Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Mon, 18 Oct 2010 03:47:19 -0500

065 
FXPQ60 PGUM 180846
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
646 PM CHST MON OCT 18 2010

.SYNOPSIS...
AN ELONGATED N-S UPPER LOW IS LOCATED JUST WEST OF THE MARIANA
ISLANDS...AS BRISK SOUTH WINDS SPREAD IN ALOFT FROM THE EAST.
THIS SHOULD PRODUCE CONDITIONS FAVORABLE FOR ISOLATED
THUNDERSTORMS DURING THE NEXT 36 HOURS OR SO. RADAR SHOWS
INCREASING SHOWERS DEVELOPING EAST AND SOUTH OF GUAM...BUT ALSO
STARTING TO POP EAST OF SAIPAN AND TINIAN AS WELL.

&&

.DISCUSSION...
NONE OF THE MODELS ARE INDICATING MUCH IN THE WAY OF SHOWERS
TONIGHT...ESPECIALLY THE UKMET. BUT IN LIGHT OF THE SHOWERS
DEVELOPING ON RADAR NOW...HAVE GONE WITH SCATTERED SHOWERS FOR
THIS EVENING...THEN WINDING DOWN TO ISOLATED BY MIDNIGHT. WITH
THE TUTT LOW JUST WEST...DIVERGENT SOUTH WINDS AT 30-40 KT ABOVE
30K FT SHOULD ENHANCE THUNDERSTORM POTENTIAL A BIT THROUGH TUE
NIGHT. BEYOND THAT GFS WANTS TO DEVELOP A WEAK CIRCULATION NW OF
THE ISLANDS WED/THU...GIVING THE MARIANAS SOUTHWEST WINDS...BUT
THE EUROPEAN MODELS ARE NOT SHOWING THAT. FOR NOW...WILL STAY
WITH PREVIOUS FORECAST WED AND BEYOND UNTIL MODELS COME INTO
BETTER AGREEMENT.

&&

.EASTERN MICRONESIA...
MOSTLY SUNNY SKIES AND ISOLATED SHOWERS HAVE PREVAILED ACROSS THE
REGION AS CLOUDS AND SHOWERS REMAIN NORTH OF ALL THE FORECAST
LOCALES EXCEPT FOR KWAJALEIN. A LARGE AREA OF CLOUDS AND SHOWERS
IS FOUND EAST OF 158E BETWEEN 10N AND 20N. WITHIN THIS AREA OF
CONVECTION...A SURFACE TROUGH EXTENDS NORTHEASTWARD FROM 10N163E
THROUGH JTWC INVEST AREA 96W AT 14N171E TO 14N172E. OBSERVATIONS
FROM THE MARSHALL ISLANDS SUPPORT MODEL ANALYSIS OF A WEAK
CIRCULATION IN CONJUNCTION WITH 96W JUST NORTHEAST OF KWAJALEIN.
GFS CONSISTENTLY CARRIES THIS FEATURE AS A WEAK CIRCULATION...
MAINTAINS IT AND EVENTUALLY MOVES IT NORTHWEST...WHILE OTHER
MODELS MERELY PROG AN OPEN TROUGH. FORECAST WIND DIRECTIONS
REMAIN DEPENDENT ON THE FUTURE EVOLUTION AND MOTION OF 96W. FOR
THE REST OF THE WEEK...SOUTHEAST TO EAST FLOW WILL RESUME WITH
MOSTLY CLOUDY CONDITIONS TRICKLING WESTWARD FROM MAJURO TO
POHNPEI THURSDAY THROUGH SATURDAY AS A WEAK SURFACE TROUGH PUSHES
THROUGH.

&&

.WESTERN MICRONESIA...
A TRICKY FORECAST IS IN STORE FOR THE REGION THE NEXT COUPLE OF
DAYS. SHOWERS ALONG THE EASTERN SIDE OF SUPER TYPHOON MEGI HAVE
RECEDED WESTWARD AWAY FROM KOROR AND THUS ISOLATED SHOWERS REMAIN
IN THE FORECAST. SATELLITE HAS SHOWN MOSTLY SUNNY CONDITIONS ALL
DAY. HOWEVER...SLIGHT CHANCE THUNDER WAS ADDED TO YAP FOR TONIGHT
AS SHOWERS AND A FEW THUNDERSTORMS APPROACH FROM THE SOUTHEAST. A
POSSIBLE WEAK CIRCULATION...JTWC INVEST AREA 97W...IS EMBEDDED IN
THIS CONVECTIVE CLUSTER AS IT DRIFTS TOWARD YAP. VISIBLE IMAGERY
SHOWS CBS JUST EAST OF YAP BUT THEY ARE ENCOUNTERING CONSIDERABLE
SHEARING ALOFT. IF THIS AREA OVERSPREADS YAP...THE YAP FORECAST
MAY REQUIRE AN UPDATE. ECMWF INITIALIZES RATHER POORLY BUT
EVENTUALLY JOINS IN WITH THE OTHER MODELS BY DAYS 2 AND 3 WITH A
WEAK CIRCULATION SEEMINGLY MEANDERING BETWEEN YAP...CHUUK AND
GUAM...WITH NO IMPRESSIVE RAIN EVENTS FOR ANY LOCATION. BY THE
END OF THE WEEK...THIS PATTERN IS PROGGED TO LIFT NORTHWARD AS
SOUTHEAST TO EAST FLOW RETURNS ACROSS THE REGION.

&&

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

$$

MIDDLEBROOKE/M. AYDLETT

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