280
FXPQ60 PGUM 130742
AFDPQ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
542 PM CHST TUE AUG 13 2013
.SYNOPSIS...
PGUA WRS-88D WAS REPAIRED LATE THIS AFTERNOON...BUT NOT IN TIME
FOR THIS FORECAST PACKAGE. LATE AFTERNOON SATELLITE IMAGERY SHOWS
ISOLATED SHOWERS NEAR THE ISLANDS AND POSSIBLE THUNDERSTORMS
FURTHER EAST. SATELLITE AND UPPER-AIR ANALYSIS SHOW THE MARIANAS
ARE BETWEEN AN UPPER-LEVEL TROUGH AND AN UPPER-LEVEL RIDGE UNDER
AN AREA OF UPPER-LEVEL DIVERGENCE. THESE FAVORABLE DYNAMICS WILL
CONTINUE TO PROVIDE ISOLATED THUNDERSTORMS THROUGH WEDNESDAY
NIGHT.
&&
.DISCUSSION...
UPPER-LEVEL DIVERGENCE WILL CONTINUE THROUGH WEDNESDAY NIGHT AS
NOTED ABOVE. THURSDAY AND THURSDAY NIGHT SHOULD SEE A BRIEF
CLEARING...THEN BACK INTO THE CLOUDS AS WE ARE NOW PRETTY MUCH
INTO WET SEASON. THE KBDI CONTINUES TO RETREAT AND IS NOW 314.
WINDS WILL REMAIN FAIRLY LIGHT...WHICH COULD LEAD TO ISLAND
THUNDER NEAR GUAM THURSDAY AFTERNOON. OTHERWISE...NO MAJOR WEATHER
MAKERS. SEEMS LIKE THE WEST SWELL FROM TYPHOON UTOR WAS
UNDERWHELMING. IT IS STILL IN THE FORECAST BUT ONLY 1 TO 2 FEET IN
SIZE. OVERALL...INHERITED GRIDS WERE QUITE GOOD AND CHANGES WERE
MINOR...MAINLY JUST THE UPGRADE TO THE CLOUDS FRIDAY ONWARD.
&&
.EASTERN MICRONESIA...
EASTERN MICRONESIA FORECAST CLOSELY FOLLOWS PERSISTENCE EXCEPT
FOR A FEW MINOR ADJUSTMENTS. A ZONE OF WEAK TRADE-WIND
CONVERGENCE IS DISCERNIBLE SOUTHEAST OF MAJURO. A SURFACE TROUGH
IS PASSING OVER POHNPEI. FOR MAJURO...ADJUSTED WINDS FROM EAST TO
NORTHEAST FOR THE FIRST TWO PERIODS. OTHERWISE...MODEST TRADE-
WIND SURGE WILL MAINTAIN A RELATIVELY DRY WEATHER PATTERN THROUGH
DAY 5 FOR BOTH MAJURO AND KOSRAE. FOR POHNPEI...SURFACE TROUGH
WILL MOVE WESTWARD TOWARD CHUUK DURING THE NEXT DAY OR
SO...TAKING THE ASSOCIATED SPOTTY DEEP CONVECTION WITH IT. STILL
EXPECT IMPROVING WEATHER DAYS 1 AND TWO AS SOUTHEAST WINDS ON THE
LEE SIDE OF THE TROUGH BACK TO EAST IN RESPONSE TO RIDGING FROM
THE EAST.
LATEST ALTIMETRY AGREES WELL WITH INITIAL WAVE WATCH HEIGHT
FIELDS. RELATIVELY BENIGN MARINE CONDITIONS ARE EXPECTED ACROSS
ALL OF MICRONESIA THROUGH DAY 5 WITH NO ADVISORIES EXPECTED.
&&
.WESTERN MICRONESIA...
FOR CHUUK...STILL EXPECT UNSETTLED WEATHER DURING THE NEXT DAY OR
SO AS THE SURFACE TROUGH PASSES THROUGH. REDUCED SHOWER COVERAGE
TO ISOLATED UNTIL AROUND MIDNIGHT...WHEN AN MCS ASSOCIATED WITH
THE TROUGH IS EXPECTED TO ARRIVE. DID BUMP WINDS UP A BIT FOR
CHUUK FIRST TWO PERIODS. 00Z SOUNDING AND GFS TIME-HEIGHT CROSS
SECTION SHOW HIGHER GRADIENT WINDS THAN EXPECTED. WEATHER FOR
DAYS 3 THROUGH 5 WILL BE DRIER AS A TRADE-WIND PATTERN ASSERTS
ITSELF.
FORECASTS FOR YAP AND KOROR INVOLVE A FEW MINOR ADJUSTMENTS.
ADDED SLIGHT CHANCE THUNDER FOR KOROR AND ISOLATED THUNDER FOR
YAP TONIGHT BASED ON UPPER-LEVEL DIVERGENCE SEEN OVERHEAD IN
WATER VAPOR IMAGERY AND 200 MB INITIAL DIVERGENCE FIELDS. MODELS
AGREE ON MORE SUBSIDENT PATTERN BEGINNING TOMORROW FOR BOTH
LOCATIONS. LIGHT WIND PATTERN SUGGESTS ISLAND THUNDER POSSIBILITY
FOR KOROR EACH DAY...BUT GFS TIME-HEIGHT CROSS SECTION AND LATEST
SOUNDING SHOW PERSISTENT SHEARING WINDS ABOVE 700 MB.
OTHERWISE...WIND FORECAST FOR BOTH LOCATIONS IS MADE WITH LOW
CONFIDENCE. A VERY WEAK MONSOON TROUGH HAS BEEN TRYING TO REFORM
NEAR KOROR AND YAP. WEAK TRANSIENT FEATURES ARE PROGGED BY ALL OF
THE MODELS FOR BOTH LOCATIONS TONIGHT THROUGH DAY 5...SO IN
GENERAL...LIGHT AND VARIABLE WIND WORDING IS WARRANTED. DID
NOWCAST WEST WINDS FOR KOROR FOR TONIGHT BASED ON THE LATEST
ASCAT ANALYSIS AND METARS. DID BRING IN SLIGHT CHANCE THUNDER FOR
YAP DAYS 4 AND 5 AS DEEPER MOISTURE SHOULD ARRIVE OVERHEAD THEN.
&&
.GUM WATCHES/WARNINGS/ADVISORIES...
GU...NONE.
MARIANAS WATERS...NONE.
&&
$$
STANKO/MCELROY/ZIOBRO