Area Forecast Discussion
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FXPQ60 PGUM 242138
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
738 AM CHST FRI JUL 25 2014

.MARIANAS SYNOPSIS...ISOLATED SHOWERS AND EAST WINDS PREVAIL
ACROSS THE MARIANAS THIS MORNING.

&&

.DISCUSSION...
THIS MORNING TWO CIRCULATION CONTINUE TO BE LOCATED ON THE
MONSOON TROUGH THAT STRETCHES ACROSS THE WESTERN PACIFIC BELOW
10N. ONE CIRCULATION IS CLOSE TO PALAU AND THE OTHER CLOSE TO
CHUUK. YESTERDAY IT SEEMED THAT THE CHUUK CIRCULATION...WHICH WAS
DOMINANT...WOULD BE THE MAJOR PLAYER. IT WAS THOUGHT THAT THE
PALAU CIRCULATION WOULD GET ABSORBED INTO THE BIGGER CHUUK ONE.
NATURE HAD OTHER IDEAS AND AT THIS TIME THE PALAU CIRCULATION HAS
BECOME DOMINANT. 24 HOUR PRESSURE FALLS ARE THE LARGEST OVER
PALAU AND YAP. CHUUKS 24 HOUR SEA LEVEL PRESSURE CHANGE IS
POSITIVE. THIS SHOWS THAT AT THIS TIME THE PALAU CIRCULATION IS
GETTING BETTER ORGANIZED. IT IS DIFFICULT TO FIND THE CHUUK
CIRCULATION ON THURSDAY NIGHTS SCATTEROMETER CHART WHILE IT IS
EASY TO FIND THE PALAU ONE. MODELS ALSO SEEM TO HAVE AGREED ON
THIS CHANGE. YESTERDAY THERE WERE BIG DIFFERENCES BETWEEN THE
MODELS BUT TODAY THEY SEEM TO BE AGREEING ON THE PALAU
CIRCULATION. THEY TAKE THE PALAU CIRCULATION NORTHWARD INTO THE
PHILIPPINE SEA THROUGH THE WEEKEND. AS IT MOVES NORTHWARD IT WILL
DRAG THE MONSOON TROUGH ACROSS THE MARIANAS STARTING SATURDAY. AS
THE MONSOON TROUGH PUSHES ACROSS THE MARIANAS THIS WEEKEND IT
WILL BE ASSOCIATED WITH DEEP LAYER MOISTURE. THIS WILL EQUAL A
FAIR CHANCE OF SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
THROUGH AT LEAST MONDAY. ONE THOUGHT THOUGH IS WHAT IF THE
CIRCULATION...AS IT MOVES INTO THE PHILIPPINE SEA... TAKES THE
BULK OF THE MOISTURE WITH IT? COULD WE SEE JUST ISOLATED SHOWERS
ACROSS THE MARIANAS THIS WEEKEND? WILL KEEP SCATTERED SHOWERS IN
THE FORECAST FOR NOW AS THE SIGNAL IN THE MODELS IS TOO STRONG TO
TAKE IT OUT.

&&

.MARINE...
A WESTERLY AND AN EAST SWELL WILL PERSIST THROUGH THE FORECAST.
THE EAST SWELL IS EXPECTED TO INCREASE A FOOT ON SATURDAY. AT
THIS TIME THE WEST SWELL IS ONLY PREDICTED TO REACH FOUR FEET.
THIS MAY CHANGE DEPENDING ON HOW MUCH WIND IS ASSOCIATED WITH THE
CIRCULATION AS IT TREKS ACROSS THE PHILIPPINE SEA. IT STILL IS
NOT CERTAIN WHAT KIND OF WIND FIELD WILL BE ASSOCIATED WITH THE
CIRCULATION SO FETCH GENERATION AREAS ARE UNKNOWN.

