359
FXHW60 PHFO 020132
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
332 PM HST SUN JUN 1 2025
SYNOPSIS
MODERATE TO LOCALLY BREEZY EAST-SOUTHEAST TRADES WILL PERSIST
THROUGH TOMORROW AS A BROAD SURFACE TROUGH DEVELOPS TO THE WEST
OF THE STATE. A DISTURBANCE ALOFT MAY ENHANCE SHOWERS A BIT
DURING THIS TIME, WITH SHOWERS FAVORING EAST AND SOUTHEAST FACING
SLOPES AND COASTS AT NIGHT, AND LEEWARD AREAS EACH AFTERNOON.
MODERATE TO LOCALLY BREEZY EAST-NORTHEAST TRADES WILL RETURN
TOMORROW NIGHT, FOCUSING SHOWERS OVER WINDWARD AND MAUKA AREAS.
THIS PATTERN WILL HOLD IN PLACE THROUGH THE REMAINDER OF THE WORK
WEEK, WITH THE TRADES POTENTIALLY EASING NEXT WEEKEND.
DISCUSSION
THIS AFTERNOON, THE SHIFT TO AN EAST-SOUTEAST STEERING FLOW CAN
BE SEEN ON RADAR AND SATELLITE IMAGERY AS LOW LEVEL CLOUDS AND
SHOWERS RIDING IN ON THE TRADES TAKE ON A SOUTHEASTERLY COMPONENT
AND MOVE SOMEWHAT PARALLEL ALONG THE ISLAND CHAIN. THIS VEERED
TRADE WIND FLOW IS THE RESULT OF A BROAD SURFACE TROUGH DEVELOPING
TO THE NORTHWEST OF THE STATE AND INTERACTING WITH THE STRONG
SURFACE RIDGE CENTERED ABOUT 2000 MILES NORTH-NORTHEAST OF
HONOLULU. IN THE UPPER LEVELS, DENSE CIRRUS CLOUDS CONTINUE TO
FILTER ACROSS THE AREA FROM THE WEST-SOUTHWEST, THANKS TO AN UPPER
LEVEL JET STREAK ARCHING ACROSS THE REGION.
THIS MODERATE TO LOCALLY BREEZY EAST-SOUTHEASTERLY LOW LEVEL FLOW
PATTERN IS EXPECTED TO CONTINUE THROUGH TOMORROW. CLOUDS AND
SHOWERS WILL FAVOR WINDWARD AND MAUKA AREAS DURING THE OVERNIGHT
TO EARLY MORNING HOURS AND LEEWARD AND INTERIOR AREAS DURING THE
AFTERNOON HOURS AS SEA BREEZES DEVELOP. THIS FLOW CAN ALSO CAUSE
LOW LEVEL CONVERGENT BOUNDARIES THAT FORM DOWNSTREAM OF EACH
ISLAND TO PROVIDE ADDITIONAL SHOWERS TO THEIR NEIGHBORING
DOWNSTREAM ISLANDS AS THEY LINE UP ALONG THE ISLAND CHAIN, AS HAS
BEEN THE CASE THIS AFTERNOON...PARTICULARLY ACROSS OAHU. SHOWER
ACTIVITY MAY BE SLIGHTLY ENHANCED ACROSS THE WESTERN END OF THE
STATE THROUGH TOMORROW AS BOTH AN UPPER LEVEL TROUGH/LOW DIVES
SOUTH TO THE WEST OF KAUAI AND BRINGS INSTABILITY ALOFT AND LOW
LEVEL MOISTURE IS FILTERED ACROSS THE AREA.
A RETURN TO BREEZY AND MORE STABLE TRADE WIND CONDITIONS IS
EXPECTED BY TOMORROW NIGHT AS UPPER LEVEL HEIGHTS RISE, DRIER AIR
FILTERS IN FROM THE EAST, AND THE SURFACE TROUGH WEAKENS AND MOVES
AWAY FROM THE STATE. THIS WILL RESULT IN A MORE TYPICAL EASTERLY
TRADE WIND PATTERN THROUGH AT LEAST THURSDAY, WITH SHOWERS
FAVORING WINDWARD AND MAUKA AREAS AND GENERALLY DRY CONDITIONS
PREVAILING ELSEWHERE. FOR THE LATTER END OF THE WEEK AND INTO THE
WEEKEND, THE TRADES MAY EASE SLIGHTLY AS A WEAK UPPER-LEVEL
TROUGH MOVES OVERHEAD AND ANOTHER BROAD SURFACE TROUGH DEVELOPS
WEST OF THE STATE. HOWEVER, THE INSTABILITY ASSOCIATED WITH THE
TROUGH ALOFT AND THE AVAILABLE MOISTURE LOOK RATHER UNIMPRESSIVE,
SO NOT EXPECTING MUCH MORE THAN PERHAPS A SLIGHT ENHANCEMENT OF
TRADE WIND SHOWERS FOR THE END OF THE FORECAST PERIOD AT THIS
TIME.
