Area Forecast Discussion
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000
FXPQ60 PGUM 270623
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
423 PM CHST THU NOV 27 2014

.MARIANAS SYNOPSIS...FRESH TO STRONG TRADE-WINDS AND A FEW SHOWERS
PREVAILED ACROSS THE MARIANAS THIS AFTERNOON.

&&

.DISCUSSION...
THIS AFTERNOON A CIRCULATION IS LOCATED FAR TO SOUTH OF THE
MARIANAS...NEAR 3N141E. LOW-LEVEL CONVERGENCE NORTH OF THE
CIRCULATION IS GENERATING AN AREA OF SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS. WHILE MUCH OF THE SHOWERS AND
THUNDERSTORMS WILL REMAIN SOUTH. A FEW THUNDERSTORMS HAVE BEEN
FORMING NEAR THE AREA SO ADDED A SLIGHT CHANCE OF THUNDERSTORMS
TO GUAM AND ROTA TONIGHT.

SATELLITE IMAGERY THIS AFTERNOON SHOWS A LINE OF SHOWERS EXTENDING
FROM SOUTH OF GUAM NORTHEASTWARD TO EAST OF 150E. A FEW MODELS
ACTUALLY SHOW THIS FEATURE AND BRING IT ACROSS THE MARIANAS
FRIDAY. ISOLATED SHOWERS SHOULD BE THE DOMINANT COVERAGE AS IT
PASSES. A SLIGHT CHANCE OF THUNDERSTORMS WERE ADDED FOR ALL OF THE
LOCAL AREA FRIDAY AND FRIDAY NIGHT AS SOME THUNDERSTORMS ARE
ALREADY OCCURRING WITH THIS AREA. THIS CONVERGENCE AREA WILL
PRODUCE ON AND OFF CLOUDS THROUGH SATURDAY. DRIER AIR WILL FILTER
INTO THE LOCAL AREA WHICH WILL KEEP SHOWERS AT A MINIMUM SUNDAY.

MODELS ARE STARTING TO AGREE ON THE DEVELOPMENT OF A TROPICAL
CYCLONE OVER THE WESTERN HALF OF MICRONESIA. BY SUNDAY NIGHT.
THEY DEPICT A CIRCULATION NEAR 5N148E. THEY AGREE ON MOVING THE
CIRCULATION NORTHWESTWARD...ALTHOUGH THEY START TO DISAGREE ON
THE EXACT TRACK AND SPEED OF THIS MOVEMENT. ON WEDNESDAY GFS AND
GFS-ENSEMBLE SHOW IT NEAR OR NORTH OF YAP. ECMWF SHOWS IT SOUTH
OF YAP. NAVGEM DOES SHOW IT ALSO...BUT HAS IT FURTHER EASTWARD
NEAR 7N145E AT THE SAME TIME.

BY THURSDAY THE GFS AND GFS-ENSEMBLE MOVES IT OUT OVER THE
PHILIPPINE SEA WEST OF GUAM. ECMWF SHOWS IT NEAR 11N130E MOVING
TOWARDS THE CENTRAL PHILIPPINES. LATER ON THE GFS AND GFS-
ENSEMBLE GET THE SYSTEM TANGLED INTO A SHEAR LINE THAT WILL BE
DRAPED OVER THE WESTERN PACIFIC. THE MODELS DO SEEM TO AGREE
THAT THE SYSTEM MAY BECOME A TROPICAL DEPRESSION OR EVEN A WEAK
TROPICAL STORM. EITHER WAY...IT WILL NOT DIRECTLY IMPACT THE
MARIANAS. THE PRESSURE GRADIENT WILL HOWEVER KEEP THE TRADE-WINDS
ELEVATED OVER THE AREA FOR PART OF THE COMING WEEK.

&&

.MARINE...
AN EAST TRADE-WIND SWELL WILL PERSIST THROUGH THE THROUGH THE
FORECAST. THE SWELL WILL BE AROUND 5 TO 7 FEET THROUGH THE
WEEKEND.

A NORTH SWELL WILL ALSO BE PRESENT THROUGH THE FORECAST. THIS
SWELL WILL BE ONLY 2 TO 3 FEET THROUGH SATURDAY. A STORM SYSTEM
NOW EAST OF JAPAN WILL INCREASE IN STRENGTH AS IT MOVES EASTWARD.
WINDS ASSOCIATED WITH THE STORM WILL PUSH HIGHER NORTH SWELLS
ACROSS THE MARIANAS BY THE COMING WEEKEND. SURF WILL BE CLOSE TO
BECOMING HAZARDOUS ON SUNDAY AND MONDAY.

THE INCREASED TRADE-WINDS OVER THE MARIANAS HAVE NECESSITATED THE
ISSUANCE OF A SMALL CRAFT ADVISORY OVER THE MARIANAS. COMBINED
SEAS HAVE ALSO INCREASED TO SMALL CRAFT LEVELS. THESE WINDS AND
SEAS SHOULD PERSIST THROUGH SATURDAY MORNING.

