Area Forecast Discussion
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558
FXPQ60 PGUM 102047
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
647 AM CHST THU FEB 11 2016

.SYNOPSIS...
A SHEAR LINE PASSES THROUGH THE MARIANAS NEAR ANATAHAN. THIS
BOUNDARY HAS BEEN WEAKENING DURING THE OVERNIGHT HOURS IN FAVOR OF
A SECONDARY BOUNDARY THAT IS BECOMING BETTER DEFINED. THIS
BOUNDARY CROSSES THE MARIANAS IN THE VICINITY OF PAGAN. AN
ELONGATED TRADE-WIND DISTURBANCE HAS CONSOLIDATED FROM BETWEEN
GUAM AND YAP TO EAST OF SAIPAN NEAR 153E. THE NORTHERN EDGE OF
THIS DISTURBANCE IS BRINGING CLOUDINESS AND ISOLATED SHOWERS TO
THE GUAM AND ROTA ZONES.

&&

.DISCUSSION...
FORECAST CONTINUES TO FOLLOW THE SAME NARRATIVE...EXCEPT FOR ONE
SHORT TERM FORECAST ADJUSTMENT TO INCREASE CLOUD COVER FOR THE
GUAM AND ROTA ZONES TODAY AS THE NORTHERN EDGE OF THE TRADE-WIND
DISTURBANCE SLIDES BY. DRY AIR COMING IN FROM THE NORTHEAST
APPEARS TO BE ERODING THE NORTHERN SIDE OF THE DISTURBANCE...
KEEPING SKIES OVER THE SAIPAN AND TINIAN ZONES CLEARER.
OTHERWISE...STILL EXPECT THE SHEAR LINE TO ARRIVE OVER SAIPAN
THIS EVENING AND EVENTUALLY PASS SOUTH OF GUAM FRIDAY NIGHT. VERY
DRY AIR BEHIND THE SHEAR LINE WILL MOVE IN FOR THE FIRST HALF OF
NEXT WEEK.

&&

.MARINE...
VAD WIND PROFILE SHOWS GRADIENT WINDS HAVE INCREASED ABOUT 5 KT
DURING THE PAST DAY OR SO TO 25 KT. THIS TREND SHOULD CONTINUE FOR
THE NEXT COUPLE OF DAYS. A SMALL CRAFT ADVISORY WILL LIKELY BE
NEEDED TONIGHT...AND HIGH SURF WILL BE A DISTINCT POSSIBILITY BY
FRIDAY NIGHT. BOTH ADVISORIES SHOULD WIND DOWN BY TUESDAY EVENING.

&&

.FIRE WEATHER...
THE PASSING TRADE-WIND DISTURBANCE IS ONLY PRODUCING ISOLATED
LIGHT SHOWERS AT PRESENT...BUT ASSOCIATED CLOUD COVER AND
INCREASED DEW POINTS MAY BE ENOUGH TO KEEP MINIMUM DAYTIME
RELATIVE HUMIDITIES ABOVE 60 PERCENT. THIS WOULD REDUCE THE FIRE
DANGER FOR TODAY. RED FLAG WARNING CONDITIONS APPEAR TO BE A
BETTER BET FOR TOMORROW...AFTER THE TRADE-WIND DISTURBANCE HAS
DEPARTED AND SKIES ARE STILL RELATIVELY CLEAR AHEAD OF THE SHEAR
LINE.

