FXPQ60 PGUM 010709

AFDPQ 



AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE TIYAN GU

509 PM CHST SUN AUG 1 2010



.SYNOPSIS...

A WEAK TROPICAL DISTURBANCE IS DRIFTING WEST-NORTHWESTWARD SOUTH

OF GUAM THIS EVENING. SURFACE CONVERGENCE NORTH OF THE

DISTURBANCE IS COUPLING WITH DIVERGENT WINDS ASSOCIATED WITH AN

UPPER-LEVEL TROUGH OVER THE REGION TO TRIGGER SOME SHOWERS AND

SLIGHT THREAT OF THUNDERSTORMS FOR THE MARIANAS.



&&



.DISCUSSION...

BASED ON THE LATEST VISIBLE AND ASCAT SATELLITE IMAGERY...THE

SUB-TROPICAL RIDGE HAS LIFTED NORTH OF 20N. THIS ALLOWS A TROUGH

OF LOW PRESSURE TO DEVELOP OVER THE PHILIPPINE SEA WEST OF THE

MARIANAS. UNDER THE SAME REASONING...A WEAK SURFACE TROUGH HAS

ALSO BEEN EXTENDED WESTWARD FROM THE DISTURBANCE SOUTH OF GUAM

ACROSS BOTH YAP AND PALAU TO JUST EAST OF MINDANAO. WITH

SOUTHWESTERLY MONSOON WINDS JUST WEST OF THE PHILIPPINES...IT IS

LOGICAL FOR THESE TROUGHS OF LOW PRESSURE TO EVENTUALLY PULL THE

MONSOONAL FLOW INTO THE PHILIPPINE SEA AS THEY BECOME BETTER

ORGANIZED. IN FACT...THIS IS EXACTLY WHAT MOST MODELS ARE

FORECASTING FOR THE NEXT SEVERAL DAYS. IF A MONSOON CIRCULATION

DID MATERIALIZE OVER THE PHILIPPINE SEA...IT WILL LIKELY CREATE

CONVERGING EAST TO SOUTHEAST SURFACE WINDS OVER THE MARIANAS.

COMBINING WITH AN UPPER TROUGH ALREADY IN THE AREA...A WET WEATHER

TREND IS POSSIBLE AT LEAST INTO MIDWEEK. HAVE INCREASED BOTH CLOUD

COVERAGE AND POP THRU WEDNESDAY BUT KEPT SCATTERED PRECIP AND

THUNDERSTORMS OUT FOR NOW.



&&



.MARINE...

TRADE-WIND SWELLS TOGETHER WITH SOUTHEAST SWELLS WILL KEEP A

COMBINED SEAS OF 4 TO 5 FEET FOR THE NEXT SEVERAL DAYS.



&&



.EASTERN MICRONESIA...

A LARGE AREA OF DEEP CONVECTION ASSOCIATED WITH TRADE-WIND

CONVERGENCE EXTENDS FROM WEST OF POHNPEI TO NEAR KWAJALEIN

TURNING EAST-SOUTHEASTWARD TO JUST SOUTH OF MAJURO. SCATTERED

SHOWERS AND ISOLATED THUNDERSTORMS ARE EXPECTED TO PERSIST

TONIGHT AND INTO TOMORROW IN THE AREAS WEST OF KWAJALEIN. A WEAK

TROUGH IS PASSING OVER MAJURO AND WILL MOVE THROUGH THE CENTRAL

AND NORTHERN MARSHALLS PRODUCING ADDITIONAL SHOWERS TONIGHT.



MAJURO BUOY SHOWS THE SE SWELL HAS PEAKED BUT HIGH SURF

ADVISORIES WILL REMAIN IN EFFECT FOR MAJURO THROUGH MONDAY AND

KOSRAE THROUGH MONDAY NIGHT INTO TUESDAY.



&&



.WESTERN MICRONESIA...

MONSOON PATTERN CONTINUES TO MATERIALIZE AS A BROAD CIRCULATION

FORMS NEAR CHUUK. HEAVY WEATHER OVER CHUUK THIS MORNING HAS ENDED

WHILE SCATTERED SHOWERS QUICKLY APPROACH YAP AND PALAU. LIGHT

WINDS REMAIN OUT OF THE NORTHWEST ACROSS THE PALAU REGION. MODELS

INDICATE CIRCULATION WILL PASS BETWEEN YAP AND GUAM WITH

SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ACROSS THE PALAU

REGION IN A SOUTHWEST FLOW EARLY TO MID WEEK. PALAU COULD SEE

HEAVY RAIN TONIGHT IN A DEVELOPING MONSOON TAIL. NIGHT SHIFT WILL

MONITOR THIS SITUATION CLOSELY. ISOLATED SHOWERS ARE EXPECTED TO

RETURN AFTER THE PASSAGE OF THE DISTURBANCE BY THE END OF THE

WEEK.



&&



.GUM WATCHES/WARNINGS/ADVISORIES...

GU...NONE.

MARIANAS WATERS...NONE.

&&



$$



CHAN/MCELROY/M. AYDLETT