Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Tue, 08 Jan 2008 03:00:10 -0600

425 
FXPQ60 PGUM 080900
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
700 PM CHST TUE JAN 8 2008

.SYNOPSIS...
88D AND VISIBLE SATELLITE IMAGERY EARLIER SHOWED SHEAR LINE 
CONVECTION TRAINING OVER GUAM AND ROTA EARLIER...BUT BEGINNING TO 
BOOMERANG NORTHWARD DURING THE AFTERNOON. A DIFFUSE TRADE-WIND 
DISTURBANCE APPEARS IN VISIBLE SATELLITE IMAGERY UPSTREAM OF THE 
MARIANAS...CENTERED AROUND 155E.

&&

.DISCUSSION...
ONE LAST-MINUTE CHANGES TO THE FORECAST SCENARIO. SHEAR LINE REMAINS 
DIFFICULT TO RESOLVE IN THE MODELS. A LATE GLANCE AT THE SATELLITE 
LOOP SHOWED THE SHEAR LINE CRACKING BACK TO THE NORTH...SO ADJUSTED 
THE FORECAST GRIDS ACCORDINGLY. NEXT MOVE WAS TO PLAY THE USUAL 
OVERNIGHT CONVECTIVE MAXIMUM AND CALLED FOR SCATTERED CONVECTION TO 
END EVERYWHERE SOON AFTER SUNRISE.

NEXT ITEM OF INTEREST IS THE TRADE-WIND DISTURBANCE TO THE EAST. GFS 
AND ECMWF BOTH SUGGEST THE DEEPEST MOISTURE ASSOCIATED WITH THE 
DISTURBANCE WILL PASS TO THE SOUTH OF GUAM...BUT ENOUGH MOISTURE 
WILL BE PRESENT TO SUPPORT MOSTLY CLOUDY SKIES WEDNESDAY AND 
WEDNESDAY NIGHT. GFS AND ECMWF BOTH BRING OTHER MINOR TRADE-WIND 
DISTURBANCES THROUGH ON SATURDAY AND MONDAY...BUT DISTURBANCES LOOK 
TOO WEAK AT PRESENT TO DEPART FROM PARTLY CLOUDY/ISOLATED WORDING 
FOR THURSDAY THROUGH TUESDAY. REFRESHED WINDS AND DEW POINTS THROUGH 
DAY 4 AND TOOK THE LIBERTY TO TRIM BACK WIND SPEEDS ON DAY 9 IN THE 
GRIDS TO ACCOUNT FOR SUSPECTED HIGH BIAS IN WIND SPEEDS TOWARD THE 
END OF THE MODEL RUN.

&&

.MARINE...
SEAS JUST ABOVE THE SCA THRESHOLD IN GUAM AND ROTA WATERS OVERNIGHT 
TONIGHT. OTHERWISE NO ADVISORIES FORESEEN. NORTH SWELL WILL DROP 
DURING THE NEXT FEW DAYS AND MAY DROP BELOW THE MODERATE RISK 
THRESHOLD BY THE END OF THE WORK WEEK.

&&

.EASTERN MICRONESIA...
LITTLE CHANGE... TRADE SURGE STILL PROGGED TO NOSE INTO THE REGION 
BY MID-WEEK. UPPED FORECAST TO SCATTERED POPS FOR POHNPEI AND KOSRAE 
STARTING THURSDAY...LEFT MAJURO UNTOUCHED. WW3 STILL FLIP-FLOPPING 
ON FORECAST COMBINED SEAS TOWARDS THE END OF THE PERIOD...18Z RUN 
PROGGED 13 FT SEAS FOR SUNDAY. LATEST RUN NOW ONLY SHOWS ABOUT 
10 FT. TOOK THE MIDDLE ROAD AND WENT WITH 10 TO 12 FT. IN ANY 
CASE...WITH FORECAST PERIOD OF 11 SECONDS THIS WILL BE AT LEAST AN 
ADVISORY EVENT. WE WILL CONTINUE TO MONITOR THE SITUATION.

&&

.WESTERN MICRONESIA...
THE GFS PROGS A WEAK CIRCULATION CURRENTLY MIGRATING NORTHWEST ALONG 
NEAR-EQUATORIAL TROUGH SOUTHEAST OF KOROR TO PASS JUST SOUTH OF YAP 
WITHIN THE NEXT 24 HOURS OR SO. ECMWF TAKES IT SLIGHTLY SOUTH OF 
THIS POSITION. IN EITHER CASE...STRONG CONVERGENCE INTO THE LOW WILL 
CAUSE SCATTERED SHOWER AND ISOLATED THUNDERSTORM ACTIVITY OVER YAP 
THROUGHOUT THE DAY TOMORROW AND SCATTERED SHOWER ACTIVITY FOR KOROR 
INTO THE WEEKEND. DO NOT THINK THE FULL BRUNT OF THE AFOREMENTIONED 
TRADE-WIND SURGE WILL MAKE IT TO CHUUK...SO HAVE KEPT GENERALLY 
PARTLY CLOUDY CONDITIONS AND ISOLATED POPS FOR MOST OF THE FORECAST 
PERIOD.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...NONE.
MARIANAS WATERS...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 PM
     CHST THIS AFTERNOON FOR PMZ153-154.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 AM CHST 
     WEDNESDAY FOR PMZ151-152.

&&

$$

MCELROY/LEE

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