&&

.EASTERN MICRONESIA...
DRY TRADE WEATHER IS EXPECTED TO CONTINUE ACROSS CHUUK AND
POHNPEI THRU FRIDAY NIGHT...AND NEAR KOSRAE UNTIL FRIDAY EVENING.
THERE WILL BE SOME CLOUDS AND A FEW SHOWERS NEAR MAJURO TODAY AND
TONIGHT AS A WEAK TRADE DISTURBANCE PASSES THRU. AFTER ITS
PASSAGE...FAIR CONDITIONS WILL RETURN FRIDAY. THIS SAME SYSTEM
MIGHT ALSO BRING SIMILAR WEATHER TO KOSRAE BY FRIDAY NIGHT...AND
TO POHNPEI AND CHUUK AROUND SATURDAY. THE SHEAR LINE OVER THE
PHILIPPINE SEA AND NORTHERN MARIANA ISLANDS HAS SLOWED DOWN ITS
SOUTHEASTWARD PROGRESSION. CURRENT MOVEMENT CARRIES THE SHEAR LINE
TO NEAR 11N JUST NORTH OF THE REGION BY SUNDAY. LATEST ASCAT
SATELLITE IMAGERY REVEALS A MORE ROBUST TRADE DISTURBANCE UPSTREAM
EAST OF THE DATE LINE NEAR 170W. IF THIS DISTURBANCE INTERACTS
WITH THE SHEAR LINE...THERE WILL BE A GREATER CHANCE OF SHOWERS
AND THUNDERSTORMS ACROSS ALL THE LOCATIONS EARLY NEXT WEEK.

TRADE WINDS HAVE DECREASED TO BETWEEN MODERATE AND FRESH FROM
CHUUK STATE EASTWARD TO THE MARSHALL ISLANDS. AS A RESULT...TRADE-
WIND WAVES AND SWELL HAVE SUBSIDED EVEN LOWER WHICH HAS ALLOWED
SURF ON KOSRAE TO FALL BELOW HAZARDOUS LEVELS THIS MORNING. FRESH
TO STRONG WINDS ASSOCIATED WITH THE SHEAR LINE WILL BEGIN TO
AFFECT THE REGION LATE FRIDAY EVENING. WIND WAVES AND SWELL
PRODUCED BY THESE WINDS WILL CAUSE SURF AND SEAS TO BUILD THIS
WEEKEND...AND MIGHT REACH HAZARDOUS LEVELS.

&&

.WESTERN MICRONESIA...
DISCUSSION FOR THE CHUUK FORECAST IS INCLUDED WITH EASTERN
MICRONESIA AS THE PATTERN IS SIMILAR TO THAT FOR POHNPEI.

CLOUD COVER WILL THIN TO PARTLY CLOUDY NEAR KOROR BY NOON TODAY
AS A WEAK SURFACE TROUGH DEPARTS THE AREA. OTHERWISE...DRY
MODERATE TO OCCASIONALLY FRESH TRADES ARE ANTICIPATED FOR BOTH
KOROR AND YAP THRU TONIGHT. A TRADE DISTURBANCE CURRENTLY MOVING
OVER GUAM SHOULD APPROACH YAP ON FRIDAY AND KOROR BY FRIDAY NIGHT.
THIS COINCIDES WITH THE ARRIVAL OF THE SHEAR LINE FROM THE NORTH
NEAR 11N. IF THE SHEAR LINE REMAINS INTACT NEAR KOROR AND YAP...
INCREASING LOW-LEVEL FORCING CAUSED BY THE DISTURBANCE COULD
ENHANCE SHOWER ACTIVITY THIS WEEKEND.

NORTH-NORTHEAST SWELL GENERATED BY FRESH WINDS NORTH OF THE SHEAR
LINE HAVE REACHED THE REPUBLIC OF PALAU AND YAP STATE. HOWEVER...
WAVE WATCH MODEL GUIDANCE AND ALTIMETRY INDICATE THE SWELL ARE NOT
HIGH ENOUGH TO PRODUCE HAZARDOUS SURF. HOWEVER AS SWELL ARRIVAL
DIRECTION SHIFTS TO THE NORTHEAST AND WAVES BUILD HIGHER THIS
WEEKEND...SURF COULD STILL RISE TO HAZARDOUS LEVELS. TOGETHER WITH
HIGHER WIND WAVES...SEAS NEAR KOROR AND YAP MIGHT ALSO BECOME
HAZARDOUS FOR SMALL CRAFT.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...FIRE WEATHER WATCH THROUGH SATURDAY AFTERNOON FOR GUZ001.

MARIANAS WATERS...NONE.
&&

$$

MCELROY/CHAN



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