693
FXHW60 PHFO 161916
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
916 AM HST SAT MAY 16 2026
SYNOPSIS
A SLIGHTLY UNSTABLE TRADE WIND FLOW WILL PREVAIL TODAY AS A
WEAKENING UPPER LEVEL LOW PRODUCES ISOLATED HEAVY SHOWERS AND
THUNDERSTORMS, MAINLY ON THE BIG ISLAND. 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 WILL DEVELOP TUESDAY AND WEDNESDAY.
SHORT TERM UPDATE
NUMEROUS SHOWERS AND THUNDERSTORMS WERE UNDERWAY ON THE BIG
ISLAND EAST AND SOUTHEAST SIDES. SO FAR RAINFALL RATES HAVE BEEN
LIGHT TO MODERATE. ISOLATED SHOWERS WERE OCCURRING ON EACH OF THE
OTHER ISLANDS. THE UPPER LEVEL SYSTEM WHICH BROUGHT SHOWERS AND
THUNDERSTORMS TO THE STATE YESTERDAY IS CONTINUING TO PULL AWAY TO
THE NORTHEAST AND ITS IMPACT ON THE ISLAND WILL DIMINISH THROUGH
TODAY. WET TRADES ARE STILL EXPECTED TOMORROW THROUGH TUESDAY,
WITH MORE TYPICAL TRADES FORECAST FROM WEDNESDAY INTO NEXT
WEEKEND. NO CHANGES ARE NEEDED AT THIS TIME.
PREV DISCUSSION
ISSUED AT 336 AM HST SAT MAY 16 2026
HEAVY SHOWERS AND THUNDERSTORMS DECREASED DRAMATICALLY YESTERDAY
EVENING AS THE UPPER LEVEL LOW OVER THE ISLANDS WEAKENED, AND
EASTERLY TRADE WINDS HAVE FOCUSED MAINLY MODERATE SHOWERS OVER
WINDWARD SLOPES OVERNIGHT. THERE IS SOME LINGERING INSTABILITY
FROM THE UPPER LOW, BUT SO FAR, ONLY A FEW HEAVY SHOWERS HAVE
BRIEFLY FLARED UP, EVEN WITH A STEADY SUPPLY OF LOW LEVEL MOISTURE
STREAMING INTO WINDWARD BIG ISLAND. GIVEN RECENT TRENDS, THE FLOOD
WATCH HAS BEEN CANCELLED.
CHANCES OF HEAVY SHOWERS AND THUNDERSTORMS WILL DIMINISH TODAY AS
THE UPPER LOW DRIFTS EASTWARD AND WEAKENS. MODERATE EASTERLY
TRADE WINDS WILL FOCUS RAINFALL OVER WINDWARD AREAS OF ALL
ISLANDS, WITH MORE SHOWER ACTIVITY EXPECTED ON BIG ISLAND DUE TO
INCREASED LOW LEVEL MOISTURE FILTERING IN FROM THE EAST.
LINGERING INSTABILITY FROM THE DEPARTING UPPER LEVEL LOW COULD
ALSO TRIGGER ISOLATED HEAVY SHOWERS AND THUNDERSTORMS ON THE BIG
ISLAND, BUT THE THREAT OF FLOODING DOES NOT APPEAR HIGH ENOUGH TO
CONTINUE THE FLOOD WATCH TODAY.
MODERATE EASTERLY WINDS AND A SOMEWHAT WET PATTERN OF MAINLY
WINDWARD AND MAUKA SHOWERS IS EXPECTED SUNDAY INTO EARLY TUESDAY.
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
CONDITIONS ARE GENERALLY EXPECTED TO BE VFR TODAY AS YESTERDAY'S
WEATHER SYSTEM CONTINUES TO WEAKEN AND MOVE AWAY FROM THE ISLANDS.
PERIODIC WINDWARD SHOWERS AND MVFR CONDITIONS CANNOT BE RULED
OUT, HOWEVER THE TREND FOR THE REST OF THE WEEKEND IS EXPECTED TO
BE A GRADUAL RETURN TOWARDS NORMAL TRADE WIND CONDITIONS.
AIRMET SIERRA REMAINS IN EFFECT FOR MOUNTAIN OBSCURATION ABOVE 020
FOR KAUAI, OAHU, AND THE BIG ISLAND, HOWEVER CONDITIONS ARE
EXPECTED TO IMPROVE BY THE AFTERNOON.
MARINE
WINDS WILL REMAIN SLIGHTLY EAST SOUTHEASTERLY THIS WEEKEND AT
MODERATE TO FRESH LEVELS. THE UPPER LEVEL DISTURBANCE THAT GAVE US
SOME SEVERE WEATHER YESTERDAY WILL BE MOVING NORTHEAST AWAY FROM
THE STATE, WITH STABILITY SLOWLY RETURNING TO THE REGION. AS A
RESULT, EXPECT DECREASING 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 WILL
CONTINUE TO DECLINE THIS WEEKEND, WITH SURF ALONG NORTH-FACING SHORES
FOLLOWING SUIT. A NEW, SHORT PERIOD NORTHWEST SWELL WILL PROVIDE
ANOTHER SMALL BUMP TO SURF ALONG NORTH-FACING SHORES BY MID-WEEK.
SURF ALONG WEST-FACING SHORES WILL REMAIN MOSTLY STEADY THIS
WEEKEND AS THE NORTHWEST SWELL INFLUENCE GRADUALLY DECLINES, BUT A
NEW, LONG-PERIOD SOUTH SOUTHWEST REINFORCEMENT ARRIVES TODAY.
A MIX OF SMALL, MEDIUM TO LONG PERIOD SOUTH SWELLS WILL MAINTAIN
SMALL SURF ALONG SOUTH-FACING SHORES FOR THE NEXT SEVERAL DAYS.
THE LONG-PERIOD SOUTH SOUTHWEST SWELL DESCRIBED ABOVE WILL
MAINTAIN SMALL SURF ALONG SOUTH-FACING SHORES TODAY. ADDITIONAL
SMALL, MEDIUM TO LONG- PERIOD SOUTH SWELL REINFORCEMENTS WILL
ARRIVE SUNDAY THROUGH MID-WEEK. SURF ALONG SOUTH-FACING SHORES
SHOULD LIFT TO SUMMER AVERAGES BY SUNDAY AND HOLD THROUGH
WEDNESDAY.
MODERATE TO FRESH TRADES WILL MAINTAIN ROUGH AND CHOPPY SURF
ALONG EAST-FACING SHORES FOR THE NEXT SEVERAL DAYS.
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
NONE.
DISCUSSION...WROE
AVIATION...EVANS
MARINE...VAUGHAN
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