&&

.EASTERN MICRONESIA...
SATELLITE IMAGERY SHOWS DEEP CONVECTION SPREAD OVER MOST OF THE
REGION. THE MONSOON TROUGH PASSES JUST NORTH OF POHNPEI AND
KOSRAE WHILE A TRADE-WIND DISTURBANCE IS FOUND OVER THE
MARSHALLS. THE MONSOON TROUGH IS EXPECTED TO SLOWLY LIFT TO THE
WEST- NORTHWEST... BUT MODELS CONTINUE TO DIFFER WIDELY RUN TO
RUN ON HOW THE TWO FEATURES WILL BEHAVE THE NEXT SEVERAL DAYS.
ECMWF SHOWS THE MONSOON TROUGH EXTENDING TOWARD THE MARSHALLS IN
RESPONSE TO THE DISTURBANCE WHILE GFS SHOWS A WEAK CIRCULATION
FORMING NEAR KOSRAE OVER THE WEEKEND AS THE DISTURBANCE CONTINUES
WESTWARD. THESE SCENARIOS LEAD TO A LOW CONFIDENCE WIND FORECAST
FOR THE NEXT SEVERAL DAYS WHICH WILL BE SUBJECT TO OCCASIONAL
FINE-TUNING. SHOWERS WILL FILL BACK IN AT POHNPEI AND KOSRAE
TODAY. MAJURO COULD SEE SOME DRYING BY SATURDAY AS THE
DISTURBANCE PASSES TO THE WEST. PRECIP FORECAST AT KOSRAE LEANS
TOWARD A DRY BIAS FOR SATURDAY AND WILL NEED TO BE WATCHED IN
CASE THE DISTURBANCE MAINTAINS DEEP CONVECTION THE NEXT 24 HOURS.

HAZARDOUS SURF IS STILL EXPECTED TO CONTINUE TODAY AT BOTH
POHNPEI AND KOSRAE...BUT SURF WILL BEGIN TO FALL OVERNIGHT AT
BOTH LOCATIONS. SURF COULD FALL BELOW HAZARDOUS LEVELS OVERNIGHT
AT KOSRAE AND SATURDAY AT POHNPEI. ALTIMETRY DATA WILL NEED TO BE
CLOSELY MONITORED FOR BUILDING SWELL AS MONSOON WEST AND
SOUTHWEST WINDS INCREASE ACROSS MICRONESIA OVER THE NEXT COUPLE
OF DAYS.

&&

.WESTERN MICRONESIA...
THE MONSOON TROUGH EXTENDS EASTWARD FROM A WEAK CIRCULATION NOW
JUST EAST OF KOROR NEAR 7N137E AND PASSES JUST NORTH OF WENO
ISLAND IN CHUUK STATE. DEEP CONVECTION IS FOUND ALONG THE SOUTH
SIDE OF THE TROUGH...GENERALLY SOUTH OF 7N...AND ALSO ALONG THE
WEST AND NORTHWESTERN PERIPHERY OF THE CIRCULATION NEAR KOROR.
CONVECTION HAS BEEN PERIODICALLY DEVELOPING BETWEEN YAP AND GUAM.
MODELS STILL INDICATE THE TROUGH AND CIRCULATION WILL LIFT
NORTHWARD OVER THE NEXT SEVERAL DAYS...WITH ECMWF PUSHING THE
CIRCULATION MORE NORTHWESTWARD. AS THESE SYSTEMS LIFT
NORTH...STRONGER WINDS WILL OVERSPREAD KOROR...YAP AND CHUUK.
SIMILARLY...SHOWERS AND THUNDERSTORMS WILL REDEVELOP AT ALL
LOCATIONS. WIND FORECASTS FOR BOTH YAP AND KOROR HAVE BEEN
ADJUSTED TO SHOW A LONGER-TERM SOUTHWEST WIND AS THE MONSOON
TROUGH LIFTS NORTHWARD AND THE CIRCULATION DEVELOPS AND
REINFORCES THE SOUTHWEST FLOW. CURRENT MODEL DATA SHOWS A GRADUAL
DRYING TREND AT KOROR BY MONDAY...AND AROUND TUESDAY FOR YAP.
SHOWERS ARE EXPECTED TO TAPER AT CHUUK BY SUNDAY...BUT THAT
DEPENDS ON HOW QUICKLY THE DISTURBANCE OVER EASTERN MICRONESIA
PUSHES TO THE WEST-NORTHWEST.

ALTIMETRY DATA SHOWS SEAS STILL SHY OF GENERATING HAZARDOUS
SURF...BUT SURF HEIGHTS ARE EXPECTED TO QUICKLY BUILD AT YAP AND
KOROR AS WEST AND SOUTHWEST WINDS INCREASE ON SATURDAY.

&&

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

$$

ZIOBRO/W. AYDLETT





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