225
FXHW60 PHFO 160657
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
857 PM HST FRI MAY 15 2026
SYNOPSIS
HEAVY SHOWERS AND THUNDERSTORMS WILL REMAIN POSSIBLE ACROSS MOST
OF THE STATE THROUGH AT LEAST TONIGHT, WHILE EASTERLY TRADE WINDS
THAT REMAIN IN PLACE ACROSS BIG ISLAND AND MAUI SPREAD TO OAHU AND
KAUAI. THE UPPER LEVEL DISTURBANCE CREATING THE ACTIVE WEATHER
WILL SLOWLY MOVE EASTWARD AND WEAKEN ON SATURDAY, LEADING TO
DECREASED CHANCES FOR HEAVY RAINFALL ACROSS MOST ISLANDS. SOMEWHAT
WET EASTERLY TRADE WINDS WILL FOCUS MOST RAINFALL ALONG WINDWARD
SLOPES SUNDAY INTO EARLY NEXT WEEK. A MORE STABLE, MODERATE TO
BREEZY TRADE WIND FLOW IS EXPECTED BY WEDNESDAY.
DISCUSSION
HEAVY SHOWERS AND THUNDERSTORMS DIMINISHED SHARPLY LATE THIS
AFTERNOON AND EVENING OVER AND AROUND OAHU. THE UPPER LEVEL LOW
THAT DROPPED OVER THE STATE EARLIER TODAY IS NOW WEAKENING, AND
THE SURFACE TROUGH THAT IT INDUCED OVER OAHU HAS FILLED AND LIFTED
TO THE NORTHWEST. THIS RESULTED IN THE DRAMATIC DECREASE IN
CONVECTION ON OAHU AS EASTERLY TRADE WINDS FILLED BACK IN, BUT NOT
BEFORE MANY STATIONS ON OAHU MEASURED BETWEEN 4 AND 7 INCHES OF
RAIN, LEADING TO FLASH FLOODING. THAT SAID, THE WEAKENING UPPER
LEVEL LOW WILL LINGER OVERHEAD AND MAINTAIN SOME THREAT OF
ADDITIONAL FLOODING TONIGHT FROM OAHU TO BIG ISLAND.
CHANCES OF HEAVY SHOWERS AND THUNDERSTORMS WILL DIMINISH FROM WEST
TO EAST ON SATURDAY AS THE UPPER LOW DRIFTS EASTWARD AND WEAKENS.
MODERATE EASTERLY TRADE WINDS WILL FOCUS RAINFALL OVER WINDWARD
AREAS, AND THE GFS AND ECMWF ARE SHOWING INCREASED MOISTURE
MOVING OVER THE BIG ISLAND AND POSSIBLY MAUI, SUGGESTING MORE
RAINFALL ACROSS THOSE WINDWARD AND SOUTHEAST SLOPES. GIVEN THE
LINGERING INSTABILITY FROM THE UPPER LEVEL LOW, HEAVY RAINFALL MAY
REMAIN A THREAT ON THE BIG ISLAND AND PERHAPS MAUI, AND WE WILL
DETERMINE IF THE FLOOD WATCH NEEDS TO REMAIN IN EFFECT FOR THOSE
ISLANDS.
MODERATE EASTERLY WINDS AND A SOMEWHAT WET PATTERN OF MAINLY
WINDWARD AND MAUKA SHOWERS IS EXPECTED BY SUNDAY. THE UPPER LOW
WILL BE REPLACED BY A BROAD AND FLAT UPPER TROUGH, WHICH WILL NOT
ALLOW THE ATMOSPHERE TO BECOME VERY STABLE. AS A RESULT, WE
CANNOT RULE OUT A BRIEFLY HEAVY SHOWER, MAINLY OVER THE HEATED
LEEWARD SLOPES OF THE BIG ISLAND AND MAUI DURING THE AFTERNOON
HOURS.
INCREASED STABILITY AND STRONGER TRADE WINDS ARE DUE LATE TUESDAY
OR WEDNESDAY. EXPECT A TYPICAL PATTERN OF MAINLY WINDWARD RAINFALL
AND MOSTLY DRY CONDITIONS LEEWARD.