VOG WILL CONTINUE TO FILTER ACROSS THE ISLAND CHAIN IN THE EAST-
SOUTHEAST FLOW, THEN TRANSITION WESTWARD OF THE SMALLER ISLANDS BY
MIDWEEK AS THE EASTERLY TRADES RETURN.
AVIATION
MODERATE TO LOCALLY BREEZY EAST-SOUTHEASTERLY WINDS ARE EXPECTED
TO PERSIST THROUGH MONDAY. TROUGHING TO THE WEST OF THE ISLANDS
HAS SIGNIFICANTLY INCREASED HIGH CLOUDS TODAY, PARTICULARLY FOR
THE WESTERN HALF OF THE STATE (THOUGH THESE HIGH CLOUDS ARE
CONTINUING TO SPREAD EASTWARD THIS AFTERNOON). THIS HAS ALSO
SUPPORTED OCCASIONAL PASSING SHOWERS AS MOISTURE EMBEDDED WITHIN
THE EAST-SOUTHEAST FLOW MOVES OVER THE ISLANDS AT TIMES. WHILE VFR
CONDITIONS ARE PRESENT AT MOST LOCATIONS, OCCASIONAL MVFR
CEILINGS AND VISIBILITIES HAVE BEEN OBSERVED IN THESE PASSING
SHOWERS. THIS PATTERN WILL CONTINUE INTO MONDAY, BUT BACKGROUND
FLOW WILL BECOME MORE EASTERLY AGAIN BY LATE MONDAY.
AIRMET SIERRA CURRENTLY REMAINS IN EFFECT FOR MOUNTAIN OBSCURATION
OVER KAUAI AND OAHU THIS AFTERNOON. THIS AIRMET WILL LIKELY
CONTINUE INTO THE EVENING AND OVERNIGHT HOURS.
ADDITIONALLY, AIRMET TANGO REMAINS IN EFFECT FOR MODERATE LOW-
LEVEL TURBULENCE DOWNWIND OF ISLAND TERRAIN. THIS AIRMET WILL
LIKELY BE NEEDED INTO MONDAY.
MARINE
FRESH EAST SOUTHEAST WINDS FORECAST THROUGH TONIGHT AS AN UPPER
LOW AND ASSOCIATED SURFACE TROUGH DEVELOP WEST OF HAWAII ON
MONDAY. A SMALL CRAFT ADVISORY (SCA) IS POSTED FOR WINDS OVER THE
TYPICAL WINDY WATERS PLUS WINDWARD MAUI WATERS THROUGH MONDAY.
THE TROUGH WILL MOVE WESTWARD AND THE SURFACE RIDGE TO THE NORTH
WILL REBUILD, CAUSING TRADE WINDS TO SHIFT BACK TO A MORE EASTERLY
DIRECTION. THE SCA WILL LIKELY BE RECONFIGURED TO THE TYPICALLY
WINDY WATERS BY MONDAY AND SHOULD REMAIN IN PLACE THROUGH AT LEAST
MIDWEEK.
THE LATE SEASON NORTHWEST SWELL WILL DECLINE TONIGHT AND SUNDAY,
WITH NORTH SHORE SURF DROPPING TO NEAR JUNE AVERAGE FOR THE FIRST
HALF OF THE WORK WEEK. TINY SURF IS EXPECTED BY THURSDAY.
SURF ALONG SOUTH-FACING SHORES WILL CONTINUE TO SEE A MIX OF SMALL
BACKGROUND SWELL FOR THE NEXT FEW DAYS, FOLLOWED BY A SMALL
INCONSISTENT SOUTHWEST SWELL LATE TUESDAY AND WEDNESDAY. A LONG-
PERIOD SOUTH-SOUTHWEST SWELL WILL BUILD ON FRIDAY AND PEAK NEXT
WEEKEND, LEADING TO SURF WELL ABOVE JUNE AVERAGE.
SURF ALONG EAST-FACING SHORES WILL GRADUALLY BUILD TO NEAR OR
ABOVE SEASONAL AVERAGE MONDAY THROUGH WEDNESDAY DUE TO A RETURN OF
FRESH TO STRONG TRADES OVER AND UPSTREAM OF THE ISLANDS.
HFO WATCHES/WARNINGS/ADVISORIES
SMALL CRAFT ADVISORY UNTIL 6 PM HST MONDAY FOR MAUI COUNTY
WINDWARD WATERS-PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND
WINDWARD WATERS-BIG ISLAND LEEWARD WATERS.
DISCUSSION...FARRIS
AVIATION...VAUGHAN
MARINE...FOSTER
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