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TROPICAL STORM ISAAC FORECAST/ADVISORY NUMBER  21
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092018
2100 UTC WED SEP 12 2018

CHANGES IN WATCHES AND WARNINGS WITH THIS ADVISORY...

THE GOVERNMENT OF FRANCE HAS ISSUED A TROPICAL STORM WATCH FOR
ST. MARTIN AND THE GOVERNMENT OF ST. MAARTEN HAS ISSUED A
TROPICAL STORM WATCH FOR ST. MAARTEN.

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 WITHIN 24 TO 36 HOURS.

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...IN THIS CASE WITHIN 24 TO 36
HOURS.

INTERESTS ELSEWHERE IN THE LEEWARD ISLANDS SHOULD MONITOR THE
PROGRESS OF ISAAC.

TROPICAL STORM CENTER LOCATED NEAR 15.4N  56.6W AT 12/2100Z
POSITION ACCURATE WITHIN  15 NM

PRESENT MOVEMENT TOWARD THE WEST OR 275 DEGREES AT  17 KT

ESTIMATED MINIMUM CENTRAL PRESSURE 1003 MB
MAX SUSTAINED WINDS  50 KT WITH GUSTS TO  60 KT.
50 KT....... 60NE  40SE   0SW  50NW.
34 KT.......150NE 100SE  20SW 120NW.
12 FT SEAS..180NE  60SE  60SW 180NW.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT.  RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.

REPEAT...CENTER LOCATED NEAR 15.4N  56.6W AT 12/2100Z
AT 12/1800Z CENTER WAS LOCATED NEAR 15.3N  55.7W

FORECAST VALID 13/0600Z 15.6N  59.0W
MAX WIND  50 KT...GUSTS  60 KT.
50 KT... 40NE  30SE   0SW  30NW.
34 KT...120NE  90SE  20SW 120NW.

FORECAST VALID 13/1800Z 15.8N  61.8W
MAX WIND  45 KT...GUSTS  55 KT.
34 KT... 80NE  70SE  10SW  80NW.

FORECAST VALID 14/0600Z 16.0N  64.8W
MAX WIND  45 KT...GUSTS  55 KT.
34 KT... 70NE  60SE   0SW  70NW.

FORECAST VALID 14/1800Z 16.0N  67.6W
MAX WIND  40 KT...GUSTS  50 KT.
34 KT... 70NE  40SE   0SW  50NW.

FORECAST VALID 15/1800Z 16.0N  72.5W
MAX WIND  40 KT...GUSTS  50 KT.
34 KT... 70NE  30SE   0SW  50NW.

EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 150 NM
ON DAY 4 AND 175 NM ON DAY 5...AND FOR INTENSITY NEAR 15 KT EACH DAY

OUTLOOK VALID 16/1800Z 16.5N  76.5W
MAX WIND  40 KT...GUSTS  50 KT.

OUTLOOK VALID 17/1800Z 17.5N  80.5W
MAX WIND  40 KT...GUSTS  50 KT.

REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 15.4N  56.6W

NEXT ADVISORY AT 13/0300Z

$$
FORECASTER BLAKE


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