650
FXHW60 PHFO 061912
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
912 AM HST THU AUG 6 2026
SYNOPSIS
LIGHT TO MODERATE TRADE WINDS WILL PREVAIL TODAY, FOLLOWED BY
INCREASING TRADE WIND SPEEDS FRIDAY THROUGH THIS WEEKEND. MOST
SHOWER ACTIVITY WILL OCCUR DURING THE NIGHTS AND EARLY MORNINGS
AND AFFECT WINDWARD AND MAUKA LOCATIONS. FROM SATURDAY AFTERNOON
THROUGH MONDAY, AN AREA OF TROPICAL MOISTURE WILL MOVE OVER
PORTIONS OF THE STATE FROM EAST TO WEST AND BRING ENHANCED SHOWER
ACTIVITY TO MAINLY MAUI COUNTY AND THE BIG ISLAND. A TYPICAL
STABLE TRADE WIND PATTERN WILL RETURN BY TUESDAY OF NEXT WEEK.
SHORT TERM UPDATE
SATELLITE AND RADAR IMAGERY THIS MORNING SHOWS A LITTLE MORE TRADE
WIND SHOWERS NEAR AND JUST UPSTREAM MAUI COUNTY AND OAHU,
THEREFORE THE PROBABILITY OF PRECIPITATION (POPS) WAS INCREASED
TODAY. OTHERWISE THE FORECAST REMAINS ON TRACK WITH TRADES
INCREASING TOMORROW, THEN INCREASING RAINFALL CHANCES THIS
SATURDAY EVENING THROUGH MONDAY.
PREV DISCUSSION
ISSUED AT 356 AM HST THU AUG 6 2026
THIS MORNING'S WATER VAPOR IMAGERY LOOP SHOWED THE CYCLONIC SPIN
OF AN UPPER LOW CENTERED AROUND 475 MILES WEST NORTHWEST OF KAUAI.
MID AND UPPER LEVEL MOISTURE COULD BE SEEN STREAMING OVER THE
STATE FROM THE SOUTHWEST, AHEAD OF THE FEATURE. AT THE SURFACE,
LOCALLY MODERATE TRADES PERSISTED AS A TROUGH FROM FORMER TC
GENEVIEVE CONTINUED TO PASS WELL TO THE NORTHEAST OF THE STATE AND
A STATIONARY FRONT REMAINED ANCHORED TO THE NORTH. SHOWERS HAVE
BEEN RATHER ISOLATED THIS MORNING WITH ACCUMULATIONS SINCE
MIDNIGHT ONLY REACHING A FEW HUNDREDTHS OF AN INCH AT SELECT
WINDWARD SITES. THE WEST WAILUAIKI STREAM RAIN GAUGE ON THE
WINDWARD SLOPE OF HALEAKALA, HOWEVER, DID PICK UP AROUND A THIRD
OF AN INCH. THE 12Z HILO UPPER AIR SOUNDING SHOWS A SUBSIDENCE
TEMPERATURE INVERSION HEIGHT OF 6000 FEET, WHICH IS TYPICAL FOR
THIS TIME OF YEAR. NOT MUCH CHANGE IS EXPECTED THROUGH FRIDAY WITH
LOW CLOUD COVER AND ISOLATED TO SCATTERED SHOWERS GENERALLY
LIMITED TO WINDWARD AND MAUKA LOCATIONS.
ON FRIDAY, BOTH THE SURFACE TROUGH TO THE NORTHEAST AND FRONT TO
THE NORTH WILL HAVE DISSIPATED, ALLOWING HIGH PRESSURE BUILD IN
THEIR WAKE. AS LOCAL SURFACE PRESSURE GRADIENTS TIGHTEN IN
RESPONSE, TRADE WINDS SHOULD RAMP UP TO MODERATE TO BREEZY LEVELS.
BY EARLY THIS WEEKEND, GLOBAL MODELS HAVE BEEN CONSISTENT IN
ADVECTING AN AREA OF DEEPER TROPICAL MOISTURE TOWARDS THE BIG
ISLAND FROM THE EAST. THE MOST RECENT GFS MODEL TIME-HEIGHT CROSS
SECTION DEPICTS THE BOUNDARY LAYER INVERSION WEAKENING, AS
CONDITIONS BECOME MORE UNSTABLE, AND MOISTURE DEEPENING UP TO
15000 FEET. THUS, FROM SATURDAY AFTERNOON THROUGH MONDAY, EMBEDDED
POCKETS OF HEAVIER RAINFALL WILL BE POSSIBLE FOR THE BIG ISLAND
AND MAUI COUNTY, ESPECIALLY FOR WINDWARD LOCATIONS. AT THIS POINT
IN TIME, IT APPEARS OAHU AND KAUAI WILL ONLY BE ON THE FRINGES OF
THIS PASSING MOISTURE. WHILE STILL TOO EARLY TO DETERMINE MORE
CONCRETE FORECAST DETAILS, A FEW INCHES OF RAINFALL ACCUMULATION
COULD FALL ON SOME OF THE WETTEST WINDWARD SITES.
TYPICAL MODERATE TRADE WIND WEATHER WILL RETURN FOR TUESDAY THROUGH
THE END OF THE WORK WEEK WITH SCATTERED SHOWERS MAINLY WINDWARD
AND MAUKA AREAS DURING THE NIGHTS AND EARLY MORNINGS.
AVIATION
MODERATE TRADE WINDS WILL PERSIST TODAY AND STRENGTHEN TO BECOME
BREEZY TOMORROW. ISOLATED SHOWERS ARE POSSIBLE TONIGHT FOR MAINLY
WINDWARD AND MOUNTAIN AREAS.
AIRMET SIERRA IN EFFECT FOR MOUNTAIN OBSCURATIONS ABOVE 2500 FT.
ACROSS NORTH THRU EAST SECTIONS OF OAHU AND MAUI.
MARINE
ISSUED AT 356 AM HST THU AUG 6 2026
MODERATE TRADES PERSIST AS SURFACE TROUGHING TO THE NORTHEAST
MAINTAINS A RATHER WEAK PRESSURE GRADIENT OVER THE STATE.
DISSIPATION OF THE TROUGH TO THE NORTHEAST COMBINED WITH RENEWED
TROUGH DEVELOPMENT SOUTH OF THE ISLANDS AND STRENGTHENING HIGH
PRESSURE TO THE NORTHEAST WILL FAVOR FRESH TO LOCALLY STRONG
TRADES BY WEEK'S END.
BACKGROUND MEDIUM AND LONG PERIOD ENERGY WILL PRODUCE SMALL SURF FOR
SOUTH FACING SHORES THROUGH FRIDAY. A SERIES OF LARGER, MEDIUM TO
LONG PERIOD SOUTH SWELLS ARRIVE BEGINNING ON SATURDAY, CAUSING SURF TO
TREND UP FOR SOUTH AND WEST FACING SHORES THIS WEEKEND INTO EARLY
NEXT WEEK. SURF MAY PEAK CLOSE TO THE HIGH SURF ADVISORY THRESHOLD BY
THE MIDDLE OF NEXT WEEK.
ALONG EAST FACING SHORES, TRADE WIND SWELL AND MODERATE TRADES
WILL SUPPORT SURF SLIGHTLY BELOW SEASONAL AVERAGES. SURF WILL BUILD
THIS WEEKEND IN RESPONSE TO STRENGTHENING TRADE WINDS. SURF ALONG
NORTH SHORES REMAINS FLAT TO TINY THROUGH THE PERIOD.
HFO WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...THOMAS
AVIATION...PECHACEK/FARRIS
MARINE...QUESADA
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