Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Tue, 30 Nov 2010 15:43:38 -0600

160 
FXPQ60 PGUM 302143
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
743 AM CHST WED DEC 1 2010

.SYNOPSIS...
AN UPPER-LEVEL LOW PASSING SOUTH OF GUAM IS EXPECTED TO STAY FAR
ENOUGH SOUTH THAT IT WILL HAVE NO EFFECT ON WEATHER OVER THE
MARIANAS WATERS. MODERATE TO FRESH TRADE WINDS AND ISOLATED
SHOWERS WILL PERSIST THROUGH THE FORECAST PERIOD.

&&

.DISCUSSION...
THUNDERSTORMS ASSOCIATED WITH THE UPPER-LEVEL LOW ARE MAINLY
STAYING SOUTH OF 12.7N. THESE FEATURES ARE MOVING ALMOST STRAIGHT
WEST SO SHOULD NOT GET ANY CLOSER TO GUAM WATERS. SATELLITE SHOWS
THE MARIANAS FROM GUAM TO SAIPAN SHOULD IN FACT BE IN AN AREA OF
SUBSIDENCE OUTSIDE THE AREA OF RISING MOTION ASSOCIATED WITH THE
UPPER-LEVEL LOW. THEREFORE THE INHERITED FORECAST OF PARTLY CLOUDY
WITH ISOLATED SHOWERS LOOKED GREAT AND NO CHANGES WERE NECESSARY.
BOTH GFS40 AND ECMWF-HIRES PROG A SHEAR LINE NEXT WEEK THAT STALLS
OUT NEAR AGRIHAN. THIS WOULD MAKE FOR A CONTINUATION OF THE
RELATIVELY DRY PATTERN WE HAVE BEEN EXPERIENCING IN THE MARIANAS.

&&

.EASTERN MICRONESIA...
ISOLATED DEEP CONVECTION CONTINUES TO SPROUT NEAR POHNPEI AND KOSRAE 
ALONG THE LEADING EDGE OF STRONGER TRADE WINDS. GFS AND ECMWF BOTH 
SUGGEST THAT SHOWERS WILL INCREASE TODAY...MAINLY NEAR POHNPEI AND 
JUST WEST OF KOSRAE...SO HAVE ADDED SCATTERED FOR POHNPEI. 
CONVECTION SHOULD BEGIN TO QUIET DOWN BY TONIGHT. CONVECTION HAS 
PULSED DOWN ALONG A WSW-ENE ORIENTED TROUGH NEAR MAJURO. SATELLITE 
IMAGERY SHOWS UPPER CLOUDS SHUFFLING EASTWARD WITH A NARROW LINE OF 
CONVECTION TRYING TO DEVELOP EAST OF MAJURO AND ACROSS THE DATE 
LINE. GFS40 AND ECMWF BOTH SHOW A BULLS-EYE OF CONVECTION OVER 
MAJURO TODAY WHILE GFS ENSEMBLE TAKES THE DRY PATH. BECAUSE
CONVECTION HAS STEADILY SHIFTED EASTWARD ALONG THE TROUGH THE PAST
24 TO 36 HOURS...AM LEANING ON THAT TREND TO CONTINUE. FORECAST
CONFIDENCE IS SOMEWHAT LOW FOR MAJURO...A FORECAST UPDATE WILL BE
NEEDED SHOULD CONVECTION QUICKLY FIRE UP ALONG THE TROUGH.

&&

.WESTERN MICRONESIA...
PREVIOUS FORECAST REASONING REMAINS SOUND SO LEFT IT PRETTY MUCH 
UNTOUCHED. CONVECTION HAS RELOCATED A LITTLE FARTHER TO THE NORTH 
AND EAST OF CHUUK THE PAST FEW HOURS BUT MODELS INDICATE INSTABILITY 
WILL PERSIST THROUGH TODAY...AIDED BY THE UPPER-LOW TO THE WEST...SO 
HAVE KEPT THE SLIGHT CHANCE OF THUNDERSTORMS. GENERALLY DRY 
CONDITIONS WILL CONTINUE FOR YAP AND PALAU FOR THE NEXT SEVERAL DAYS 
BUT MODELS DO INDICATE INCREASING LOW- AND MID-LEVEL MOISTURE BY 
FRIDAY AS THE TUTT MOVES WESTWARD.

&&

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

$$

STANKO/W. AYDLETT

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