Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Mon, 14 Jan 2008 14:03:14 -0600

781 
FXPQ60 PGUM 142003
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
603 AM CHST TUE JAN 15 2008

.SYNOPSIS...
WSR-88D HAS BEEN DOWN FOR REPAIRS SO ONLY INTERMITTENT RADAR 
PRODUCTS WERE AVAILABLE FOR THE LATEST FORECAST UPDATE. LOOKS LIKE 
FUTURE SHIFTS WILL BE DEVOID OF RADAR DATA FOR ABOUT A WEEK UNTIL A 
NEW AZIMUTH ENCODER CAN BE PROCURED. FROM WHAT HAS COME IN...STILL 
LOOKS LIKE ISOLATED SHOWER COVERAGE IS OUT THERE. A VIGOROUS 
TRADE-WIND DISTURBANCE WAS BEGINNING TO PASS WELL TO THE SOUTH OF 
GUAM. QUITE A BIT OF CIRRUS OUTFLOW FROM THIS SYSTEM CAN BE SEEN 
ADVECTING NORTHWARD OVER THE MARIANAS IN IR SATELLITE IMAGERY. ALL 
OF THE DEEP CONVECTION IS CONFINED TO SOUTH OF 10N. LOOKING UPSTREAM 
OF THE MARIANAS...ONLY VERY MINOR TRADE-WIND DISTURBANCES ARE 
EVIDENT. 

&&

.DISCUSSION...
TRADE-WIND REGIME SOLIDLY ENTRENCHED. PARTLY CLOUDY SKIES AND 
ISOLATED SHOWERS WILL BE THE GENERAL RULE. ONLY WEATHER DECISION OF 
NOTE WAS WHETHER OR NOT TO GO WITH MOSTLY CLOUDY SKIES TODAY DUE TO 
THE EXTENSIVE CIRRUS CANOPY OVERHEAD IN IR SATELLITE IMAGERY. GFS 
TIME-HEIGHT CROSS SECTION SUGGESTS MID AND HIGH-LEVEL CLOUDS WILL BE 
PREVALENT. HOWEVER...STARS WERE VISIBLE THROUGH THE CIRRUS AT 
FORECAST TIME SO ELECTED TO LEAVE PARTLY CLOUDY WORDING UNTOUCHED 
FOR TODAY. RAN GUST GRIDS OUT THROUGH DAY 9 USING A GUST FACTOR OF 
35 PERCENT. BOTH ECMWF AND GFS MODEL RUNS BRING A SHEAR LINE THROUGH 
THE MARIANAS SUNDAY AND MONDAY. HAVE LEFT GRIDS UNEDITED DURING THIS 
TIME FRAME FOR NOW.

&&

.EASTERN MICRONESIA...
SCATTERED SHOWERS AND A FEW THUNDERSTORMS CONTINUE TO TRACK ACROSS 
POHNPEI AND KOSRAE THIS MORNING AS TRADE-WIND CONVERGENCE REMAINS IN 
THE AREA. LATEST MODEL RUN INDICATES THE CONVERGENCE ZONE WILL BE 
SHIFTED SOUTH AND WEST OF BOTH ISLANDS BY WEDNESDAY MORNING. FRESH 
TRADES WILL BRING IMPROVING CONDITIONS OVER POHNPEI INTO THE 
WEEKEND. HOWEVER FOR KOSRAE...CONVERGENCE ZONE IS EXPECTED TO MOVE 
BACK NORTH BY WEDNESDAY NIGHT WITH MORE SHOWERS. A WEAK TRADE-WIND 
DISTURBANCE WEST OF THE DATELINE IS SLOWLY MAKING ITS WAY INTO THE 
SOUTHERN MARSHALL ISLANDS. PERIODS OF SCATTERED SHOWERS WILL LAST 
THROUGH WEDNESDAY AND THEN DECREASE IN COVERAGE TOWARD THE WEEKEND.

COMPUTER GUIDANCE SUGGESTS SURF HEIGHTS ON CHUUK...POHNPEI AND 
KOSRAE ARE BACK AT ADVISORY LEVEL. SURF WILL BEGIN TO SUBSIDE ON 
THURSDAY FOR CHUUK AND POHNPEI...DURING THE WEEKEND FOR KOSRAE. ON 
MAJURO SURF WILL REMAIN AT ADVISORY LEVEL UNTIL SATURDAY.

&&

.WESTERN MICRONESIA...
AN INTENSIFYING SURFACE TROUGH IS TEAMED UP WITH UPPER-LEVEL
DIVERGENCE OVER CHUUK...PRODUCING HEAVY SHOWERS AND ISOLATED
THUNDERS. CONDITIONS WILL BEGIN TO IMPROVE EARLY WEDNESDAY AS THIS
SYSTEM PULLS FURTHER WEST. DRY TRADES FROM THE NORTHEAST WILL
STABILIZE THINGS BY THURSDAY. PALAU AND YAP WILL BEGIN TO FEEL THE
IMPACT OF THE SAME TROUGH EARLY WEDNESDAY MORNING AND LAST INTO
THURSDAY. THIS SYSTEM IS SHOWING SIGNS OF FURTHER DEVELOPMENT AND
NEEDS TO BE MONITORED CLOSELY.

&&

.MARINE...
PRIMARY FORECAST CONCERN CENTERS ON POTENTIAL FOR SMALL CRAFT 
ADVISORY FOR COMBINED SEAS. LOOKS LIKE A GOOD CHANCE BEGINNING LATER 
TONIGHT THROUGH WEDNESDAY NIGHT. WILL ADD TO CWF SYNOPSIS 
PARAGRAPH...BUT SINCE THE SCA IS EVENT-DRIVEN...WILL LEAVE TO DAY 
SHIFT TO ADD TO HAZARD GRIDS. MARINE SWELL GRIDS LOOKED GOOD WITH 
SOME MINOR ADJUSTMENTS MADE. TRADE-WIND WAVES AND SWELL WILL COMBINE 
WITH NORTH SWELL TO PRODUCE MODERATE RISK ON NORTH AND EAST-FACING 
REEFS DURING THE NEXT SEVERAL DAYS. BELIEVE SURF ON NORTH-FACING 
EXPOSURES WILL APPROACH THE ADVISORY THRESHOLD ON SAIPAN WED 
NITE...BUT WILL REFRAIN FROM AN ADVISORY FOR NOW AS SAIPAN WAVE 
WATCH TABULAR DATA ARE ACTUALLY FOR 16N147.5E...ABOUT 135 MILES 
NORTHEAST OF SAIPAN.

&&

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

$$

MCELROY/CHAN

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