977
FXHW60 PHFO 150644
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
844 PM HST THU MAY 14 2026
SYNOPSIS
MODERATE TO LOCALLY BREEZY TRADE WINDS WILL CONTINUE TONIGHT,
WITH PERIODS OF SHOWERS FAVORING WINDWARD MOUNTAIN AREAS. AN
UPPER LEVEL LOW WILL BRIEFLY MOVE OVER THE REGION ON FRIDAY,
ENHANCING THREATS FOR LOCALLY HEAVY RAINFALL AND ISOLATED
THUNDERSTORMS. WHILE WIDESPREAD HEAVY RAIN IS NOT ANTICIPATED,
POCKETS OF HEAVY RAIN WITH LOCALIZED FLOODING IMPACTS ARE POSSIBLE
THROUGH FRIDAY NIGHT. WETTER THAN NORMAL CONDITIONS WILL LINGER
INTO SUNDAY.
SHORT TERM UPDATE
THE SATELLITE IMAGERY THIS EVENING SHOWS AN EXTENSIVE BAND OF
UNSTABLE LOW LEVEL CUMULUS CLOUDS BUILDS INTO THE ISLANDS FROM THE
SOUTHEAST DIRECTION. A LARGE BAND OF FREQUENT THUNDERSTORMS
CONTINUES TO FIRE ALONG THE EASTERN FLANK OF AN UPPER LOW ROUGHLY
300 MILES NORTH OF KAUAI. THIS UPPER LOW WILL CONTINUE TO DRIFT
SOUTH, TOWARDS KAUAI AND OAHU TONIGHT, AND SOME OF THESE
THUNDERSTORMS MAY REACH THE WESTERN ISLANDS BY FRIDAY MORNING.
ELEVATED THREATS FOR ADVISORY LEVEL FLOODING WITH WATER PONDING ON
AREA ROADWAYS BY FRIDAY. WE REMAIN LESS CONFIDENT ON WARNING LEVEL
FLOOD EVENTS, THEREFORE WE CONTINUE TO KEEP THE FLOOD WATCH IN
RESERVE UNTIL THIS SYSTEM GETS CLOSER TO THE ISLANDS AND WE CAN SEE
MORE SMALLER SCALE (MESOSCALE) CONVECTIVE HEAVY SHOWER DEVELOPMENT
RELATIVE TO THE ISLANDS.
LARGE SCALE GLOBAL WEATHER MODELS CONTINUE TO SHOW THE CENTER OF
THE UPPER LOW REACHING THE ISLAND OF KAUAI AROUND NOON HST ON
FRIDAY, THEN THE LOW KICKS OUT SLOWLY TO THE EAST AND WEAKENS ON
SUNDAY, WHERE ENHANCED SHOWERS WILL CONTINUE TO PRODUCE A WET
TRADE WIND WEATHER PATTERN ACROSS THE STATE.
THE KILAUEA VOLCANO ON THE BIG ISLAND CONTINUES TO ERUPT IN A
FOUNTAIN OF LAVA THIS EVENING, TRADE WINDS ARE BLOWING MOST OF THE
ASHFALL (TEPHRA) FROM THE VOLCANO AREA TOWARDS THE SOUTHWEST INTO
THE KAU DISTRICT. A SPECIAL WEATHER STATEMENT (SPSHFO) FOR THIS
EVENT WAS ISSUED THIS AFTERNOON DUE TO LIMITED ASHFALL IMPACTS IN
A TRADE WIND WEATHER PATTERN.
UPDATED THE OVERNIGHT TO EARLY FRIDAY MORNING FORECAST THIS
EVENING TO INCREASE CLOUDS AND SHOWERS ALONG THIS DEVELOPING LOW
LEVEL CLOUD BAND SPREADING ACROSS THE ISLAND CHAIN.
PREVIOUS DISCUSSION
ISSUED AT 358 PM HST THU MAY 14 2026
HIGH PRESSURE FAR NORTH OF THE STATE CONTINUES TO MAINTAIN BREEZY
TRADE WINDS ACROSS THE REGION THIS AFTERNOON, WITH CLOUDS AND
SHOWERS FOCUSING PRIMARILY OVER WINDWARD AND MAUKA AREAS. THESE
LOCALLY BREEZY TRADES WILL CONTINUE INTO THE EVENING HOURS, BUT
ARE ANTICIPATED TO WEAKEN TO MORE MODERATE LEVELS OVERNIGHT.
AN UPPER LEVEL LOW THAT CAN CURRENTLY BE SEEN ON WATER VAPOR
IMAGERY ENTERING THE NORTHERN OFFSHORE WATERS THIS AFTERNOON IS
EXPECTED TO CONTINUE DIGGING SOUTHWARD TOWARDS THE ISLAND CHAIN
TONIGHT. LATEST GLOBAL GUIDANCE REMAINS IN GOOD AGREEMENT THAT
THIS UPPER LOW WILL ARRIVE NEAR KAUAI IN THE PRE-DAWN HOURS FRIDAY
MORNING, THEN MOVE OVER THE GARDEN ISLE DURING THE DAY WITH
TEMPERATURES ALOFT AT 500MB ANTICIPATED TO BE AS COLD AS -15C.
