Area Forecast Discussion
Issued by NWS

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

000
FXPQ60 PGUM 220944 CCA
AFDPQ

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE TIYAN GU
427 PM CHST WED OCT 22 2014

CORRECTED TYPO

.MARIANAS SYNOPSIS...
A SHEAR LINE ALONG WITH A WELL-DEFINED LINE OF SHOWERS AND
THUNDERSTORMS ARE PRESENT ACROSS THE FAR NORTHERN MARIANAS. A WEAK
CIRCULATION AND TROUGH ARE FOUND SOUTHEAST OF GUAM. SHOWERS
ASSOCIATED WITH THE TROUGH ARE APPROACHING EASTERN MARIANAS COASTAL
WATERS.

&&

.DISCUSSION...
THE CIRCULATION AND SURFACE TROUGH SOUTHEAST OF THE MARIANAS WILL
SLOWLY PUSH NORTHWARD...THEN WESTWARD THROUGH THURSDAY. WINDS WILL
VEER FROM THE EAST TO THE SOUTHEAST THURSDAY AND INTRODUCE DEEPER
TROPICAL MOISTURE TO THE MARIANAS. ADJUSTED SKY COVER TO MOSTLY
CLOUDY THURSDAY THROUGH FRIDAY NIGHT TO ACCOUNT FOR THE PASSAGE OF
THE CIRCULATION/TROUGH. SATELLITE AND RADAR IMAGERY INDICATE ONLY
ISOLATED SHOWER COVERAGE AT THE MOMENT. GFS AND NAVGEM ARE STILL THE
DRIER NWP SOLUTIONS WHILE THE ECMWF HOLDS OFF ON INCREASED SHOWERS
UNTIL FRIDAY NIGHT. UNCERTAINTY EXISTS REGARDING THIS SYSTEM SINCE
IT IS A SMALL FEATURE AND PROBABLY NOT BEING HANDLED WELL BY MODELS.
ONCOMING SHIFT SHOULD ASSESS IF AN UPDATE IS NEEDED IN CASE SHOWERS
INCREASE FASTER THAN EXPECTED. FOR NOW...ONLY ISOLATED SHOWERS ARE
EXPECTED THU THROUGH FRI NIGHT OWING TO AT LEAST SOME CONSISTENCY TO
THE GFS AND NAVGEM RUNS OVER THE LAST 24 HOURS. MODEL AGREEMENT
BECOMES POOR AFTER THE PASSAGE OF THE CIRCULATION/TROUGH OVER THE
SOUTHERN MARIANAS WITH ECMWF KEEPING THE AREA UNDER AMPLE MOISTURE
AND WIDESPREAD SHOWER ACTIVITY WHILE GFS AND NAVGEM CONTINUE TO BE
THE LESS AGGRESSIVE FORECAST...EVEN IN THE LONG TERM. THE FORECAST
FOR NEXT WEEK IS LARGELY PERSISTENCE WITH A DRY TRADE-WIND PATTERN
EMERGING. A FEW MORE MODEL RUNS WILL BE NEEDED BEFORE A CONSENSUS
CAN BE MADE REGARDING ANY CHANGES IN THE FORECAST FOR NEXT WEEK.

&&

.MARINE...
SAIPAN BUOY SHOWED A RAPID RISE IN SEAS OVERNIGHT AS THE NORTH-
NORTHEAST SWELL BUILT IN SAIPAN WATERS. SWELL HAS REACHED GUAM AND
HAS BEEN SLIGHTLY LARGER THAN WW3 MODEL OUTPUT WITH SAIPAN BUOY
INDICATING A 7-FOOT 12 SECOND NNE SWELL. THUS...A HIGH SURF ADVISORY
WAS ISSUED THIS MORNING WITH SURF HEIGHTS OF 8 TO 9 FEET LIKELY
CONTINUING OVERNIGHT. SURF IS EXPECTED TO FALL SLIGHTLY THURSDAY BUT
A SECONDARY LONG-PERIOD SWELL FROM THE NORTHEAST WILL INCREASE
FRIDAY BRINGING SURF TO ADVISORY LEVELS ONCE AGAIN. SURF SHOULD FALL
BELOW ADVISORY LEVELS LATE SATURDAY NIGHT OR EARLY SUNDAY MORNING.

&&

.EASTERN MICRONESIA...
AN AREA OF SHOWERS AND THUNDERSTORMS PUSHED ACROSS POHNPEI TODAY.
SATELLITE IMAGERY SHOWED THAT THIS AREA WAS WEAKENING BUT LINGERING
SCATTERED SHOWERS ARE LIKELY FOR AT LEAST PART OF THE NIGHT. WHILE
THE CHANCE OF THUNDERSTORMS IS LOW...A FEW MAY OCCUR SO ADDED A
SLIGHT CHANCE OF THUNDERSTORMS TO THE POHNPEI FORECAST FOR TONIGHT.
LOW-LEVEL CONVERGENCE WILL KEEP SKIES MOSTLY CLOUDY ACROSS POHNPEI
THROUGH SATURDAY.

