Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Sat, 25 Sep 2010 03:29:18 -0500

118 
FXPQ60 PGUM 250829
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
629 PM CHST SAT SEP 25 2010

.SYNOPSIS...
RADAR AND SATELLITE SHOW SCATTERED SHOWERS MAINLY JUST SOUTH OF
GUAM...BUT WITH A FEW OF THE SHOWERS MOVING THROUGH THE GUAM/ROTA
WATERS. THE BIG FEATURE ON SATELLITE IS THE E-W BAND OF CLOUDS AND
SHOWERS EXTENDING FROM SW OF GUAM EASTWARD TO NORTH OF POHNPEI.
THIS IS A RESULT OF LOW-LEVEL CONVERGENCE BETWEEN 10-15 KT
EASTERLIES NORTH OF THE BAND AND LIGHT SOUTHEAST WINDS SOUTH OF
IT. 

&&

.DISCUSSION...
LATEST GFS IS BIG A DEPARTURE FROM PREVIOUS RUNS...BRINGING QUITE
A BIT MORE RAINFALL TO GUAM THAN PREVIOUS VERSIONS...MAINLY FROM
THE NORTHERN FRINGES OF THE CONVERGENCE ZONE DESCRIBED ABOVE. IF
GFS IS RIGHT...GUAM COULD SEE SCATTERED SHOWERS THE NEXT FEW DAYS
WHILE TINIAN AND SAIPAN GET ONLY ISOLATED. HOWEVER...NOGAPS AND
UKMET KEEP MOST OF THE SHOWERS SOUTH OF GUAM...CONSISTENT WITH
PREVIOUS RUNS. FOR NOW...NOT ENOUGH CONFIDENCE IN GFS TO GO WITH
SCATTERED...BUT WITH THE CONVERGENCE ZONE SO CLOSE TO THE 
SOUTH...HAVE OPTED FOR MOSTLY CLOUDY WITH ISOLATED SHOWERS AND
THUNDERSTORMS. WITH WEATHER VERY DEPENDENT ON THE EXACT PLACEMENT
OF THE CONVERGENCE ZONE...UNCERTAINTY IS RATHER HIGH FOR THIS
FORECAST. BUT IN ANY CASE...GUAM WILL PROBABLY SEE SOMEWHAT MORE
RAINFALL THAN ISLANDS TO THE NORTH THE NEXT FEW DAYS.

&&

.MARINE...
NORTH SWELL STILL EXPECTED TO ARRIVE IN FORCE LATE SUNDAY NIGHT OR
MONDAY...WHICH SHOULD KEEP THE RIP RISK MODERATE ON NORTH FACING
REEFS FOR A FEW DAYS. INCREASING TRADE SWELL WILL ALSO KEEP THE
RISK MODERATE ON EAST FACING REEFS.

&&

.EASTERN MICRONESIA...
AN ITCZ IS STRETCHING ACROSS THE REGION ALONG 9N FROM NORTH OF CHUUK 
EASTWARD TO THE MARSHALL ISLANDS. SURFACE TROUGHS MIGRATING ALONG 
THE CONVERGENCE ZONE ARE EXPECTED TO CAUSE PERIODS OF SHOWERS AND 
ISOLATED THUNDERSTORMS FOR MAJURO AND POHNPEI THRU THIS WEEKEND... 
AND EVENTUALLY OVER CHUUK BY EARLY NEXT WEEK. BEING FARTHER SOUTH OF 
THE CONVERGENCE ZONE...KOSRAE SHOULD ONLY RECEIVE A PERIOD OF WIDELY 
SCATTERED SHOWERS SUNDAY EVENING INTO MONDAY. TOWARD MIDWEEK... 
SLIGHTLY WEAKER TRADES CAN EASE CONVERGENCE-INDUCED SHOWER ACTIVITY 
FROM EAST TO WEST. 

&&

.WESTERN MICRONESIA...
WITH TYPHOON MALAKAS MOVED AS FAR NORTH AS EAST OF JAPAN...THE 
SURFACE RIDGE SOUTH OF IT IS WEAKENING OVER THE PHILIPPINE SEA THIS 
EVENING. THIS IS ALLOWING TRADE WINDS TO INFILTRATE WESTWARD INTO 
WESTERN MICRONESIA. CONVERGENCE IN THE VICINITY OF A SURFACE WAVE 
TRACKING WESTWARD SOUTH OF GUAM WILL COMBINE WITH DIVERGENT WINDS 
ALOFT TO FIRE UP ISOLATED CONVECTION OVER BOTH YAP AND PALAU FOR THE 
REST OF THE WEEKEND. AFTERWARD...AN UPPER-LEVEL TROUGH PASSING OVER 
IS GOING TO MAINTAIN THE CHANCE FOR MORE SHOWERS INTO MIDWEEK. A 
NORTH SWELL FROM TYPHOON MALAKAS HAS ALREADY REACHED THE MARIANAS 
AND WILL ALSO ARRIVE AT YAP AND PALAU BY MONDAY. IT IS ANTICIPATED 
TO CREATE HIGHER SURF ALONG NORTH FACING SHORES BUT SHOULD REMAIN 
BELOW ADVISORY LEVELS.

&&

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

$$

MIDDLEBROOKE/CHAN

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