888
FXPQ50 PGUM 061933
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
533 AM CHST TUE APR 7 2026
MARIANAS UPDATE
WIDELY SCATTERED SHOWERS THIS MORNING, PRETTY MUCH AS FORECAST, SO
HARDLY ANY CHANGES WERE MADE. PLEASE CHECK THE TROPICAL SYSTEMS
SECTION FOR SOME UPDATED INFORMATION THAT WILL AFFECT NEXT WEEK'S
WEATHER THOUGH.
TROPICAL SYSTEMS
THE CENTER OF INVEST AREA 90W IS NEAR 4N AND 160E. 90W IS NOW A
SLOWLY CONSOLIDATING TROPICAL DISTURBANCE WITH LOW WIND SHEAR AND
WARM SEA SURFACE TEMPERATURES, GOOD MOISTURE, ETC. THE MODELS ARE
SNAPPING INTO EXCELLENT AGREEMENT, AND TAKE 90W TO THE WEST-NORTHWEST
ANYWHERE FROM THE ROTA CHANNEL TO A LITTLE WAYS SOUTH OF GUAM. ECMWF,
GFS, GEFS, CMCE, NAVGEM, AND ICON ARE ALL POINTING TOWARD THIS
GENERAL SOLUTION. 24 HOUR PRESSURE FALLS AT POHNPEI ARE ONLY 0.5 MB,
AND THE PRESSURE FALLS AT GUAM ARE 1.2 MB, BUT THE SAME 24 HOUR
PRESSURE FALLS AT CHUUK ARE 3.0 MB!
EASTERN MICRONESIA UPDATE
HARDLY ANY CHANGES WERE MADE TO EASTERN MICRONESIA. IT WAS FORECAST
TO BE RATHER WET, AND IT IS. A NEWER ALTIMETRY PASS SHOWED THAT THE
10 FOOT SEAS WEREN'T DOWN TO POHNPEI YET, SO A SMALL CRAFT ADVISORY
IS NOT NEEDED AT THIS TIME. WE WILL HAVE TO KEEP AN EYE ON THAT
THOUGH, AS THEY ARE KIND OF CLOSE.
WESTERN MICRONESIA UPDATE
A MINOR TWEAK TO WESTERN MICRONESIA. REDUCED THE SHOWERS AT YAP TO
ISOLATED, LEFT THE SKIES PARTLY SUNNY THOUGH. ALTHOUGH CHUUK DOESN'T
LOOK NUMEROUS RIGHT NOW, WITH THAT 24 HOUR PRESSURE FALL, I EXPECT
SHOWERS TO FILL IN THERE, SO LEFT THAT IN PLACE.
PREV DISCUSSION
/ISSUED 825 PM CHST MON APR 6 2026/
MARIANAS SYNOPSIS...
A DRY TRADE-WIND PATTERN CONTINUE ACROSS MARIANAS THIS EVENING AS A
TRADE-WIND SURGE WEAKENS NEAR THE MARIANAS BUT CONTINUES NORTH OF
POHNPEI AND KOSRAE SATELLITE AND RADAR IMAGERY SHOWING SPOTTY
SHOWERS MOVING THROUGH THE FLOW THIS EVENING, BUT JUST EAST OF 150E,
A SUBTLE TRADE-WIND TROUGH IS DRIFTING WESTWARD AND EXPECTED TO MOVE
THROUGH THE MARIANAS TUESDAY. BUOY DATA AROUND GUAM AND SAIPAN ARE
REPORTING SEAS AROUND BETWEEN 6 AND 8 FEET, WHILE ALTIMETRY AND
DRIFTING BUOYS SHOWING SEAS AROUND 8 TO 10 FEET EAST OF THE
MARIANAS.
DISCUSSION...
