Area Forecast Discussion
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FXPQ60 PGUM 222136
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
736 AM CHST TUE SEP 23 2014

.MARIANAS SYNOPSIS...AN ACTIVE MONSOON TROUGH WITH AN ASSOCIATED
CIRCULATION WILL BRING WET WEATHER TO THE MARIANAS THE NEXT FEW
DAYS.

&&

.DISCUSSION...
A MONSOON TROUGH STRETCHED ACROSS THE MARIANAS IN THE VICINITY OF
GUAM. A CIRCULATION WAS ON THE TROUGH SOUTHEAST OF GUAM NEAR
12N148E. MODELS AGREE ON PUSHING THE CIRCULATION IN A GENERAL
NORTHERLY DIRECTION. GFS AND GFS-ENSEMBLE KEEP THE CIRCULATION
EAST OF THE MARIANA ISLANDS WHILE THE ECMWF HAS THE CIRCULATION
PASSING ACROSS PAGAN. THE LATITUDE OF THE CIRCULATION APPEARS
SIMILAR IN ALL THE MODELS BEING BETWEEN 18N AND 20N BY THURSDAY.

THE CIRCULATION IS THE SUBJECT OF A TROPICAL STORM FORMATION
ALERT. THIS MEANS THE SYSTEM COULD DEVELOP INTO A TROPICAL
CYCLONE WITHIN THE NEXT 24 HOURS. JAPANESE METEOROLOGICAL
ADMINISTRATION SHOW IT AS A TROPICAL DEPRESSION IN 24 HOURS.
MODELS AGREE AS THEY DEVELOP THE SYSTEM INTO AT LEAST A TROPICAL
STORM...BUT THEY ALSO AGREE THAT IT WILL WAIT UNTIL IT IS NORTH
OF 20N.

MODELS AGREE ON SCATTERED SHOWERS TODAY WITH A LESSER CHANCE OF
SHOWERS THEREAFTER. DID NOT CHANGE THE FORECAST IN THAT SCATTERED
SHOWERS ARE ONLY EXPECTED TODAY. SINCE THIS IS A DEVELOPING
SYSTEM AND THE MODELS MAY NOT BE HANDLING THIS PERFECTLY.
SCATTERED SHOWERS COULD BE POSSIBLE FOR A LONGER PERIOD OF TIME.
WINDS ARE EXPECTED TO INCREASE ONLY SLIGHTLY AS THE BULK OF THE
DEVELOPMENT OF THE SYSTEM WILL BE AWAY FROM THE LOCAL AREA.
EXPECT 10 TO 15 MPH TODAY AND TONIGHT WITH 10 TO 20 MPH WEDNESDAY
THROUGH THURSDAY.

&&

.MARINE...
A WEST SWELL AND A NORTHEAST SWELL ARE PRESENT THIS MORNING OVER THE
LOCAL AREA. WITH THE CIRCULATION TO OUR EAST DEVELOPING EXPECT THE
NORTHEAST SWELL TO INCREASE. IT WILL ALSO GRADUALLY BECOME MORE
NORTHERLY AS THE SYSTEM MOVE NORTH OF THE LOCAL AREA. THE WEST SWELL
WILL GRADUALLY BECOME SOUTHWEST BY WEDNESDAY.

&&

.EASTERN MICRONESIA...
THE MONSOON CIRCULATION...JTWC INVEST AREA 98W CENTERED EAST-
SOUTHEAST OF GUAM NEAR 12N148E IS THE SUBJECT OF A TROPICAL
CYCLONE FORMATION ALERT THIS MORNING. IT HAS BEEN SHOWING SIGNS
OF DEVELOPING WITH WIDESPREAD DEEP CONVECTION FLARING UP NEAR THE
CENTER FOR THE PAST 6 HOURS. LATEST IR SATELLITE LOOP ALSO
INDICATES A SOUTHEASTERLY FLOW TOWARD 98W HAS FORMED ACROSS
POHNPEI AND KOSRAE. THIS CONVERGING SURFACE FLOW WILL COUPLE WITH
DIVERGENT NORTHEAST WINDS ALOFT TO TRIGGER ISOLATED CONVECTION
FOR BOTH LOCALES THRU WEDNESDAY. FARTHER EAST...A NEAR-EQUATORIAL
TROUGH REACHES EASTWARD FROM ANOTHER CIRCULATION CENTERED JUST
WEST OF MAJURO AT 8N169E TO BEYOND THE DATE LINE AT 9N. SURFACE
CONVERGENCE NEAR THESE FEATURES WILL KEEP SOME SHOWERS NEAR
MAJURO TODAY. WITH BOTH THE CIRCULATION AND NEAR-EQUATORIAL
TROUGH DRIFTING WEST-NORTHWESTWARD AWAY FROM MAJURO...WEAKER
SOUTHEASTERLY WINDS TO THE SOUTH SHOULD PROVIDE DRIER WEATHER FOR
THE CAPITAL BY LATE THIS EVENING. HOWEVER THESE SAME FEATURES
COULD POSSIBLY PASS NORTH OF KOSRAE BUT REACH POHNPEI AROUND
WEDNESDAY NIGHT. WEATHER NEAR MAJURO COULD ALSO BECOME WETTER
AGAIN TOWARD THE WEEKEND AS A TRADE DISTURBANCE APPROACHES FROM
THE DATE LINE.

&&

.WESTERN MICRONESIA...
LATEST ASCAT/WINDSAT STREAMLINE ANALYSIS REVEALS FRESH SOUTHWEST
WINDS JUST NORTH OF WENO ISLAND IN CHUUK STATE THIS MORNING. THIS
MONSOONAL SURGE SHOULD BEGIN TO WEAKEN AS THE MONSOON CIRCULATION
EAST-SOUTHEAST OF GUAM LIFTS NORTHWARD TODAY AND TONIGHT.
HOWEVER... THESE CONVERGENT SOUTHWEST WINDS COULD STILL SPARK OFF
A FEW THUNDERSTORMS THRU WEDNESDAY AFTERNOON. BY WEDNESDAY
NIGHT...A WEAK SURFACE RIDGE SHOULD FORM OVER CHUUK AND PROMOTE
FAIRER CONDITIONS FOR MIDWEEK. TOWARD THE WEEKEND...THE NEAR-
EQUATORIAL TROUGH AND ASSOCIATED CIRCULATION CURRENTLY NEAR THE
MARSHALL ISLANDS COULD INTRODUCE SHOWERS FOR THE ISLAND.

MONSOONAL WEST WINDS ACROSS PALAU AND YAP STATE ARE GRADUALLY
INCREASING BASED ON ASCAT/WINDSAT ANALYSIS. WITH THE MONSOONAL
CIRCULATION NEAR GUAM DEVELOPING FURTHER TODAY AND TONIGHT...
MONSOONAL WEST WINDS ACROSS BOTH LOCATIONS SHOULD RISE TO
MODERATE BY WEDNESDAY. THIS MIGHT SET UP AN UNSTABLE PATTERN
ACROSS KOROR AND YAP FROM WEDNESDAY TO AT LEAST FRIDAY. FUTURE
SHIFTS NEED TO MONITOR FOR POSSIBLE HIGHER SHOWER COVERAGE AND
SEAS.

&&

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

$$

ZIOBRO/CHAN





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