604
FXHW60 PHFO 150158
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
358 PM HST THU MAY 14 2026
SYNOPSIS
BREEZY TRADE WINDS WILL PERSIST INTO THIS EVENING, WITH SHOWERS
FAVORING WINDWARD AND MAUKA AREAS. AN UPPER LEVEL DISTURBANCE WILL
BRIEFLY MOVE OVER THE STATE ON FRIDAY AND WILL BRING THE THREAT
OF HEAVY RAIN AND ISOLATED THUNDERSTORMS OVER SELECT AREAS. WHILE
WIDESPREAD HEAVY RAIN IS NOT ANTICIPATED, POCKETS OF HEAVY RAIN
WITH SOME FLOODING IMPACTS WILL BE POSSIBLE ON FRIDAY. WETTER THAN
NORMAL CONDITIONS WILL LIKELY PERSIST THROUGH THE WEEKEND,
ESPECIALLY OVER WINDWARD AND MAUKA AREAS, WHERE SCATTERED SHOWERS
ARE EXPECTED.
DISCUSSION
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 ARE EXPECTED FOR NEXT DAY OR SO.
LOW CEILINGS AND SHOWERS ARE EXPECTED AT TIMES ALONG WINDWARD AND
MAUKA LOCATIONS THROUGH TONIGHT WITH DOMINANT VFR AND BRIEF PERIODS
OF MVFR. AN UPPER LOW NEAR THE STATE MAY PROVIDE THE POTENTIAL FOR
PERIODS OF HEAVY DOWNPOURS THROUGH FRIDAY, ESPECIALLY OVER THE
CENTRAL ISLANDS.
AIRMET TANGO REMAINS IN EFFECT FOR LOW-LEVEL TURBULENCE OVER AND
IN THE LEE OF TERRAIN DUE TO THE BREEZY TRADES THROUGH AT LEAST
TONIGHT.
MARINE
HIGH PRESSURE FAR NORTH OF THE ISLANDS WILL MAINTAIN LOCALLY
STRONG TRADES THROUGH THIS EVENING BEFORE THE PATTERN CHANGES. AN
UPPER LEVEL LOW IS INDUCING A SURFACE TROUGH JUST TO THE NORTH OF
KAUAI THIS AFTERNOON AND AS IT MOVES SOUTH, IT WILL CAUSE THE
WINDS TO VEER EAST-SOUTHEAST AND WEAKEN TO MODERATE TO FRESH
SPEEDS TOMORROW INTO THE WEEKEND. THE SMALL CRAFT ADVISORY (SCA)
HAS BEEN EXTENDED FOR THE WINDIER ZONES OF MAUI COUNTY AND THE BIG
ISLAND THROUGH 6 AM HST FRIDAY MORNING. THE UPPER LEVEL
DISTURBANCE WILL BRING THE THREAT OF HEAVY RAIN AND ISOLATED
THUNDERSTORMS TO THE ISLAND CHAIN ON FRIDAY.
A NEW SMALL TO MODERATE, LONG PERIOD NW TO NNW (320 DEGREE TO 330
DEGREE) SWELL WILL LIKELY PEAK LATE THIS AFTERNOON INTO THE
EVENING AND PRODUCE ABOVE AVERAGE SURF ALONG NORTH FACING SHORES.
OBSERVATIONS AT BUOY 51001 SHOWED THIS SWELL PEAKED AT ABOUT 5
FEET 14 SECONDS AROUND MID MORNING. THIS SWELL SHOULD GRADUALLY
FADE TONIGHT INTO 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 GALES INITIALLY PASSING SOUTH OF NEW ZEALAND AND NOW SETTING
UP TO ITS EAST SHOULD SEND A SERIES OF SMALL SOUTH SWELLS TO THE
HAWAIIAN ISLANDS ALL THROUGHOUT NEXT WEEK. SURF SHOULD RISE TO
NEAR THE SUMMER AVERAGE AROUND SUNDAY AND HOLD THROUGH THE WEEK.
MEANWHILE ALONG EAST FACING SHORES, LOCALLY STRONG TRADES WILL
MAINTAIN ROUGH AND CHOPPY SURF. A SLIGHT DECREASE OF WIND SWELL IS
EXPECTED TONIGHT INTO THE WEEKEND AS THE TRADES WEAKEN TO
MODERATE TO LOCALLY FRESH SPEEDS.
TIDES PEAK AROUND 2.5 FT MLLW THIS WEEKEND. COMBINED WITH ONGOING
TRADES AND A MODEST BOOST IN SOUTH SWELL, WATER LEVELS WILL PEAK
AROUND 3.0 FT LATE THIS WEEKEND INTO EARLY NEXT WEEK. MINOR
OVERWASH OF LOW LYING COASTAL AREAS WILL BE POSSIBLE DURING THE
AFTERNOON HIGH TIDES AT THIS TIME.
HFO WATCHES/WARNINGS/ADVISORIES
SMALL CRAFT ADVISORY UNTIL 6 AM HST FRIDAY FOR MAALAEA BAY-
PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG
ISLAND SOUTHEAST WATERS.
DISCUSSION...VAUGHAN
AVIATION...TS
MARINE...FARRIS
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