Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Mon, 27 Sep 2010 16:50:36 -0500

353 
FXPQ60 PGUM 272149
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
749 AM CHST TUE SEP 28 2010

.SYNOPSIS...
PGUA WSR-88D SHOWS ISOLATED SHOWERS MOVING THROUGH THE MARIANAS
WATERS WITH SCATTERED SHOWERS JUST SOUTH OF GUAM. AN UPPER-LEVEL
TROUGH IS COUPLING WITH TRADE-WIND CONVERGENCE TO PRODUCE
SCATTERED SHOWERS NEAR YAP AND JUST EAST OF MAJURO ALSO.

&&

.DISCUSSION...
SHOWERS ASSOCIATED WITH UPPER-LEVEL LOW ARE JUST SOUTH OF GUAM
RIGHT NOW. SATELLITE LOOKS LESS FAVORABLE FOR SCATTERED SHOWERS
TONIGHT AND WEDNESDAY...BUT MOS STILL SEEMS TO LIKE THEM SO IT
COULD FILL IN. THIS WOULD BE THE MOST LIKELY CAUSE OF ANY MAJOR
SHIFTS IN FORECAST PHILOSOPHY AS THE DAY GOES ON.

&&

.MARINE...
LARGE SWELLS FROM FORMER TYPHOON MALAKAS SHOULD START DECREASING
THIS AFTERNOON. THIS WILL ALLOW SEA HEIGHTS TO DECREASE FROM 7
FEET TO 3 TO 4 FEET BY THE END OF THE WEEK. THE SURF SHOULD DROP
BELOW HAZARDOUS LEVELS THIS AFTERNOON.

&&

.EASTERN MICRONESIA...
A GENTLE TRADE-WIND REGIME ALONG WITH A DRIER AIR MASS AT MID LEVELS 
WILL PROMOTE FAIR CONDITIONS FOR POHNPEI INTO WEDNESDAY NIGHT...AND 
KOSRAE THRU THIS EVENING. LATEST ASCAT SATELLITE IMAGERY SHOWS A 
NEAR-EQUATORIAL TROUGH EXTENDING SOUTHEASTWARD FROM NORTH OF MAJURO 
TO 7N177E...THEN TURNS NORTHEASTWARD THRU THE DATE LINE AND FORMER 
CPHC INVEST AREA 97C TO BEYOND 170W AT 10N. THE LEADING EDGE OF THE 
TROUGH IS EXPECTED TO INTRODUCE CLOUDINESS OVER MAJURO TODAY AND 
PERIODS OF SCATTERED SHOWERS BY THIS EVENING. AS IT SLOWLY EXTENDS 
WESTWARD...IT MIGHT ALSO AFFECT KOSRAE BY WEDNESDAY AND POHNPEI ON 
THURSDAY. A MODERATE TO FRESH SOUTHEAST TRADE SURGE IS PRESENT OVER 
THE SOUTHERN HEMISPHERE EAST OF THE DATE LINE. WITH STRONGER TRADES 
EXPECTED TO STAY NORTH OF 10N OVER THE NORTHERN HEMISPHERE...THE 
SOUTHEAST SURGE WILL CROSS THE EQUATOR AND KEEP THE EASTERN HALF OF 
OF THE NEAR-EQUATORIAL TROUGH ALONG WITH 97C NEAR 9N BY MIDWEEK. 
THIS SCENARIO SHOULD CAUSE THE BULK OF THE SHOWER ACTIVITY 
ASSOCIATED WITH THE TROUGH TO STAY NORTH OF MAJURO...AND ALSO ALLOW 
DRIER SOUTHEASTERLY FLOW TO RETURN OVER BOTH KOSRAE AND POHNPEI 
AFTER MIDWEEK.

&&

.WESTERN MICRONESIA...
THE WEAK CIRCULATION HAS DRIFTED FARTHER NORTHWEST OF CHUUK 
OVERNIGHT. HOWEVER...AN UPPER-LEVEL TROUGH IN THE VICINITY MIGHT 
STILL SPARK A THUNDER OR TWO TODAY. THEN WEAKER TRADES ALONG WITH 
DRIER MID-LEVEL AIR FROM THE SOUTHEAST ARE GOING TO SPREAD FAIR 
WEATHER OVER THE ISLAND BY THIS EVENING. TOWARD THE WEEKEND...THE 
REMNANTS OF THE AFOREMENTIONED NEAR-EQUATORIAL TROUGH COULD INCREASE
THE CHANCE FOR SHOWERS.

A PRONOUNCED SURFACE TROUGH IS EVIDENT BETWEEN KOROR AND YAP THIS 
MORNING. SURFACE CONVERGENCE ALONG THE EASTERN SIDE OF THE TROUGH IS 
COUPLING WITH DIVERGENT FLOW ALOFT TO TRIGGER SCATTERED CONVECTION 
OVER YAP AND WILL REMAIN SO THRU TONIGHT. AS THE TROUGH SLOWLY 
MIGRATES WESTWARD LATE TONIGHT...THIS CONVECTION WILL ALSO IMPACT 
KOROR AS WELL. MOST MODELS ARE MERGING THE WEAK CIRCULATION NEAR 
CHUUK INTO THE TROUGH NORTH OF KOROR AND YAP...THEN TAKING THEM INTO 
THE PHILIPPINE SEA ON THURSDAY. SURFACE RIDGING TO THE SOUTHEAST OF 
THE TROUGH SHOULD FINALLY PROVIDE QUIETER WEATHER FOR BOTH LOCATIONS 
TOWARD THE WEEKEND. HIGHER SURF ALONG NORTH FACING SHORES WILL PEAK 
AROUND 7 FEET THRU THIS EVENING...THEN BEGINS TO SUBSIDE ON 
WEDNESDAY.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...HIGH SURF ADVISORY UNTIL 11 AM CHST THIS MORNING FOR GUZ001>004.

MARIANAS WATERS...NONE.
&&

$$

STANKO/CHAN

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