Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Wed, 29 Dec 2010 14:49:36 -0600

146 
FXPQ60 PGUM 292049
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
649 AM CHST THU DEC 30 2010

.SYNOPSIS...A FEW SHOWERS COULD BE SEEN ON RADAR THIS MORNING OVER
THE LOCAL AREA. ISOLATED SHOWERS AND EAST TRADE-WINDS ARE EXPECTED
TODAY. 

&&

.DISCUSSION...
NORTHEAST WINDS OF THIS MORNING WILL GRADUALLY GIVE WAY TO
EASTERLIES BY NOON TIME. SOUTHEASTERLY WINDS PREVAIL TONIGHT
THROUGH SATURDAY THEN EAST SATURDAY NIGHT. WINDS WILL BE LIGHT
DURING THE DAY SATURDAY AS A NEUTRAL POINT PASSES CLOSE TO SAIPAN.

QUANDARY EXIST AS TO FINAL POSITION OF A SOUTHWARD MOVING SHEAR
LINE EXPECTED IN THE AREA THIS WEEKEND. A FEW DAYS AGO MODELS
PREDICTED THAT THE SHEAR LINE WOULD MAKE IT TO GUAM. LATER MODEL
OUTPUT KEPT THE SHEAR LINE NORTH OF SAIPAN. NOW GFS AND NGPS
BRING THE SHEAR LINE DOWN TO JUST NORTH OF SAIPAN. GFS-E AND
ECMWF PUSH IT DOWN TO GUAM SUNDAY NIGHT AT LEAST IN THE WIND
FIELD. GFS-E RAIN PATTERN KEEPS RAINFALL SAIPAN NORTHWARD. WILL
KEEP CURRENT FORECAST AND PROG SHEAR LINE TO REMAIN NORTH OF
SAIPAN. AT THIS TIME KEPT SHOWERS ISOLATED THROUGH FORECAST. GFS
AND NGPS HAS BEEN SHOWING FOR THE LAST FEW DAY WHAT APPEARS TO BE
A TROUGH PASSING SOUTH OF GUAM MONDAY AND TUESDAY. IT SEEMS THAT
THE BULK OF THE MOISTURE REMAINS SOUTH OF THE MARIANAS THEREFORE
WILL KEEP SHOWERS ISOLATED FOR THAT TIME PERIOD. DID INTRODUCE
MOSTLY CLOUDY SKIES MONDAY NIGHT AND TUESDAY.

&&

.MARINE...
EAST TRADE-WIND SWELL AND A NORTHWEST SWELL WILL PERSIST THROUGH
THE FORECAST. THE TRADE-WIND SWELL WILL BE A MINOR PLAYER IN THE
COMING FORECAST WITH THE NORTHWEST SWELL BECOMING THE HEAVY
HITTER. THE NORTHWEST SWELL WILL REMAIN AROUND FOUR FEET THROUGH
SATURDAY NIGHT. A STORM SYSTEM IS EXPECTED TO DEVELOP ACROSS THE
NORTHWEST PACIFIC OVER THE NEXT FEW DAYS. STRONG WINDS BEHIND AN
ASSOCIATED COLD FRONT WILL GENERATE SWELL ACROSS THE NORTHWEST
PACIFIC WHICH WILL ENTER THE LOCAL AREA LATE SATURDAY NIGHT AND
SUNDAY. BY MONDAY THIS SWELL IS PREDICTED TO REACH 9 TO 10 FEET.
IT WILL REMAIN THIS WAY FOR AT LEAST THE FIRST HALF OF NEXT WEEK.
THE SWELL PERIOD IS EXPECTED TO BE 13 TO 14 SECONDS. THIS SWELL
HEIGHT AND PERIOD WOULD GENERATE SURF OF UP TO 14 FEET ON WEST
AND NORTH FACING REEFS. THEREFORE HIGH SURF ADVISORIES WILL MOST
LIKELY BE NEEDED PART OF NEXT WEEK. WHILE IT IS EXPECTED THAT THE
SURF WILL PEAK AROUND 14 FEET FOR MOST OF THE TIME THERE COULD BE
PERIODS OF SLIGHTLY HIGHER SURF...ESPECIALLY AROUND TIMES OF HIGH
TIDE. TIDE TABLE FOR THIS TIME SHOW THAT THE LEVEL OF THE HIGH
TIDE WILL BE AROUND TWO FEET. THIS ADDED TO 14 FEET WILL EQUAL 16
FEET. SURF OF THIS HEIGHT WILL MOST LIKELY CAUSE BRIEF PERIODS
INUNDATION ON A FEW BEACHES ON NORTH AND WEST FACING SHORES.
THERE ARE STILL A FEW DAYS TO SORT THINGS OUT BUT THIS WILL BE
WATCHED FOR THIS POSSIBILITY. THE LARGE SWELL WILL ALSO HELP
RAISE SEAS TO SMALL CRAFT ADVISORY LEVEL AT THAT TIME.

