Area Forecast Discussion
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000
FXPQ60 PGUM 281923
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
523 AM CHST SAT NOV 29 2014

.MARIANAS SYNOPSIS...
A SMALL DISTURBANCE ALONG A SHEAR-LINE FRAGMENT IS GENERATING
SHOWERS AND THUNDERSTORMS 50 TO 150 MILES SOUTHEAST THROUGH
SOUTHWEST OF GUAM...WITH PLENTY OF DISTANT LIGHTNING VISIBLE
THROUGH THE NIGHT FROM GUAM. ANOTHER SHEAR-LINE SEGMENT HAS A FEW
SHOWERS ALONG IT FROM NEAR SAIPAN SOUTHWESTWARD TO ABOUT 130 MILES
WEST OF GUAM. IN BETWEEN...DRY AIR HAS SPREAD OVER GUAM AND ROTA
WITH DEWPOINTS IN THE LOWER 70S. GUAM BUOYS ARE INDICATING SEAS OF
8 TO 9 FEET. RADAR WINDS ARE STILL 25-30 KT AT 2000 FEET AND ABOVE
WITH WINDS GUSTING OVER 20 KT AT GUAM AND OVER 25 KT AT SAIPAN.

&&

.DISCUSSION...
IT APPEARS THE BULK OF THE SHOWERS WILL BY-PASS THE MARIANAS TO
THE SOUTHWEST THIS MORNING...LEAVING ISOLATED SHOWERS FOR THE NEXT
FEW DAYS. OVERALL...VERY LITTLE CHANGE MADE TO THE PREVIOUS
FORECAST EXCEPT TO INCREASE CLOUDINESS FOR TODAY...AND BUMP UP
WINDS A BIT TODAY TO ACCOUNT FOR CURRENT CONDITIONS.

MODELS ARE STILL GRAPPLING WITH THE POTENTIAL FOR TROPICAL
CYCLONE FORMATION OVER THE NEXT WEEK OR SO...WITH A DIFFERENT
PLAN WITH EACH MODEL RUN. FOR THE LAST COUPLE OF RUNS...THE GFS
AND ECMWF HAVE BEEN DEVELOPING A CYCLONE IN THE CHUUK-POHNPEI
REGION AND MOVING IT GENERALLY WNW. THE ECMWF TAKES A DEVELOPING
CYCLONE BETWEEN YAP AND KOROR THIS COMING WEDNESDAY...THEN FORMS A
SECOND CYCLONE BETWEEN YAP AND CHUUK THE FOLLOWING MONDAY. THE 12Z
GFS FORMS TWIN CIRCULATIONS SOUTH OF CHUUK AND POHNPEI SUNDAY
NIGHT AND MONDAY...THEN MERGES THEM TUES NIGHT AND MOVES THE
RESULT AS A TYPHOON BETWEEN YAP AND GUAM WED NIGHT AND THURSDAY.
BUT THE EARLIER 06Z GFS TAKES THE STORM MUCH FURTHER SOUTH...NEAR
YAP.

SINCE SATELLITE SHOWS PLENTY OF DISTURBED WEATHER AROUND POHNPEI
AND KOSRAE...CYCLONE DEVELOPMENT SEEMS QUITE POSSIBLE THE NEXT FEW
DAYS...BUT DETAILS ARE FAR FROM SETTLED. AS A RESULT...FORECAST
CONFIDENCE BEYOND THE NEXT 3 DAYS OR SO IS LOW...AND RESIDENTS OF
THE MARIANAS SHOULD KEEP TABS ON ANY CHANGES TO THE FORECAST FOR
THE NEXT FEW DAYS.

&&

.MARINE...
SMALL CRAFT ADVISORY IS STILL IN EFFECT...AS WINDS ARE STILL IN
THE 20-25 KT RANGE THIS MORNING OUT OVER THE WATER...AND SEAS ARE
NEAR 9 FT AT THE RITIDIAN BUOY. BUT MODELS ARE CONSISTENT IN
BRINGING WINDS DOWN TO 15-20 KT BY LATE AFTERNOON WHEN THE
ADVISORY EXPIRES.

