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Hurricane Maria Intermediate Advisory Number 18A
NWS National Hurricane Center Miami FL       AL152017
200 PM AST Wed Sep 20 2017

...AIR FORCE HURRICANE HUNTER PLANE FINDS MARIA'S CENTER JUST
OFFSHORE OF THE NORTHWESTERN COAST OF PUERTO RICO...


SUMMARY OF 200 PM AST...1800 UTC...INFORMATION
----------------------------------------------
LOCATION...18.5N 66.9W
ABOUT 15 MI...20 KM W OF ARECIBO PUERTO RICO
ABOUT 95 MI...155 KM E OF PUNTA CANA DOMINICAN REPUBLIC
MAXIMUM SUSTAINED WINDS...115 MPH...185 KM/H
PRESENT MOVEMENT...NW OR 305 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...961 MB...28.38 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Hurricane Warning is in effect for...
* U.S. Virgin Islands
* British Virgin Islands
* Puerto Rico, Culebra, and Vieques
* Dominican Republic from Cabo Engano to Puerto Plata
* Turks and Caicos Islands and the Southeastern Bahamas

A Tropical Storm Warning is in effect for...
* Dominican Republic west of Puerto Plata to the northern border of
the Dominican Republic and Haiti
* Dominican Republic west of Cabo Engano to Punta Palenque

A Hurricane Watch is in effect for...
* Dominican Republic from Isla Saona to Cabo Engano

A Hurricane Warning means that hurricane conditions are expected
somewhere within the warning area.  Preparations to protect life and
property should be rushed to completion.

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area.

A Hurricane Watch means that hurricane conditions are possible
within the watch area.  A watch is typically issued 48 hours before
the anticipated first occurrence of tropical-storm-force winds,
conditions that make outside preparations difficult or dangerous.

Interests elsewhere in Hispaniola and the Bahamas should monitor the
progress of Maria.

For storm information specific to your area in the United States,
including possible inland watches and warnings, please monitor
products issued by your local National Weather Service forecast
office. For storm information specific to your area outside the
United States, please monitor products issued by your national
meteorological service.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
At 200 PM AST (1800 UTC), the center of Hurricane Maria was located
by an Air Force Reserve Hurricane Hunter aircraft just offshore of
the northwestern coast of Puerto Rico near latitude 18.5 North,
longitude 66.9 West.  Maria is moving toward the northwest near 12
mph (19 km/h), and this general motion with a gradual decrease in
forward speed is expected through early Friday. On the forecast
track, the center of Maria will move away from the northwestern
coast of Puerto Rico this afternoon.  The center will then pass
offshore of the northeastern coast of the Dominican Republic tonight
and Thursday and then move near the Turks and Caicos Islands and
southeastern Bahamas Thursday night and Friday.

Maximum sustained winds are near 115 mph (185 km/h) with higher
gusts.  Maria is a category 3 hurricane on the Saffir-Simpson
Hurricane Wind Scale.  Little change in strength is forecast during
the next 48 hours, and Maria is expected to remain a dangerous major
hurricane through Friday.

Hurricane-force winds extend outward up to 60 miles (95 km) from
the center, and tropical-storm-force winds extend outward up to 150
miles (240 km).  A sustained wind of 45 mph (72 km/h) with a gust
to 77 mph (124 km/h) was recently reported at Mayaguez, Puerto
Rico.  A sustained wind of 46 mph (74 km/h) with a gust to 76 mph
(122 km/h) was recently reported at Cabo Rojo, Puerto Rico.

The minimum central pressure based on the aircraft data is 961 mb
(28.38 inches).


HAZARDS AFFECTING LAND
----------------------
WIND:  Hurricane conditions are occurring over portions of Puerto
Rico, and tropical storm conditions are continuing over the
remainder of Puerto Rico and the Virgin Islands.  Tropical storm
conditions are likely beginning in the warning areas in the
Dominican Republic, and hurricane conditions should start in the
hurricane warning area tonight. Tropical storm conditions are
expected to begin in the Turks and Caicos Islands and the
southeastern Bahamas Thursday morning, with hurricane conditions
starting Thursday evening.

Wind speeds atop and on the windward sides of hills and mountains
and on high-rise buildings could be much stronger than the near-
surface winds indicated in this advisory.

STORM SURGE:  The combination of a dangerous storm surge and the
tide will cause normally dry areas near the coast to be flooded by
rising waters moving inland from the shoreline.  The water is
expected to reach the following heights above ground if the peak
surge occurs at the time of high tide...

Puerto Rico...6 to 9 ft

The deepest water will occur along the immediate coast near and to
the north and east of the landfall location, where the surge will be
accompanied by large and destructive waves.  Surge-related flooding
depends on the relative timing of the surge and the tidal cycle, and
can vary greatly over short distances.  For information specific to
your area, please see products issued by your local National Weather
Service forecast office.

A dangerous storm surge accompanied by large and destructive waves
will raise water levels by as much as 4 to 6 feet above normal tide
levels in the hurricane warning area in the Dominican Republic, and
1 to 3 ft elsewhere along the northern coasts of the Dominican
Republic and Haiti.

A dangerous storm surge accompanied by large and destructive waves
will raise water levels by as much as 10 to 15 feet above normal
tide levels in the hurricane warning area near and to the north of
the center of Maria for both the Southeastern Bahamas and the Turks
and Caicos Islands.

RAINFALL:  Maria is expected to produce the following rainfall
totals through Friday:

Puerto Rico...20 to 25 inches, isolated 35 inches
U.S. and British Virgin Islands...additional 5 to 10 inches,
isolated 15 inches
Northern and eastern Dominican Republic, Turks and Caicos and
southeast Bahamas...8 to 16 inches, isolated 20 inches
Northern Haiti...2 to 4 inches

Rainfall on these islands will cause life-threatening flash floods
and mudslides

TORNADOES:  Several tornadoes are possible over Puerto Rico and the
U.S. Virgin Islands today.

SURF:  Swells generated by Maria are affecting the Leeward Islands,
Puerto Rico, and the Virgin Islands.  These swells will begin
affecting the northern coast of Hispaniola, the Turks and Caicos
Islands, and the Southeastern Bahamas during the next day or two.
These swells are likely to cause life-threatening surf and rip
current conditions.  Please consult products from your local weather
office.


NEXT ADVISORY
-------------
Next complete advisory at 500 PM AST.

$$
Forecaster Berg

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