the Virgin Islands, and Puerto Rico.

4. Life-threatening flash floods and mudslides from heavy rainfall
are expected across the Leeward Islands, including Puerto Rico and
the U.S. and British Virgin Islands.


FORECAST POSITIONS AND MAX WINDS

INIT  18/1500Z 14.7N  60.1W  105 KT 120 MPH
 12H  19/0000Z 15.1N  61.2W  115 KT 130 MPH
 24H  19/1200Z 15.9N  62.6W  125 KT 145 MPH
 36H  20/0000Z 16.8N  64.1W  130 KT 150 MPH
 48H  20/1200Z 17.6N  65.5W  130 KT 150 MPH
 72H  21/1200Z 19.5N  68.5W  125 KT 145 MPH
 96H  22/1200Z 21.5N  71.0W  120 KT 140 MPH
120H  23/1200Z 24.0N  72.5W  110 KT 125 MPH

$$
Forecaster Beven

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