Area Forecast Discussion
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FXPQ60 PGUM 282154
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
754 AM CHST FRI AUG 29 2014

.MARIANAS SYNOPSIS...
AN UPPER-LEVEL LOW PASSING NORTH OF THE MARIANAS WILL CREATE
ISOLATED THUNDERSTORMS IN ADDITION TO THE USUAL ISOLATED SHOWERS
THROUGH SATURDAY NIGHT. PGUA WSR-88D SHOWS THESE THUNDERSTORMS ARE
CURRENTLY MAINLY IN THE SOUTHERN GUAM WATERS. IR SATELLITE AND
LIGHTNING DATA SHOW THEM TO BE MUCH MORE EXTENSIVE TO THE EAST...
AND THEY ARE TRACKING WESTWARD ALONG WITH THE LOW. THE VAD WIND
PROFILE REVEALS EAST-NORTHEAST WINDS OF 12 TO 19 KNOTS THROUGH THE
LOWEST 15 THOUSAND FEET OF THE AIR.

&&

.DISCUSSION...
UPPER-LEVEL LOW IS PROVIDING COOLER AIR IN THE UPPER ATMOSPHERE.
THIS DESTABILIZING INFLUENCE IS ALLOWING MANY OF THE ISOLATED
SHOWERS TO BECOME THUNDERSTORMS. ON SATURDAY NIGHT THE LOW IS
EXPECTED TO DRIFT FAR ENOUGH AWAY THAT ITS INFLUENCE WILL WANE.
THE BIG FEATURE IN THE MARIANAS FORECAST WILL THEN BE THE MONSOON
TROUGH...WHICH IS PROGGED TO DEVELOP AND MOVE OVER THE MARIANAS BY
BOTH THE GFS AND ECMWF-HIRES. PER THE CLIMATE PREDICTION CENTER
MJO UPDATE...THE MADDEN-JULIAN OSCILLATION IS CURRENTLY RATHER
WEAK AND INCOHERENT. THEREFORE...THE MONSOON TROUGH IS EXPECTED TO
REMAIN WEAK. BOTH MODELS AGREE WITH NO WINDS EXCEEDING 10 KNOTS.
THE GENERAL PICTURE IS IN GOOD AGREEMENT...JUST THE DETAILS THAT
COULD BE SUBJECT TO TWEAKS. THESE MIGHT INCLUDE EXACT TIMING OF
ONSET OF WESTERLY WINDS AND TIMING OF ANY PERIODS OF SCATTERED
SHOWERS.

EAST-NORTHEAST SWELLS WILL REMAIN AT 2 TO 3 FEET THROUGH MUCH OF
NEXT WEEK. THESE BENIGN SEA CONDITIONS ARE WELL BELOW ADVISORY
CRITERIA.

&&

.EASTERN MICRONESIA...
A BROAD LOW-LEVEL CIRCULATION IS SLOWLY DRIFTING WESTWARD AWAY FROM
POHNPEI THIS MORNING. A SURFACE TROUGH ASSOCIATED WITH IT IS ALSO
LIFTING NORTHWESTWARD AND WILL PASS NORTHEAST OF THE ISLAND TODAY.
THIS COULD TRIGGER A THUNDERSTORM OR TWO OVER THE NORTHERN WATERS.
BY THIS EVENING...SURFACE RIDGING ALREADY OVER KOSRAE AND MAJURO
WILL GRADUALLY SHIFT WESTWARD AND SUSTAIN PLEASANT WEATHER FOR
POHNPEI...KOSRAE THRU THIS WEEKEND AND MAJURO UNTIL SUNDAY. BOTH IR
AND ASCAT SATELLITE IMAGERY REVEAL A DISTINCT TRADE-WIND CONVERGENT
BOUNDARY STRETCHING NORTHEASTWARD FROM EQ175E TO WELL BEYOND THE
DATE LINE AT 155W. THIS FEATURE IS GOING TO SLIDE WESTWARD OVER THE
NEXT FEW DAYS WHICH COULD BRING WET WEATHER FROM EAST TO WEST ACROSS
THE REGION BY EARLY NEXT WEEK.

LONG PERIOD SOUTHEAST SWELL PRODUCED BY PERSISTENT MODERATE TO FRESH
WINDS NEAR FIJI AND SAMOA IN THE SOUTHERN HEMISPHERE WILL CONTINUE
TO IMPACT KOSRAE AND POHNPEI STATES UNTIL EARLY NEXT WEEK...AND
COULD SPREAD TO THE MARSHALL ISLANDS DURING THIS WEEKEND. HIGHER
SURF AND RIP CURRENT RISKS ARE ANTICIPATED ALONG SOUTH AND SOUTHEAST
FACING SHORES BUT HAZARDOUS SURF IS NOT EXPECTED.

&&

.WESTERN MICRONESIA...
THE BROAD CIRCULATION MENTIONED ABOVE IS APPROACHING WENO ISLAND IN
CHUUK STATE TODAY AND WILL MOVE THRU THE AREA TONIGHT AND SATURDAY.
IN CONJUNCTION WITH TWO UPPER-LEVEL TROUGHS PROGRESSING WESTWARD
FROM EASTERN MICRONESIA...WIDELY SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS ARE ANTICIPATED UNTIL SATURDAY EVENING. AFTERWARD...
SURFACE RIDGING FROM THE EAST SHOULD STABILIZE THINGS BY SUNDAY.

THE UPPER-LEVEL LOW AND RELATED TROUGH ARE MIGRATING WESTWARD AWAY
FROM KOROR AND YAP THIS MORNING. THEREFORE LIGHT AND VARIABLE WINDS
ASSOCIATED WITH A NEUTRAL AREA BETWEEN THE CIRCULATION OVER MINDANAO
AND THE ONE NEAR CHUUK WILL PROMOTE A DRY REGIME ACROSS BOTH
LOCATIONS FOR THE NEXT FEW DAYS. MODELS ARE TRANSFORMING THE
CIRCULATION NEAR CHUUK INTO A WEAK MONSOONAL SYSTEM OVER THE
PHILIPPINE SEA EARLY NEXT WEEK. UNDER THIS SCENARIO...SHOWERY
WEATHER IS POSSIBLE FOR THE AREA BY MONDAY.

&&

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

$$

STANKO/CHAN





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