Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Thu, 23 Sep 2010 16:15:03 -0500

758 
FXPQ60 PGUM 232114
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
714 AM CHST FRI SEP 24 2010

.SYNOPSIS...HIGH PRESSURE WILL BUILD ACROSS THE MARIANAS TODAY
KEEPING WINDS LIGHT. RADAR AND SATELLITE SHOWED A FEW SHOWERS
MOVING ACROSS THE REGION THIS MORNING.

&&

.DISCUSSION...
A SLIGHT CHANGE MADE TO FORECAST. RIDGE BUILDING OVER AREA TO THE
SOUTH OF MALAKAS WILL ALLOW WINDS OVER THE MARIANAS TO SLACK OFF
TODAY. THE HIGH LEVEL CLOUDINESS GENERATED BY MALAKAS...THAT HAD
BEEN STREAMING OVER THE AREA THE LAST FEW DAYS...HAS DECREASED AS
THE STORM MOVES NORTHWARD. THIS DECREASE IN CLOUD COVER SHOULD
ALLOW MORE SUNLIGHT AND INCREASED DAYTIME HEATING. WITH THE LIGHT
WINDS AND THIS DAYTIME HEATING ADDED A SLIGHT CHANCE OF
THUNDERSTORMS OVER GUAM AND ASSOCIATED COASTAL WATERS TODAY.
WINDS EXPECTED TO INCREASE JUST ENOUGH ON SATURDAY TO PRECLUDE
THE DEVELOPMENT OF AFTERNOON THUNDERSTORMS. WINDS WILL BE SOUTH-
SOUTHEAST TODAY BECOMING EAST BY SATURDAY MORNING. EAST TRADE-
WINDS AND ISOLATED SHOWERS ARE ALL THAT IS EXPECTED THROUGH MUCH
OF THE COMING WEEK.

&&

.MARINE...
EAST TRADE-WIND SWELL WILL PERSIST THROUGH THE FORECAST PERIOD.
WW3 HAD A NORTH-NORTHWEST SWELL THAT WAS GENERATED BY TYPHOON
MALAKAS ARRIVING TODAY. WW3 KEPT THIS SWELL AT TWO FEET THROUGH
THE WEEKEND. THIS EXPECTED SWELL WOULD PRODUCE A SURF OF UP TO 3
FEET ON NORTH AND WEST FACING REEFS TODAY. ONE EARLY MORNING SURF
OBSERVATION SHOWED SURF AT 5 TO 6 FEET ON THESE EXPOSURES. A HIGH
TIDE OF 2 FEET IS EXPECTED THIS MORNING AND THIS MAY BE BRIEFLY
PUSHING UP THE SURF. WILL WATCH THIS AND HOPE FOR MORE SURF OBS
TO CLARIFY THE SITUATION AS DAY SHIFT MAY HAVE TO BUMP UP SURF
HEIGHTS. IT IS POSSIBLE THAT THE WW3 MODELS DID NOT HAVE GOOD
WIND DATA AND HAVE UNDERESTIMATED THE SWELL PRODUCED BY MALAKAS.
AT ANY RATE MALAKAS IS EXPECTED TO BE A TYPHOON BEFORE
TRANSITIONING INTO A FAIRLY STRONG EXTRA-TROPICAL LOW. WINDS
AROUND THE EXTRA- TROPICAL MALAKAS WILL CONTINUE TO PUSH SWELLS
TOWARDS THE MARIANAS. ALL THIS ADDS UP TO SURF OF AT LEAST 6 TO 8
FEET ON NORTH FACING REEFS TUESDAY. SINCE THE MODELS HAVE BEEN
UNDER ESTIMATING THE SWELLS IT IS CONCEIVABLE THAT SURF MAY
BRIEFLY BECOME HAZARDOUS BY MIDWEEK.

&&

.EASTERN MICRONESIA...
CONVECTION ALONG THE ITCZ CONTINUES WILL AFFECT MAJURO THROUGH
THE MORNING HOURS. MODELS CONTINUE TO KEEP MOST OF THE SHOWER
ACTIVITY TO THE NORTH OF KOSRAE BUT MAJURO AND POHNPEI WILL MOST
LIKELY EXPERIENCE SHORT PERIODS OF SCATTERED SHOWERS THROUGH THE
WEEKEND. HOWEVER...ISOLATED SHOWERS ARE EXPECTED TO BE THE
PREVAILING CONDITIONS OVER THE NEXT FEW DAYS WITH NO MAJOR
FEATURE DEPICTED IN THE MODEL SOLUTIONS. NORTHEAST TRADE-WIND
GENERATED SWELL CONTINUES TO SUBSIDE ACROSS THE MARSHALL ISLANDS
WITH THE MAJURO BUOY SHOWING SLOWLY FALLING SEA HEIGHTS OVER THE
LAST 12 HOURS.

&&

.WESTERN MICRONESIA...
SURFACE RIDGE EXTENDING FROM YAP WEST TO THE SOUTHERN PHILIPPINE
ISLANDS IS PROVIDING MOSTLY CLEAR CONDITIONS OVER YAP...WITH A
FEW MORE SHOWERS TO THE SOUTH AROUND KOROR. GIVEN THE CONVECTIVE
PATTERN OBSERVED OVER THIS AREA DURING THE LAST FEW DAYS AND
CONSISTENT MODEL RUNS...EXPECT ONLY ISOLATED SHOWERS CONTINUE
THROUGH THE WEEKEND FOR BOTH YAP AND KOROR. CHUUK SHOULD SEE
SIMILAR CONDITIONS AS POHNPEI OVER THE NEXT FEW DAYS. DRIER
SOUTHEAST FLOW AND ONLY ISOLATED SHOWERS SHOULD PERSIST OVER
CHUUK THROUGH EARLY NEXT WEEK.

&&

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

$$

ZIOBRO/WILLIAMS

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