711
FXPQ50 PGUM 210716
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
516 PM CHST FRI FEB 21 2025
MARIANAS SYNOPSIS
LATEST SATELLITE IMAGERY IS SHOWING PARTLY CLOUDY SKIES AND SPOTTY
LIGHT SHOWERS OVER GUAM AND ROTA, WITH MOSTLY CLOUDY SKIES AND
ISOLATED TO LOW-END SCATTERED SHOWERS OVER TINIAN AND SAIPAN.
LOCAL BUOYS AND LATEST ALTIMETRY DATA ARE INDICATING SEAS OF 8 TO 10
FEET ACROSS THE COASTAL WATERS. WINDS ARE MODERATE TO FRESH WITH
STRONG GUSTS.
DISCUSSION
THE WEAKENING BOUNDARY THAT DROPPED SOUTH INTO SAIPAN AND TINIAN
TODAY CONTINUES TO WASH OUT WITH SHOWERS DIMINISHING. CONVERGENT FLOW
ALONG A SHEAR LINE SOUTHEAST OF THE MARIANAS WILL DRIFT NORTHWEST
INTO GUAM AND ROTA AND BRING SCATTERED SHOWERS LATE TONIGHT INTO THE
WEEKEND, BUT LIKELY STAYING SOUTH OF TINIAN AND SAIPAN. FOR NEXT
WEEK, MAINLY ISOLATED SHOWERS EXPECTED WITH BRIEF PERIODS OF LOW-END
SCATTERED SHOWERS POSSIBLE WITH PASSING TRADE DISTURBANCES. GUSTY
WINDS ARE EXPECTED OVER THE COMING DAYS. THIS, ALONG WITH THE DRY
CONDITIONS, WILL RESULT IN FIRE WEATHER CONCERNS AND A FIRE WEATHER
WATCH IS IN EFFECT THROUGH SUNDAY AFTERNOON. MORE INFORMATION CAN BE
FOUND BELOW IN THE FIRE WEATHER SECTION.
MARINE/SURF
WINDS AND SEAS ARE EXPECTED TO BE HAZARDOUS TO SMALL CRAFT THROUGH
THE WEEKEND AND LIKELY INTO NEXT WEEK. FRESH WINDS WITH STRONG TO
NEAR-GALE GUSTS WITH A STRONG SUBTROPICAL RIDGE TO THE NORTH AND
MULTIPLE SHEAR LINES PASSING THROUGH THE MARIANAS. COMBINED SEAS WILL
BE 8 TO 10 FT AS A LARGER NORTHERLY SWELL, TRADE SWELL AND WIND
WAVES IMPACT THE REGION. WINDS AND SEAS ARE EXPECTED TO INCREASE
FURTHER EARLY NEXT WEEK.
THE NORTH SWELL HAS COME IN A BIT LARGER AND A HIGH SURF AND HIGH
RISK OF RIP CURRENTS CONTINUES THROUGH SATURDAY NIGHT. A MODERATE
RISK OF RIP CURRENTS IS ALSO EXPECTED FOR WEST AND EAST FACING REEFS.
AS THE NORTHERLY SWELL SUBSIDES ON SUNDAY, THE EAST-NORTHEAST TRADE
SWELL IS EXPECTED TO INCREASE. THE RIP RISK IS EXPECTED TO BECOME
HIGH FOR EAST FACING REEFS. IN ADDITION, THE SURF AND RIP RISK COULD
STAY HIGH FOR NORTH FACING REEFS.
FIRE WEATHER
A FEW SHOWERS BROUGHT 0.02 INCHES OF RAIN YESTERDAY, WHICH
ALLOWED FOR THE KBDI TO RISE TO 651. WINDS WILL BE QUITE GUSTY
THROUGH THE WEEKEND. HOWEVER, A MOISTENING TREND WITH HIGH RELATIVE
HUMIDITY VALUES AND AN INCREASED POTENTIAL FOR SHOWERS IS EXPECTED
THROUGH THE WEEKEND, WHICH COULD RESULT IN REDUCED FIRE DANGER
THREAT. THE RED FLAG WARNING HAS BEEN ALLOWED TO EXPIRE, HOWEVER, THE
FIRE WEATHER WATCH IS STILL IN EFFECT FROM THIS EVENING THROUGH
SUNDAY AFTERNOON.
