732
FXHW60 PHFO 091350
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
350 AM HST WED SEP 9 2026
SYNOPSIS
LIGHT AND VARIABLE FLOW WILL PERSIST ACROSS THE ISLANDS THIS
MORNING WITH EAST OR SOUTHEASTERLY WINDS FILLING IN ACROSS BIG
ISLAND AND MAUI COUNTY LATER TODAY. A WEAK BAND OF RESIDUAL
MOISTURE STRETCHING SOUTHEAST FROM TROPICAL STORM LOWELL DOWN TO
BIG ISLAND AND PORTIONS OF MAUI COUNTY MAY BRING A RENEWED THREAT
OF HEAVY SHOWERS, WHILE SEA BREEZES TRIGGER SPOTTY AFTERNOON
SHOWERS ACROSS THE REST OF THE STATE. TRADE WINDS WILL SLOWLY
BUILD OVER THE STATE LATE TONIGHT INTO THURSDAY, BUT CONDITIONS
WILL REMAIN SOMEWHAT WET. DRIER TRADE WIND WEATHER IS EXPECTED TO
DEVELOP THURSDAY NIGHT THROUGH THE WEEKEND.
DISCUSSION
LATEST IR SATELLITE IMAGERY LOOP SHOWS A WEAKENED AND HIGHLY
SHEARED TROPICAL STORM LOWELL DRIFTING NORTHWARD, BEYOND OUR
OFFSHORE WATERS, SEVERAL HUNDRED MILES NORTH NORTHWEST OF KAUAI. A
BAND, OR RIBBON, OF ENHANCED MOISTURE CAN ALSO BE SEEN EXTENDING
SOUTHEAST FROM LOWELL DOWN THROUGH MAUI AND THE BIG ISLAND. THE
12Z HILO SOUNDING INDICATED A LOWER LEVEL MOISTURE DEPTH OF 13,000
FEET AND A PWAT (PRECIPITABLE WATER) VALUE OF 2.1", SIGNIFICANTLY
HIGHER THAN THE EARLY SEPTEMBER AVERAGE OF 1.4". THIS HEALTHY
MOISTURE PROFILE, ALONG WITH LIGHT TO LOCALLY MODERATE EAST OR
EAST SOUTHEAST FLOW, WILL HELP MAINTAIN SCATTERED SHOWERS THIS
MORNING ALONG WINDWARD AND SOUTHEAST BIG ISLAND AS WELL AS THE
EASTERN SLOPES OF HALEAKALA ON MAUI. ELSEWHERE, A DRIER ATMOSPHERE
CONTINUES TO DOMINATE WITH LIMITED SHOWER COVERAGE. BOTH THE GFS
AND ECMWF SHOW THE RIBBON OF MOISTURE DRAPED OVER THE EASTERN
THIRD OF THE STATE DURING THE AFTERNOON. THIS, COMBINED WITH
DIURNAL HEATING, WILL AID IN MORE ROBUST SHOWER ACTIVITY OVER THE
BIG ISLAND INTERIOR. MODELS INDICATE RATHER MARGINAL INSTABILITY,
BUT STILL ENOUGH FOR A SLIGHT CHANCE OF THUNDERSTORMS. SIMILAR
CONDITIONS ARE EXPECTED OVER HALEAKALA ON MAUI, BUT CONFIDENCE IS
A BIT LOWER. MAUI COUNTY APPEARS TO SIT ON THE LEADING EDGE OF
THIS MOISTURE AS IT SLOWLY DRIFTS EAST TO WEST ACROSS THE STATE.
STILL, A FEW HEAVIER AFTERNOON SHOWERS ARE POSSIBLE, ESPECIALLY
OVER THE SOUTHWEST SLOPES OF HALEAKALA NEAR KULA. THE FLOOD WATCH
WILL REMAIN IN EFFECT THROUGH THIS AFTERNOON BIG ISLAND. HOWEVER,
DIURNALLY DRIVEN SEA BREEZES COULD BRING SHOWERS TO INTERIOR
REGIONS OF THE REMAINING SMALLER ISLANDS.
BY THURSDAY, LIGHT TO MODERATE TRADES WILL RETURN TO THE ENTIRE
STATE. THE DEEPER MOISTURE, NOW CAUGHT UP IN THE TRADES, MAY
BRING AN ENHANCEMENT TO MAINLY WINDWARD SHOWERS ON ALL ISLANDS.
SOME OF THESE SHOWERS MAY OCCASIONALLY PUSH OVER THE TERRAIN AND
ONTO THE LEEWARD SIDES. ONCE AGAIN, DIURNALLY DRIVEN HEAVIER
SHOWERS ARE FORECAST TO DEVELOP OVER BIG ISLAND'S INTERIOR AND
UPPER SLOPES OF MAUNA KEA AND MAUNA LOA DURING THE AFTERNOON.
FRIDAY THROUGH THE WEEKEND, TROUGHING FAR NORTHEAST OF THE STATE
WILL HELP TO EASE TRADES BACK INTO THE LIGHT TO MODERATE RANGE
WITH A MORE TYPICAL TRADE SHOWERS CONCENTRATED ALONG WINDWARD
LOCATIONS IN THE NIGHT TO EARLY MORNING HOURS.