&&

.EASTERN MICRONESIA...
A VERY ACTIVE PATTERN REMAINS ACROSS THE AREA WITH HEAVIEST
SHOWERS AND THUNDERSTORMS FOUND JUST SOUTH AND WEST OF POHNPEI
AND KOSRAE... AND FARTHER EAST ABOUT TO REACH MAJURO. A BROAD
TROUGH OF LOW PRESSURE SOUTH OF 5N IS COMBINING WITH A TRADE-WIND
SURGE NORTH OF 5N TO MAINTAIN SUCH DEEP AND ACTIVE CONVECTION.
MODELS SHOW WEAK CIRCULATIONS FORMING ALONG THE TROUGH NEAR THE
EQUATOR AND PUSHING WESTWARD. THIS WILL ACT TO PERIODICALLY
INCREASE WINDS AT VARIOUS LOCALES DUE TO TIGHTENING OF THE
PRESSURE GRADIENT. FOR THE NEXT FEW DAYS...EXPECT FRESH TO STRONG
TRADES AT ALL LOCATIONS WITH PERIODS OF SCATTERED SHOWERS.
SHOWERS WILL BE HEAVIEST TONIGHT AT MAJURO AS A NEW SURGE PUSHES
THROUGH. A SLIGHTLY DRIER PERIOD IS ANTICIPATED OVER THE WEEKEND
BUT THEN ANOTHER BAND OF TRADE-WIND CONVERGENCE AND SHOWERS IS
EXPECTED TO DEVELOP NEAR MAJURO AROUND SUNDAY OR MONDAY.

WITH KALO BUOY INDICATING SEAS OF 7 TO 8 FT AND ALTIMETRY DATA
SHOWING 9 TO 12 FT...HAVE MAINTAINED HIGH SURF ADVISORY FOR BOTH
KOSRAE AND MAJURO. SEAS WILL GRADUALLY SUBSIDE AT MAJURO
FRIDAY... BUT HAZARDOUS SURF MAY PERSIST AT KOSRAE THROUGH FRIDAY
NIGHT.

&&

.WESTERN MICRONESIA...
CHUUK HAS SEEN OFF-AND-ON SHOWERS AND THUNDERSTORMS TODAY WITH
SLIGHTLY CALMER WEATHER THIS AFTERNOON BUT SATELLITE IMAGERY
SHOWS ANOTHER SURGE OF SHOWERS AND THUNDERSTORMS MOVING IN FROM
THE EAST. MODELS INDICATE WET CONDITIONS WILL PERSIST THROUGH
FRIDAY BEFORE QUIETING DOWN BRIEFLY FRIDAY NIGHT. SATURDAY AND
SUNDAY ARE LOOKING TO BE SOMEWHAT WETTER AGAIN AS ANOTHER
INVERTED TROUGH OR WEAK CIRCULATION PASSES BY TO THE SOUTH AND
CAUSES WINDS TO INCREASE ACROSS THE AREA.

FOR YAP AND PALAU...SHOWERS AND THUNDERSTORMS ARE CLOSING IN BUT
REMAIN JUST EAST OF BOTH LOCATIONS. WETTER WEATHER WILL REACH YAP
THIS EVENING AND KOROR OVERNIGHT. A BROAD BUT WEAK CIRCULATION
WELL SOUTHEAST OF YAP WILL PASS BY TO THE SOUTH AND MAINTAIN A
BROAD AREA OF LOW-LEVEL CONVERGENCE FOCUSED OVER YAP AND KOROR.
SATURDAY AND SUNDAY WILL BE A LITTLE DRIER BUT STILL THE OVERALL
PATTERN WILL BE FAIRLY UNSTABLE. MODELS DIVERGE FOR MONDAY AND
TUESDAY WITH GFS SHOWING A PAIR OF WEAK CIRCULATIONS PASSING
NORTHWESTWARD OVER THE AREA AS COMPARED TO ECMWF SHOWING JUST ONE
CIRCULATION. WIND FORECAST FOR NOW FOLLOWS THE MORE ORGANIZED
WIND PATTERN OF THE ECMWF...BUT SHOULD THE GFS SOLUTION PAN
OUT...WIND AND PRECIP FORECASTS WILL NEED SOME FINE-TUNING.

MARINE FORECASTS KEEP SEAS LOW ENOUGH SUCH THAT HAZARDOUS SURF IS
NOT EXPECTED AT THIS TIME...HOWEVER...SHOULD A CIRCULATION
DEVELOP SUNDAY OR MONDAY...THE SLIGHTLY INCREASED WINDS MAY BUILD
SEAS ENOUGH TO GENERATE HAZARDOUS SURF EARLY NEXT WEEK.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...NONE.
MARIANAS WATERS...SMALL CRAFT ADVISORY UNTIL 6 AM CHST SATURDAY FOR PMZ151>154.

&&

$$

ZIOBRO/W. AYDLETT





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