419
FXHW60 PHFO 161954
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
954 AM HST WED SEP 16 2026
SYNOPSIS
BREEZY TRADES EXPECTED THROUGH THE MIDDLE OF NEXT WEEK. AN UPPER
LEVEL TROUGH AND MOISTURE ASSOCIATED WITH THE REMNANTS OF NORBERT
WILL FILL IN ACROSS THE STATE FROM EAST TO WEST THURSDAY INTO
FRIDAY, INCREASING THE CHANCES OF HEAVY RAIN, ISOLATED
THUNDERSTORMS, AND FLASH FLOODING, ESPECIALLY FOR THE WINDWARD AND
MAUKA AREAS. DRIER AIR WILL MOVE BACK IN THIS WEEKEND BEHIND THE
DEPARTING TROUGH. MOISTURE FROM THE REMNANTS OF TROPICAL
DEPRESSION 15-E MAY BRING ANOTHER ROUND OF ENHANCED TRADE SHOWERS
AROUND NEXT TUESDAY AND WEDNESDAY.
DISCUSSION
MORNING SATELLITE IMAGERY SHOWS AN UPPER LEVEL LOW AROUND 1500 MI
NORTH-NORTHEAST OF THE ISLANDS WITH A TROUGH EXTENDING
SOUTHWESTWARD. A FEW LIGHT SHOWERS WERE MOVING TOWARDS THE WESTERN
HALF OF THE STATE WITH OTHERWISE PARTLY CLOUDY CONDITIONS MAINLY
ON THE WINDWARD SIDE OF THE ISLANDS. WEAK TRADES WILL STRENGTHEN
TODAY AS THE UPPER LEVEL TROUGH APPROACHES.
THE UPPER LEVEL TROUGH WILL DIG SOUTHWEST TONIGHT INTO THURSDAY,
PULLING IN REMNANT MOISTURE FROM NORBERT. SATELLITE IMAGERY SHOWS
A BROAD AREA OF PRECIPITABLE WATER IN EXCESS OF 2" TO THE EAST,
WHICH IS FORECAST TO MOVE INTO THE EASTERN HALF OF THE STATE LATER
TODAY, SPREADING ACROSS THE REMAINING ISLANDS TONIGHT INTO
THURSDAY. DEEPER MOISTURE AND INCREASING INSTABILITY WILL BRING
MODERATE TO LOCALLY HEAVY SHOWERS AND A SLIGHT CHANCE OF
THUNDERSTORMS, WITH THE HIGHEST THREAT OF THUNDERSTORMS ACROSS THE
BIG ISLAND THURSDAY AFTERNOON. HEAVIEST RAIN IS EXPECTED ON THE
WINDWARD AND MAUKA AREAS. WITH SOIL MOISTURE LIKELY STILL HIGH
FROM PREVIOUS HEAVY RAIN EVENTS, THERE IS AN INCREASED RISK OF
FLASH FLOODING WHERE HEAVIER SHOWERS AND THUNDERSTORMS OCCUR.
MOISTURE WILL DECREASE FROM EAST TO WEST LATE FRIDAY THROUGH THE
WEEKEND. THERE IS THE POTENTIAL FOR ANOTHER ROUND OF INCREASING
MOISTURE FROM THE REMNANTS OF TROPICAL DEPRESSION 15-E MOVING
INTO AROUND TUESDAY TO WEDNESDAY OF NEXT WEEK. ENSEMBLES SHOW AT
LEAST A WEAK LOW-LEVEL WAVE ASSOCIATED WITH THIS MOISTURE, THOUGH
FURTHER ALOFT ONLY 6% OF THE ENSEMBLE MEMBERS HAVE SOME FORM OF
TROUGHING WHILE THE REMAINDER KEEP US UNDER A RIDGE, LIMITING THE
POTENTIAL FOR HEAVIER SHOWERS.
