Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Mon, 15 Nov 2010 12:31:29 -0600

766 
FXPQ60 PGUM 151831
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
431 AM CHST TUE NOV 16 2010

.SYNOPSIS...
LATEST IR SATELLITE IMAGERY HAS A RATHER DIFFUSE SHEAR LINE NEAR
GUAM AND EASTWARD ALONG THE 12TH PARALLEL TO BEYOND 160E. RADAR
IMAGERY REMAINS UNAVAILABLE. AN INFLOW ANTICYCLONE IS CENTERED
EAST OF THE MARIANAS NEAR 17N153E. A WEAKNESS IN THE UPPER-LEVEL
RIDGE IS PRESENT WEST OF THE MARIANAS NEAR 140E.

&&

.DISCUSSION...
NO SIGNIFICANT CHANGES TO FORECAST REASONING. SURFACE HIGH
PRESSURE IS CURRENTLY BUILDING TO THE NORTH OF THE MARIANAS...BUT
BELIEVE WINDS WILL SLACKEN A BIT AS THE WEEK PROGRESSES. GRIDS
ALREADY REFLECT THIS. GFS AND ECMWF GUIDANCE HAVE LOW PRESSURE
REPEATEDLY DEVELOPING EAST OF JAPAN DURING MID WEEK. THIS WILL
WEAKEN THE SUBTROPICAL RIDGE. THE SUBTROPICAL RIDGE SHOULD
RESTRENGTHEN NEXT WEEKEND. PRIMARY FORECAST CONCERN REVOLVES
AROUND THE EXACT POSITION AND CONFIGURATION OF THE SHEAR LINE
PRESENTLY NEAR GUAM. GFS BRINGS THE SHEAR LINE BACK TO THE NORTH
AND INCREASES ASSOCIATED QPF WITH TIME. WV SATELLITE IMAGERY
SUGGESTS THE MARIANAS WILL REMAIN BENEATH A SUBSIDENT UPPER-LEVEL
RIDGE FOR AT LEAST A LITTLE WHILE...BUT GFS AND ECMWF WORK IN
SOME UPPER-LEVEL DYNAMICS FROM THE WEST ON WEDNESDAY AND
THURSDAY. HAVE ALSO SEEN ISENTROPIC LIFT AUGMENT SHEAR LINE
ASSOCIATED QPF IN THE PAST. THIS WILL HAVE TO BE WATCHED. PRIME
TIME FOR SCATTERED SHOWERS WOULD BE WEDNESDAY NIGHT AND THURSDAY
MORNING. WILL HOLD OFF ON INCREASING POPS FOR NOW AS CONFIDENCE
REMAINS LOW ON THE EXACT TIMING AND POSITIONING OF SUCH AN EVENT.
BEYOND THU...GFS AND ECMWF LIFT THE SHEAR LINE BACK TO THE NORTH
OF SAIPAN.

&&

.MARINE...
MARINE SWELL GRIDS IN GOOD SHAPE. MODERATE RIP CURRENT RISK LEVEL
SURF IS STILL EXPECTED TO PREVAIL ON EAST FACING REEFS DURING THE
NEXT COUPLE OF DAYS. IPAN BUOY COMES IN WITH SIGNIFICANT SWELL
HEIGHTS BETWEEN 6.5 AND 7 FEET AND 85 DEGREE WATER TEMPERATURE.
WAVE WATCH TABULAR DATA STILL CALLS FOR GRADUALLY DECLINING SURF
ON EAST FACING REEFS FOR THE NEXT FEW DAYS. NORTH SWELL IS DUE IN
FRI NITE...BUT SHOULD ONLY BE ENOUGH TO GENERATE SURF TO MODERATE
RIP CURRENT RISK LEVELS ON RESPECTIVE EXPOSURES. ASCAT IMAGERY
REMAINS UNAVAILABLE DUE TO AN INTERNET OUTAGE.

&&

.EASTERN MICRONESIA...
CONVECTION HAS CONSOLIDATED WEST OF MAJURO...NEAR KOSRAE AND
SOUTH OF POHNPEI DURING THE PAST SEVERAL HOURS. ANIMATED
SATELLITE IMAGERY SUGGESTS THAT SHOWERS SHOULD BEGIN TO WRAP UP
NEAR KOSRAE AROUND MIDDAY TODAY WITH INCREASING CLOUDS OVER
POHNPEI AS CONVECTIVE ACTIVITY NUDGES SLIGHTLY NORTHWARD TONIGHT.
MODELS HINT AT INCREASED CLOUD COVER OVER ALL OF EASTERN
MICRONESIA TOWARD THE END OF THE WEEK BUT ONLY A MARGINAL
INCREASE IN SHOWER COVERAGE IS EXPECTED FOR NOW.

&&

.WESTERN MICRONESIA...
THE WEAK CIRCULATION CENTERED SOUTHEAST OF YAP AND KOROR
YESTERDAY IS NO LONGER DISCERNIBLE IN IR IMAGERY BUT LATEST
SURFACE ANALYSIS INDICATES A NEAR-EQUATORIAL TROUGH EXTENDING
FROM SOUTHEAST OF YAP AND KOROR TO THE PHILIPPINES. IN RESPONSE
TO THE PROXIMITY OF THE TROUGH...WIND SPEEDS HAVE DECREASED ON
KOROR OVERNIGHT AND WILL LIKELY REMAIN AS SUCH TODAY. MODELS PROG
THE TROUGH TO MOVE WESTWARD TODAY AND TONIGHT WITH SCATTERED
SHOWERS DEVELOPING OVER KOROR TONIGHT AS EAST WINDS INCREASE. BY
WEDNESDAY THE TROUGH WILL MOVE OUT OF THE AREA AND SHOWERS WILL
BECOME ISOLATED. THE TROUGH WILL BE FARTHER SOUTH OF YAP. THUS
ISOLATED SHOWERS ARE EXPECTED OVER YAP FOR THE NEXT SEVERAL DAYS.
A SLOW MOVING TROUGH NEAR CHUUK HAS KEPT SCATTERED SHOWERS AND A
FEW THUNDERSTORMS LOCKED IN PLACE OVER WATERS SOUTH OF WENO.
SATELLITE IMAGERY SHOWS LITTLE CHANGE IN THE PLACEMENT OF SHOWERS
DURING THE PAST SEVERAL HOURS. MODELS ALSO CONFINE THE SHOWERS
JUST TO THE SOUTH OF WENO. ACCORDINGLY...HAVE DECIDED TO SPLIT
THE CHUUK MARINE ZONE. FOR TODAY...WILL FORECAST ISOLATED SHOWERS
OVER THE NORTHERN HALF OF CHUUK WATERS AND SCATTERED SHOWERS OVER
THE SOUTHERN HALF. THE TROUGH SHOULD EXIT TO THE WEST LATER TODAY
AND PULL THE SCATTERED SHOWERS OUT OF THE AREA TEMPORARILY UNTIL
A BAND OF CONVECTION STRETCHING EASTWARD FROM SOUTH OF POHNPEI TO
KOSRAE PASSES OVER THE AREA WEDNESDAY NIGHT.

&&

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

$$

MCELROY/W. AYDLETT

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