THIS TRADE-WIND PATTERN IS EXPECTED THROUGH AT LEAST THE MIDDLE OF
THE WEEK, THOUGH THE SUBTLE TROUGH JUST EAST OF 150E IS EXPECTED TO
MOVE THROUGH THE MARIANAS TUESDAY, AND HI-RES AND GLOBAL MODELS
SUPPORT SOME SCATTERED SHOWERS MOVING INTO THE MARIANAS WITH THE
TROUGH AND POTENTIALLY LINGERING INTO TUESDAY NIGHT. THE TRADE-WIND
SURGE IS WEAKENING NEAR THE MARIANAS BUT REMAINS A NOTABLE FEATURE
NORTH OF POHNPEI AND KOSRAE CREATED BY THE PRESSURE GRADIENT BETWEEN
AN AREA OF HIGH PRESSURE SHIFTING EASTWARD ACROSS THE NORTHERN
PACIFIC AND THE NEAR-EQUATORIAL TROUGH (NET) WITH THE EMBEDDED
CIRCULATION NEAR POHNPEI (INVEST 90W). WINDS ARE EXPECTED TO BE
AROUND 15 TO 20 MPH ACROSS THE MARIANAS THROUGH THURSDAY. A BROAD
CIRCULATION, BEING MONITORED AS INVEST 90W, IS CURRENTLY NEAR POHNPEI
AND MODELS SUPPORT A GRADUAL DEVELOPMENT AS IT MOVES NORTHWEST. THERE
IS STILL A LARGE AMOUNT OF UNCERTAINTY IF INVEST 90W WILL HEAD
DIRECTLY TOWARDS THE MARIANAS OR IF THERE WILL BE A MORE NORTHEAST OR
SOUTHERN TRACK OVERALL. FOR NOW, WE ARE WATCHING THE POTENTIAL FOR
SHOWERS, THUNDERSTORMS, AND GUSTY WINDS AROUND THE MARIANAS, WITH
CURRENT TIMING BEING SOMETIME BETWEEN FRIDAY AND EARLY NEXT WEEK,
BASED ON CURRENT GUIDANCE. THIS FORECAST WILL BE CLOSE MONITORED AND
UPDATED AS IT BECOMES MORE CLEAR HOW INVEST 90W WILL DEVELOP IN
EASTERN MICRONESIA.
MARINE...
THE TRADE-WIND SURGE NEAR THE MARIANAS IS WEAKENING ALLOWING
SUSTAINED WINDS TO DROP BELOW 22 KT, THOUGH STRONG TO NEAR GALE
GUSTS ARE STILL POSSIBLE TONIGHT. HOWEVER, THE EASTERLY TRADE
SWELL, WIND WAVES, AND SLOWLY DECREASING SECONDARY NORTH SWELL
WILL KEEP SEAS AROUND 10 FEET THROUGH TUESDAY, KEEPING THE SMALL
CRAFT ADVISORY IN EFFECT THROUGH TUESDAY. SEAS ARE EXPECTED TO
SUBSIDE TO AROUND 7 TO 9 FEET TUESDAY NIGHT THROUGH THURSDAY.
BEYOND THURSDAY, A CIRCULATION CURRENTLY NEAR POHNPEI, INVEST 90W,
IS EXPECTED TO GRADUALLY DEVELOP AS IT MOVES NORTHWEST LATER IN
THE WEEK AND INTO THE WEEKEND. THOUGH THE EVENTUAL TRACK IS
UNCERTAIN, THIS COULD CAUSE WINDS AND SEAS TO REBUILD FRIDAY AND
INTO THE WEEKEND, BRINGING CONDITIONS BACK TO HAZARDOUS LEVELS TO
SMALL CRAFT.
TROPICAL SYSTEMS...
THE JOINT TYPHOON WARNING CENTER (JTWC) AND NATIONAL WEATHER SERVICE
ARE MONITORING INVEST 90W, A BROAD CIRCULATION WITHIN THE NEAR-
EQUATORIAL TROUGH (NET), NEAR 4.7N 157.7E AND SOUTH-SOUTHWEST OF
POHNPEI. THIS IS HELPING TO GENERATE A BAND OF NUMEROUS, LOCALLY
HEAVY SHOWERS AND ISOLATED THUNDERSTORMS ACROSS POHNPEI AND EXTENDING
EASTWARD TO KOSRAE. GUSTY WINDS ARE POSSIBLE IN THIS CONVECTION,
ESPECIALLY AS A TRADE- WIND SURGE EXTENDS ACROSS THE REGION NEAR AND
TO NORTH OF THE MAIN ISLANDS OF CHUUK, POHNPEI, AND KOSRAE INTO THE
MARSHALL ISLANDS. INVEST 90W IS EXPECTED TO SHIFT NORTHWEST OVER THE
NEXT FEW DAYS. DEVELOPMENT OF INVEST 90W IS CURRENTLY EXPECTED TO BE
GRADUAL, WITH DEVELOPMENT INTO A SIGNIFICANT CYCLONE (TROPICAL
DEPRESSION) UNLIKELY OVER THE NEXT COUPLE OF DAYS, SO JTWC HAS INVEST
90W RATED AS "SUB-LOW" FOR DEVELOPMENT AS OF THIS DISCUSSION, AND
WILL CONTINUE TO EVALUATE THE POTENTIAL FOR DEVELOP OVERNIGHT. THIS
WILL LIFT THE BAND OF LOCALLY HEAVY SHOWERS AND THUNDERSTORMS
NORTHWESTWARD, BUT KEEP A UNSETTLED WEATHER PATTERN, WITH THE
POTENTIAL FOR HEAVY RAINFALL AND GUSTY WINDS, ACROSS CHUUK, POHNPEI,
KOSRAE, AND TO A LESSER EXTENT MAJURO, OVER THE NEXT FEW DAYS. MODELS
GUIDANCE DO GENERALLY AGREE THAT INVEST 90W MAY EVENTUALLY DEVELOP
INTO A TROPICAL CYCLONE AS IT LIFTS NORTHWEST, BUT THE EVENTUAL PATH
IS MORE UNCERTAIN, ESPECIALLY FOR THE MARIANAS. FOR NOW CONTINUE TO
MONITOR THE LATEST FORECAST INFORMATION AS INVEST 90W EVOLVES.