&&

.EASTERN MICRONESIA...
SATELLITE IMAGERY SHOWS DEVELOPING MID-LEVEL CLOUD COVER ALONG WEAK 
CONVERGING TRADE WINDS OVER THE FORECAST LOCATIONS BUT SHOWERS 
CONTINUE TO BE SPARSE WITHIN THIS REGION. CONVECTION FORMING 
SOUTHEAST OF KOSRAE WILL PASS TO THE SOUTH OF THE AREA THROUGH THE 
DAY. OTHERWISE....GENERALLY DRY CONDITIONS WITH A SLIGHT INCREASE IN 
TRADE WINDS WILL CONTINUE OVER THE NEXT COUPLE OF DAYS. MODELS SHOW 
THE NEXT DISTURBANCE IS EXPECTED TO AFFECT POHNPEI OVER THE WEEKEND 
BUT FORECAST CONFIDENCE IS STILL FAIRLY LOW AS MODEL SOLUTIONS 
DIVERGE APPRECIABLY DURING THIS PERIOD.

SWELL GENERATED BY A STRONG LOW PROGGED TO DEVELOP EAST OF JAPAN IS 
EXPECTED TO ARRIVE AT POHNPEI EARLY MONDAY MORNING AND KOSRAE BY 
MONDAY NIGHT MAY ALLOW SURF TO RISE ABOVE ADVISORY LEVELS. ALTHOUGH 
A DOWNWARD TREND IN SWELL HAS BEEN NOTICED IN THE PAST FEW WAVE 
WATCH RUNS...THE NORTH SWELL WILL STILL BE SUFFICIENT TO CREATE HIGH 
SURF CONDITIONS AT POHNPEI AND KOSRAE EARLY NEXT WEEK.

&&

.WESTERN MICRONESIA...
DELAYED ONSET OF SCATTERED SHOWERS FOR THE AFTERNOON HOURS AT KOROR 
AND TONIGHT FOR YAP AS IR IMAGERY SHOWS LIMITED SHOWER ACTIVITY 
EARLY THIS MORNING. MODELS ARE IN FAIR AGREEMENT IN INITIALIZING 
WIDESPREAD CONVECTION OVER KOROR LATER TODAY AND THIS EVENING AS THE 
TROUGH AXIS MOVES CLOSER THE AREA. SIMILARLY DRY CONDITIONS OVER 
EASTERN MICRONESIA WILL ALSO CONTINUE AT CHUUK THROUGH FRIDAY NIGHT 
BEFORE SHOWER ACTIVITY INCREASES OVER THE WEEKEND. 

NORTH SWELL WILL ARRIVE SUNDAY FOR BOTH YAP AND KOROR WITH AN 
ADVISORY ISSUANCE LIKELY NEEDED BY SATURDAY AFTERNOON. SWELL SHOULD 
ARRIVE LATE SUNDAY NIGHT AT CHUUK...WITH AN ADVISORY LIKELY BY 
SUNDAY.

&&

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

$$

ZIOBRO/WILLIAMS

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