Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Mon, 13 Dec 2010 00:10:46 -0600

238 
FXPQ60 PGUM 130610
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
410 PM CHST MON DEC 13 2010

.SYNOPSIS...
SURFACE RIDGING AND UPPER-LEVEL CONVERGENCE PREDOMINATE. AN
INVERTED SURFACE TROUGH IS PASSING WELL TO THE SOUTH OF GUAM. THE
ATTENDANT CONVECTION IS CONFINED TO SOUTH OF 11N...BUT CONVERGENT
TRADE-WINDS EAST OF THE TROUGH ARE PRODUCING SOME ISOLATED
SHOWERS NORTH OF CHUUK AND POHNPEI BETWEEN 10N AND 14N FROM 150E
TO 160E.

&&

.DISCUSSION...
NO SIGNIFICANT CHANGES TO FORECAST REASONING. INHERITED FORECAST
ALREADY FACTORS IN THE VERY DRY SHORT TERM ENVIRONMENT. SOMEWHAT
MOISTER AIR SHOULD BE ARRIVING TOMORROW COURTESY OF THE ZONE OF
WEAK TRADE-WIND CONVERGENCE PRESENTLY NORTH OF CHUUK AND POHNPEI.
OTHERWISE...NO SIGNIFICANT WEATHER MAKERS ARE FORESEEN THROUGH
THE FORECAST PERIOD.

&&

.MARINE...
IPAN BUOY COMES IN WITH A MAXIMUM SIGNIFICANT SWELL HEIGHT OF
AROUND 5 FEET FROM 070 DEGREES. THIS INITIALIZES WELL WITH THE
GRIDDED TRADE-WIND SWELL. RECENT GUAM SURF OBS SUGGEST NORTH
SWELL HAVE ALREADY PEAKED BUT WILL RETAIN NORTH SWELL GRIDS
DECLINING TO 2 FEET BY TUESDAY MORNING. IN ANY CASE...SURF ON
NORTH AND EAST FACING REEFS SHOULD REMAIN AT MODERATE RIP CURRENT
RISK LEVELS FOR THE NEXT FEW DAYS.

&&

.EASTERN MICRONESIA...
PLEASANT WEATHER REMAINS IN PLACE ACROSS THE REGION. WEAK SURFACE
TROUGHS ARE LOCATED NEAR POHNPEI AND JUST EAST OF THE DATELINE.
UPPER-LEVEL WINDS HAVE PUSHED CLOUD TOPS SOUTHEASTWARD OVER
POHNPEI WHILE SHOWERS IN THE VICINITY OF POHNPEI SLOWLY PUSH
WESTWARD. GFS GUIDANCE HOLDS SHOWERS IN PLACE OVER POHNPEI ALMOST
INTO WEDNESDAY. ECMWF AND UKMET GUIDANCE WASH OUT THE WESTERNMOST
TROUGH WITH SHOWERS TAPERING BY TOMORROW MORNING. AT THIS
POINT...FORECAST WILL LEAN TOWARDS A DRIER MORE CLIMATOLOGICAL
OUTLOOK. THE TROUGH NEAR THE DATELINE LOOKS UNIMPRESSIVE IN
SATELLITE IMAGERY. MODEL GUIDANCE SHOWS LITTLE EVIDENCE FOR
ANYTHING MORE THAN ISOLATED SHOWERS THROUGH THE WEEK.

&&

.WESTERN MICRONESIA...
CONVECTION ASSOCIATED WITH A FAIRLY IMPRESSIVE SURFACE TROUGH
PRESENTLY LOCATED BETWEEN YAP AND CHUUK WILL BEGIN MOVING OVER
YAP AND KOROR TONIGHT. SATELLITE IMAGERY SHOWS DEEP CONVECTION
EAST OF YAP BUT MODEL ANALYSIS SHOWS UPPER-LEVEL DYNAMICS ARE
SPREADING TOWARDS BOTH KOROR AND YAP FROM THE EAST-SOUTHEAST.
HAVE ACCORDINGLY ADDED A SLIGHT CHANCE OF THUNDERSTORMS TO THE
FORECAST FOR TONIGHT. GFS NEAR TERM GUIDANCE AND SATELLITE TRENDS
STILL SUGGEST SCATTERED SHOWERS WILL BECOME ISOLATED OVER BOTH
LOCATIONS TUESDAY AFTERNOON. A WEAK SURFACE TROUGH LOCATED NEAR
POHNPEI WILL BRING MOSTLY CLOUDY CONDITIONS LATER TONIGHT.
DESPITE THE RATHER SMALL AREAL COVERAGE OF SHOWERS WITH THIS
SYSTEM AT PRESENT...MODELS KEEP CLOUDS THROUGH MUCH OF THE WEEK
AT CHUUK.

&&

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

$$

MCELROY/M. AYDLETT

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