&&

.EASTERN MICRONESIA...
SATELLITE IMAGERY SHOWS CONVECTION BEGINNING TO INCREASE ACROSS THE
MARSHALL ISLANDS IN RESPONSE TO A TRADE-WIND CONVERGENCE ZONE
SETTING UP OVER THE REGION. MODELS ARE IN GOOD AGREEMENT IN
INCREASING SHOWERS THROUGH TODAY AND TONIGHT SO ADVANCED ONSET OF
SCATTERED SHOWERS TO TONIGHT. THE TRADE-WIND CONVERGENCE ZONE IS
EXPECTED TO BREAK DOWN EARLY NEXT WEEK WITH SCATTERED SHOWERS ENDING
LATE MONDAY. THE DEVELOPING TROPICAL DISTURBANCE SOUTHWEST OF KOSRAE
IS EXPECTED TO MOVE WESTWARD OVER THE WEEKEND BRINGING SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS TO POHNPEI TODAY AND TONIGHT.
MODELS INDICATE DRIER CONDITIONS AT KOSRAE TONIGHT THROUGH TUESDAY
AS THE TROPICAL DISTURBANCE MOVES FARTHER AWAY AND SHOWERS
ASSOCIATED WITH TRADE-WIND CONVERGENCE STAY TO THE NORTH. FOR
POHNPEI...LONG TERM FORECAST REMAINS DIFFICULT WITH LOW FORECAST
CONFIDENCE. AN EXTENDED ACTIVE PATTERN APPEARS LIKELY IN MODEL
OUTPUT BUT WILL WAIT TO SEE WHAT THE TROPICAL DISTURBANCE TO THE
SOUTHEAST WILL DO OVER THE WEEKEND BEFORE EXTENDING SCATTERED
SHOWERS THROUGH EARLY NEXT WEEK.

A VIGOROUS NORTH PACIFIC LOW PRESSURE SYSTEM IS GENERATING LARGE
NORTH-NORTHWEST SWELL THAT WILL EVENTUALLY IMPACT EASTERN MICRONESIA
BEGINNING EARLY MONDAY. THE POTENTIAL FOR ADVISORY-LEVEL SURF ON
NORTH FACING EXPOSURES CERTAINTY EXISTS EARLY NEXT WEEK ESPECIALLY
FOR KOSRAE AND MAJURO. FORTUNATELY...THE MOON WILL BE AT FIRST
QUARTER PHASE LIMITING ASTRONOMICAL HIGH TIDES. NONETHELESS...THIS
WILL BE A SIGNIFICANT NORTH-NORTHWEST SWELL THAT WILL LIKELY CAUSE
HAZARDOUS SURF TO BEGIN MONDAY FOR KOSRAE AND MAJURO.

&&

.WESTERN MICRONESIA...
THE TROPICAL DISTURBANCE SOUTHEAST OF POHNPEI IS EXPECTED TO USHER
IN SCATTERED SHOWERS OVER CHUUK BY TONIGHT. MODEL SOLUTIONS ARE
QUITE DIVERGENT AFTER TAU 36 SO FORECAST CONFIDENCE IS LOW REGARDING
A LINGERING ACTIVE WEATHER PATTERN AT CHUUK MONDAY THROUGH WEDNESDAY.
FOR YAP AD KOROR...FORECAST IS HIGHLY DEPENDENT ON THE EVOLUTION
OF THE TROPICAL DISTURBANCE SOUTHEAST OF POHNPEI. LATEST GFS BRINGS
THE SYSTEM NORTH OF YAP LATE WEDNESDAY WHILE ECMWF BRINGS IT BETWEEN
YAP AND KOROR. ONLY MADE MINOR ADJUSTMENTS TO THE FORECAST UNTIL
MODELS COME INTO A BETTER CONSENSUS. IN THE SHORT TERM...INFRARED
IMAGERY INDICATED MARKEDLY DRIER AIR FILTERING INTO YAP STATE WITH
ONLY A SLIGHT CHANCE OF SHOWERS EXPECTED AT YAP TODAY.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...NONE.
MARIANAS WATERS...SMALL CRAFT ADVISORY UNTIL 5 PM CHST THIS AFTERNOON
     FOR PMZ151>154.

&&

$$

MIDDLEBROOKE/WILLIAMS





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