515
FXHW60 PHFO 130638
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
838 PM HST MON OCT 12 2026
SYNOPSIS
LIGHT TO MODERATE TRADES WITH LOCAL LAND AND SEA BREEZES WILL
BECOME MODERATE TO LOCALLY FRESH ON TUESDAY AS WINDS STRENGTHEN A
LITTLE. TRADE WINDS THEN WEAKEN ON WEDNESDAY, FOLLOWED BY
RESTRENGTHENING TOWARDS THE END OF THE WEEK INTO THE WEEKEND.
SHOWERS OVERALL WILL BE LIGHT AND FOCUS OVER WINDWARD AND MOUNTAIN
AREAS WITH LIGHT LEEWARD CLOUD BUILDUPS TODAY. MORE SHOWER
COVERAGE IS EXPECTED TONIGHT THROUGH TOMORROW MORNING FOR THE BIG
ISLAND DUE TO A WEAK TROUGH TRANSITING THEN DISSIPATING TOMORROW.
DRIER CONDITIONS TAKE HOLD BY MID WEEK FOLLOWED BY SLIGHTLY WETTER
TRADES THIS WEEKEND.
SHORT TERM UPDATE
SHOWERS ARE MOVING ONSHORE THIS EVENING ALONG WINDWARD BIG ISLAND
AS THE TROUGH MOVES WESTWARD OVER THE ISLAND. THESE SHOWERS ARE
ANTICIPATED TO CONTINUE THROUGHOUT THE NIGHT. INCREASED SHOWER
CHANCES TO NEAR 100% FOR WINDWARD BIG ISLAND THOUGHOUT THE NIGHT,
AND INCREASED QPF AS WELL. OTHERWISE, THE PREVIOUS FORECAST
REMAINS ON TRACK.
PREV DISCUSSION
ISSUED AT 308 PM HST MON OCT 12 2026
THIS AFTERNOON, THE HAWAIIAN ISLANDS ARE POSITIONED BETWEEN TWO
WEAK TROUGHS, ONE TO THE NORTHWEST, AND ANOTHER TO THE EAST. A
RELATIVELY DRY AIRMASS LINGERS OVER THE REGION WITH A STABLE 5,000
FT INVERSION IN PLACE FOR THE SMALLER ISLANDS. THE BIG ISLAND
TODAY IS BEING INFLUENCED BY A PASSING WEAK TROUGH, WITH A 12,000
FT INVERSION AND A FEW HEAVIER SHOWERS. THIS TROUGH IS ALSO BEING
SUPPORTED BY A PASSING MID LEVEL LOW. THE SHOWERS OVER WINDWARD
BIG ISLAND SHOULD LINGER TONIGHT INTO TOMORROW MORNING, THEN
DISSIPATE AS THE SURFACE TROUGH WEAKENS, AND THE MID LEVEL LOW
DRIFTS EAST. SHOWERS OVER LEEWARD BIG ISLAND TODAY SHOULD
DISSIPATE AFTER SUNSET AS DAYTIME HEATING DISAPPEARS AND TYPICAL
NIGHT TIME LAND BREEZES BEGIN.
SOME OF THE MOISTURE ASSOCIATED WITH THE WEAK TROUGH COULD SPREAD
TO THE SMALLER ISLANDS, BRINGING OCCASIONALLY SCATTERED SHOWERS
TO WINDWARD AND MOUNTAIN AREAS TUESDAY. BY WEDNESDAY, CONDITIONS
ARE FORECAST TO BECOME DRIER, AND WINDS DECREASE, BRINGING ONLY A
FEW POP UP CLOUDS TO LEEWARD AND INTERIOR AREAS. TRADE WINDS THEN
ARE EXPECTED TO INCREASE THURSDAY INTO THE WEEKEND AS HIGH
PRESSURE TO THE NORTH BECOMES ESTABLISHED AND STRENGTHENS. AS
TRADE WINDS INCREASE, PASSING SHOWERS WILL FAVOR WINDWARD AND
MOUNTAIN AREAS, AND COULD INCREASE SLIGHTLY THIS WEEKEND.
AVIATION
GENERALLY LIGHT TO OCCASIONALLY MODERATE TRADES WILL PERSIST
THROUGH THE PERIOD. LIGHTER WINDS MAY ALLOW LOCALIZED SEA BREEZES
TO DEVELOP DURING THE DAYTIME HOURS. THICKENING AFTERNOON CLOUDS
WITH SCATTERED SHOWERS OVER WINDWARD-FACING SLOPES IS POSSIBLE.
