Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Sat, 4 Sep 2010 15:48:12 -0500

999 
FXPQ60 PGUM 042048
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
648 AM CHST SUN SEP 5 2010

.SYNOPSIS...MOSTLY CLOUDY SKIES WITH A SLIGHT CHANCE OF
THUNDERSTORMS TODAY AND TONIGHT. ISOLATED SHOWERS THROUGH THE
FORECAST. AN UPPER-LEVEL LOW IS LOCATED NEAR 23N141E. UPPER-LEVEL
DIVERGENCE ASSOCIATED WITH THIS LOW GENERATED SCATTERED SHOWERS
AND ISOLATED THUNDERSTORMS BOTH EAST AND WEST OF THE ISLANDS.

&&

.DISCUSSION...
LITTLE CHANGE TO FORECAST. CONFIDENCE IN THE FORECAST IS NOT AS
HIGH AS ONE WOULD LIKE. UPPER-LEVEL LOW NORTHWEST OF THE MARIANAS
HAS DUG DOWN AS FAR SOUTH AS IT PROBABLY WILL AND IS NOW MOVING
WESTWARD. UPPER-LEVEL DIVERGENCE GENERATED AREAS OF SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS TO THE EAST AND WEST OF THE
MARIANAS THIS MORNING. IF THE UPPER-LOW IS MOVING WEST WILL SOME
OF THE UPPER DIVERGENCE MOVE ACROSS THE LOCAL AREA. MODELS HINT
AT THIS BUT FELT ONE COULD NOT JUSTIFY PUTTING SCATTERED SHOWERS
IN THE FORECAST. A SLIGHT CHANCE OF THUNDERSTORMS WAS ALREADY IN
THE FORECAST THROUGH TONIGHT AND WITH THE UPPER LOW IN THE REGION
FELT IT WAS BEST TO KEEP THEM IN. MODELS TRY TO DRY US OUT
THROUGH THE REMAINDER OF THE FORECAST BUT THEN AGAIN THEY HAVE
BEEN SAYING THAT FOR A FEW DAYS...COULD THE WET AND CLOUDY
WEATHER HANG ON LONGER THAN EXPECTED. WINDS WILL BE BASIC EAST
TRADE-WINDS THROUGH THE FORECAST. EVEN CONFIDENCE IN THIS...AT
LEAST IN THE NEAR TERM...IS IN QUESTION. COULD THE LARGE AREA OF
SHOWERS AND THUNDERSTORMS...THAT WAS TO THE EAST OF THE ISLANDS
FOR MUCH OF THE MORNING...PUSH OUT AN OUTFLOW BOUNDARY. ON FRIDAY
AN AREA OF SHOWERS TO THE EAST OF THE ISLANDS DID PUSH OUT AN
OUTFLOW BOUNDARY WHICH MOVED OVER THE MARIANAS. WINDS ASSOCIATED
WITH THE BOUNDARY BRIEFLY ELEVATED WINDS DURING FRIDAY AFTERNOON.
WITH NO EVIDENCE TO SUPPORT THE EXISTENCE OF SAID BOUNDARY WILL
LEAVE OUT OF FORECAST.

&&

.MARINE...
EAST TO OCCASIONALLY SOUTHEAST SWELLS OF FOUR FEET ARE ALL THAT
IS EXPECTED THROUGH THE FORECAST. RIP CURRENT RISK WILL REMAIN
LOW THROUGH AT LEAST MIDWEEK.

&&

.EASTERN MICRONESIA...
CONVECTION HAS STEADILY DISSIPATED ACROSS THE AREA WHILE PUSHING
FARTHER NORTH TO BETWEEN 8N AND 10N DUE TO GENTLE TO MODERATE
SOUTHEAST WINDS. NEARER POHNPEI...CONVECTION DIPS TOWARD THE WSW.
THIS WILL KEEP SCATTERED SHOWERS AT POHNPEI FOR THE FIRST PART OF
TODAY BEFORE SHOWERS SHIFT FARTHER WEST. MODELS KEEP A WEAKENED
TRADE-WIND CONVERGENCE ZONE NORTH OF POHNPEI...KOSRAE AND MAJURO
FOR MUCH OF THE WEEK WITH THE EXCEPTION OF A FEW BRIEF PULSES OF
INCREASED SHOWER ACTIVITY AS WEAK SURFACE TROUGHS PASS THROUGH
THE REGION...BUT AT THIS POINT...MODEL GUIDANCE GIVES NO REASON
TO EXPECT ANYTHING MORE THAN ISOLATED SHOWERS THROUGH THURSDAY.

&&

.WESTERN MICRONESIA...
UPPER-LEVEL DIVERGENCE NEAR CHUUK...YAP AND PALAU IS PROVIDING
SUFFICIENT UPLIFT TO PRODUCE SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS. ALTHOUGH CHUUK EXPERIENCED A BRIEF ROUND OF
SCATTERED SHOWERS OVERNIGHT...THE BULK OF SHOWER ACTIVITY IS
EXPECTED TO REMAIN WEST TODAY. THE DRY PATTERN OVER EASTERN
MICRONESIA WILL THEN SPREAD WESTWARD LIKELY KEEPING SHOWERS
LIMITED TO ISOLATED FOR THE WEEK. FOR YAP AND PALAU...UPPER LEVEL
CONDITIONS WILL REMAIN FAVORABLE FOR ISOLATED THUNDERSTORMS
THROUGH TODAY. INCREASING LOW-LEVEL CONVERGENCE WILL TRIGGER
SCATTERED SHOWERS AND POSSIBLY A FEW THUNDERSTORMS MONDAY NIGHT
AND TUESDAY.

&&

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

$$

ZIOBRO/W. AYDLETT

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