327
FXHW60 PHFO 160303 CCA
AFDHFO
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE HONOLULU HI
503 PM HST WED OCT 15 2025
SYNOPSIS
A WET TRADE WIND PATTERN BEGINS DEVELOPING EARLY THURSDAY MORNING
AND MATURES THIS WEEKEND INTO NEXT WEEK. THUNDERSTORMS WILL BE
POSSIBLE AT TIMES, PARTICULARLY AT NIGHT, DURING THIS STRETCH.
DISCUSSION
CLOSED LOW POSITIONED ABOUT 300 MILES NE OF HONOLULU IS SLOWLY
ADVANCING SOUTHWESTWARD TOWARD THE WESTERN HALF OF THE ISLAND CHAIN
WHERE IT WILL RESIDE THROUGH AT LEAST THE FIRST HALF OF THE WEEKEND.
OBSERVED SOUNDINGS INDICATE A TRADE WIND INVERSION SLOPING FROM
AROUND 6.5KFT AT HILO TO 13KFT AT LIHUE, INDICATING LOSS OF
STABILITY OVER THE WESTERNMOST ISLANDS. BENEATH THE CLOSED LOW
ITSELF, OVER THE OPEN OCEAN, VISIBLE IMAGERY INDICATES THAT SHOWERS
ARE NOT PARTICULARLY WIDESPREAD BUT ARE TOPPING OUT AROUND 15KFT TO
GO ALONG WITH A FEW THUNDERSTORMS WHERE LAPSE RATES ARE STEEPEST,
AROUND 6.5C/KM.
THIS ENVIRONMENT WILL SPREAD OVER THE ISLANDS LATE TONIGHT INTO
EARLY THURSDAY, PARTICULARLY OVER OAHU AND KAUAI WHERE THE MID-LEVEL
LOW IS MODELED TO RESIDE BY TOMORROW MORNING. THE FIRST WAVE OF
DEEPER MOISTURE WILL REACH THE ISLANDS DURING THIS TIME BRINGING AN
INCREASE IN SHOWER COVERAGE AND INTENSITY. LOW STABILITY AND BREEZY
TRADES SUGGEST A HIGH LIKELIHOOD OF SHOWERS PENETRATING LEEWARD OVER
OAHU. LAPSE RATES WILL GRADUALLY STEEPEN TO 7C/KM BY SATURDAY NIGHT
SUGGESTING A TENDENCY FOR SHOWER INTENSITY, BUT NOT NECESSARILY
SHOWER COVERAGE, TO INCREASE DURING THE SAME TIME PERIOD. ISOLATED
THUNDERSTORMS WILL ALSO BE POSSIBLE, PARTICULARLY WHERE LOW-LEVEL
CONVERGENCE IS MAXIMIZED WITHIN ISLAND PLUMES OVER THE WATERS WEST OF
THE ISLANDS. THUNDER CANNOT BE RULED OUT ELSEWHERE, BUT IS
COMPARABLY LESS LIKELY OVER THE ISLANDS THEMSELVES. THE EXCEPTION
MAY BE THE BIG ISLAND THIS WEEKEND, WHERE POTENTIAL FOR AFTERNOON
THUNDERSTORMS WILL BE WORTH MONITORING AS MID-LEVEL LAPSE RATES
STEEPEN. ALL TOLD, EXPECT A TRANSITION TO A WETTER TRADE WIND
PATTERN WITH EMBEDDED HEAVY SHOWERS AND ISOLATED THUNDERSTORMS
BEGINNING EARLY THURSDAY MORNING. BREEZY TRADE WINDS WILL FAVOR
PROGRESSIVE, FAST-MOVING SHOWERS THAT WILL NOT BE PRONE TO CAUSING
FLOODING ISSUES.
RENEWED UPPER LOW DEVELOPMENT EARLY NEXT WEEK SETS THE STAGE FOR A
CONTINUED WET TRADE WIND PATTERN THROUGH MUCH OF NEXT WEEK.
AVIATION
HIGH PRESSURE FAR NORTHEAST OF THE ISLANDS WILL MAINTAIN MODERATE
TO LOCALLY BREEZY EASTERLY TRADE WINDS THROUGH TOMORROW NIGHT. AN
UPPER LOW TO THE NORTHEAST WILL DRIFT SOUTHWEST AND POSITION
ITSELF JUST TO THE WEST OF STATE. THIS UPPER LOW WILL PARTIALLY
DESTABILIZE THE ATMOSPHERE TONIGHT THROUGH TOMORROW, ALLOWING
SOME BANDS OF PASSING SHOWERS TO BECOME MORE INTENSE, AND CLOUD
TOPS TO BECOME HIGHER.
