Area Forecast Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
000
FXPQ60 PGUM 282059
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
659 AM CHST SAT AUG 29 2015

.SYNOPSIS....LIGHT NORTHWEST WINDS AND A FEW SMALL SHOWERS PREVAIL
ACROSS THE MARIANAS THIS MORNING. LIGHT WINDS AND ISOLATED SHOWERS
ARE ALL THAT IS EXPECTED THROUGH THE WEEKEND AND INCLUDING MOST OF THE
COMING WEEK.

&&

.DISCUSSION...
LITTLE CHANGE MADE TO THE FORECAST. LIGHT NORTHWEST WINDS NEAR A
WEAK TROUGH WILL PREVAIL ACROSS THE MARIANAS THIS MORNING. WINDS
WILL BECOME WEST BY LATE THIS AFTERNOON. SOUTHWEST WINDS ARE
EXPECTED ON SUNDAY. WEAK HIGH PRESSURE WILL BUILD INTO THE AREA
MONDAY BRINGING EAST WINDS WITH IT. WINDS ARE PREDICTED TO BE
LIGHT THROUGH THE FORECAST.

SOUNDING DATA AND WATER VAPOR IMAGERY SHOW DRY AIR IN PLACE ACROSS
THE MARIANAS. MODELS KEEP DEEP LAYER MOISTURE AT A MINIMUM TODAY
AND SUNDAY WITH ONLY A SLIGHT INCREASE BY THE FIRST HALF OF THE
COMING WEEK. WITH THE LOW MOISTURE EXPECT ONLY A FEW SHOWERS
THROUGH THE NEXT FEW DAYS.

&&

.MARINE...
RITIDIAN AND SAIPAN BUOY DATA SHOWS SEAS ARE AROUND 7 TO 9 FEET.
THESE SAME BUOYS SHOW A NORTH SWELL OF BETWEEN 6 TO 8 FEET WITH A
PERIOD OF AROUND 13 TO 15 SECONDS. THIS IS A BIT HIGHER THAN WW3
PREDICTIONS FOR GUAM INDICATE BUT CLOSER TO SAIPANS PREDICTION.
THIS NORTH SWELL IS FROM THE REMAINS OF ATSANI WHICH HAS BECOME A
LARGE LOW PRESSURE SYSTEM EAST OF JAPAN. THIS LOW PRESSURE SYSTEM
IS MOVING SLOWLY NORTHWARD.

EXPECT HAZARDOUS SURF HEIGHT FROM THIS SWELL OF 8 TO 10 FEET ON NORTH
AND EAST FACING REEFS. AT TIMES THE BUOY DATA POINTS TOWARDS HIGHER
SURF. WITH A PERIOD OF 15 SECONDS THE THE ENERGY IN THE SURF WILL
PRODUCE DANGEROUS RIP CURRENTS.

AT VARIOUS TIMES THIS MORNING THE SWELL HEIGHT DECREASED AT
RITIDIAN BUOY BUT CAME BACK UP AGAIN AFTER SUNRISE. WITH THE
HEIGHT OF THE SWELL IN FLUX NOT CERTAIN IF THE HAZARDOUS SURF
WILL END AS PREDICTED LATE THIS AFTERNOON. WW3 DATA HINT THAT THE
SWELL SHOULD EBB ENOUGH TO ALLOW THE SURF TO DECREASE BUT MODELS
HAVE BEEN KNOWN TO LOWER THE SWELL TOO QUICKLY. IT IS POSSIBLE
THAT THE HIGH SURF ADVISORY MAY NEED TO BE EXTENDED. THE DAY SHIFT
WILL EVALUATE THE SITUATION AND EXTEND IF NECESSARY.

&&

.EASTERN MICRONESIA...
LATEST ASCAT SATELLITE IMAGERY INDICATES MODERATE CONVERGENT WEST
TO SOUTHWEST WINDS ARE GRADUALLY SHIFTING WESTWARD AWAY FROM KOSRAE.
THIS HAS ALLOWED DRIER CONDITIONS ALREADY OVER MAJURO TO SPREAD
WESTWARD OVER KOSRAE THIS MORNING. FOR POHNPEI AND CHUUK...SPORADIC
CONVECTION ASSOCIATED WITH CONVERGENT WINDS WILL CONTINUE THRU THIS
EVENING. AS THE RIDGE OF HIGH PRESSURE DRIFTS FARTHER WESTWARD FROM
THE SURFACE TROUGH AND CIRCULATION NEAR 12N163E...CONVERGENT WINDS
ACROSS CHUUK AND POHNPEI SHOULD DECREASE. THEREFORE EXPECT DRIER
WEATHER TO REACH THESE TWO LOCALES BY SUNDAY NIGHT. FOR NEXT
WEEK...A LIGHT WIND REGIME MIGHT DEVELOP ACROSS ALL THE FORECAST
POINTS WHICH SHOULD PROLONG FAIR WEATHER.

THE TREND ON ALTIMETRY OVER THE PAST FEW DAYS INDICATES A GRADUAL
DECLINE ON SEA HEIGHTS FROM THE MARSHALL ISLANDS WESTWARD TO NEAR
KOSRAE. THIS IS PROBABLY CONTRIBUTED BY DECREASING WEST TO SOUTHWEST
SWELL AS THE WINDS SLOWLY WEAKEN FROM EAST TO WEST. THIS TREND
SHOULD CONTINUE TO POHNPEI AND CHUUK OVER THE NEXT FEW DAYS.

&&

.WESTERN MICRONESIA...
REASONING FOR CHUUK FORECAST IS INCLUDED IN THE EASTERN MICRONESIA
SECTION DUE TO A SIMILAR WEATHER PATTERN.

MONSOONAL WINDS ARE STRENGTHENING ACROSS THE REPUBLIC OF PALAU AND
YAP STATE THIS MORNING BASED ON ASCAT DATA. HOWEVER...WV SATELLITE
LOOPS REVEAL AN AREA OF STRONG SUBSIDENCE ARRIVING AT YAP TODAY AND
WILL REACH KOROR TONIGHT. THIS FEATURE IS GOING TO MAINTAIN PARTLY
CLOUDY SKIES ACROSS BOTH LOCATIONS THRU SUNDAY. BY SUNDAY EVENING...
THE COMBINATION OF MODEST CONVERGENT MONSOONAL WINDS AND INCREASING
MID TO UPPER-LEVEL MOISTURE IS EXPECTED TO INTRODUCE A WETTER
REGIME.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...HIGH SURF ADVISORY UNTIL 6 PM CHST THIS EVENING FOR GUZ001>004.

MARIANAS WATERS...NONE.
&&

$$

ZIOBRO/CHAN



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