Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Wed, 29 Sep 2010 03:03:48 -0500

144 
FXPQ60 PGUM 290803 AAA
AFDPQ 

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE TIYAN GU
600 PM CHST WED SEP 29 2010

.SYNOPSIS...
SHOWERS ARE PLENTIFUL ALL AROUND THE MARIANAS AS A TROUGH APPROACHES
FROM THE EAST...BUT THE MARIANAS WATERS HAVE BEEN IN A RELATIVE
DRY SLOT MOST OF THE AFTERNOON. LOW-LEVEL VORTICITY ASSOCIATED WITH
THE TROUGH IS EVIDENT ON RADAR EAST AND SOUTHEAST OF GUAM...AND
THE LEADING EDGE OF THE MASS OF SHOWERS TO THE EAST IS MAKING SLOW
BUT STEADY PROGRESS TO THE WEST AND NORTHWEST.

&&

.DISCUSSION...
LATEST GFS/UKMET AND RADAR/SATELLITE TRENDS AGREE ON THE TROUGH
MOVING WEST OVERNIGHT AND THURSDAY...ACCOMPANIED BY SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS. SHOWERS SHOULD TAPER OFF LATE
IN THE DAY THURSDAY...BUT LINGERING MOISTURE SHOULD KEEP ISOLATED
SHOWERS/THUNDER GOING THURSDAY NIGHT. ONCE THE TRADE DISTURBANCE
MOVES OFF WESTWARD...GFS INDICATES SIGNIFICANT DRYING IN THE MID
AND UPPER LEVELS FOR FRIDAY AND THE WEEKEND AS WEAK SURFACE
RIDGING DEVELOPS OVER THE REGION. A DEEP LAYER OF LIGHT AND
VARIABLE WINDS WOULD NORMALLY SUGGEST A CHANCE OF ISLAND SHOWERS
SAT/SUN...BUT LACK OF MOISTURE WILL LIKELY KILL THAT POSSIBILITY.

&&

.MARINE...
NORTH SWELL IS DEFINITELY ON THE WAY OUT...AND SHOULD SEE STEADILY
DECLINING SEAS AND SURF THROUGH SATURDAY.

&&

.EASTERN MICRONESIA...
FAIR WEATHER IS EXPECTED TO CONTINUE OVER POHNPEI THRU TONIGHT AS 
DRY GENTLE TRADE WINDS DOMINATE THE AREA. SATELLITE IMAGERY 
INDICATES THE LOW-LEVEL TROUGH OVER THE MARSHALL ISLANDS IS SOUTH OF 
MAJURO. ITS LEADING EDGE HAS MOVED WEST OF KOSRAE BUT HAS THINNED 
OUT ON SATELLITE. WEAKER CONVERGENCE SOUTHEAST OF THE TROUGH AXIS 
WILL MAINLY CREATE SOME CLOUDS AND A FEW SHOWERS FOR MAJURO INTO 
THURSDAY. AS THE TROUGH KEEPS SLIDING WESTWARD...IT WILL ALSO 
INCREASE THE CHANCE FOR SOME SHOWERS TO POHNPEI ON THURSDAY AND 
CHUUK BY FRIDAY NIGHT. AFTERWARD...WEAKER TRADES BEHIND THE TROUGH 
ARE GOING TO PROMOTE ANOTHER ROUND OF DRY CONDITIONS FOR MAJURO AND 
KOSRAE TOWARD THE WEEKEND...AND FOR POHNPEI AND CHUUK OVER THE 
WEEKEND. HOWEVER... INCREASING TRADE CONVERGENCE FROM THE EAST MIGHT 
START A WETTING TREND FOR THE MARSHALLS EARLY NEXT WEEK.

&&

.WESTERN MICRONESIA...
THE WEAK SURFACE CIRCULATION...ITS ASSOCIATED TROUGH AND THE 
ASSOCIATED CONVECTION IS NORTHWEST OF KOROR THIS EVENING. WEAK 
CONVERGING WINDS SOUTH OF THIS FEATURE CAN TAKE ADVANTAGE OF 
UPPER-LEVEL DIVERGENCE TO SPARK ISOLATED THUNDERSTORMS THRU THIS 
EVENING. THE NEXT POTENTIAL WEATHER MAKER FOR WESTERN MICRONESIA 
WILL BE ANOTHER SURFACE TROUGH PASSING SOUTH OF...AND OVER GUAM THIS 
EVENING. AS IT CLOSES INTO YAP ON THURSDAY...CONVECTIVE ACTIVITY MAY 
FIRE UP AT YAP. THE BULK OF THE ACTION MIGHT STAY JUST NORTH OF 
KOROR. IN THE WAKE OF THE PASSAGE OF THIS SECOND TROUGH...FAIR 
WEATHER CURRENTLY OVER EASTERN MICRONESIA SHOULD FINALLY ARRIVE OVER 
THE WEEKEND.  FAIR WEATHER IS EXPECTED TO CONTINUE OVER CHUUK INTO 
FRIDAY AS DRY GENTLE TRADE WINDS DOMINATE THE AREA. THE TROUGH 
RUNNING FROM EASTERN MICRONESIA WILL INCREASE THE CHANCE FOR SHOWERS 
AT CHUUK LATE FRIDAY AND FRIDAY NIGHT. THE WEAKER TRADES BEHIND THE 
TROUGH SHOULD PROMOTE FAIR TO MOSTLY CLOUDY WEATHER FOR CHUUK ON 
SATURDAY. SURF OF AROUND 6 FT ALONG NORTH FACING SHORES WILL 
GRADUALLY SUBSIDE TO BETWEEN 4 AND 5 FEET BY FRIDAY. 

&&

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

$$

MIDDLEBROOKE/DEVITA

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