A SURFACE TROUGH IS STRETCHED ACROSS THE MARSHALL ISLANDS. SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS COULD BE FOUND SOUTH OF MAJURO
THIS AFTERNOON. WHILE THE BULK OF THE ACTIVITY WILL REMAIN SOUTH OF
MAJURO...IT WILL PRODUCE ISOLATED SHOWERS AND A SLIGHT CHANCE OF
THUNDERSTORMS TONIGHT THROUGH THURSDAY NIGHT.

THIS SAME TROUGH WILL MOVE WEST AND CAUSE WINDS TO BECOME NORTHEAST
AT KOSRAE THURSDAY NIGHT. IT WILL BRING SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS TO KOSRAE FRIDAY AND FRIDAY NIGHT. HIGH
PRESSURE WILL BUILD ACROSS KOSRAE AND MAJURO SATURDAY AND SUNDAY.

&&

.WESTERN MICRONESIA...
A SURFACE TROUGH OF LOW PRESSURE CONTINUES TO STRETCH ACROSS THE
WESTERN HALF OF MICRONESIA. THE TROUGH AXIS WAS NORTH OF 10N.
CONVERGENCE SOUTH OF THE TROUGH BROUGHT SOME PATCHES OF SHOWERS AND
THUNDERSTORMS ACROSS PALAU AND YAP THIS AFTERNOON. WHILE ISOLATED
SHOWERS ARE EXPECTED TO BE THE PREDOMINANT COVERAGE... ISOLATED
THUNDERSTORMS ARE ALSO POSSIBLE ACROSS PALAU TONIGHT.

A CIRCULATION COULD BE FOUND ALONG THE TROUGH JUST SOUTH OF GUAM
THIS AFTERNOON. THIS TROUGH WILL PUSH SOUTHWEST TOWARD YAP. MODELS
SHOW IT WILL PASS CLOSE TO YAP ON THURSDAY. AT THIS TIME THE MODELS
KEEP THE WEATHER RATHER BENIGN NEAR THE CENTER OF THE CIRCULATION.
THE CIRCULATION LOOKS AS THOUGH IT WILL PUSH THE SHOWERS NOW NEAR
PALAU AND YAP FURTHER SOUTHWARD AS IT MOVES OVER YAP. THE
CIRCULATION WILL MOVE WEST TO 130E BY FRIDAY. IN THE WAKE OF THE
CIRCULATION...EAST TRADE WINDS WILL BUILD ACROSS PALAU AND YAP BY
THE END OF THE WEEK.

THE SOUTHWEST WINDS AT CHUUK TODAY WILL GIVE WAY TO NORTHEAST TRADE
WINDS THURSDAY NIGHT. FAIR WEATHER WILL PREVAIL ACROSS CHUUK THROUGH
THURSDAY NIGHT. MODELS SHOW A CIRCULATION DEVELOPING SOUTH OF CHUUK
THIS WEEKEND. WHILE MOST OF THE ACTIVITY WILL REMAIN SOUTH OF
CHUUK...MOSTLY CLOUDY SKIES AND A SLIGHT CHANCE THUNDERSTORMS WILL
PREVAIL FROM FRIDAY THROUGH MONDAY.

STRONG WINDS ASSOCIATED WITH A STORM SYSTEM IN THE NORTH PACIFIC
PRODUCED SWELLS THAT HAVE GENERATED HIGH SURF ACROSS THE MARIANAS
THIS AFTERNOON. MODELS SHOW LONG-PERIOD SWELLS PUSHING ACROSS YAP
AND PALAU SOMETIME THIS WEEKEND. AT THIS TIME...THESE SWELLS DO NOT
APPEAR TO BE HIGH ENOUGH TO GENERATE HAZARDOUS SURF AT THESE TWO
LOCATIONS. THIS SHOULD BE WATCHED AS THESE SWELLS WERE NOT EXPECTED
TO PRODUCE HAZARDOUS SURF ACROSS THE MARIANAS. AT ANY RATE EVEN IF
HAZARDOUS SURF DOES NOT OCCUR...THESE LONG PERIOD SWELLS...UP TO 14
SECONDS...MAY STILL PRODUCE A HIGHER RIP CURRENT RISK THIS WEEKEND.
THE SAME WAVE MODELS ALSO SHOW THE SURF POSSIBLY APPROACHING
HAZARDOUS AT CHUUK LATE FRIDAY NIGHT. AGAIN...EVEN IF SURF DOES NOT
REACH HAZARDOUS LEVELS...THE RIP CURRENT RISK WOULD LIKELY INCREASE.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...HIGH SURF ADVISORY UNTIL 4 PM CHST SUNDAY FOR GUZ001>004.

MARIANAS WATERS...NONE.
&&

$$

WILLIAMS/ZIOBRO





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.