Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Sun, 26 Sep 2010 16:23:06 -0500

936 
FXPQ60 PGUM 262122
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
722 AM CHST MON SEP 27 2010

.SYNOPSIS...
PGUA WSR-88D SHOWS SCATTERED SHOWERS SOUTH AND WEST OF THE
MARIANAS WATERS...WITH ISOLATED SHOWERS MOVING IN. AN UPPER-LEVEL
TROUGH WILL ADD A FEW THUNDERSTORMS TO THE MIX. TRADE-WIND
CONVERGENCE AND SURFACE TROUGHS ARE CREATING SCATTERED SHOWERS
NEAR PALAU...CHUUK AND KWAJALEIN.

&&

.DISCUSSION...
LITTLE IN THE WAY OF SIGNIFICANT WEATHER MAKERS EXPECTED. SMALL
WRINKLES IN THE TRADE-WIND FLOW WILL DOUBTLESS CREATE MORE SHORT-
LIVED BOUTS OF SCATTERED SHOWERS. THESE ARE DIFFICULT FOR THE
MODELS TO RESOLVE DUE TO HORIZONTAL RESOLUTION CONSTRAINTS. ALSO
THE MODELS DO NOT DO ALL THAT WELL WITH UPPER-LEVEL TROUGHS
EITHER. INHERITED FORECAST SEEMED TO BE IN EXCELLENT SHAPE SO DID
NOT MAKE ANY SIGNIFICANT CHANGES.

&&

.MARINE...
EAST TRADE-WIND SWELL AND NORTH SWELL FROM FORMER TYPHOON MALAKAS
ARE COMBINING TO MAKE THE SEAS A LITTLE ROUGHER THAN USUAL. SURF
MAY APPROACH HIGH SURF ADVISORY CRITERIA BUT THE WAVE HEIGHTS
SHOULD STAY WELL BELOW SMALL CRAFT THRESHOLDS.

&&

.EASTERN MICRONESIA...
AN ITCZ IS STRETCHING EASTWARD FROM A WEAK CIRCULATION NORTHWEST OF 
POHNPEI TO THE MARSHALL ISLANDS. AS IMPULSES TRACKING WESTWARD ALONG 
THE ITCZ CONVERGE TOWARD THE CIRCULATION...CONVERGING WINDS WILL 
CONTINUE TO TRIGGER PERIODS OF SHOWERS AND A FEW THUNDERSTORMS FOR 
POHNPEI AT LEAST THRU THIS EVENING. AS THE CIRCULATION BEGINS TO 
DRIFT W-NW ON TUESDAY...THE CONVERGENCE ZONE SHOULD LIFT FARTHER 
NORTH OF THE ISLAND AND ALLOW GRADUAL IMPROVEMENT BY MIDWEEK. MUCH 
WEAKER SOUTHEASTERLIES SOUTH OF THE ITCZ WILL KEEP RELATIVELY FAIR 
WEATHER OVER KOSRAE THRU TUESDAY NIGHT. EXPECT SHOWER COVERAGE TO 
DECREASE THIS AFTERNOON AS THE EASTERN END OF THE ITCZ MOVES FARTHER 
WEST OF MAJURO. LATEST IR AND ASCAT SATELLITE IMAGERY REVEALS A 
TROPICAL DISTURBANCE...CPHC INVEST AREA 97C EAST OF THE DATE LINE 
NEAR 8N173W AND SLOWLY MIGRATING W-SW. BASED ON ITS CURRENT 
MOTION...IT WILL BEGIN TO IMPACT MAJURO BY TUESDAY EVENING AND 
POSSIBLE KOSRAE ON WEDNESDAY. 

&&

.WESTERN MICRONESIA...
THE WEAK CIRCULATION JUST NORTHEAST OF CHUUK REMAINED ALMOST
STATIONARY OVERNIGHT. SHOWERS AND ISOLATED THUNDERSTORMS ARE
OCCURRING NEAR ITS CENTER AND ALONG A LINE OF CONVERGING WINDS
EXTENDING SOUTHWESTWARD FROM THE CENTER TO SOUTHWEST OF CHUUK. THE
CHANCE FOR THIS ACTIVITY TO SPREAD OVER CHUUK WILL STEADILY
INCREASE THRU TODAY. MODERATE TRADE WINDS FROM NORTH OF 10N ARE
ANTICIPATED TO SLOWLY STEER THE CIRCULATION W-NW AND CAUSE IT TO
PASS JUST NORTH OF CHUUK ON TUESDAY WITH THE LINE OF CONVECTION
DRAPING OVER THE ISLAND. CONDITIONS COULD THEN BECOME DRIER AFTER
MIDWEEK AS LIGHTER SOUTHEAST TRADES TAKE CONTROL OF THE AREA.

ANOTHER WEAK CIRCULATION IS ALSO PRESENT NORTHEAST OF KOROR THIS 
MORNING. MEANWHILE...A MID TO UPPER HIGH NEAR THE MARIANAS IS 
PROVIDING DIVERGENT WINDS ALOFT OVER THE REGION. SURFACE CONVERGENCE 
ALONG A TROUGH EXTENDING SOUTHWARD FROM THE CIRCULATION IS COUPLING 
WITH THE DIVERGENT WINDS TO CREATE SCATTERED CONVECTION OVER KOROR 
THIS MORNING AND WILL LAST INTO THIS EVENING. WITH THE CIRCULATION 
ALREADY NORTHWEST OF YAP...FAIRER WEATHER IS EXPECTED TODAY. THEN A 
WEAK SURFACE TROUGH CURRENTLY SOUTH OF GUAM MIGHT INTRODUCE ANOTHER 
ROUND OF INSTABILITY FOR BOTH LOCATIONS TONIGHT AND TUESDAY. FORECAST 
AFTER MIDWEEK DEPENDS ON THE FUTURE TRACK OF THE AFOREMENTIONED 
CIRCULATION CURRENTLY NEAR CHUUK. A W-NW TRACK WILL TAKE IT OVER THE 
PHILIPPINE SEA AND MIGHT FORM A SURFACE RIDGE WITH LIGHT AND 
VARIABLE WINDS OVER WESTERN MICRONESIA. SWELLS FROM FORMER TYPHOON 
MALAKAS WILL CAUSE HIGHER SURF ALONG NORTH FACING SHORES BY THIS 
EVENING BUT NO ADVISORY IS EXPECTED.

&&

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

$$

STANKO/CHAN

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