Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Sun, 19 Sep 2010 02:58:03 -0500

037 
FXPQ60 PGUM 190757
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
557 PM CHST SUN SEP 19 2010

.SYNOPSIS...
PGUA WSR-88D SHOWS ISOLATED SHOWERS IN THE MARIANAS WATERS... WITH
SCATTERED SHOWERS DEVELOPING JUST TO THE SOUTHEAST. THESE SHOWERS
ARE ASSOCIATED WITH A DEVELOPING TROPICAL DISTURBANCE ABOUT 400
MILES EAST OF GUAM. THE MAIN AREA OF SHOWERS WITH THIS DISTURBANCE
IS BETWEEN 10N AND 20N FROM 150E TO 160E. ELSEWHERE A TRADE- WIND
TROUGH IS CREATING SCATTERED SHOWERS JUST EAST AND NORTH OF YAP.
TRADE-WIND CONVERGENCE IS GENERATING SCATTERED SHOWERS WITHIN 100
MILES OF A LINE FROM 1.5N 137E TO 10N 157E.

&&

.DISCUSSION...
DEVELOPING TROPICAL DISTURBANCE EAST OF THE MARIANAS IS
DEFINITELY THE 800 POUND GORILLA IN THE FORECAST ROOM TONIGHT. IT
IS NOW THE SUBJECT OF A TROPICAL CYCLONE FORMATION ALERT FROM THE
JOINT TYPHOON WARNING CENTER. SINCE IT IS JUST BEGINNING TO PULL
ITSELF TOGETHER...WINDS WILL REMAIN FAIRLY LOW...WITH RAIN BEING
THE BIG STORY. THE NEXT FEW HOURS DO NOT LOOK SO BAD...SO WENT
WITH SCATTERED LOCALLY HEAVY SHOWERS AFTER MIDNIGHT AND MONDAY.
THE CONVECTION WITH THE DISTURBANCE IS WEAKENING AT THE MOMENT
BUT WILL ATTRIBUTE THAT TO CYCLING...A COMMON PHENOMENON WITH
NASCENT TROPICAL CYCLONES. EXPECT IT TO PICK UP AGAIN IN A FEW
HOURS. THIS ALSO AGREES WELL WITH THE GENERAL DIURNAL CYCLE SO
FOR ALL THOSE REASONS AFTER MIDNIGHT SEEMED TO BE THE BEST BET.
JUST COULD NOT FIND ANY WIND GRIDS THAT DEFINITELY SEEMED BETTER
THAN THE CURRENT GRIDS SO DID NOT CHANGE THE WINDS AT ALL. IN
FACT...LIGHT AND VARIABLE SEEMS GOOD BASED ON THE ASCAT OF 10
KNOTS OR LESS THROUGHOUT THE LATITUDES OF THE MARIANAS WATERS.
TWEAKED TEMPERATURES TONIGHT AND MONDAY DOWN BASED ON EXPECTED
RAINFALL. AS HAS BEEN THE PATTERN THIS YEAR...VIRTUALLY ALL
TROPICAL CYCLONE ACTIVITY IS DEVELOPING AT THE UPPER-LEVEL
ANTICYCLONIC AREAS BETWEEN THE CELLS OF THE TROPICAL UPPER
TROPOSPHERIC TROUGH.

&&

.EASTERN MICRONESIA...
SHOWERS ASSOCIATED WITH A WEAK TRADE WIND CONVERGENCE ZONE WILL
AFFECT MAJURO THIS EVENING AND POSSIBLY KOSRAE LATER TONIGHT.
FAIRLY QUIET CONDITIONS ARE EXPECTED THROUGH THE NEXT FEW DAYS AS
MODELS INDICATE A NORTHWARD PROGRESSION OF DRIER ESE TO SE TRADE
FLOW OVER THE REGION. CONVERGING SOUTHEAST FLOW INTO TROPICAL
DISTURBANCE 90W WELL TO THE NORTH OF CHUUK IS GENERATING
SCATTERED CONVECTION JUST TO THE NORTH OF POHNPEI WITH CONVECTION
ASSOCIATED WITH TRADE-WIND CONVERGENCE MOVING INTO THE AREA
MONDAY. OTHERWISE...MODELS SHOW NO MAJOR WEATHER FEATURES
AFFECTING ANY OF THE FORECAST LOCATIONS IN THE LONG-TERM.

&&

.WESTERN MICRONESIA...
LATEST SATELLITE IMAGERY AND 00Z SOUNDING DATA SHOW TRADE-WIND
CONVERGENCE ZONE AND ASSOCIATED CONVECTION HAVE MOVED TO THE
NORTHWEST OF CHUUK...WITH ONLY ISOLATED SHOWERS APPARENT BEHIND
THIS BOUNDARY. GFS IN PARTICULAR INITIALIZED WELL IN THIS AREA SO
WEIGHTED SHORT TERM FORECAST ACCORDINGLY...WITH ONLY ISOLATED
SHOWERS EXPECTED THROUGH TUESDAY. A SURFACE TROUGH EVIDENT IN
ASCAT AND SATELLITE DATA IS PROGRESSING WESTWARD OVER YAP THIS
EVENING THAT WILL BRING A PERIOD OF SCATTERED SHOWERS OVER THE
AREA FOR TONIGHT. SHOWERS ASSOCIATED WITH THIS FEATURE ARE
EXPECTED TO PASS TO THE NORTH OF KOROR MONDAY. HOWEVER...A BROAD
AREA OF CONVECTION ALONG A TRADE-WIND CONVERGENCE ZONE WILL
GRADUALLY PUSH NORTHWEST ALLOWING INCREASED SHOWERS COVERAGE
TUESDAY AND POSSIBLY TUESDAY NIGHT FOR KOROR.

&&

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

$$

STANKO/WILLIAMS

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