Area Forecast Discussion
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000
FXPQ60 PGUM 032021
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
621 AM CHST FRI SEP 4 2015

.SYNOPSIS...
LATEST ASCAT ANALYSIS REVEALS A CIRCULATION CENTERED JUST
SOUTHEAST OF GUAM. VAD WIND PROFILE INDICATES THIS SYSTEM IS
UNDERGOING STRONG WIND SHEAR ABOVE 25K FT. RADAR SCAN SHOWS AN MCS
ASSOCIATED WITH THE CIRCULATION APPROACHING THE GUAM AND ROTA
MARINE ZONES FROM THE EAST. OTHERWISE...THE MONSOON TROUGH BETWEEN
130E AND 160E LOOKS RELATIVELY QUIET.

&&

.DISCUSSION...
SHORT TERM FORECAST IS MADE WITH LOW CONFIDENCE. RADAR TRENDS
SUGGEST BOTH GUAM AND ROTA COULD EXPERIENCE SCATTERED...EVEN
NUMEROUS SHOWER COVERAGE LATER THIS MORNING...BUT POOR
ORGANIZATION OF THE TROPICAL DISTURBANCE CURRENTLY PASSING THROUGH
SUGGESTS THE CONVECTION WILL SHEAR APART BEFORE IT ARRIVES OVER
THE FORECAST ZONES. MODELS ALL AGREE ON THIS DRY BIAS FORECAST
SCENARIO. IF NOT...FORECAST WILL NEED TO BE UPDATED BY MID MORNING
TO INCREASE SHOWER COVERAGE...ESPECIALLY FOR THE GUAM AND ROTA
ZONES. AFTER TODAY...MONSOON TROUGH LIFTS SLOWLY NORTHWARD.
CONVERGENT WEST WINDS SHOULD PROVIDE CONTINUED LOW-LEVEL FORCING
FOR SHOWERS AND THUNDERSTORMS THROUGH AT LEAST THE FIRST HALF OF
NEXT WEEK. HAVE ADDED MENTION OF THUNDER FOR MONDAY AND TUESDAY OF
NEXT WEEK. BEYOND TUESDAY...ENVIRONMENT STILL LOOKS FAVORABLE FOR
THUNDER. MODEL GUIDANCE SUGGESTS MONSOONAL ENVIRONMENT COULD
GENERATE SCATTERED SHOWERS OVER THE FORECAST ZONES AT TIMES NEXT
WEEK...BUT IT IS TOO EARLY TO PINPOINT EXACTLY WHEN AND WHERE
THESE EVENTS MIGHT OCCUR.

&&

.MARINE...
BUOY READINGS INDICATE COMBINED SEAS IN THE 3 TO 5-FOOT RANGE.
HAVE ADJUSTED SECONDARY SWELL TODAY AND TONIGHT PER BUOY SPECTRUM
PLOTS TO COME FROM THE NORTHEAST AND HAVE ADDED A FOOT TO THE
SECONDARY TODAY AND TONIGHT. OTHERWISE...HAVE LEFT SWELL GRIDS
UNCHANGED. MODEL GUIDANCE STILL SUPPORTS INCREASING NORTHEAST
SWELL FROM TY KILO AND INCREASING MONSOON WAVES AND SWELL EARLY
NEXT WEEK.

&&

.EASTERN MICRONESIA...
THE MONSOON TROUGH REMAINS STRETCHED TO THE NORTH OF EASTERN
MICRONESIA AND DIPS SOUTHEASTWARD TOWARD A WEAK DISTURBANCE
CENTERED NEAR 8N180. CLOUDS AND SHOWERS HAVE DIMINISHED NEAR
POHNPEI AND KOSRAE BUT SHOWERS AND THUNDERSTORMS ARE FOUND NEARER
MAJURO. SHOWER COVERAGE WILL INCREASE TO SCATTERED ON MAJURO
LATER THIS AFTERNOON BUT WILL DECREASE BACK TO ISOLATED SATURDAY.
THE PROXIMITY OF THE TROUGH WILL MAINTAIN ISOLATED THUNDERSTORMS
IN THE AREA THROUGH SATURDAY NIGHT. DRY WEATHER FOR POHNPEI AND
KOSRAE WILL END OVER THE WEEKEND AS THE MONSOON TROUGH DIPS
SOUTHWARD. POHNPEI WILL SEE WETTER CONDITIONS SUNDAY...WHILE MOST
OF THE SHOWERS STAY JUST NORTH OF KOSRAE.

WAVE MODELS CONTINUE TO INDICATE INCREASING NORTH SWELL OVER THE
WEEKEND AND EARLY NEXT WEEK AS TY KILO DRIFTS BY WAKE ISLAND. THE
LARGEST IMPACT WILL BE IN THE FAR NORTHERN ATOLLS OF THE
MARSHALLS THIS WEEKEND AND EARLY NEXT WEEK. NORTHERN ATOLL
SHADOWING SHOULD REDUCE THE SIZE OF THE SWELL REACHING MAJURO.
POHNPEI AND CHUUK WILL SEE LONG PERIOD NORTH SWELL BUILDING EARLY
NEXT WEEK. MODELS SHOW SIMILAR TRENDS FOR KOSRAE...BUT OVERALL
SWELL IS EXPECTED TO BE SLIGHTLY SMALLER.

&&

.WESTERN MICRONESIA...
A NARROW BAND OF SHOWERS AND THUNDERSTORMS IS SEEN OVER YAP. THE
MONSOON TROUGH LIES JUST TO THE NORTH OF YAP AND CHUUK. MOST
CONVECTION IS CENTERED NEAR A WEAK CIRCULATION CENTERED NEAR THE
MARIANAS WHICH WILL SLIDE TO THE WEST-NORTHWEST. KOROR AND CHUUK
WILL SEE QUIETER WEATHER IN THE SHORT TERM WHILE YAP SEES AN
INCREASE IN SHOWERS TONIGHT. THE MONSOON TROUGH WILL BECOME MORE
ACTIVE OVER THE WEEKEND AND EARLY NEXT WEEK. THIS WILL BRING
ISOLATED THUNDERSTORMS TO CHUUK BY MONDAY. HOWEVER...MOST ACTIVITY
WILL REMAIN JUST NORTH OF KOROR...NEARER TO YAP. COMBINED SEAS ARE
STILL EXPECTED TO INCREASE NEAR CHUUK NEXT WEEK...SEE EASTERN
MICRONESIA DISCUSSION FOR MORE DETAILS ON TIMING.

&&

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

$$

MCELROY/W. AYDLETT



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