Area Forecast Discussion
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FXPQ60 PGUM 201845
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
445 AM CHST SUN SEP 21 2014

.MARIANAS SYNOPSIS...
RADAR SHOWS SOME SHOWERS EAST OF GUAM AND ROTA...ASSOCIATED WITH A
WEAK INVERTED TROUGH ALONG 148E. OTHERWISE...LIGHT EAST WINDS AND
ISOLATED SHOWERS ARE PRESENT ACROSS THE MARIANAS WATERS. SEAS ARE
RUNNING 3-4 FT AT THE BUOYS.

&&

.DISCUSSION...
GFS QUICKLY WEAKENS THE TROUGH AND ASSOCIATED SHOWERS OUT EAST
LATER THIS MORNING AND DIURNAL TRENDS FAVOR KILLING OFF MOST OF
THE SHOWERS AS WELL. BY THE END OF THE DAY...THE DEVELOPING
MONSOON TROUGH FORECAST BY THE GFS/ECMWF/NAVGEM WILL ALREADY BE
TAKING SHAPE IN THE MARIANAS...EXTENDING WEST FROM A CIRCULATION
NORTH OF POHNPEI CENTERED NEAR 14N157E. THE OVERALL FORECAST
REMAINS THE SAME AS PREVIOUS...EXCEPT HAVE EXTENDED ISOLATED
THUNDERSTORMS THAT START ON MONDAY THROUGH THE WEEK AS THE
DEVELOPING MONSOON CIRCULATION MOVES SLOWLY NW THE NEXT FEW DAYS
AND A MONSOON TAIL TRIES TO DEVELOP SOUTH OF IT...KEEPING
CONDITIONS IN THE MARIANAS UNSETTLED FOR AN EXTENDED PERIOD.

&&

.MARINE...
MARINE GRIDS LOOK FINE AS IS...AND HAVE MADE NO CHANGES. COMBINED
SEAS LATE IN THE WEEK WILL BE HEAVILY DEPENDENT ON HOW STRONG OUR
DEVELOPING CIRCULATION BECOMES. GFS IS QUITE AGGRESSIVE WITH IT...
BUT THAT IS A KNOWN BIAS. ECMWF IS SLOWER...WHICH LOOKS REASONABLE
AND SEAS ARE BASED MAINLY ON IT.

&&

.EASTERN MICRONESIA...
A MONSOON TROUGH IS DEVELOPING ACROSS THE REGION AS PREDICTED BY THE
GFS40. A WEAK CIRCULATION IS PRESENT ALONG THE TROUGH TO THE NORTH
OF KOSRAE. THIS SITUATION WILL MAINTAIN AN OVERALL UNSTABLE PATTERN
OVER THE REGION FOR THE NEXT FEW DAYS...HOWEVER MOST OF THE ACTIVITY
WITH THE TROUGH WILL REMAIN NORTH OF 10N. THE LATEST GFS INDICATES
THE TROUGH AND CIRCULATION WILL DRIFT WEST-NORTHWESTWARD OVER THE
NEXT FEW DAYS WITH WEAK RIDGING BUILDING IN OVER KOSRAE TONIGHT...
GIVING KOSRAE A BRIEF PERIOD OF DRY CONDITIONS TONIGHT INTO MONDAY.
AS THE MONSOON TROUGH CONTINUES TO DEVELOP...EXPECT MOIST CONDITIONS
TO CONTINUE OVER THE REGION THROUGH MIDWEEK. MAJURO WILL SEE THE
QUICKEST RETURN TO FAIR CONDITIONS...WITH DRIER WEATHER EXPECTED
THERE BY TUESDAY. THE DRIER PATTERN WILL MOVE INTO KOSRAE BY
WEDNESDAY. FOR POHNPEI...IT IS A LITTLE MORE DIFFICULT TO SEE WHEN
THE DRIER CONDITIONS WILL MOVE IN. THE GFS40 DEVELOPS THE CIRCULATION
NORTH OF KOSRAE FAIRLY QUICKLY AND MOVES IT WEST-NORTHWESTWARD...
BRINGING DRIER CONDITIONS TO POHNPEI BY WEDNESDAY. THE ECMWF ALSO
DEVELOPS THE CIRCULATION...BUT A BIT SLOWER. THIS KEEPS MOIST
CONDITIONS IN AT POHNPEI THROUGH THE END OF THE WEEK. CHOSE TO
MAINTAIN INHERITED FORECAST FOR NOW TO SEE WHICH MODEL IS MORE IN
LINE WITH WHAT ACTUALLY OCCURS.

&&

.WESTERN MICRONESIA...
A MONSOON TROUGH EXTENDS NORTHEASTWARD FROM NEAR EQ131E THROUGH A
BROAD CIRCULATION CENTERED SOUTH OF YAP...THEN CONTINUES
NORTHEASTWARD INTO EASTERN MICRONESIA. THIS TROUGH DEVELOPED AS
PREDICTED BY THE GFS40 OVER THE LAST FEW DAYS. KOROR AND YAP WILL
SEE A FEW SHOWERS AROUND THE AREA AS THE CIRCULATION AND TROUGH
DRIFT NORTHWARD THROUGH TONIGHT WITH THE TROUGH ESTABLISHING ITSELF
NORTH OF 10N BY MONDAY. DRIER CONDITIONS WILL THEN BE IN PLACE OVER
BOTH LOCATIONS THROUGH THE END OF THE WEEK. FOR CHUUK...CONVERGING
WINDS EAST OF THE CIRCULATION WILL BRING A PERIOD OF SCATTERED
SHOWERS TO THE STATE TONIGHT AND MONDAY. CONDITIONS WILL IMPROVE A
BIT MONDAY NIGHT AS THE TROUGH AND CIRCULATION DRIFT FURTHER NORTH.
THOUGH THE SHOWERS WILL DECREASE TO ISOLATED...AN OVERALL UNSTABLE
PATTERN WILL CONTINUE OVER CHUUK THROUGH THE END OF THE WEEK.

&&

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

$$

MIDDLEBROOKE/KLEESCHULTE





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