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Tropical Storm Isaac Intermediate Advisory Number 21A
NWS National Hurricane Center Miami FL       AL092018
800 PM AST Wed Sep 12 2018

...NOAA HURRICANE HUNTER AIRCRAFT CURRENTLY INVESTIGATING ISAAC...


SUMMARY OF 800 PM AST...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...15.4N 57.2W
ABOUT 260 MI...420 KM ENE OF MARTINIQUE
ABOUT 295 MI...470 KM E OF GUADELOUPE
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...W OR 275 DEGREES AT 20 MPH...31 KM/H
MINIMUM CENTRAL PRESSURE...1003 MB...29.62 INCHES


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

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
* Martinique
* Dominica
* Guadeloupe

A Tropical Storm Watch is in effect for...
* Antigua
* Montserrat
* St. Kitts and Nevis
* Saba and St. Eustatius
* St. Martin and St. Maarten

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area, in this case within 24
hours.

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, in this case within 24 hours.

Interests elsewhere in the Leeward Islands should monitor the
progress of Isaac.

For storm information specific to your area, please monitor
products issued by your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 800 PM AST (0000 UTC), the center of Tropical Storm Isaac was
located near latitude 15.4 North, longitude 57.2 West. Isaac is
moving toward the west near 20 mph (31 km/h), and this general
motion with a decrease in forward is expected to continue through
the weekend. On the forecast track, Isaac is forecast to move across
the central Lesser Antilles and into the eastern Caribbean Sea on
Thursday, and then move across the eastern and central Caribbean Sea
through Saturday.

Maximum sustained winds are near 60 mph (95 km/h) with higher
gusts.  Some weakening is forecast during the next 48 hours.

Tropical-storm-force winds extend outward up to 175 miles (280 km)
from the center.

The estimated minimum central pressure is 1003 mb (29.62 inches).


HAZARDS AFFECTING LAND
----------------------
RAINFALL:  Isaac is expected to produce total rainfall accumulations
of 2 to 4 inches with isolated amounts up to 8 inches across
Martinique, Dominica, and Guadeloupe.  Rainfall of 1 to 2 inches
with isolated amounts to 4 inches are forecast across Puerto Rico
and the southern United States Virgin Islands, with up to an inch
anticipated across the remaining Windward and Leeward Islands.  This
rainfall may cause life-threatening flash flooding.

WIND:  Tropical storm conditions are expected on Martinique,
Dominica, and Guadeloupe early Thursday.  Tropical storm conditions
are possible within the tropical storm watch area on Thursday.

STORM SURGE:  Some coastal flooding is possible in areas of onshore
winds.  Near the coast, the surge will be accompanied by large
waves.

SURF:  Swells generated by Isaac are affecting portions of the
Lesser Antilles.  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 1100 PM AST.

$$
Forecaster Berg

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