Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Thu, 16 Sep 2010 16:37:53 -0500

828 
FXPQ60 PGUM 162137
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
737 AM CHST FRI SEP 17 2010

.SYNOPSIS...
PGUA WSR-88D SHOWS ISOLATED SHOWERS AND THUNDERSTORMS MOVING
THROUGH THE MARIANAS WATERS. THIS IS THE LEADING EDGE OF A LARGE
AREA OF SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS PRODUCED BY
THE COMBINATION OF AN UPPER-LEVEL TROUGH AND A TRADE-WIND
DISTURBANCE BETWEEN 8N AND 21N FROM 149E TO 170E.

&&

.DISCUSSION...
UPPER-LEVEL TROUGH IS STILL THE DOMINANT FORCE BEHIND OUR RATHER
LACKLUSTER WET SEASON. SCATTERED SHOWERS WILL ARRIVE BY SUNDAY AND
STAY THROUGH MONDAY. AFTER THIS THE WEATHER WILL GET A BIT DRIER
AGAIN. JUST TWEAKED THE FIRST PERIOD GRIDS TO GET MORE CLOUDS AND
EXTEND THUNDER THROUGH THE ENTIRE ZONE GROUP. IT WAS THEN NO
LONGER NECESSARY TO SPLIT THE ZONES.

&&

.MARINE...
IT WILL BE DIFFICULT FOR THE BUOY TO FALL FARTHER FROM ITS CURRENT
23 INCHES. EVEN THOUGH SWELL WILL RISE A BIT OVER THE NEXT FEW
DAYS MARINE CONDITIONS WILL REMAIN BENIGN. THERE IS A POSSIBILITY
OF A WEST-NORTHWEST SWELL FROM TYPHOON FANAPI SOUTH OF OKINAWA.

&&

.EASTERN MICRONESIA...
A WEAK SURFACE TROUGH MIGRATING SLOWLY WESTWARD ALONG GENTLE TRADE 
WIND FLOW WILL KEEP SOME SHOWERS OVER CHUUK THRU SATURDAY 
AFTERNOON...POHNPEI INTO THIS EVENING AND KOSRAE THRU THIS 
AFTERNOON. THEN DRIER TRADES ALREADY OVER MAJURO ARE EXPECTED TO 
PROMOTE FAIRER CONDITIONS WESTWARD OVER THE WEEKEND. LATEST ASCAT 
SATELLITE IMAGERY REVEALS A MODERATE TO FRESH TRADE-WIND SURGE 
APPROACHING THE DATE LINE BETWEEN 5N AND 15N. AN ITCZ HAS FORMED 
ALONG THE SOUTHERN EDGE OF THE SURGE...ORIENTING NORTHEASTWARD FROM 
5N180 TO WELL SOUTH OF THE HAWAIIAN ISLANDS. CONVECTION ASSOCIATED 
WITH THE LEADING EDGE OF THE ITCZ IS ALREADY FLARING UP NEAR 5N180. 
ANTICIPATE THIS CONVECTION TO SPREAD OVER MAJURO BY SATURDAY EVENING 
AND GRADUALLY EXTENDS WESTWARD DURING EARLY NEXT WEEK. 

&&

.WESTERN MICRONESIA...
A SURFACE RIDGE IS ANCHORED OVER WESTERN MICRONESIA WITH LIGHT AND 
VARIABLE WINDS. SIMULTANEOUSLY...BOTH WV SATELLITE IMAGERY AND 
LATEST YAP SOUNDING DATA INDICATE MUCH DRIER AIR AT MID TO UPPER 
LEVELS ADVECTING NORTHWESTWARD FROM THE EQUATOR. THE COMBINATION OF 
THESE TWO FEATURES WILL SUPPORT QUIET WEATHER FOR BOTH YAP AND PALAU 
THRU THE WEEKEND. WHEN TYPHOON FANAPI FINALLY PULLS FARTHER NORTH
OF 20N BY EARLY NEXT WEEK...THE SURFACE RIDGE WILL SHIFT NORTHWEST
OF THE REGION. THIS SHOULD ALLOW GENTLE TO MODERATE TRADE WINDS TO
FILTER BACK OVER WESTERN MICRONESIA. HOWEVER...TRADE-WIND
DISTURBANCES EMBEDDED WITHIN THE TRADE-WIND FLOW MIGHT INTRODUCE
MORE SHOWER ACTIVITY.

&&

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

$$

STANKO/CHAN

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