Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Sun, 21 Nov 2010 02:46:51 -0600

210 
FXPQ60 PGUM 210846
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
646 PM CHST SUN NOV 21 2010

.SYNOPSIS...
FRONTAL BOUNDARY AND ASSOCIATED CONVECTION LIE OVER THE NORTHERN 
CNMI. WEAK LOW-LEVEL VORTICITY CENTER WAS EVIDENT IN AN ENHANCING 
FIELD OF CUMULUS WEST OF ROTA. A TRADE-WIND TROUGH WAS GENERATING 
CONVECTION NEAR POHNPEI. WINDS WERE JUST LIGHT ENOUGH AND PWAT JUST 
HIGH ENOUGH FOR THUNDERSTORMS TO FORM OVER AND JUST WEST OF APRA 
HARBOR EARLIER THIS AFTERNOON. THE THUNDERSTORMS HAVE SINCE 
DISSIPATED.

&&

.DISCUSSION...
INITIAL FORECAST CONCERN REVOLVES AROUND WHETHER OR NOT CONVECTION 
IN THE CNMI WILL PROPAGATE FAR ENOUGH SOUTH TO AFFECT THE FORECAST 
ZONES. SATELLITE IMAGERY AND NEAR-TERM MODEL GUIDANCE BOTH SUGGEST 
THE SUBTROPICAL RIDGE WILL REMAIN STRONG ENOUGH TO FEND OFF THE 
CONVECTION. 00Z SOUNDING REVEALS THE INFLUENCE OF THE RIDGING AND 
SHOWED A PWAT DOWN A BIT FROM THE PREVIOUS SOUNDING TO 1.61 INCHES 
AND A RELATIVELY LOW TRADE-WIND INVERSION CENTERED AROUND 800 MB. 
GFS TIME-HEIGHT CROSS SECTION CARRIES EVEN SHALLOWER MOISTURE ON 
MONDAY...SO WILL ESCHEW PM THUNDER IN THE VICINITY OF GUAM TOMORROW. 
NEXT POTENTIAL WEATHER MAKER IS THE AFOREMENTIONED TROUGH NEAR 
POHNPEI. MODE GUIDANCE SUGGESTS THE LIONS SHARE OF THE ASSOCIATED 
CONVECTION SHOULD PASS SOUTH OF GUAM AROUND WEDNESDAY NIGHT. WILL GO 
AHEAD AND BRING MOSTLY CLOUDY SKIES IN BEGINNING ON WEDNESDAY 
EVENING AND LEAVE MOSTLY CLOUDY WORDING IN THROUGH FRIDAY. 
OTHERWISE...LONG TERM FORECAST LOOKS RELATIVELY UNEVENTFUL.

&&

.MARINE...
MARINE SWELL GRIDS MERELY REQUIRED A FEW MINOR ADJUSTMENTS. IPAN 
BUOY COMES IN WITH A DOMINANT NE SWELL AND A LESSER TRADE-WIND SWELL 
FROM THE EAST. EXISTING SWELL GRIDS CARRY BOTH COMPONENTS THROUGH 
THE FORECAST PERIOD IN AGREEMENT WITH WAVE WATCH MODEL GUIDANCE. AS 
THESE SWELL COMPONENTS CONTINUE TO ARRIVE THEY SHOULD MAINTAIN 
MODERATE RIP CURRENT RISK LEVEL SURF ON NORTH AND EAST FACING REEFS 
THROUGH AT LEAST MID WEEK.

&&

.EASTERN MICRONESIA...
THE ONLY MAJOR WEATHER FEATURE OVER EASTERN MICRONESIA IS A 
TRADE-WIND DISTURBANCE MOVING THRU POHNPEI AND KOSRAE THIS EVENING. 
EXPECT SHOWERS AND EVEN A THUNDERSTORM OR TWO TO CONTINUE OVER BOTH 
LOCATIONS INTO MONDAY. CONVERGING TRADE WINDS EAST OF THE 
DISTURBANCE WILL ALSO CAUSE SIMILAR CONDITIONS FOR MAJURO THRU THIS 
EVENING. THIS AREA OF SHOWERS IS GOING TO SHIFT WESTWARD AND PROLONG 
SHOWER ACTIVITY OVER POHNPEI INTO TUESDAY BUT SHOULD PASS NORTH OF 
KOSRAE INSTEAD. AROUND MIDWEEK...ANOTHER TRADE DISTURBANCE CURRENTLY 
SOUTHWEST OF HAWAII NEAR 6N165W MIGHT ARRIVE AT MAJURO WITH MORE 
SHOWERS.

&&

.WESTERN MICRONESIA...
THE LEADING EDGE OF THE TRADE DISTURBANCE OVER POHNPEI IS 
APPROACHING CHUUK THIS EVENING AND WILL BRING A PERIOD OF WET 
WEATHER THRU MONDAY NIGHT. AFTERWARD...DRIER NORTHEASTERLY TRADES 
SHOULD INTRODUCE GRADUAL IMPROVEMENT AROUND MIDWEEK. FARTHER 
WEST...A SURFACE TROUGH IS STEADILY DRIFTING WESTWARD TOWARD YAP. 
HOWEVER THE BULK OF THE PRECIP IS CONCENTRATING ALONG 6N AND MIGHT 
PASS SOUTH OF YAP DURING MIDWEEK. SURFACE CONVERGENCE NEAR THE 
SOUTHEASTERN END OF A NEAR-EQUATORIAL TROUGH WILL CONTINUE TO BE 
ENHANCED BY UPPER-LEVEL DIVERGENCE...AND GENERATE CONVECTION OVER 
PALAU THROUGH MONDAY. THEN THE SURFACE TROUGH PASSING SOUTH OF YAP 
WILL AFFECT PALAU WITH MORE RAINY WEATHER THRU MIDWEEK. FINALLY... 
ISOLATED-SHOWERS REGIME SHOULD RETURN BY THURSDAY AS WEAKER TRADES 
FROM THE EAST INFILTRATE THE REGION.

&&

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

$$

MCELROY/CHAN

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
To unsubscribe from WX-TROPL send e-mail to [email-masked] with
"unsub wx-tropl" in the body of your message. For help with WX-TROPL
write to [email-masked]. For more information on tropical weather products, see the NHC Homepage at http://www.nhc.noaa.gov.