MVFR CEILINGS AND VISIBILITIES WITHIN PERIODS OF PASSING SHOWERS
OVER EASTERN-FACING BIG ISLAND REGIONS WILL LIKELY IMPACT HTO.
OTHERWISE, VFR CONDITIONS WILL PREVAIL OVER MOST TERMINALS.
AIRMET SIERRA IS IN EFFECT FOR MOUNTAIN OBSCURATION ALONG BIG
ISLAND'S EAST AND SOUTHEAST-FACING SLOPES UNTIL FURTHER NOTICE.
MARINE
ISSUED AT 308 PM HST MON OCT 12 2026
GENTLE TO MODERATE TRADE WINDS WILL GRADUALLY INCREASE FROM EAST
TO WEST THROUGH TUESDAY AS A WEAK LOW FILLS NORTHWEST OF KAUAI
AND A SURFACE RIDGE BUILDS NORTH OF THE STATE. MODERATE TO LOCALLY
FRESH TRADES WILL STRENGTHEN THURSDAY AS SURFACE HIGH PRESSURE
BUILDS FAR NORTH OF THE STATE, AND A SMALL CRAFT ADVISORY (SCA)
WILL LIKELY BE NEEDED FOR THE TYPICALLY WINDY WATERS AROUND BIG
ISLAND AND MAUI. TRADES WILL FURTHER STRENGTHEN FRIDAY INTO THE
WEEKEND AND MAY REQUIRE AN EXPANSION OF THE SCA TO ADDITIONAL
WATERS.
SMALL SURF WILL PERSIST ALONG NORTH FACING SHORES INTO THE
EVENING. A FRESH, LONG PERIOD NORTHWEST SWELL WILL BUILD LATE
TONIGHT AND TUESDAY, PUSHING SURF ALONG NORTH AND WEST FACING
SHORES TO NEAR SEASONAL AVERAGE THROUGH WEDNESDAY. THIS SWELL
WILL DECLINE THURSDAY AND FRIDAY. A MEDIUM PERIOD NORTH-
NORTHWEST SWELL WILL BUILD LATE FRIDAY AND WILL BE THE MAIN
SOURCE TO PRODUCE SURF AROUND SEASONAL AVERAGE DURING THE
WEEKEND, THOUGH A SMALL LONGER PERIOD NORTHWEST SWELL WILL ALSO
ARRIVE DURING THE WEEKEND.
SOUTH SHORE SURF WILL REMAIN ABOVE SEASONAL AVERAGE THROUGH THE
AFTERNOON THEN GRADUALLY LOWER TONIGHT THROUGH WEDNESDAY AS A
LONG PERIOD SOUTH-SOUTHWEST SWELL SLOWLY DECLINES. ANOTHER LONG
PERIOD SOUTH SWELL WILL PRODUCE SURF NEAR SEASONAL AVERAGE FRIDAY
AND SATURDAY.
SURF ALONG EAST FACING SHORES WILL REMAIN SMALL THROUGH THURSDAY
AS SMALL WIND WAVES AND TINY EAST SWELL PERSIST. CHOPPY SURF WILL
INCREASE SLIGHTLY AS TRADE WINDS STRENGTHEN ACROSS THE REGION
FRIDAY INTO THE WEEKEND.
FIRE WEATHER
ISSUED AT 308 PM HST MON OCT 12 2026
LIGHT TO MODERATE TRADE WINDS WILL CONTINUE FOR THE FIRST HALF OF
THE WEEK. DRY AIR WILL KEEP RH LEVELS NEAR- CRITICAL VALUES FOR
PARTS OF THE STATE THROUGH THE WEEK, BUT WINDS WILL BE LIGHT.
INVERSION HEIGHTS RANGE FROM 5,000 FEET TOWARD LIHUE TO 12,000
FEET NEAR HILO. WINDS INCREASE FOR THE SECOND HALF OF THE WEEK,
BUT MOISTURE IMPROVES MARGINALLY.
HFO WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM UPDATE...VAUGHAN
DISCUSSION...TSAMOUS
AVIATION...BLOOD
MARINE...WROE
FIRE WEATHER....TSAMOUS
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