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204
FXPQ60 PGUM 220900
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
700 PM CHST MON SEP 22 2014

.MARIANAS SYNOPSIS...
RADAR SHOWS MAINLY ISOLATED SHOWERS AND THUNDERSTORMS THIS AFTERNOON
BUT THE COVERAGE IS GRADUALLY INCREASING AND SATELLITE SHOWS AREAS
OF SHOWERS SOUTH OF GUAM NEAR 12N AND MORE SHOWERS AND THUNDERSTORMS
EAST OF GUAM NEAR 148E...WHICH ARE EDGING OUR WAY. ASCAT ANALYSIS
SHOWS A CIRCULATION NEAR 11N151E THAT IS ASSOCIATED WITH INVEST
98W. VAD GRADIENT WINDS ARE NORTH 5 TO 10 KT BUT SURFACE WINDS
RANGE FROM NE TO NW IN THE LOCAL OBSERVATIONS. BUOYS SHOW COMBINED
SEAS NEAR 4 FEET WITH DIRECTIONAL COMPONENTS FROM WEST...AND
NORTHEAST.

&&

.DISCUSSION...
SPECIAL WEATHER STATEMENT WAS ISSUED FOR MARIANA ISLANDS BECAUSE OF
THE DEVELOPING DISTURBANCE CENTERED SOUTHEAST OF GUAM NEAR 11N151E.
TRACKING THIS DISTURBANCE/CIRCULATION WILL BE OUR MAIN FORECAST
PROBLEM THIS WEEK. THE FORECAST WAS UPGRADED TO SCATTERED SHOWERS
TONIGHT AND TUESDAY BASED ON THE AREAS OF SHOWERS MOVING OUR WAY
FROM THE EAST AND NORTHEAST. MODEL SOLUTIONS HAVE DIVERGED TODAY
MORE THAN PREVIOUS RUNS...MAINLY BECAUSE THE GFS INITIALIZED THE
CIRCULATION TOO FAR NORTHEAST...AND THAT MAKES THE FORECAST MORE
DIFFICULT. LATER FORECASTS WILL LIKELY NEED ADJUSTMENTS AS THE
SITUATION BECOMES BETTER DEFINED IN THE COMING DAYS.

&&

.MARINE...
MARINE CONDITIONS WILL DETERIORATE DURING THE COMING DAYS...AND
THE MONSOON CIRCULATION NEAR 11N151E WILL LIKELY MOVE TOWARD THE
NORTHERN MARIANAS. NORTHEAST COMPONENTS OF SWELL AND WIND WAVES
ARE ALREADY ARRIVING ALONG WITH THE SMALL SOUTHWEST SWELL THAT
PERSISTS. SMALL ADJUSTMENTS WERE NEEDED FOR BOTH THE WIND AND
WAVE GRIDS.

&&

.EASTERN MICRONESIA...
A MONSOON CIRCULATION CONTINUES TO SLOWLY DEVELOP NORTH OF CHUUK
NEAR 11N151E. A MONSOON TROUGH CURVES TO NEAR KWAJALEIN AT 9N169E. A
WEAK RIDGE EXTENDS WESTWARD FROM SOUTH OF MAJURO ALONG 3N TO 5N TO
SOUTH OF POHNPEI. FAIR WEATHER WILL PERSIST AT POHNPEI THE NEXT FEW
DAYS WITH MONSOON-TYPE WEATHER DISPLACED TO THE NORTH AND NORTHWEST.
LOW-LEVEL CONVERGENCE WILL MAINTAIN CLOUDS AND SHOWERS AT KOSRAE
TONIGHT AND TUESDAY. WEATHER HAS BEEN FAIRLY QUIET TODAY AT MAJURO
WITH A STEADY WEST WIND. VIS SATELLITE SHOWS SHOWERS AND A FEW
THUNDERSTORMS JUST SOUTHEAST OF MAJURO AND EXTENDING TOWARDS THE
DATE LINE. THESE SHOWERS ARE ASSOCIATED WITH A SURFACE TROUGH THAT
WILL REACH THE MARSHALL ISLANDS OVERNIGHT. SCATTERED SHOWERS WILL
REACH MAJURO TONIGHT AND CONTINUE THROUGH TUESDAY. MODELS SHOW THIS
TROUGH WILL HEAD WEST-NORTHWEST KEEPING MUCH OF THE WEATHER JUST
NORTH OF KOSRAE AND POHNPEI. ANOTHER DISTURBANCE IS PROGGED TO
DEVELOP NEAR THE MARSHALL ISLANDS LATE THURSDAY AND FRIDAY. MODELS
HAVE SHOWN THIS SIGNAL A COUPLE DAYS NOW SO WILL GO AHEAD AND
INTRODUCE MORE SHOWERS AND ISOLATED THUNDERSTORMS TO MAJURO FOR THE
END OF THE WEEK.

&&

.WESTERN MICRONESIA...
THE MONSOON CIRCULATION CONTINUES TO DEVELOP NORTH OF CHUUK NEAR
11N151E. SATELLITE ANIMATION SHOWS WIDE-SPREAD HEAVY SHOWERS JUST
WEST AND NORTH OF WENO. MUCH DRIER WEATHER IS FOUND EAST AND SOUTH
OF WENO. LATEST OBSERVATIONS SHOW GUSTY SOUTH-SOUTHWEST WINDS AND
SHOWERS HAVE RETURNED. SCATTERED SHOWERS WILL TAPER DOWN TO ISOLATED
AROUND MIDNIGHT AS THE BULK OF THE WEATHER IS EXPECTED TO SLOWLY
SHIFT NORTH. THIS WILL HAVE TO BE WATCHED CLOSELY IN CASE THERE IS
ANY SHIFT IN THE MONSOON SURGE TO BRING ADDITIONAL SHOWERS
OVERNIGHT. WEATHER WILL CONTINUE TO WIND DOWN THROUGH WEDNESDAY AS
THE CIRCULATION SLOWLY HEADS NORTH OR NORTH-NORTHWEST THROUGH
MIDWEEK. DRIER CONDITIONS AND LIGHTER WINDS EXPECTED ON THURSDAY.
SEAS WERE BUMPED UP DUE TO THE INCREASED SOUTHWEST WINDS. COMBINED
SEAS OF 5 TO 7 FEET TONIGHT ACROSS CHUUK STATE WILL SLOWLY DIMINISH
TO BETWEEN 4 AND 5 FEET BY THURSDAY.

A BENIGN WEATHER PATTERN WILL BE IN PLACE AT YAP AND KOROR THROUGH
THE END OF THE WEEK. PRIMARY WEATHER FEATURE REMAINS THE MONSOON
TROUGH SITUATED JUST NORTH OF BOTH LOCATIONS AND THE DEVELOPING
CIRCULATION NORTH OF CHUUK. ISOLATED SHOWERS ARE EXPECTED THROUGH
SATURDAY WITH ISOLATED THUNDERSTORMS POSSIBLE WEDNESDAY AND THURSDAY
AT BOTH YAP AND KOROR DUE TO STRENGTHENING SOUTHWEST WINDS FLOWING
INTO THE DEVELOPING CIRCULATION. SEAS WILL INCREASE 1 TO 3 FEET IN
RESPONSE TO THE INCREASING WINDS LATER THIS WEEK.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...NONE.
MARIANAS WATERS...NONE.
&&

$$

SIMPSON/M. AYDLETT






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