Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Fri, 24 Dec 2010 14:15:22 -0600

862 
FXPQ60 PGUM 242015
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
615 AM CHST SAT DEC 25 2010

.SYNOPSIS...
RADAR AND SATELLITE SHOW SOMEWHAT MOISTER AIR IS IN PLACE TODAY
VERSUS THE VERY DRY AIR OF YESTERDAY. TRADE-WIND INVERSION HAS
LIFTED TO AROUND 10K FEET...SUPPORTING ISOLATED SHOWERS. A SHEAR
LINE CONTINUES TO LINGER NEAR ANATAHAN...BUT IR SATELLITE IMAGERY
SHOWS IT BECOMING MORE DIFFUSE.

&&

.DISCUSSION...
NO SIGNIFICANT CHANGES TO FORECAST GRIDS OR REASONING. DID
REFRESH WIND AND DEW POINT GRIDS. MODEL GUIDANCE SUGGESTS DEEP
LAYER RIDGING WILL REMAIN IN CONTROL OF THE WEATHER. PARTLY
CLOUDY SKIES AND ISOLATED SHOWERS WILL PREVAIL THROUGH THE
FORECAST PERIOD. ANY SHEAR LINES ARE EXPECTED TO REMAIN TO THE
NORTH OF SAIPAN AS THE PRIMARY TRADE-WIND CONVERGENCE ZONE IS
CONFINED TO SOUTH OF 10N.

&&

.MARINE...
TRIMMED A FOOT FROM THE TRADE SWELL HEIGHT TODAY TO INITIALIZE
WITH THE IPAN BUOY. STILL EXPECT COMBINED SEAS TO APPROACH 8 FEET
BY SUNDAY AS NORTH SWELL ARRIVE. NORTH AND EAST SWELL WILL
MAINTAIN MODERATE RIP CURRENT RISK LEVEL SURF ON RESPECTIVE
EXPOSURES FOR AT LEAST THE NEXT SEVERAL DAYS.

&&

.EASTERN MICRONESIA...
SURFACE RIDGING HAS FINALLY SHIFTED EAST OF THE DATE LINE...
ALLOWING MODERATE TO FRESH TRADE WINDS TO FLOW INTO EASTERN
MICRONESIA THIS MORNING. BASED ON SATELLITE IMAGERY...THE LEADING
EDGE OF THE TRADES IS RIGHT ON TOP OF POHNPEI IN THE FORM OF A
SURFACE TROUGH. THIS FEATURE WILL CAUSE SOME PASSING SHOWERS FOR
THE ISLAND UNTIL THIS EVENING. FARTHER EAST...A TRADE DISTURBANCE
IS CROSSING THE DATE LINE BETWEEN 5N AND 13N. EXPECT THIS
DISTURBANCE TO BRING SOMEWHAT WETTER WEATHER FOR MAJURO BY
MIDNIGHT TONIGHT...KOSRAE ON SUNDAY AND EVENTUALLY OVER POHNPEI
EARLY NEXT WEEK. DID NOT COMMIT TO SCATTERED SHOWERS DURING THIS
TIME FRAME AS WATER VAPOR SATELLITE IMAGERY SHOWS STRONG WIND
SHEAR AND INCREASING SUBSIDENCE ALOFT OVER EASTERN MICRONESIA.
DECREASING QPF AMOUNTS IN SHORT TERM MODEL GUIDANCE ALSO SUPPORT
THIS FORECAST SCENARIO. TRADE-WIND CONVERGENCE IN THE WAKE OF THE
DISTURBANCE WILL LIKELY PROLONG THE INCREASED SHOWER COVERAGE FOR
THE ENTIRE REGION THRU MIDWEEK.

A NORTHEAST SWELL IS GENERATING SURF ON CHUUK AND POHNPEI JUST
BELOW ADVISORY HEIGHTS. HOWEVER...THE SWELL HAVE ALREADY BEGUN TO
GRADUALLY SUBSIDE. SATELLITE-DERIVED SEA HEIGHTS AND LOCAL SURF
REPORTS SUPPORT THIS ASSESSMENT. ON THE OTHER HAND...TRADE-WIND
ENERGY HEADED WESTWARD FROM THE MARSHALLS WILL EVENTUALLY REACH
CHUUK BY SUNDAY EVENING. THIS IS ALREADY EXPECTED TO CAUSE A HIGH
SURF EVENT ON KOSRAE BY THIS AFTERNOON...THEREFORE AN ADVISORY
HAS BEEN ISSUED.

&&

.WESTERN MICRONESIA...
ABUNDANT SUNSHINE IS ANTICIPATED FOR CHUUK TODAY AS LATEST
SOUNDINGS INDICATE VERY DRY AIR ABOVE 700 MB. ON SUNDAY THE
AFOREMENTIONED SURFACE TROUGH PRESENTLY NEAR POHNPEI WILL TRIGGER
A BRIEF PERIOD OF SHALLOW SHOWERS ON SUNDAY. DEEPER MOISTURE WILL
FINALLY BEGIN TO SPREAD IN FROM THE EAST TOWARD MIDWEEK...
INCREASING SHOWER CHANCES. MOIST SOUTHEASTERLY FLOW ALOFT WILL
ENHANCE SHOWERS CAUSED BY CONVERGING SURFACE WINDS ACROSS BOTH YAP
AND KOROR THROUGH SUNDAY. TOWARD MIDWEEK...THE ENVIRONMENT OVER
KOROR AND YAP WILL ONCE AGAIN BECOME FAVORABLE FOR SHOWER
FORMATION AS TRADE CONVERGENCE AND LOW-LEVEL MOISTURE INCREASE.

&&

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

$$

MCELROY/CHAN

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