AVIATION
AN UPPER LEVEL LOW MOVING OVER MAUI COUNTY THIS EVENING WILL KEEP
UNSETTLED EASTERLY WET TRADE WINDS IN THE FORECAST WITH PERIODS
OF MVFR CONDITIONS ACROSS THE EASTERN HALF OF THE STATE LASTING
INTO SATURDAY. SHOWER ACTIVITY WILL DECREASE FROM WEST TO EAST
THIS WEEKEND AS THE UPPER LOW WEAKENS AND CONTINUES TO MARCH
EASTWARD.
AIRMET SIERRA REMAINS IN EFFECT FOR MOUNTAIN OBSCURATION OVER
KAUAI, OAHU, MOLOKAI, LANAI AND MAUI.
MARINE
WINDS WILL REMAIN SLIGHTLY EAST SOUTHEASTERLY THIS WEEKEND AT
MODERATE TO FRESH LEVELS. BY SATURDAY, THE UPPER DISTURBANCE THAT
GAVE US SOME SEVERE WEATHER TODAY WILL BE MOVING NORTHEAST AWAY
FROM THE STATE, WITH STABILITY SLOWLY RETURNING TO THE REGION. AS
A RESULT, EXPECT DECREASING HEAVY SHOWERS AND THUNDERSTORMS ACROSS
THE WATERS. A MORE TYPICAL EASTERLY TRADE WIND PATTERN WILL
RETURN NEXT WEEK.
A SMALL, MEDIUM PERIOD NORTH NORTHWEST (320-330 DEGREE) SWELL
THAT PEAKED LAST NIGHT WILL CONTINUE TO SLOWLY DECLINE TONIGHT.
SURF ALONG NORTH AND WEST FACING SHORES WILL FOLLOW SUIT, EASING
DURING THE WEEKEND.
A MIX OF SMALL, MEDIUM TO LONG PERIOD SOUTH SWELLS WILL MAINTAIN
SMALL SURF ALONG SOUTH-FACING SHORES THIS WEEKEND. A SERIES OF
GALE LOWS PASSING SOUTH OF NEW ZEALAND SHOULD SEND SMALL SOUTH
SWELL ENERGY INTO THE SOUTHERN WATERS THROUGH NEXT WEEK. SURF
SHOULD LIFT TO SUMMER AVERAGES AROUND SUNDAY AND HOLD THROUGH
WEDNESDAY. MODERATE TO FRESH TRADES WILL MAINTAIN ROUGH AND
CHOPPY SURF ALONG EAST-FACING SHORES.
TIDES WILL PEAK AROUND 2.5 TO 3.0 FT MLLW THIS WEEKEND. MINOR
OVERWASH OF LOW LYING COASTAL AREAS WILL BE POSSIBLE DURING TIMES
OF HIGH TIDE.
HFO WATCHES/WARNINGS/ADVISORIES
FLOOD WATCH UNTIL 6 AM HST SATURDAY FOR WAIANAE COAST-OAHU NORTH
SHORE-OLOMANA-CENTRAL OAHU-WAIANAE MOUNTAINS-LANAI MAUKA-
KAHOOLAWE-MAUI WINDWARD WEST-MAUI LEEWARD WEST-HALEAKALA SUMMIT-
KONA-KOHALA-BIG ISLAND INTERIOR-BIG ISLAND SUMMITS-EAST HONOLULU-
HONOLULU METRO-EWA PLAIN-KOOLAU WINDWARD-KOOLAU LEEWARD-MOLOKAI-
LANAI WINDWARD-LANAI LEEWARD-LANAI SOUTH-MAUI CENTRAL VALLEY
NORTH-MAUI CENTRAL VALLEY SOUTH-WINDWARD HALEAKALA-KIPAHULU-
SOUTH MAUI/UPCOUNTRY-SOUTH HALEAKALA-BIG ISLAND SOUTH-BIG ISLAND
SOUTHEAST-BIG ISLAND EAST-BIG ISLAND NORTH.
DISCUSSION...WROE
AVIATION...BOHLIN
MARINE...WALSH
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