013
FXHW60 PHFO 020205 CCA
AFDHFO
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE HONOLULU HI
405 PM HST WED OCT 1 2025
SYNOPSIS
HIGH PRESSURE NORTHEAST OF THE STATE WILL BE DISPLACED FARTHER
NORTHEAST BY A TROUGH NORTH OF THE STATE BEGINNING THURSDAY. THIS
WILL WEAKEN BACKGROUND WINDS AS THEY BECOME MORE EAST
SOUTHEASTERLY, ALLOWING LOCALIZED DAYTIME SEA BREEZES AND
OVERNIGHT LAND BREEZES EACH DAY INTO THE WEEKEND. MODERATE TRADES
MAY BUILD BACK DURING THE SECOND HALF OF THE WEEKEND INTO EARLY
NEXT WEEK AS A NEW HIGH BUILDS NORTH OF THE STATE.
DISCUSSION
ACCORDING TO THE HAWAIIAN VOLCANO OBSERVATORY, EPISODE 34 OF
KILAUEA'S ONGOING HALEMA'UMA'U ERUPTION ABRUPTLY ENDED THIS
MORNING AT 7:03AM HST. WHILE THIS LATEST ACTIVE EPISODE OF THE
ERUPTION HAS ENDED, VOG COULD CONTINUE TO AFFECT PORTIONS OF THE
BIG ISLAND THROUGH THE NEXT COUPLE OF DAYS.
ELSEWHERE, LATEST SATELLITE IMAGERY AND RADAR DATA SHOWS THAT THE
BAND OF CLOUDS AND SHOWERS THAT MOVED INTO THE ISLANDS ON MODERATE
EASTERLY TRADE WINDS EARLIER TODAY HAS LARGELY DIMINISHED. SOME
LOCATIONS, PARTICULARLY ALONG WINDWARD OAHU, PICKED UP MORE THAN A
QUARTER OF AN INCH OF RAIN EARLIER THIS MORNING, BUT VERY LITTLE
RAINFALL HAS BEEN MEASURED ACROSS THE STATE SINCE MID-DAY. THE
AFTERNOON UPPER AIR SOUNDING FROM HILO SHOWED A STRONG INVERSION
AROUND 8000 FEET, WHILE THE INVERSION AT LIHUE REMAINS WEAKER DUE
TO THE PROXIMITY OF AN UPPER LOW TO THE NORTH-NORTHWEST OF THE
STATE.
OVER THE NEXT COUPLE OF DAYS, A TROUGH APPROACHING FROM THE
NORTHWEST WILL WEAKEN BEFORE REACHING THE ISLANDS. HOWEVER, AS
THIS TROUGH APPROACHES, SURFACE HIGH PRESSURE THAT IS CURRENTLY
CENTERED ROUGHLY 800 MILES NORTHEAST OF HONOLULU WILL BE DISPLACED
FARTHER EAST AWAY FROM THE ISLANDS. THIS WILL DISRUPT OUR TYPICAL
EASTERLY TRADE WIND FLOW BY WEAKENING WINDS AND VEERING THEM TO
BECOME MORE EASTERLY TO SOUTHEASTERLY THURSDAY INTO FRIDAY. AS A
RESULT OF THE WEAKER EAST TO SOUTHEAST WINDS, THERMALLY DRIVEN
DAYTIME SEA BREEZES AND OVERNIGHT LAND BREEZES ARE EXPECTED TO
DEVELOP. THIS PATTERN WILL FAVOR SHOWERS ALONG INTERIOR AND
UPSLOPE SECTIONS OF THE ISLANDS FROM LATE MORNING THROUGH EARLY
EVENING EACH DAY, THEN CLEARING OVERNIGHT. ADDITIONALLY,
DOWNSTREAM CONVERGENCE ALONG THE LEEWARD SIDES OF ISLAND MOUNTAINS
COULD PRODUCE PLUMES OF CLOUDS AND SHOWERS THAT EXTEND WEST TO
NORTHWEST FROM EACH ISLAND. THIS "ISLAND PLUME" EFFECT HAS THE
POTENTIAL TO BRIEFLY ENHANCE RAINFALL AMOUNTS OVER OAHU AND KAUAI
IN PARTICULAR WITH THIS SOUTHEASTERLY WIND REGIME FROM THURSDAY
THROUGH SATURDAY.
GUIDANCE INDICATES THAT EASTERLY TRADES WILL BUILD BACK INTO THE
REGION DURING THE LATTER PART OF THE WEEKEND/INTO EARLY NEXT WEEK
AS A NEW HIGH DEVELOPS AND STRENGTHENS FAR NORTH OF THE STATE.