AVIATION
SOUTHERLY FLOW REMAINS OVER THE ISLANDS WITH NOW TROPICAL STORM
LOWELL NORTH OF THE MAIN HAWAIIAN ISLANDS. LOWELL WILL CONTINUE TO
WEAKEN AND MOVE FURTHER AWAY FROM THE ISLANDS. THE SOUTHERLY FLOW
WILL REMAIN IN PLACE FOR MUCH OF TODAY, BUT EXPECT TRADES TO
SLOWLY FILTER BACK IN TONIGHT AND TOMORROW FROM EAST TO WEST.
MOISTURE BEING PULLED NORTH, PARTICULARLY OVER MAUI AND THE BIG
ISLAND IS PRODUCING MOUNTAIN OBSCURATION TO THOSE AREAS. LINGERING
CLOUDS AND SHOWERS OVER KAUAI IS HAVING THE SAME IMPACT THERE. ALL
THESE ISLANDS ARE EXPERIENCED PERIODS OF MVFR CONDITIONS, AND AS
SUCH, AIRMET SIERRA FOR MOUNTAIN OBSCURATION REMAINS IN EFFECT.
SOME IMPROVEMENT IS ANTICIPATED TODAY FOR KAUAI AS A DRIER
AIRMASS TO THE SOUTH AND SOUTHEAST MOVES OVER THE GARDEN ISLE.
SATELLITE DERIVED PRECIPITABLE WATER SUGGESTS THAT THE CLOUDS AND
SHOWERS WILL LIKELY LINGER OVER MAUI AND THE BIG ISLAND.
WITH LIGHT SOUTHERLY WINDS EXPECTED, NOT ANTICIPATING ANY AIRMETS
FOR TURBULENCE TODAY.
MARINE
TROPICAL STORM LOWELL IS TRACKING AWAY FROM THE HAWAIIAN ISLANDS
THIS MORNING. THE FAR NORTHWESTERN OFFSHORE WATERS NOW LIE AT THE
FRINGES OF LOWELL'S TROPICAL STORM-FORCE WIND FIELD, WHICH SHOULD
ALLOW THE TROPICAL STORM WARNING TO BE DROPPED LATER THIS
MORNING. ELSEWHERE, LIGHT AND VARIABLE WINDS WILL GRADUALLY
TRANSITION TO LIGHT TO MODERATE EASTERLY TRADE WINDS THROUGH THE
REMAINDER OF THE WEEK.
SURF ALONG SOUTH FACING SHORES REMAINS CHOPPY, BUT BELOW ADVISORY
CRITERIA, FROM A MIX OF LINGERING SOUTHWEST AND WEST SWELLS FROM
TROPICAL STORM LOWELL THAT WILL CONTINUE FADE TODAY. A MODERATE,
MEDIUM-PERIOD SOUTH SWELL ORIGINATING SOUTHEAST OF NEW ZEALAND WILL
LINGER FOR THE NEXT FEW DAYS, KEEPING SOUTH SHORE SURF HEIGHTS
ELEVATED. THIS SWELL FADES GRADUALLY THROUGH THE WEEKEND, BY WHICH
POINT SOUTH SHORE SURF IS EXPECTED TO BECOME SMALL.
SURF ALONG EAST FACING SHORES REMAINS ELEVATED FROM A MEDIUM-PERIOD
EAST SWELL GENERATED BY FORMER TROPICAL CYCLONE MARIE. WITH LIGHT
TRADE WINDS, SURF WILL HOVER NEAR SEASONAL AVERAGES THROUGH FRIDAY.
THE EAST SWELL WILL FADE GRADUALLY, ALLOWING SURF TO FALL BELOW
SEASONAL AVERAGES BY THIS WEEKEND. SURF ALONG NORTH FACING SHORES
CONTINUES TO RECEIVE A SMALL BUMP DUE TO LOWELL. THIS SHORT-PERIOD
NORTHWEST SWELL WILL QUICKLY FADE, ALLOWING SURF TO BECOME TINY ALONG
NORTH FACING SHORES ON THURSDAY AS LOWELL WEAKENS AND TRACKS AWAY
FROM THE ISLANDS.
FIRE WEATHER
FIRE WEATHER RISK WILL REMAIN LOW THE NEXT SEVERAL DAYS DUE RATHER
LIGHT WINDS AND LINGERING MOISTURE. EXPECT A SLIGHT CHANCE OF
THUNDERSTORMS OVER THE BIG ISLAND THIS AFTERNOON AND POSSIBLY
THURSDAY AFTERNOON. TEMPERATURE INVERSION HEIGHTS ARE EXPECTED TO
REMAIN ELEVATED OR WEAK.
HFO WATCHES/WARNINGS/ADVISORIES
FLOOD WATCH THROUGH THIS AFTERNOON FOR BIG ISLAND-
DISCUSSION...THOMAS
AVIATION...M BALLARD
MARINE...QUESADA
FIRE WEATHER...THOMAS
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