Area Forecast Discussion
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FXPQ60 PGUM 232150
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
750 AM CHST THU JUL 24 2014

.MARIANAS SYNOPSIS...ISOLATED SHOWERS AND A FEW THUNDERSTORMS
COULD BE SEEN OVER THE MARIANAS THIS MORNING.

&&

.DISCUSSION...
AN UPPER-LEVEL LOW WAS CENTERED NEAR SAIPAN THIS MORNING. SHORTLY
AFTER SUNRISE A FEW THUNDERSTORMS WERE OBSERVED NEAR THE CENTER
OF THE UPPER LOW JUST EAST OF SAIPAN. WHILE THERE MAYBE A BRIEF
THUNDERSTORM OR TWO NEAR TINIAN AND SAIPAN THIS MORNING ...FEEL
THAT THE BULK OF THE ACTIVITY IS WEST AND SOUTH OF THE LOCAL AREA
AND MOVING AWAY.

AGAIN THE BIG QUESTION TODAY IS WHAT WILL HAPPEN TO THE
CIRCULATION SOUTH OF CHUUK LOCATED NEAR 7N148E. MODELS STILL
PREDICT THAT IT WILL CONTINUE TO INTERACT WITH ANOTHER
CIRCULATION JUST NORTH OF YAP. A FEW MODELS MERGE THESE
SYSTEMS...NOTABLY THE ECMWF. THE GFS SEEMS TO BRIEFLY MERGE THEM
BUT THEN BOTH OF THE CIRCULATIONS COME BACK TO LIFE SHORTLY
THEREAFTER. THE GFS THEN MOVES THE TWO CIRCULATIONS NORTHWARD
WITH ONE PASSING WEST OF THE MARIANAS AND THE OTHER EAST OF THE
ISLANDS. ECMWF MAKES THE YAP CIRCULATION THE DOMINANT FEATURE AND
MOVES IT INTO THE PHILIPPINE SEA. NONE OF THESE OUTCOMES SEEMS TO
BE THE BEST SOLUTION. THE DOMINANT CIRCULATION IS THE ONE NEAR
CHUUK WITH THE YAP ONE BEING MINOR. CAN NOT SEE THE YAP
CIRCULATION BECOMING THE BIG PLAYER AS IN THE ECMWF. WHILE A TWIN
CIRCULATION IS POSSIBLE IT DOES NOT SEEM TO FIT THE CURRENT
SITUATION.

WITH SO MUCH DIFFERENCE IN THE MODELS FEEL CONFIDENT IN THE
FORECAST ONLY UP TO FRIDAY NIGHT. MOST LIKELY THE CHUUK
CIRCULATION WILL REMAIN THE BIG BOY AND MOVE NORTHWEST AND IN THE
PROCESS PULL THE MONSOON TROUGH NORTH OVER THE MARIANAS THIS
WEEKEND.

THE CERTAINTY IN WHAT HAPPENS WITH THE WINDS DECREASES AFTER
FRIDAY NIGHT. CONFIDENCE REMAINS HIGHER IN THE RAINFALL
DEPARTMENT OF THE FORECAST. NO MATTER WHAT MODEL SOLUTION YOU LOOK
AT THEY ALL AGREE ON A WET WEEKEND. AS THE MONSOON TROUGH PUSHES
ACROSS THE MARIANAS THIS WEEKEND IT WILL BE ASSOCIATED WITH DEEP
MOISTURE. THIS WILL EQUAL A FAIR CHANCE OF SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS THIS WEEKEND.

&&

.MARINE...
A WESTERLY AND AN EAST SWELL WILL PERSIST THROUGH THE FORECAST.
THE WEST SWELL IS FORECAST TO DECREASE A FOOT ON FRIDAY WHILE THE
EAST SWELL WILL RISE BY A FOOT THE SAME DAY.

AS WITH THE WIND FORECAST THE SEA AND SWELL FORECAST FEEL
CONFIDENT ONLY THROUGH FRIDAY NIGHT. BECAUSE THE MODELS ARE SO
DIFFERENT OVER THE WEEKEND NOT CERTAIN WHAT KIND OF SEA OR SWELL
WILL BE DEVELOPED. IT IS NOT CERTAIN WHAT KIND OF WIND FIELD WILL
BE ASSOCIATED WITH THE MONSOON LOW SO FETCH GENERATION AREA IS
UNKNOWN.