AVIATION
MODERATE TO LOCALLY BREEZY TRADE WINDS WILL STRENGTHEN TO BREEZY
LEVELS THIS AFTERNOON AND A TROUGH WILL APPROACH THE AREA FROM
THE EAST. SHOWERS AND LOW CLOUDS ASSOCIATED WITH THAT TROUGH WILL
INCREASE WITH THE TRADE WIND FLOW FROM EAST TO WEST STARTING
EARLY TONIGHT FOR THE EASTERN HALF OF THE STATE, THEN SPREAD WEST
LATE TONIGHT INTO TOMORROW MORNING. MORE WIDESPREAD MVFR
CONDITIONS WILL BE POSSIBLE AS THE MOISTURE ASSOCIATED WITH THE
TROUGH MOVES IN, ESPECIALLY FOR WINDWARD AND MOUNTAIN AREAS.
NO AIRMETS ARE CURRENTLY IN EFFECT. THERE IS THE POSSIBILITY FOR
AIRMET TANGO DURING THE AFTERNOON ONCE TRADE WINDS STRENGTHEN.
THERE IS ALSO POTENTIAL FOR AIRMET SIERRA LATER TODAY AS CLOUDS
INCREASE ON THE WINDWARD SLOPES.
MARINE
A BROAD TROUGH, ASSOCIATED WITH THE REMNANTS OF TROPICAL STORM NORBERT,
WILL APPROACH THE STATE FROM THE EAST TODAY, ALLOWING MODERATE TO
LOCALLY STRONG NORTHEAST TRADES TO DEVELOP TODAY. A SMALL CRAFT
ADVISORY REMAINS IN EFFECT FOR TYPICALLY WINDY WATERS AROUND THE
BIG ISLAND AND MAUI COUNTY THROUGH TONIGHT. AFTER THE TROUGH MOVES
THROUGH THE STATE THURSDAY INTO FRIDAY, A SURFACE HIGH FAR
NORTHEAST OF THE STATE WILL MAINTAIN MODERATE TO LOCALLY STRONG
TRADES THROUGH THE FORECAST PERIOD. ABOVE NORMAL MOISTURE AND
UPPER LEVEL SUPPORT WILL ALLOW ISOLATED THUNDERSTORMS WITH HEAVY
RAIN AND GUSTY OUTFLOWS TO DEVELOP OVER THE OFFSHORE WATERS THIS
AFTERNOON THROUGH SATURDAY.
A SERIES OF LONG TO MEDIUM PERIOD SOUTH-SOUTHWEST TO SOUTH SWELLS
WILL CONTINUE FILL TODAY. SMALL INCONSISTENT SURF WILL GRADUALLY
BUILD TODAY BECOMING MORE CONSISTENT THROUGH THE REST OF WEEK.
SURF WILL NEAR HIGH SURF ADVISORY THRESHOLDS BY THIS WEEKEND AS
SWELLS SHIFT MORE OUT OF A SOUTH DIRECTION.
SURF ALONG EAST- FACING SHORES INCREASES TODAY INTO THURSDAY AS
TRADE WINDS STRENGTHEN AND A SMALL, MEDIUM- PERIOD EAST SWELL FROM
THE REMNANTS OF NORBERT ARRIVES. FLAT TO TINY SURF ALONG NORTH
FACING SHORES IS EXPECTED THROUGH THE FORECAST PERIOD.
FIRE WEATHER
FIRE WEATHER RISK SHOULD REMAIN LOW THROUGH THE REMAINDER OF THE
WEEK DUE TO MODERATE TO BREEZY WINDS AND INCREASED RELATIVE
HUMIDITY AND MOISTURE FROM THE REMNANTS OF NORBERT. SHOWERS WILL
DRAMATICALLY INCREASE LATE TONIGHT THROUGH EARLY FRIDAY. INVERSION
HEIGHTS WILL BE AROUND 7,500 TO 8,500 FT.
HFO WATCHES/WARNINGS/ADVISORIES
SMALL CRAFT ADVISORY UNTIL 6 AM HST THURSDAY FOR ALENUIHAHA
CHANNEL-BIG ISLAND LEEWARD WATERS-BIG ISLAND SOUTHEAST WATERS-
MAALAEA BAY-PAILOLO CHANNEL.
DISCUSSION...SS
AVIATION...PHILLIPS
MARINE...ALMANZA
FIRE WEATHER...SS
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