539
FXHW60 PHFO 220109
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
309 PM HST THU AUG 21 2025
SYNOPSIS
HIGH PRESSURE NORTH OF THE ISLANDS WILL MAINTAIN MODERATE TO
LOCALLY BREEZY TRADE WINDS THROUGH THE WEEKEND, FOLLOWED BY A
SLIGHT DECREASE IN WINDS EARLY NEXT WEEK. STABLE SUMMERTIME
CONDITIONS WILL BRING PERIODS OF MAINLY WINDWARD AND MAUKA
SHOWERS, WHILE MOST LEEWARD AREAS REMAIN RATHER DRY.
DISCUSSION
A STABLE AND RATHER DRY TRADE WIND FLOW REMAINS IN PLACE. BROAD
SURFACE HIGH PRESSURE FAR NORTH OF THE STATE IS NOT PARTICULARLY
STRONG BY AUGUST STANDARDS, BUT THE ITCZ IS DISPLACED NORTH OF
10N, LEADING TO A SOMEWHAT TIGHT PRESSURE GRADIENT THAT IS
DRIVING LOCALLY BREEZY TRADE WINDS OVER THE ISLANDS. A MID-LEVEL
RIDGE IS MAINTAINING STABLE CONDITIONS WITH AN INVERSION BASED
BETWEEN 5,000 AND 7.000 FT, AND NO ORGANIZED MOISTURE IS NOTED IN
THE TRADE WIND FLOW. AS A RESULT, WINDWARD RAINFALL HAS BEEN
MINIMAL SINCE MID MORNING, AND LEEWARD AREAS HAVE BEEN DRY, EVEN
ACROSS THE KONA SLOPES OF THE BIG ISLAND WHERE AFTERNOON SHOWERS
ARE USUALLY ACTIVE IN AUGUST.
LITTLE CHANGE IS EXPECTED TO THE RELATIVELY DRY AND STABLE TRADE
WIND WEATHER PATTERN THROUGH SUNDAY. TRADES MAY EASE A NOTCH AND
SHIFT OUT OF A MORE EASTERLY DIRECTION FOR MONDAY AND TUESDAY AS
THE SURFACE RIDGE TO THE NORTH IS BRIEFLY WEAKENED. THE MID-LEVEL
RIDGE SHOULD REMAIN STRONG ENOUGH TO MAINTAIN STABLE CONDITIONS,
AND AN AREA OF TROPICAL MOISTURE MAY CLIP THE BIG ISLAND ON MONDAY
OR TUESDAY, THOUGH ODDS FAVOR THE MOISTURE PASSING TO THE SOUTH.
LONGER TERM GUIDANCE SUGGESTS MODERATE TRADES AND CONTINUED
MODEST SHOWER ACTIVITY FOR THE SECOND PART OF NEXT WEEK.
AVIATION
MODERATE TO BREEZY TRADE WINDS WILL CONTINUE THROUGH THE NEXT
SEVERAL DAYS AS HIGH PRESSURE REMAINS TO THE NORTHEAST AND STABLE
CONDITIONS PREVAIL. CLOUDS AND SHOWERS WILL FOCUS PRIMARILY OVER
THE WINDWARD AND MOUNTAIN AREAS, PARTICULARLY OVERNIGHT AND INTO
THE MORNING HOURS. MVFR CONDITIONS WILL BE POSSIBLE IN SHOWERS,
OTHERWISE VFR WILL LIKELY PREVAIL.
NO AIRMETS ARE CURRENTLY IN EFFECT.
MARINE
A HIGH PRESSURE RIDGE NORTH OF THE HAWAIIAN ISLANDS WILL MAINTAIN
FRESH TO LOCALLY STRONG TRADE WINDS THROUGH EARLY NEXT WEEK. THE
SMALL CRAFT ADVISORY (SCA) REMAINS IN EFFECT FOR THE WINDIER
WATERS AND CHANNELS NEAR MAUI COUNTY AND THE BIG ISLAND THROUGH
SATURDAY. THIS SCA WILL LIKELY CONTINUE FOR THESE WINDIER WATERS
INTO EARLY NEXT WEEK.
A SERIES OF SMALL OVERLAPPING MEDIUM AND LONG PERIOD SOUTH
(170-190 DEGREE) SWELLS WILL CONTINUE FOR THE REST OF THIS WEEK,
WITH SURF HEIGHTS NEAR THE SUMMERTIME AVERAGE THROUGH FRIDAY
ALONG SOUTH FACING SHORES. SURF HEIGHTS SHOULD DECREASE TO
BACKGROUND LEVELS EARLY NEXT WEEK AS THE SWELL ENERGY FADES.
ANOTHER SMALL, LONG PERIOD SOUTH SWELL WILL ARRIVE BY MIDWEEK NEXT
WEEK.
CHOPPY CONDITIONS WILL CONTINUE FOR EAST FACING SHORES THROUGH
THE FORECAST PERIOD DUE TO THE PERSISTENT FRESH TRADES. SURF ALONG
NORTH FACING SHORES WILL REMAIN NEARLY FLAT THROUGH NEXT WEEK.
PEAK HIGH TIDES ASSOCIATED WITH THE LUNAR CYCLE WILL LEAD TO
MINOR COASTAL FLOODING ALONG SHORELINES AND LOW LYING COASTAL
AREAS DURING THE AFTERNOON HIGH TIDES THROUGH FRIDAY AFTERNOON. A
COASTAL FLOOD STATEMENT REMAINS IN EFFECT FOR MINOR COASTAL
FLOODING.
FIRE WEATHER
TRADE WINDS WILL REMAIN IN THE MODERATE TO LOCALLY BREEZY RANGE
INTO SUNDAY, WHILE A RIDGE ALOFT MAINTAINS AN INVERSION BETWEEN
5,000 AND 7,000 FT. UNDER THIS STABLE AND RATHER DRY WEATHER
PATTERN, RELATIVE HUMIDITY WILL DROP INTO THE LOW TO MID 40S
PERCENT RANGE EACH AFTERNOON, BRINGING NEAR CRITICAL FIRE WEATHER
CONDITIONS. WE DO NOT ANTICIPATE FIRE WEATHER HEADLINES THROUGH
THE WEEKEND, BUT FIRE WEATHER CONCERNS WILL BE ELEVATED.
HFO WATCHES/WARNINGS/ADVISORIES
SMALL CRAFT ADVISORY UNTIL 6 PM HST SATURDAY FOR MAALAEA BAY-
PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG
ISLAND SOUTHEAST WATERS.
DISCUSSION...WROE
AVIATION...TSAMOUS
MARINE...FARRIS/VAUGHAN
FIRE WEATHER...WROE
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