&&

.EASTERN MICRONESIA...
A QUIET PATTERN EXISTS OVER THE MARSHALLS WHILE SHOWERS AND
THUNDERSTORMS ARE FOUND NEARER KOSRAE AND POHNPEI ALONG THE
EASTERN END OF A MONSOON TROUGH. THE MONSOON TROUGH IS EXPECTED
TO GRADUALLY LIFT NORTHWARD OVER THE NEXT COUPLE OF DAYS. FOR
NOW...WETTEST CONDITIONS ARE EXPECTED TO BE FOUND AT KOSRAE
THROUGH FRIDAY NIGHT. POHNPEI WILL STILL SEE ISOLATED
THUNDERSTORMS...BUT MODELS SHOW FEWER SHOWERS THERE. A SURFACE
TROUGH WILL BRING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS TO
MAJURO BY TONIGHT. SCATTEROMETRY DATA SHOWS A SWATH OF 20 TO 25
KNOT SOUTHWEST WINDS SOUTH OF CHUUK AND POHNPEI. RESULTANT SWELL
WILL REACH POHNPEI AND KOSRAE OVER THE NEXT COUPLE OF DAYS...BUT
SURF HEIGHTS SHOULD STAY JUST SHY OF HAZARDOUS SURF CRITERIA AT
BOTH LOCATIONS.

&&

.WESTERN MICRONESIA...
A COMPLICATED PATTERN REMAINS OVER THE REGION WITH A TROPICAL
DISTURBANCE NEAR YAP AT 10N137E AND ANOTHER DISTURBANCE FOUND
SOUTHWEST OF CHUUK NEAR 7N148E. MODEL AND SCATTEROMETER DATA SHOW
THAT THE SYSTEM NEARER YAP HAS BEEN SLOWLY DROPPING SOUTHWARD
WITH CONVECTION PROCEEDING SOUTHWARD SLIGHTLY FASTER. UPPER-LEVEL
SHEAR REMAINS FAIRLY STRONG AND WILL CONTINUE TO LIMIT THE
DISTURBANCE FROM REALLY GETTING ORGANIZED FOR THE TIME BEING.
MEANWHILE... SCATTERED TO NUMEROUS SHOWERS ARE FOUND NEAR AND
SOUTH OF THE DISTURBANCE IN CHUUK STATE. MOST CONVECTION REMAINS
SOUTH OF THE TROUGH AXIS BUT IS EXPECTED TO GRADUALLY SPREAD
NORTHWARD THE NEXT SEVERAL DAYS AS THE TROUGH AND CIRCULATION
LIFT NORTHWARD. WITH THAT SAID...PERIODS OF SCATTERED SHOWERS ARE
EXPECTED THE NEXT COUPLE OF DAYS AT BOTH KOROR AND CHUUK BUT
WETTER WEATHER IS NOT REALLY EXPECTED TO DEVELOP AT YAP UNTIL
LATER ON FRIDAY AS THE TROUGH LIFTS NORTH.

LATEST MODEL RUNS SHOW THE TROUGH REMAINING NEARLY STATIONARY
EAST- TO-WEST OF YAP FOR THE SHORT TERM THEN PULLING BACK UP TO
THE NORTH. WHILE OVERHEAD...SURFACE WINDS WILL BE VARIABLE...BUT
WINDS WILL TURN TO THE SOUTHWEST AND INCREASE IN SPEED ONCE THE
TROUGH STARTS TO SHIFT TO THE NORTH. MODERATE TO FRESH NORTHWEST
TO WEST WINDS WILL GRADUALLY SHIFT TO WEST OR SOUTHWEST AND
INCREASE IN SPEED THE NEXT COUPLE OF DAYS AT KOROR. WINDS AT
CHUUK ARE A LITTLE LESS CERTAIN. SOUTH WINDS WILL RANGE BETWEEN
10 AND 20 KNOTS. GFS SHOWS THAT WINDS COULD GET A LITTLE STRONGER
FROM A FASTER-DEVELOPING CIRCULATION TO THE WEST. ECMWF REMAINS
SOMEWHAT MORE CONSERVATIVE AND DOES NOT SHOW THE CIRCULATION
DEVELOPING TOO QUICKLY AS IT HEADS NORTH OVER WESTERN CHUUK
STATE.

SEAS ARE EXPECTED TO BUILD AT ALL THREE LOCATIONS OVER THE NEXT
FEW DAYS AS WINDS INCREASE SOUTH OF THE MONSOON TROUGH. TIMING IS
STILL UNCERTAIN...BUT CHUUK COULD SEE SURF REACHING HAZARDOUS
LEVELS LATE FRIDAY AND AROUND SATURDAY FOR YAP AND KOROR.

&&

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

$$

ZIOBRO/W. AYDLETT





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