EASTERN MICRONESIA...
THE MUCH-TALKED ABOUT DISTURBANCE THAT WE EXPECTED TO BECOME AN
INVEST HAS FORMED. CURRENTLY, IT'S RATED AS "SUB-LOW", BUT, GIVEN
SATELLITE TRENDS AND AFTER COORDINATING WITH THE JOINT TYPHOON
WARNING CENTER (JTWC), AN UPGRADE FROM "SUB-LOW" TO "LOW" IS PROBABLE
TONIGHT. THE MAIN DIFFERENCE IS WITH "SUB-LOW" WE HAVE A BROAD
CIRCULATION THAT WE'RE WATCHING. WHEN JTWC ISSUES A "LOW" RATING, IT
MEANS TROPICAL CYCLONE DEVELOPMENT IS UNLIKELY DURING THE NEXT 24
HOURS. HOWEVER, IT IS A "STEP UP" IN CONFIDENCE THAT SOMETHING MAY
FORM. AS FOR IT'S CURRENT LOCATION, VISIBLE IMAGERY SUGGESTS THE
DEVELOPING LLCC (LOW-LEVEL CIRCULATION CENTER) IS NEAR 5N158E, TO THE
SOUTH-SOUTHWEST OF POHNPEI.
THE MAIN IMPACT FOR ALL OF THE REGION WAS INCREASED RAINFALL
POTENTIAL, AND THIS WAS REFLECTED IN THE FORECAST. THE BEST CHANCE OF
SEEING THIS IS AT POHNPEI AND KOSRAE, WHERE CATEGORICAL (80 PERCENT
POTENTIAL AND ABOVE) POPS (PROBABILITY OF PRECIPITATION) WERE
INSERTED FOR THE NEXT 24 TO 36 HOURS, TRAILING OFF TO JUST TONIGHT AT
MAJURO, AS YOU'RE AT THE TAIL END OF THE MOISTURE CONVERGENCE
ASSOCIATED WITH INVEST 90W. ADDITIONALLY, LOCALLY HEAVY RAINFALL
WORDING WAS USED FOR POHNPEI AND KOSRAE, WITH WIND GUSTS TO 30 KNOTS
ALSO ADDED AT POHNPEI, DUE TO CLOSE PROXIMITY TO THE SYSTEM.
CONVECTION HAS DEFINITELY INCREASED IN COVERAGE AND STRENGTH, WITH
CLOUD TOP TEMPERATURES EAST OF POHNPEI (WHERE CONVECTION IS
STRONGEST) HAVING OCCASIONALLY TOPPED -90 DEG. C., INDICATING CLOUD
TOPS PROBABLY EXCEEDING 55,000 FEET TALL. FOR THE LATTER HALF OF THE
WEEK, RAINFALL POTENTIAL WILL DECREASE FROM EAST TO WEST.
FOR OUR MARINERS, GENTLE TO FRESH WINDS WILL BECOME LIGHT TO GENTLE
BY THE WEEKEND. SEAS ARE CHOPPY AND CURRENTLY JUST BELOW THE 10 FOOT
THRESHOLD FOR HAZARDOUS CONDITIONS TO SMALL CRAFT OPERATIONS AT
POHNPEI. THESE CONDITIONS ARE EXPECTED TO CONTINUE THROUGH WEDNESDAY,
AS IS HIGH SURF FOR POHNPEI AND KOSRAE, SO PRACTICE CAUTION IF
TRAVELING ACROSS THE WATERS. SEAS AND SURF WILL THEN DIMINISH FOR THE
LATTER HALF OF THE WEEK.
CORRECTED TYPOS
WESTERN MICRONESIA...