MOST OF THE SHOWERS ARE EXPECTED OVER WINDWARD AND MOUNTAIN
AREAS, WITH THE EXCEPTION OF LEEWARD BIG ISLAND, WHERE AFTERNOON
CLOUD AND SHOWER DEVELOPMENT IS EXPECTED. ALTHOUGH THERE WILL BE
INCREASED INSTABILITY FROM THE UPPER LOW, THE PRESENCE OF DRY MID
LEVEL AIR SHOULD INHIBIT WIDESPREAD SHOWER COVERAGE, KEEPING MOST
TAF SITES WITH PREVAILING VFR AND OCCASIONAL MVFR CONDITIONS.
ISOLATED THUNDERSTORMS ARE POSSIBLE, PRIMARILY FOR THE NORTHWEST
HALF OF THE STATE TOMORROW.
NO AIRMETS ARE IN EFFECT, HOWEVER MTN OBSC IS POSSIBLE EARLY
TOMORROW MORNING DUE TO INCREASING CLOUDS AND SHOWERS. AIRMET
TANGO WILL LIKELY BE NEEDED LATER THIS AFTERNOON AS THE UPPER LOW
INCREASES THE CHANCES OF MID TO UPPER LEVEL TURBULENCE.
MARINE
MODERATE TO FRESH TRADE WINDS HAVE FILLED IN ACROSS THE HAWAIIAN
COASTAL WATERS AS A WEAK SURFACE TROUGH OVER THE NORTHERN WATERS
ADVANCES WEST OF THE AREA AND DISSIPATES. A SMALL CRAFT ADVISORY
(SCA) FOR WINDS AROUND MAUI COUNTY AND THE BIG ISLAND HAS BEEN
EXTENDED THROUGH 6 PM HST FRIDAY. AN APPROACHING UPPER LOW MAY
BRING ISOLATED THUNDERSTORMS TO THE NORTHERN WATERS FROM LATE
TONIGHT INTO THE WEEKEND.
MODERATE TO LONG PERIOD NW SWELL ENERGY WILL GENERALLY PERSIST
OVER THE NEXT COUPLE OF DAYS AS A SERIES OF NW SWELLS FILTER
ACROSS THE AREA, MAINTAINING NEAR TO ABOVE AVERAGE SURF ALONG
NORTH-FACING SHORES THROUGH FRIDAY. A BRIEF, NNW SWELL WILL MOVE
THROUGH LATE FRIDAY, BUT SHOULD TAPER OFF QUICKLY ON SATURDAY.
SURF ALONG NORTH-FACING SHORES WILL TREND DOWN THROUGH THE
WEEKEND.
A SERIES OF SMALL, MEDIUM TO LONG PERIOD S SWELLS WILL CONTINUE TO
FILTER INTO THE AREA THROUGH THE REST OF THE WEEK AND INTO THE
WEEKEND, KEEPING SOUTH-FACING SHORES FROM GOING FLAT. EAST-FACING
SHORES WILL REMAIN SMALL THROUGH THE NEAR TERM, BUT WILL SEE
INCREASING SHORT PERIOD ACTION AS TRADES STRENGTHEN OVER THE
LATTER PART OF THE WEEK.
FIRE WEATHER
WIND SPEEDS AND AFTERNOON MINIMUM HUMIDITY LEVELS WILL LIKELY
REMAIN BELOW CRITICAL FIRE WEATHER THRESHOLDS THIS WEEK. UNSTABLE
CONDITIONS WILL PRODUCE INCREASING WET WEATHER ACROSS THE STATE
INTO NEXT WEEK. LOCALLY HEAVY RAIN AND THUNDERSTORMS ARE POSSIBLE
DURING THIS TIME. INVERSION HEIGHT OVER MAUI AND THE BIG ISLAND IS
AROUND 6.5KFT THIS AFTERNOON. DURING THE NEXT SEVERAL DAYS, IT
WILL LIKELY TEND TO LIFT AND WEAKEN.
HFO WATCHES/WARNINGS/ADVISORIES
SMALL CRAFT ADVISORY UNTIL 6 AM HST THURSDAY FOR MAALAEA BAY-
PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG
ISLAND SOUTHEAST WATERS.
DISCUSSION...JVC
AVIATION...TSAMOUS
MARINE...FARRIS
FIRE WEATHER...JVC
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