THIS WILL LEAD TO INCREASING INSTABILITY OVER THE STATE, AND THE
STRENGTH OF THE UPPER LEVEL LOW WILL INDUCE A SURFACE TROUGH,
SERVING AS A TRIGGER FOR HEAVY SHOWERS AND ISOLATED THUNDERSTORMS.
GIVEN THAT THE UPPER LOW IS EXPECTED TO BE CENTERED OVER KAUAI AT
ITS CLOSEST PASS, THE BEST FORCING IS EXPECTED TO BE OVER OAHU
AND PARTS OF MAUI COUNTY, WHERE GUIDANCE IS SHOWING OVER 1000
J/KG OF CAPE BY FRIDAY AFTERNOON. OF PARTICULAR NOTE, LATEST QPF
GUIDANCE HAS TRENDED UPWARD, AND THE OFFICIAL FORECAST HAS BEEN
ADJUSTED ACCORDINGLY, BUT WITH GREAT UNCERTAINTY. IN PARTICULAR,
SOME GUIDANCE IS HINTING AT THE POSSIBILITY OF A PLUME OF MOISTURE
DEVELOPING FROM MOLOKAI TOWARDS OAHU FROM LATE MORNING INTO THE
AFTERNOON WITHIN A SLIGHTLY MORE ESE WIND REGIME. SHOULD THIS
OCCUR, THERE IS POTENTIAL FOR HEAVY RAIN TO TRAIN OVER PORTIONS OF
OAHU, WHICH COULD LEAD TO FLOODING CONCERNS. THIS SCENARIO IN A
FEW HI-RES MEMBERS THAT MAKE UP THE NATIONAL BLEND OF MODELS (NBM)
IS LIKELY THE REASON FOR AN UNUSUALLY LARGE DISCREPANCY BETWEEN
THE QPF 50TH PERCENTILE FOR OAHU ON FRIDAY AND THE MEAN, WITH THE
MEAN BEING SIGNIFICANTLY HIGHER. MEANWHILE, RAPID REFRESH
FORECAST SYSTEM (RRFS) MEMBERS SEEMINGLY RANGE FROM NOT MUCH
NOTABLE RAIN OVER THE ISLANDS ON FRIDAY, TO INTERIOR AND LEEWARD
AFTERNOON CONVECTION DEVELOPMENT, TO PLUMING AND POTENTIAL
TRAINING OF HEAVY RAIN AND THUNDERSTORMS LEADING TO FLOODING.
THESE SCENARIOS ARE SIMILAR (THOUGH TO A LESSER DEGREE) FOR KAUAI
AND THE ISLANDS OF MAUI COUNTY AS WELL, AND SLIGHT DEVIATIONS OF
THE MAIN UPPER LOW COULD SHIFT CONVECTIVE FOCUS EAST OR WEST
ACCORDINGLY. IN SUMMARY, THE QPF FORECAST FOR FRIDAY HAS
SIGNIFICANT AND UNUSUAL UNCERTAINTY. THERE LIKELY WILL BE HEAVY
RAIN OVER SOME LOCATIONS, AND GIVEN LIGHTER LOW-LEVEL WINDS,
SHOWERS COULD BE SLOW MOVING WITH THE POTENTIAL FOR ANCHORING ON
ISLAND TERRAIN. HOWEVER, NOT CONFIDENT ENOUGH AT THIS POINT TO
ISSUE A FLOOD WATCH GIVEN THE MESOSCALE EFFECTS THAT COULD BE AT
PLAY AND THE LACK OF A CLEAR FOCUS OR CONSENSUS, BUT IT IS
CERTAINLY WORTH KEEPING AN EYE ON FOR FLOODING IMPACTS. AT THIS
TIME, HAVE OPTED INSTEAD TO CONTINUE THE HEAVY RAIN AND
THUNDERSTORM MENTIONS IN THE FORECAST.
THIS WEEKEND, THE UPPER LEVEL LOW WILL BEGIN TO DRIFT FURTHER
AWAY FROM THE STATE, WHICH SHOULD DECREASE THE THREAT OF
THUNDERSTORMS. WHILE THE INSTABILITY DECREASES OVER THE WEEKEND,
LOW LEVEL MOISTURE WILL INCREASE FROM THE SOUTHEAST WITH
PRECIPITABLE WATER VALUES APPROACHING 2 INCHES BY LATE SATURDAY
OVER WINDWARD BIG ISLAND. PERIODS OF HEAVY RAIN WILL BE POSSIBLE
OVER WINDWARD AND SOUTHEAST BIG ISLAND THIS WEEKEND, WITH SOME
ENHANCED SHOWERS POSSIBLE ELSEWHERE ACROSS THE STATE. BY NEXT
WEEK, A MORE TYPICAL TRADE WIND PATTERN LOOKS TO RETURN TO THE
REGION.