EASTERN MICRONESIA
EASTERN MICRONESIA IS NOW LOOKING A BIT DRIER THAN PREVIOUS
FORECASTS. LATEST SATELLITE IMAGERY SHOWS ONLY SPOTTY SHOWERS ACROSS
THE REGION NORTH OF 5N, WITH LOW-END SCATTERED SHOWERS SEEN TO THE
EAST OF KOSRAE, SOUTH OF 5N. A WEAK TROUGH ALONG WITH A BAND OF
TRADE-WIND CONVERGENCE LOOKS TO MOVE INTO KOSRAE ON SATURDAY,
BRINGING LOW-END SCATTERED SHOWERS TO THE ISLAND SATURDAY AND
SATURDAY NIGHT. OTHERWISE, EASTERN MICRONESIA CAN EXPECT A DRY TRADE-
WIND PATTERN WITH LITTLE RAINFALL OVER THE NEXT SEVERAL DAYS.
MEANWHILE, CHANGES ARE IN STORE FOR THE MARINE ENVIRONMENT. LATEST
ALTIMETRY DATA, ALONG WITH THE POHNPEI BUOY, SHOWS SEAS OF 5 TO 6
FEET. FARTHER NORTHWEST, HIGH WINDS BEHIND A STRONG LOW PRESSURE
SYSTEM ARE GENERATING AN INCREASING LONG-PERIOD NORTHERLY SWELL THAT
IS EXPECTED TO MOVE INTO EASTERN MICRONESIA OVER THE WEEKEND. ALONG
WITH THE INCREASING NORTHERLY SWELL, HIGH PRESSURE MOVING EASTWARD
FROM JAPAN WILL SPREAD A TRADE-WIND SURGE ACROSS THE REGION. THIS
WILL BRING FRESH WINDS WITH STRONG GUSTS AND AN INCREASING TRADE
SWELL TO THE REGION. THESE FACTORS LOOK TO COMBINED TO BRING SMALL
CRAFT ADVISORY LEVEL SEAS AND WIND TO THE ISLANDS. A SMALL CRAFT
ADVISORY MAY BE ISSUED, STARTING AS EARLY AS SATURDAY NIGHT.
WESTERN MICRONESIA
SATELLITE IMAGERY SHOWS SHOWERS HAVE REMAIN SPOTTY ACROSS CHUUK
STATE AS A DRY TRADE-WIND PATTERN CONTINUES TO BE THE MAIN WEATHER
PATTERN ACROSS CHUUK. OVER BY YAP AND PALAU, THE TRADE-WIND SURGE
DISCUSSED YESTERDAY IS NOT AS IMPRESSIVE TODAY AS THE AREA OF HIGH
PRESSURE PRODUCING THE PRESSURE GRADIENT AND STRONGER WINDS IS MOVING
EASTWARD AND STARTING TO MOVE FURTHER AWAY FROM YAP AND PALAU.
SATELLITE SCATTEROMETER DATA STILL SHOWS SMALLER POCKETS OF 20 TO 25
KTS WINDS MAINLY NEAR YAP AND NORTH OF PALAU AND ALONG THE SHEAR LINE
FRAGMENT EAST OF YAP AND JUST SOUTH OF THE MARIANAS. CONVERGENCE
ALONG THE SHEAR LINE FRAGMENT AND WEAKENING TRADE-WIND SURGE IS
CREATING MOSTLY CLOUDY SKIES OVER YAP AND PALAU, WITH SOME SCATTERED
SHOWERS STARTING TO MOVE INTO PALAU THIS EVENING. THERE HAS BEEN SOME
SHORT-LIVED THUNDERSTORMS RECORDED BY THE GLOBAL LIGHTNING DETECTION
(GLD) NETWORK WELL EAST OF PALAU AND SOUTH OF YAP, SO ADDED A SLIGHT
CHANCE OF THUNDESTORMS TO THE COASTAL WATERS FORECAST OF PALAU FOR
TONIGHT TO HIGHLIGHT THAT THERE IS A SLIM CHANCE THAT A THUNDERSTORM
COULD DEVELOP NEAR PALAU. AS THE AREA OF STRONGER WINDS CONTINUES TO
MOVE EASTWARD, WINDS ARE EXPECTED TO DECREASE SLIGHTLY AT YAP AND
PALAU THROUGH SUNDAY, WHILE BECOMING BREEZY AT CHUUK AROUND SUNDAY.
