442
FXHW60 PHFO 210133
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
333 PM HST MON JUL 20 2026
SYNOPSIS
MODERATE TRADES TURN BREEZY MID-WEEK DELIVERING SHOWERS WINDWARD
AND MAUKA THROUGH THE PERIOD.
DISCUSSION
DEEPER MOISTURE (RELATIVE TO LAST NIGHT) LURKS IMMEDIATELY UPSTREAM
AND WILL BE USHERED THROUGH THE FORECAST AREA TONIGHT THROUGH
TUESDAY BY PERSISTENT MODERATE TRADES IN THE LOWEST LEVELS. FOR THE
MOST PART, A TYPICAL DISTRIBUTION OF SHOWERS FOCUSED WINDWARD AND
MAUKA IS EXPECTED. HOWEVER, VEERING WINDS WITHIN THE DEEPENING
BOUNDARY LAYER (UP TO APPROXIMATELY 10KFT) YIELDS POTENTIAL FOR SOME
LEEWARD CONVERGENCE DOWNWIND OF MAUI COUNTY POTENTIALLY BRINGING
ENHANCED SHOWER COVERAGE TO LEEWARD OAHU MAINLY AFTER MIDNIGHT
TONIGHT CONTINUING INTO TUESDAY MORNING. AS THIS MOISTURE ADVANCES
WEST OF THE ISLANDS MID-WEEK, TRADES REBOUND UNDER A BROAD LOW
AMPLITUDE SUBTROPICAL RIDGE. BREEZY TRADES, HIGH STABILITY, AND
LIMITED SHOWERS FOCUSED WINDWARD AND MAUKA THEN PREVAIL THROUGH THE
WEEKEND.
AVIATION
MODERATE TO LOCALLY BREEZY TRADE WINDS WILL PERSIST THROUGH
TUESDAY AND INCREASE SLIGHTLY WEDNESDAY. THIS MORNING, AN AREA OF
ENHANCED MOISTURE MOVED ONTO WINDWARD MAUI COUNTY, WHERE
WIDESPREAD MVFR CONDITIONS HAVE NECESSITATED AIRMET SIERRA FOR
MOUNTAIN OBSCURATION, AND AS THE MOISTURE SPREADS WESTWARD, THE
AIRMET WILL LIKELY BE EXPANDED TO ADDITIONAL ISLANDS OVERNIGHT.
VFR CONDITIONS WILL PREVAIL OVER MOST LEEWARD AREAS. DRIER
CONDITIONS ARE EXPECTED TO BUILD IN FROM THE EAST LATE WEDNESDAY.
MARINE
THE TRADE WINDS WILL HOLD AT MOSTLY MODERATE SPEEDS TODAY THROUGH
TUESDAY AS VERY BROAD TROUGHING HAS PRODUCED A WEAKNESS IN THE
SUBTROPICAL RIDGE TO THE NORTHWEST OF THE HAWAIIAN ISLANDS. TRADE
WINDS STRENGTHEN TO FRESH AND LOCALLY STRONG SPEEDS WEDNESDAY
THROUGH FRIDAY AS HIGH PRESSURE STRENGTHENS NORTH OF THE ISLAND
CHAIN.
SURF OBSERVATIONS CONTINUE TO SHOW ADVISORY LEVEL SURF AFFECTING
SOUTH FACING SHORES TODAY. A HIGH SURF ADVISORY REMAINS IN EFFECT
THROUGH TUESDAY AFTERNOON, DURING WHICH TIME THE SWELL IS EXPECTED TO
HOLD AND KEEP SURF AT LOWER-END ADVISORY LEVELS. THIS SWELL WILL THEN
SLOWLY FADE DURING THE MIDDLE OF THE WEEK. A NEW LONG-PERIOD SOUTH
SWELL ARRIVES TUESDAY NIGHT, BUILDS ON WEDNESDAY, AND PEAKS ON
THURSDAY, KEEPING SURF ELEVATED ABOVE THE SUMMERTIME AVERAGE THROUGH
THE WEEKEND.
SURF ALONG EAST-FACING SHORES WILL REMAIN SLIGHTLY BELOW SEASONAL
LEVELS TODAY THROUGH WEDNESDAY AS THE TRADES EASE UPSTREAM OF THE
ISLANDS. EAST SHORE SURF SHOULD THEN BUILD BACK CLOSE TO SEASONAL
LEVELS LATE THIS WEEK AND THROUGH THE WEEKEND AS STRONGER TRADES
RETURN OVER AND UPSTREAM ON THE ISLANDS. ADDITIONALLY, SWELL GENERATED
BY FORMER TROPICAL CYCLONE ELIDA MAY GIVE A SLIGHT BOOST TO EAST
SHORE SURF DURING THE MIDDLE OF THE WEEK. THIS WEEKEND, LARGER SURF
FOR EAST SHORES GENERATED BY TROPICAL STORM FAUSTO IS POSSIBLE.
SURF ALONG NORTH-FACING SHORES WILL REMAIN AT FLAT TO TINY LEVELS
THROUGH THE WEEKEND.
HFO WATCHES/WARNINGS/ADVISORIES
HIGH SURF ADVISORY UNTIL 6 PM HST TUESDAY FOR ALL SOUTH-FACING
SHORES.
DISCUSSION...JVC
AVIATION...WROE
MARINE...QUESADA
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