211
FXHW60 PHFO 061330
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
330 AM HST MON OCT 6 2025
SYNOPSIS
A BAND OF EMBEDDED SHOWERS ARE BEING ESCORTED BY A TROUGH JUST
NORTH OF THE HAWAIIAN ISLANDS THIS MORNING, BRINGING PERIODS OF
ISOLATED SHOWERS TO KAUAI AND OAHU TODAY. WINDS WILL WEAKEN AND
BECOME MORE SOUTHEASTERLY, LEADING TO THE DEVELOPMENT OF A LAND
AND SEA BREEZE REGIME, PERSISTING THROUGH THURSDAY. THEREAFTER,
MODERATE TRADES RETURN AT THE END OF THE WEEK.
DISCUSSION
LATEST SATELLITE IMAGERY CONTINUES TO SHOW AN UNAMBIGUOUS BAND OF
EMBEDDED SHOWERS ESCORTED BY A NORTH TO SOUTH PROPAGATING TROUGH
JUST NORTH OF THE HAWAIIAN ISLANDS. MODEL GUIDANCE OF THE GFS AND
ECMWF HAS DONE A FAIRLY DECENT JOB IDENTIFYING THIS TROUGH,
PORTRAYING ISOLATED SHOWER ACTIVITY DESCENDING UPON KAUAI EARLY
THIS MORNING AND IS PROGGED TO EXTEND FURTHER SOUTHWARD INTO OAHU
SHORTLY THEREAFTER BEFORE DISSIPATING. AN UPTICK IN SHOWER
ACTIVITY HAS BEEN PRESENTED OVER KAUAI AND DIALED DOWN OVER OAHU
AS THIS FEATURE PASSES SOUTHWARD, BUT GIVEN THE QUICK NATURE OF
THE TROUGH AND ITS WEAKENING STATUS, ANTICIPATED RAINFALL
ACCUMULATIONS ARE EXPECTED TO BE MINIMAL. THAT SAID, A CLEAR-CUT
MID-LEVEL LOW NEAR 29N 150W AS OF 0300 HST (13Z), WHERE TOWERING
CUMULUS AND HEAVIER SHOWERS ARE BEING OBSERVED WELL NORTHEAST OF
THE ISLANDS ARE EXPECTED TO KEEP DISTANCE AWAY FROM THE ISLANDS,
AND NOT IMPACTFUL TO HAWAIIAN WEATHER TODAY.
A SECONDARY TROUGH, SLIGHTLY WEAKER IN COMPOSITION, EXTENDS
SOUTHEASTWARD FROM THE AFOREMENTIONED MID-LEVEL LOW AND IS SLOWLY
MEANDERING WESTWARD. WINDS ACROSS THE HAWAIIAN ISLANDS HAVE
NOTICEABLY EASED IN RESPONSE OF EACH PASSING TROUGH, PROGGED TO
VEER EAST-SOUTHEASTERLY, RESULTING IN A MORE PRONOUNCED LAND AND
SEA BREEZE REGIME LASTING THROUGH EARLY THURSDAY. IN SUCH A
PATTERN WHERE THE LOCAL SCALE WINDS ARE VIRTUALLY ABSENT, ISLAND
HEATING WILL SUPPORT SEA BREEZES DURING THE DAY, WHICH WILL
ENHANCE LEEWARD AND INTERIOR SHOWER ACTIVITY, AND OVERNIGHT
COOLING WILL DRIVE LAND BREEZES AT NIGHT, CLEARING THE NIGHT SKIES
AND LIMITING SHOWERS.
LIGHT TO MODERATE TRADES BEGIN TO REESTABLISH LATE THURSDAY WITH
THE INTRODUCTION OF A STRONG HIGH PRESSURE RIDGE AXIS BUILDING IN
FAR TO THE NORTHEAST OF THE REGION. LATEST MODEL GUIDANCE SUGGESTS
THIS PRESSURE RIDGE WILL SLOWLY MIGRATE SOUTHWARD TOWARD THE
MIDDLE OF NEXT WEEKEND, INDICATIVE OF MODERATE TRADES ACROSS MUCH
OF THE STATE DURING THIS TIME. THERE IS A BIT OF UNCERTAINTY IN
THE FORECAST FOR THE LATTER HALF OF THE WEEK, HOWEVER, AS SOME
DETERMINISTIC MODEL GUIDANCE IS HINTING AT ANOTHER SURFACE TROUGH
DEVELOPING JUST NORTH OF THE HAWAIIAN ISLANDS LATE THIS WEEK,
WHICH WOULD DISRUPT WINDS AND INCREASE SHOWER ACTIVITY. CONFIDENCE
REMAINS LOW CONCERNING THE EXACT TIMING AND PLACEMENT, OR WHETHER
THE FEATURE WILL DEVELOP.