AVIATION
MODERATE TO LOCALLY BREEZY TRADES. LOW CIGS AND SHRA POSSIBLE
ALONG WINDWARD AND MAUKA LOCATIONS WITH SOME SPILLOVER POSSIBLE
INTO LEEWARD AREAS. MVFR CONDS IN ANY HEAVIER SHRA BUT VFR SHOULD
PREVAIL. AN UPPER LOW NEAR THE STATE MAY PROVIDE THE POTENTIAL
FOR PERIODS OF +RA AND ISOL TSTMS, ESPECIALLY OVER WESTERN SIDE
OF THE STATE. CONDS MAY DETERIORATE TO IFR/MVFR IN THOSE
LOCATIONS.
AIRMET SIERRA IS IN EFFECT FOR MTN OBSC FOR WINDWARD LOCATIONS OF
ALL ISLANDS DUE TO CLDS AND SHRA.
AIRMET TANGO IS IN EFFECT FOR LOW-LEVEL TURB LEE OF TERRAIN DUE
TO THE BREEZY TRADES.
MARINE
HIGH PRESSURE FAR NORTH OF THE ISLANDS WILL MAINTAIN MODERATE TO
LOCALLY FRESH TRADES THROUGH THIS EVENING. AN UPPER LEVEL LOW AND
ITS SURFACE REFLECTION OF A SURFACE TROUGH NORTH OF KAUAI THIS
AFTERNOON WILL TURN WEAKENING WINDS MORE EAST SOUTHEAST FROM
TOMORROW INTO THE WEEKEND. THE SMALL CRAFT ADVISORY (SCA) HAS BEEN
EXTENDED FOR THE WINDIER ZONES OF MAUI COUNTY AND BIG ISLAND
THROUGH 6 AM HST FRIDAY MORNING. THE CLOSE PROXIMITY OF THE UPPER
LOW, ALONG WITH DISTURBANCES COMING UP AROUND THE LOW FROM THE
SOUTH SOUTHWEST, WILL INCREASE THE THREAT FOR WIDESPREAD RAIN
WITH PERIODS OF LOCALLY HEAVY RAIN AND ISOLATED THUNDERSTORMS
ACROSS THE ENTIRE ISLAND CHAIN AND SURROUNDING WATERS TOMORROW.
A SMALL, MODERATE PERIOD NORTH NORTHWEST (320-330 DEGREE) SWELL
WILL CONTINUE ITS PEAK THIS EVENING AND PRODUCE NEAR TO SLIGHTLY
ABOVE HEAD HIGH SURF ALONG MANY NORTH-FACING SHORES. THIS SWELL
WILL GRADUALLY FADE FROM LATE TONIGHT THROUGH THE WEEKEND.
A MIX OF SMALL, MEDIUM TO LONG PERIOD SOUTH SWELLS WILL MAINTAIN
SMALL SURF ALONG SOUTH-FACING SHORES INTO THE WEEKEND. A SERIES
OF GALE LOWS PASSING SOUTH OF NEW ZEALAND SHOULD SEND A SERIES OF
SMALL SOUTH SWELLS TO THE HAWAIIAN ISLANDS THROUGH NEXT WEEK.
SURF SHOULD LIFT TO NEAR SUMMER AVERAGES AROUND SUNDAY AND THIS
WILL HOLD THROUGH THE WEEK. LOCALLY MODERATE TO FRESH TRADES WILL
MAINTAIN ROUGH AND CHOPPY SURF ALONG EAST-FACING SHORES.
TIDES WILL PEAK AROUND 2.5 FT MLLW THIS WEEKEND. COMBINED WITH
ONGOING TRADES AND A SMALL SOUTH SWELL BUMP, WATER LEVELS WILL
PEAK NEAR 3.0 FT EARLY NEXT WEEK. MINOR OVERWASH OF LOW LYING
COASTAL AREAS WILL BE POSSIBLE DURING TIMES OF HIGH TIDE.
HFO WATCHES/WARNINGS/ADVISORIES
SMALL CRAFT ADVISORY UNTIL 6 AM HST FRIDAY FOR ALENUIHAHA
CHANNEL-BIG ISLAND LEEWARD WATERS-BIG ISLAND SOUTHEAST WATERS-
MAALAEA BAY-PAILOLO CHANNEL.
SHORT TERM...BOHLIN
PREVIOUS DISCUSSION...VAUGHAN
AVIATION...WALSH
MARINE...BLOOD
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