Area Forecast Discussion
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FXPQ60 PGUM 200712 AAA
AFDPQ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE TIYAN GU
505 PM CHST SUN APR 20 2014

UPDATED TO INCLUDE MICRONESIA DISCUSSIONS

.MARIANAS SYNOPSIS...
AN OLD FRONTAL BOUNDARY REMAINS STALLED OVER THE FAR NORTHERN
CNMI. AN EMBEDDED CIRCULATION IS SITUATED WITHIN THE BOUNDARY
NEAR 20N145E. JTWC MEDIUM INVEST AREA 98W IS PASSING TO THE NORTH
OF KOROR. SCATTERED SHOWERS ASSOCIATED WITH BOTH OF THESE
FEATURES WILL NOT BE AFFECTING THE FORECAST ZONES...BUT SURFACE
TROUGHING BETWEEN THEM COULD PROVIDE JUST ENOUGH LOW-LEVEL
FORCING TO TRIGGER A CB OR TWO UNTIL THE TROUGHING SHIFTS FARTHER
TO THE WEST. A NEW TROPICAL DISTURBANCE HAS DEVELOPED IN THE
NEAR-EQUATORIAL TROUGH NEAR KOSRAE. THIS SYSTEM HAS BECOME
BETTER ORGANIZED DURING THE PAST 24 HOURS.

&&

.DISCUSSION...
LATEST FORECAST PACKAGE INVOLVES ONLY A FEW MINOR ADJUSTMENTS.
ADDED SLIGHT CHANCE OF THUNDER FOR TONIGHT BASED ON THE PROXIMITY OF
THE SURFACE TROUGH IN THE PHILIPPINE SEA. DRY TRADE WINDS ARE
STILL ON SCHEDULE TO INVADE ON MONDAY. DRIER PATTERN WILL HANG ON
THROUGH THURSDAY. NEXT POSSIBLE WEATHER MAKER IS THE SYSTEM NEAR
KOSRAE. MODELS ARE ALL IN GENERAL AGREEMENT THAT CLOUDINESS FROM
THIS SYSTEM AND AN APPROACHING SHEAR LINE WILL BE AFFECTING THE
MARIANAS FROM FRIDAY THROUGH EARLY NEXT WEEK. AS A RESULT...HAVE
BROUGHT IN MOSTLY CLOUDY SKIES DAYS 6 THROUGH 10.

&&

.MARINE...
RELATIVELY QUIET MARINE CONDITIONS WILL CONTINUE UNTIL MID WEEK.
A MODERATE TRADE-WIND SURGE WILL ARRIVE DURING THE MIDDLE OF THE
WEEK...BUT SEAS AND SURF SHOULD REMAIN WELL BELOW ADVISORY
THRESHOLDS. HOWEVER...BOTH ECMWF AND GFS AGREE THAT A VERY STRONG
COLD FRONT WILL BE PUSHING SOUTH FROM JAPAN DURING THE END OF THE
WEEK. EVENT APPEARS TO BE ROBUST ENOUGH TO PRODUCE HIGH SURF AND
CAUSE SEAS TO BUILD TO ADVISORY LEVELS. STILL PLENTY OF MODEL
RUNS AHEAD BUT A SCENARIO THAT CERTAINLY BEARS WATCHING.

&&

.EASTERN MICRONESIA
A BROAD CIRCULATION EMBEDDED WITHIN THE NEAR-EQUATORIAL TROUGH CAN
BE SEEN SOUTH OF KOSRAE NEAR 3N163E. LATEST SOUNDING DATA FROM CHUUK
AND POHNPEI REVEALS MID-LEVEL DRYNESS BETWEEN 750 AND 450MB. THIS
POCKET OF DRY AIR WILL COMBINE WITH A SURFACE RIDGE NORTHWEST OF THE
CIRCULATION TO PROMOTE A PERIOD OF PLEASANT WEATHER FOR CHUUK THRU
MONDAY NIGHT...AND POHNPEI UNTIL MONDAY AFTERNOON. FOR KOSRAE...
STRONG CONVERGING LOW-LEVEL WINDS ALONG THE NORTHERN PERIPHERY OF
THE CIRCULATION WILL MAINTAIN INCLEMENT WEATHER UNTIL AT LEAST
MONDAY EVENING. FARTHER EAST...FRESH TRADE WINDS ARE PROGRESSING
ACROSS THE MARSHALL ISLANDS TOWARD THE EASTERN END OF THE
NEAR-EQUATORIAL TROUGH. WIDESPREAD CONVECTION GENERATED BY THIS
PROCESS IS SPREADING NORTHWARD INTO MAJURO THIS EVENING AND THIS
TREND WILL CONTINUE THRU MONDAY NIGHT.

THE SUB-TROPICAL RIDGE CURRENTLY STRETCHING NORTHEASTWARD FROM NORTH
OF CHUUK TO BEYOND WAKE ISLAND WILL BE WEAKENED BY A FRONTAL
BOUNDARY PUSHING EASTWARD FROM SOUTH OF JAPAN OVER THE NEXT FEW
DAYS. THIS SHOULD ALLOW THE CIRCULATION AND ITS ASSOCIATED
NEAR-EQUATORIAL TROUGH TO LIFT WEST-NORTHWESTWARD OVER KOSRAE AND
MAJURO TOWARD POHNPEI AND CHUUK. THEREFORE EXPECT WET WEATHER TO
GRADUALLY SHIFT FROM KOSRAE AND MAJURO INTO POHNPEI BY MONDAY
EVENING...AND CHUUK BY TUESDAY NIGHT. MODERATE TRADES WILL THEN
USHER IN A DRYER PATTERN FOR MAJURO AND KOSRAE AROUND MIDWEEK. AS
THE CIRCULATION CONTINUES TO MOVE NORTHWEST OF POHNPEI AND CHUUK...
THIS SAME DRYER PATTERN MIGHT ALSO ARRIVE AT BOTH LOCALES TOWARD THE
WEEKEND.

&&

.WESTERN MICRONESIA
REASONING FOR THE CHUUK FORECAST CAN BE FOUND UNDER THE EASTERN
MICRONESIA SECTION ABOVE. A TROPICAL DISTURBANCE...JTWC MEDIUM
INVEST AREA 98W IS PULLING FARTHER NORTHWEST OF KOROR AND YAP INTO
THE PHILIPPINE SEA THIS EVENING. MODEST CONVERGING SOUTH TO
SOUTHEAST WINDS IN ITS WAKE COULD STILL SPARK A FEW THUNDERSTORMS
NEAR YAP THRU MONDAY NIGHT. MEANWHILE LIGHT AND VARIABLE WINDS SOUTH
OF THE DISTURBANCE MIGHT INDUCE ISLAND THUNDERSTORMS NEAR KOROR THRU
TUESDAY. AFTERWARD GENTLE TRADES FILTERING WESTWARD FROM EASTERN
MICRONESIA SHOULD BRING IN MORE STABLE WEATHER FOR THE AREA NEAR
MIDWEEK. TOWARD THE WEEKEND...THE NEAR-EQUATORIAL TROUGH EXTENDING
WESTWARD FROM THE CIRCULATION CURRENTLY SOUTH OF KOSRAE WILL BEGIN
TO AFFECT YAP AND KOROR WITH AN INCREASING CHANCE OF SHOWERS.

&&

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

$$

MCELROY/CHAN








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