DUE TO THE LIMITED MOISTURE ACROSS THE REGION, A FAIRLY DRY TRADE-
WIND PATTERN IS EXPECTED TO CONTINUE ACROSS THE REGION THROUGH THE
WEEKEND AND INTO NEXT WEEK, WITH SHOWERS LIMITED TO ALONG THE SHEAR
LINE FRAGMENT NEAR THE MARIANAS AND ANY TRADE-WIND TROUGHS MOVING
THROUGH THE REGION. A SIMILAR INCREASE IN WINDS NEAR YAP AND PALAU IS
LOOKING MORE LIKELY FOR NEXT WEEK AS A COLD FRONT/SHEAR LINE DROPS
SOUTH TOWARDS THE MARIANAS AND WINDS INCREASE AHEAD OF THE FRONTAL
SYSTEM AS ANOTHER AREA OF HIGH PRESSURE PUSHES OFF OF MAINLAND ASIA.
ALTIMETRY SHOWS SEAS HAVE INCREASED SLIGHTLY TO AROUND 5 TO 6 FEET
AT CHUUK THIS EVENING, WHILE THE BUOY NEAR PALAU IS REPORTING SEAS
BETWEEN 7 AND 9 FEET. ALTIMETRY SHOWS SEAS ARE STILL AROUND 7 TO 10
FEET AT YAP, PRIMARILY DRIVEN BY THE POCKETS OF STRONGER WINDS AROUND
20 TO 25 KNOTS SEEN AROUND YAP AND NORTH OF PALAU ON SCATTEROMETER
DATA, SO THE SMALL CRAFT ADVISORY (SCA) FOR YAP REMAINS IN EFFECT
THROUGH EARLY SATURDAY MORNING. AS THE WEAKENING TRADE-WIND SURGE
CONTINUES EASTWARD, SEAS WILL BUILD AT CHUUK TO AROUND 8 FEET LATER
THIS WEEKEND, BUT THE HIGHEST SEAS AND STRONGEST WINDS ARE EXPECTED
TO BE AROUND OR NORTH OF 10N, SO STILL NOT EXPECTING HAZARDOUS MARINE
CONDITIONS AT THIS TIME. WINDS AROUND YAP AND PALAU SHOULD RELAX
SATURDAY AND SUNDAY ALLOWING SEAS TO DROP 1 TO 2 FEET, AND ALLOWING
THE SCA TO END AT YAP SATURDAY MORNING. PALAU'S BUOY SHOWS MOST OF
THE NORTH TO NORTHEAST SWELLS ARE SHORT PERIOD (LESS THAN 10 SECONDS)
OR A MIX OF SWELL AND WIND WAVES, SO SURF WILL BE ELEVATED ALONG
NORTH AND EAST FACING REEFS, BUT SHOULD REMAIN BELOW HIGH SURF
CRITERIA OF 12 FEET ALONG EAST REEFS AND 9 FEET ALONG NORTH REEFS
THROUGH THE WEEKEND. A SIMILAR PATTERN TO THE LAST COUPLE OF DAYS
LOOKS TO DEVELOP AGAIN EARLY NEXT WEEK AS A COLD FRONT/SHEAR LINE
DROPS SOUTH TOWARDS THE MARIANAS AND WINDS INCREASE AHEAD OF THE
FRONTAL SYSTEM AS ANOTHER AREA OF HIGH PRESSURE PUSHES OFF OF
MAINLAND ASIA. THIS MAY CAUSE MARINE CONDITIONS TO BECOME HAZARDOUS
AT YAP AND EVEN PALAU AROUND MONDAY OR TUESDAY AS WINDS INCREASE UP
TO AROUND 22 KNOTS AND SEAS BUILD BACK UP TO AROUND 10 FEET. THIS
COULD SPREAD TO CHUUK LATER IN THE WEEK, SO CONTINUE TO MONITOR THE
FORECAST TO SEE HOW THIS PATTERN EVOLVES.
GUM WATCHES/WARNINGS/ADVISORIES
GU...HIGH RIP CURRENT RISK THROUGH SUNDAY NIGHT FOR GUZ001.
HIGH SURF ADVISORY UNTIL 5 AM CHST MONDAY FOR GUZ001.
FIRE WEATHER WATCH FROM 6 PM CHST THIS EVENING THROUGH SUNDAY
AFTERNOON FOR GUZ001.
MP...HIGH RIP CURRENT RISK THROUGH SUNDAY NIGHT FOR MPZ001>003.
HIGH SURF ADVISORY UNTIL 5 AM CHST MONDAY FOR MPZ001>003.
MARIANAS WATERS...SMALL CRAFT ADVISORY UNTIL 5 AM CHST MONDAY FOR
PMZ151>154.
MARIANAS: SLAGLE
EAST MICRONESIA: KLEESCHULTE
WEST MICRONESIA: SCHANK
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