AVIATION
LIGHT TO MODERATE NORTHERLY WINDS ARE PUSHING A BAND OF LOW LEVEL
CLOUDS WITH EMBEDDED SHOWERS OVER KAUAI EARLY THIS MORNING. THIS
BAND IS EXPECTED TO PUSH OVER OAHU DURING MORNING COMMUTE HOURS
AND DISSIPATE OVER THE ISLAND THROUGH THE AFTERNOON. AIRMET
SIERRA IS CURRENTLY IN EFFECT FOR MTN OBSC OVER N TO SE SECTIONS
OF KAUAI AS THIS BAND OF SHOWERS DRIFTS SOUTH GENERATING PERIODS
OF MVFR CONDITIONS. AIRMET SIERRA MAY NEED TO BE EXPANDED FOR OAHU
AS THIS BAND CONTINUES TO DRIFT SOUTH AND SETTLE OVER THE ISLAND
LATER THIS MORNING AND AFTERNOON.
WINDS ARE EXPECTED TO WEAKEN A NOTCH THIS AFTERNOON AND VEER MORE
SOUTHERLY AS THE TROUGH WEAKENS AND RETROGRADES WEST AND OTHER
TROUGH DEEPENS EAST OF THE STATE. EXPECT AFTERNOON SEABREEZE
CONDITIONS WILL DEVELOP EACH AFTERNOON GENERATING PERIODS OF MVFR
CONDITIONS OVER SHELTERED LEEWARD AND INTERIOR LOCATIONS. LAND
BREEZE WILL DEVELOP OVERNIGHT WITH CONDITIONS IMPROVING TO MOSTLY
VFR CONDITIONS. THIS PATTERN IS EXPECTED TO REPEAT OVER THE NEXT
COUPLE OF DAYS.
MARINE
A TROUGH OVER THE NORTHWEST COASTAL WATERS IS MOVING SOUTHEAST
AND WILL MOVE OVER KAUAI THIS MORNING. AS THE TROUGH MOVES OVER
KAUAI, SCATTERED SHOWERS ARE EXPECTED ALONG THE TROUGH WITH MODERATE
NORTHEAST TRADE WINDS FILLING IN OVER KAUAI WATERS, WHILE
ELSEWHERE GENTLE TO LOCALLY MODERATE EASTERLY TRADE WINDS ARE
EXPECTED THROUGH TONIGHT. ANOTHER TROUGH NORTHEAST OF THE OFFSHORE
WATERS WILL SLOWLY DRIFT WEST OVER THE NEXT FEW DAYS. TUESDAY
THROUGH THURSDAY LIGHT TO GENTLE SOUTHEAST FLOW ACROSS ALL ZONES
ARE EXPECTED AND WILL ALSO GIVE WAY TO LOCALIZED LAND AND SEA
BREEZES. MODERATE TRADES WILL FILL IN FROM EAST TO WEST AT THE END
OF THE WEAK AS HIGH PRESSURE BUILDS FAR NORTHEAST AND DRIFTS
SOUTHEAST.
THE CURRENT MODERATE NORTH-NORTHWEST SWELL THAT PEAKED WELL ABOVE
HIGH SURF ADVISORY (HSA) LEVELS SUNDAY HAS BEGUN TO DECLINE QUICKLY
OVERNIGHT AND WILL CONTINUE TO DECLINE TODAY. ALSO, A SMALL MEDIUM
TO LONG PERIOD NORTHWEST (320 DEG) SWELL IS EXPECTED TO FILL IN
THIS AFTERNOON, PEAK TONIGHT AND SLOWLY DECLINE TUESDAY. NO SIGNIFICANT
NORTH SWELLS ARE EXPECTED THROUGH THE WEEK EXCEPT THE POTENTIAL
FOR A MODERATE MEDIUM TO LONG PERIOD NORTHWEST (320 DEG) SWELL
SUNDAY INTO EARLY NEXT WEEK.
A SMALL, LONG- PERIOD SOUTHWEST SWELL HAS STARTED TO FILL IN
OVERNIGHT WITH LONG PERIOD 16 SECOND FORERUNNERS. THE SWELL IS
EXPECTED TO PEAK TODAY BEFORE SUBSIDING TUESDAY. ANOTHER SMALL
LONG- PERIOD SOUTHWEST (200 DEG) SWELL IS POSSIBLE BY THE LATER
HALF OF THE WEEK. SURF ALONG EAST- FACING SHORES WILL REMAIN BELOW
AVERAGE THROUGH THE WEEK EXCEPT FOR SELECT SHORELINES EXPOSED TO
THE CURRENT NORTH SWELL TODAY.
PEAK HIGH TIDES ASSOCIATED WITH THE LUNAR CYCLE WILL LEAD TO MINOR
COASTAL FLOODING ALONG SHORELINES AND LOW LYING COASTAL AREAS
STARTING TUESDAY THROUGH THE WEEKEND. COASTAL FLOODING WILL
COINCIDE WITH THE DAILY PEAK TIDE EACH AFTERNOON.
FIRE WEATHER
LIGHT WINDS AND INCREASED SHOWERS WILL HELP MAINTAIN BELOW
CRITICAL FIRE WEATHER THRESHOLDS FOR THE NEXT SEVERAL DAYS.
TEMPERATURE INVERSION HEIGHTS ACROSS THE STATE WILL RANGE FROM
7000 TO 8000 FEET THROUGH TONIGHT.
HFO WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...PIERCE
AVIATION...ALMANZA
MARINE...SHIGESATO
FIRE WEATHER...PIERCE
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