THE MAIN TWO FEATURES IN THE REGION CONTINUE TO BE THE NEAR
EQUATORIAL TROUGH (NET) AND THE TRADE-WIND SURGE. THE NET ENTERS THE
REGION NEAR EQ130E AND EXTENDS EASTWARD ACROSS THE SOUTHERN PORTION
OF WESTERN MICRONESIA WHERE IT CONTINUES INTO EASTERN MICRONESIA.
SOUTH OF THE NET AXIS, ISOLATED TO SCATTERED SHOWERS ARE SEEN ON
SATELLITE IMAGERY.
FOR PALAU AND YAP, A DRY TRADE-WIND PATTERN REMAINS OVER THE REGION.
ISOLATED SHOWERS ARE ANTICIPATED TO REMAIN THROUGH THE WEEK. WINDS
ARE EXPECTED TO BE AROUND 10 TO 15 KNOTS AROUND PALAU, THEN THESE
WINDS ARE ANTICIPATED TO BEGIN TO FALL TO 5 TO 10 KTS AROUND
TUESDAY. WINDS AROUND YAP ARE EXPECTED TO DIMINISH TO 5 TO 15 KTS
THROUGH THURSDAY, AND CONTINUE TO FALL FRIDAY.
FOR CHUUK, AN UNSETTLED WEATHER PATTERN IS IN STORE FOR THE AREA.
INVEST 90W IS LOCATED SOUTH OF POHNPEI, AND IS PRODUCING SHOWERS TO
THE EAST OF CHUUK. THESE SHOWERS ARE EXPECTED TO MOVE INTO CHUUK'S
REGION TONIGHT. ALSO, THESE SHOWERS ARE EXPECTED BUILD FROM TODAY'S
SCATTERED TO WIDESPREAD AS EARLY AS TUESDAY NIGHT. THESE SHOWERS ARE
ANTICIPATED TO REMAIN WHILE INVEST 90W REMAINS NEAR BY. DURING THIS
TIME, SHOWERS MAY BE HEAVY AT TIMES, WITH RAIN RATES IN THE 2 TO 4
INCHES FOR A 24 HOUR PERIOD ON OUR MOST AGGRESSIVE MODELS. AROUND THE
MIDDLE OF THE WEEK, SHOWERS ARE ANTICIPATED TO DIMINISH AS INVEST
90W MOVES TO THE NORTHWEST AND THE OUTER BANDS TAKE OVER AS THE
WEATHER MAKER FOR THE REGION. THESE SHOWERS ARE ANTICIPATED TO BE
SCATTERED AS THEY ARE FORMED ALONG THE WESTERLY INFLOW OF INVEST 90W.
NEAR THE END OF THE WEEK, CHUUK MAY RETURN TO A DRIER PATTERN.
COMBINED SEAS VARY OVER THE REGION WITH THE LOWEST IN THE WEST AND
THE HIGHEST IN THE EAST. SEAS OVER THE REGION ARE BETWEEN 2 TO 4 FEET
TO THE WEST OF PALAU, SEAS NEAR YAP ARE 4 TO 6 FEET AND BUILD TO 8
TO 11 FEET NEAR CHUUK. AT CHUUK, A SMALL CRAFT ADVISORY (SCA) AND A
HIGH SURF ADVISORY (HSA) ALONG NORTH FACING REEFS ARE IN EFFECT.
SEAS FOR CHUUK ARE EXPECTED TO CREST AROUND TUESDAY. THE SEAS AND
SURF WILL TAKE SOME TIME TO FALL BELOW THE 10 FOOT (FOR SEAS) AND 9
FOOT (FOR SURF) THRESHOLDS. CURRENT ESTIMATIONS ARE FOR WEDNESDAY
MORNING, HOWEVER, SEAS AND SURF MAY REMAIN ELEVATED FOR A BIT LONGER.
SEAS ARE EXPECTED TO CONTINUE TO SUBSIDE FOR THE REMAINDER OF THE
WEEK.
GUM WATCHES/WARNINGS/ADVISORIES
GU...HIGH RIP CURRENT RISK THROUGH WEDNESDAY AFTERNOON FOR GUZ001.
MP...HIGH RIP CURRENT RISK THROUGH WEDNESDAY AFTERNOON FOR
MPZ001>003.
MARIANAS WATERS...SMALL CRAFT ADVISORY UNTIL 5 PM CHST THIS
AFTERNOON FOR PMZ151>154.
MARIANAS/EAST AND WEST MICRONESIA/TROPICAL UPDATE: STANKO
MARIANAS/TROPICAL: SCHANK
EAST MICRONESIA: DOLL
WEST MICRONESIA: BOWSHER
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