HOWEVER, GLOBAL MODELS DIFFER SIGNIFICANTLY REGARDING THE
DEVELOPMENT OF A TROUGH NORTHEAST OF THE ISLANDS BY THE MIDDLE OF
NEXT WEEK. THIS COULD CAUSE SIGNIFICANT DIFFERENCES IN THE WIND
AND SHOWER REGIMES NEAR THE END OF THE SEVEN DAY FORECAST.
AVIATION
MODERATE TRADES WILL PERSIST AND GRADUALLY VEER ESE TOMORROW INTO
FRIDAY. LOW CLOUDS AND SHOWERS WILL MAINLY FOCUS OVER WINDWARD
AND MOUNTAIN AREAS, PARTICULARLY OVERNIGHT INTO THE EARLY MORNING
HOURS. THE SLIGHTLY VEERED TRADE WIND FLOW MAY ALLOW FOR SEA
BREEZES TO DEVELOP ACROSS LEEWARD AREAS EACH AFTERNOON, BRINGING
CLOUDS AND ISOLATED SHOWERS TO THOSE AREAS. MVFR CONDITIONS WILL
BE POSSIBLE IN ANY SHOWERS THROUGH THE PERIOD. OTHERWISE, VFR WILL
PREVAIL.
NO AIRMETS ARE IN EFFECT. AIRMET SIERRA MAY BE NEEDED ACROSS SOME
WINDWARD AREAS TONIGHT IF SHOWER COVERAGE BECOMES SUFFICIENT.
KILAUEA ERUPTION EPISODE 34 ENDED THIS MORNING AT 7:03 AM HST.
THE POTENTIAL FOR ASH TO IMPACT AVIATION HAS DIMINISHED, SO VA
SIGMET WHISKEY HAS BEEN CANCELLED.
MARINE
SURFACE HIGH PRESSURE NORTH OF THE STATE WILL SLOWLY MOVE
NORTHEAST AS A TROUGH PASS FAR NORTH OF THE AREA THROUGH FRIDAY.
MODERATE TRADES WILL GRADUALLY WEAKEN TO LIGHT TO GENTLE SPEEDS
THURSDAY AND VEER EAST SOUTHEAST THURSDAY NIGHT AND FRIDAY. A NEW
HIGH WILL FILL IN FROM THE NORTHWEST OVER THE WEEKEND ALLOWING
MODERATE EAST NORTHEAST TRADE WINDS TO RETURN.
A SMALL, MEDIUM PERIOD NORTH NORTHWEST SWELL HAS ARRIVED LOCALLY
BASED ON THE HANALEI NEAR SHORE BUOY WITH SWELL ENERGY INCREASING
IN THE 16-14 SECOND BAND. THIS SWELL WILL CONTINUE TO BUILD DOWN
THE ISLAND CHAIN REST OF TODAY GENERATING SMALL SURF ALONG NORTH
AND WEST FACING SHORES INTO THURSDAY. THIS SWELL WILL BEGIN TO
FADE FRIDAY INTO THE WEEKEND. A MODERATE, MEDIUM PERIOD NORTHWEST
SWELL IS EXPECTED TO FILL IN SATURDAY, AND PEAK LATE SATURDAY
INTO SUNDAY. THIS SWELL WILL BUILD SURF HEIGHTS TO WELL OVER HEAD
HIGH ALONG MANY NORTH AND WEST- FACING SHORES BY SUNDAY BEFORE
FADING INTO EARLY NEXT WEEK.
A SMALL, LONG PERIOD SOUTH SOUTHWEST SWELLS WILL FILL IN TONIGHT, PEAK
THURSDAY, BEFORE FADING FRIDAY INTO THE WEEKEND KEEPING SMALL SURF
ALONG SOUTH FACING SHORES. ANOTHER SMALL LONG, PERIOD SOUTH SOUTHWEST
SWELL IS EXPECTED TO ARRIVE LATE OVER THE WEEKEND INTO EARLY NEXT
WEEK.
SURF ALONG EAST-FACING SHORES WILL REMAIN BELOW AVERAGE INTO EARLY
NEXT WEEK.
FIRE WEATHER
WIND SPEEDS WILL REMAIN BELOW CRITICAL FIRE WEATHER THRESHOLDS
FOR THE NEXT SEVEN DAYS. TEMPERATURE INVERSION HEIGHTS ACROSS THE
STATE WILL RANGE FROM 7,000 TO 8,500 FEET.
HFO WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...VAUGHAN
AVIATION...FARRIS
MARINE...ALMANZA
FIRE WEATHER...VAUGHAN
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