618
FXHW60 PHFO 150136
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
336 PM HST SUN SEP 14 2025
SYNOPSIS
LOCALLY BREEZY TRADES DELIVER LIMITED CLOUDS AND SHOWERS WINDWARD
AND MAUKA THROUGH THURSDAY. AN UPTICK IN SHOWERS CAN BE EXPECTED
THEREAFTER AS A BATCH OF DEEPER MOISTURE MOVES THROUGH THE AREA.
DISCUSSION
LOCALLY BREEZY TRADES PREVAIL BENEATH A STOUT INVERSION WHICH
SLOPES GENTLY UPWARD FROM AROUND 5KFT AT LIHUE TO 8KFT AT HILO.
SHALLOW SATURATION AROUND 3KFT IN DEPTH ATOP THE BOUNDARY LAYER
SUPPORTS ISOLATED TO SCATTERED LIGHT SHOWERS THAT WILL INCREASE IN
COVERAGE TONIGHT THROUGH EARLY TOMORROW MORNING. FLAT,
TEXTURELESS STRATOCU ON VISIBLE IMAGERY ARE SYMPTOMATIC OF THE
RESIDENT HIGH STABILITY ENVIRONMENT AND WILL CHANGE VERY LITTLE
DURING THE NEXT FEW DAYS, PARTICULARLY AS EASTERLY DRY ADVECTION
CENTERED AROUND 700MB REINFORCES EXISTING STABILITY.
FURTHER NORTH, A COLD FRONT EXTENDING FROM LOW PRESSURE IN THE
GULF OF ALASKA IS DRAPED ALONG AND SOUTH OF 40N. THE LONG RANGE
GUIDANCE MAINTAINS SOLID CONSENSUS THAT THIS FRONT WILL SEED THE
TRADES WITH DEEPER MOISTURE LATE THIS WEEK AS BUILDING HIGH
PRESSURE PINCHES OFF THE TAIL END OF THE FRONT. THIS MOISTURE THEN
PIVOTS TOWARD THE HAWAIIAN ISLANDS BRINGING AN INCREASE IN TRADE
WIND SHOWERS BY WEEK'S END.
AVIATION
HIGH PRESSURE NORTH OF THE STATE AND A WEAK TROUGH TO THE
SOUTHEAST WILL KEEP MODERATE TO BREEZY EASTERLY TRADE WINDS IN THE
FORECAST THROUGH MONDAY. CLOUDS AND SHOWERS WILL FAVOR WINDWARD
AND MOUNTAIN AREAS, PARTICULARLY AT NIGHT, THOUGH STABLE
CONDITIONS ALOFT WILL LIMIT SHOWER ACTIVITY OVERALL. VFR
CONDITIONS WILL PREVAIL OUTSIDE OF ANY BRIEF PASSING SHOWERS.
NO AIRMETS ARE IN EFFECT AND NONE ARE ANTICIPATED TO BE NEEDED
THROUGH MONDAY.
MARINE
THE PRESSURE GRADIENT BETWEEN A WEAK HIGH NORTH OF THE ISLANDS
AND AN AREA OF LOW PRESSURE SOUTH OF THE ISLANDS WILL RESULT IN
CONTINUED MODERATE TO LOCALLY STRONG TRADE WINDS THROUGH MONDAY
AFTERNOON. THEREFORE, A SMALL CRAFT ADVISORY (SCA) REMAINS IN
EFFECT FOR THE WINDIER CHANNELS AND WATERS SURROUNDING MAUI COUNTY
AND THE BIG ISLAND. THE HIGH TO THE NORTH WILL SLIGHTLY WEAKEN ON
TUESDAY AS A FRONT MOVES ACROSS THE NORTH PACIFIC, ALLOWING
TRADES TO BRIEFLY EASE. IT IS EXPECTED TO RESTRENGTHEN BY MID-
WEEK, WITH SCA WINDS LIKELY TO RETURN AT THAT TIME.
THE RECENT SMALL, MEDIUM PERIOD NORTH SWELL WILL SLOWLY DECLINE
THROUGH MONDAY. ANOTHER MEDIUM PERIOD NORTH SWELL ARRIVAL
THURSDAY MAY CAUSE A SLIGHT BUMP IN LATE WEEK SURF ALONG NORTH-
FACING SHORES.
A SMALL, MEDIUM- TO LONG-PERIOD SOUTH SWELL WILL KEEP SURF ALONG
SOUTH-FACING SHORES NEAR THE SEPTEMBER AVERAGE INTO THE FIRST
PART OF MONDAY. THIS SWELL WILL THEN GRADUALLY DECLINE LATE
MONDAY THROUGH MID-WEEK. A COUPLE OF VERY SMALL REINFORCEMENTS
ARE EXPECTED THROUGHOUT THE WEEK, THOUGH SURF WILL REMAIN SMALL. A
SLIGHTLY LARGER, LONG-PERIOD SWELL IS FORECAST TO ARRIVE IN THE
ISLANDS FRIDAY NIGHT, BOOSTING SOUTH SHORE SURF NEXT WEEKEND.
EAST FACING SHORES WILL SEE TYPICAL TRADE WIND GENERATED ENERGY
THROUGHOUT THE FORECAST PERIOD.
FIRE WEATHER
LOW HUMIDITY PERSISTS WITH SUSTAINED WINDS APPROACHING CRITICAL
FIRE WEATHER THRESHOLDS FOR A FEW HOURS EACH AFTERNOON THROUGH
MONDAY. EXPECT DECREASING FIRE WEATHER RISK FROM TUESDAY INTO
NEXT WEEKEND DUE TO HIGHER AFTERNOON MINIMUM HUMIDITY LEVELS.
HFO WATCHES/WARNINGS/ADVISORIES
SMALL CRAFT ADVISORY UNTIL 6 PM HST MONDAY FOR MAALAEA BAY-
PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG
ISLAND SOUTHEAST WATERS.
DISCUSSION...JVC
AVIATION...FARRIS
MARINE...VAUGHAN
FIRE WEATHER...JVC
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