129
FXHW60 PHFO 071355
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
355 AM HST FRI AUG 7 2026
SYNOPSIS
TRADES WILL INCREASE TO MODERATE TO BREEZY LEVELS BY THIS
AFTERNOON AND CONTINUE THROUGH THE WEEKEND. AN AREA OF DEEPER
MOISTURE WILL APPROACH THE BIG ISLAND FROM THE EAST LATE SATURDAY,
THEN MOVE WESTWARD THROUGH MONDAY AND BRING AN ENHANCEMENT OF
SHOWER ACTIVITY TO MAINLY WINDWARD PORTIONS OF MAUI AND THE BIG
ISLAND. A TYPICAL STABLE TRADE WIND PATTERN WILL RETURN BY TUESDAY
OF NEXT WEEK.
DISCUSSION
WATER VAPOR IMAGERY LOOP SHOWS CYCLONIC SPIN FROM AN UPPER LOW
LOCATED AROUND 425 MILES NORTHWEST OF KAUAI. THIS FEATURE
CONTINUES TO DRAW UPPER LEVEL MOISTURE (IN THE FORM OF ISOLATED
AREAS OF THIN CIRRUS CLOUDS) NORTHWARD OVER THE ISLANDS FROM THE
TROPICS. CLOSER TO THE SURFACE, SOME WEAK RADAR RETURNS HAVE BEEN
NOTED DRIFTING TOWARDS THE WINDWARD COASTS, CAUGHT UP IN THE
TRADE WIND FLOW. ACCUMULATION HAS BEEN LIGHT WITH THESE SHOWERS,
HOWEVER, WITH ONLY A FEW HUNDREDTHS OF AN INCH OF REPORTED AT
A HANDFUL OF WINDWARD AND MAUKA STATIONS.
TRADE WINDS WILL INCREASE TO MODERATE TO LOCALLY BREEZY LEVELS AS
HIGH PRESSURE NORTH OF THE REGION BECOMES MORE WELL ESTABLISHED
THIS AFTERNOON THROUGH THE WEEKEND. A FAIRLY SHALLOW SUBSIDENCE
INVERSION HEIGHT OF AROUND 5000 FEET WILL HELP CAP VERTICAL CLOUD
DEVELOPMENT AND LEAD TO MAINLY ISOLATED TO SCATTERED SHOWERS
ALONG WINDWARD AND MAUKA LOCATIONS. EXPECT SOME CLOUD AND SHOWER
DEVELOPMENT ALONG THE SOUTH KONA SLOPES ON THE BIG ISLAND DURING
THE AFTERNOONS, AS LOCAL SEA BREEZES DEVELOP.
BY LATE SATURDAY, MODELS HAVE BEEN CONSISTENT IN SHOWING A DEEPER
PUSH OF LOW TO MID LAYER TROPICAL MOISTURE REACHING THE BIG
ISLAND FROM THE EAST. THE LATEST GFS TIME-HEIGHT CROSS SECTION
INDICATES A WEAKENING SUBSIDENCE INVERSION WITH MOISTURE DEEPENING
UP TO ROUGHLY 15000 FEET. WITH MODEST INSTABILITY AND SUFFICIENT
MOISTURE IN PLACE, POCKETS OF MODERATE TO HEAVY SHOWERS WILL BE
POSSIBLE. BOTH THE ECMWF AND GFS SHOW SOME OF THE MOISTURE PUSHING
WESTWARD INTO WINDWARD MAUI AND TO A LESSER EXTENT THE REST OF
THE SMALLER ISLANDS. THIS SHOULD AT LEAST ADD SOME ENHANCEMENT TO
SHOWERS STATEWIDE FROM LATE SATURDAY TO MONDAY. THOUGH IT IS STILL
TOO EARLY TO FINE TUNE THE FORECAST STORM TOTAL AMOUNTS, TYPICALLY
WETTER WINDWARD LOCATIONS ON MAUI AND THE BIG ISLAND COULD PICK
UP A COUPLE INCHES OF RAINFALL ACCUMULATION. SUFFICIENT
INSTABILITY MAY EXIST FOR A RUMBLE OF THUNDER SUNDAY AFTERNOON
OVER THE SOUTH OR SOUTHWEST SLOPES OF MAUNA LOA ON THE BIG ISLAND,
BUT CONFIDENCE IS TOO LOW AT THIS TIME TO ADD TO THE CURRENT
FORECAST PACKAGE.
TYPICAL SUMMERTIME STABLE TRADE WIND WEATHER WILL RETURN TUESDAY
THROUGH THE END OF THE WEEK WITH SCATTERED SHOWERS MAINLY WINDWARD
AND MAUKA AREAS DURING THE NIGHTS AND EARLY MORNINGS.
AVIATION
TRADE WINDS ARE FORECAST TO RAMP UP INTO THE WEEKEND AS THE
DRIVING HIGH STRENGTHENS AND PUSHES SLIGHTLY CLOSER TO HAWAII.
STABILITY WILL ALSO BE INCREASING TODAY AS AN UPPER LOW TO THE
WEST LIFTS AWAY. LEEWARD TURBULENCE WILL LIKELY INCREASE AROUND
TONIGHT OR SATURDAY, BUT NO AIRMET WILL BE NEEDED FOR NOW.
A BAND OF LOW CLOUDS AND SHOWERS WILL MOVE ONTO WINDWARD BIG
ISLAND THIS MORNING, THEN BECOME MORE DIFFUSE AS IT SPREADS
WESTWARD. MOUNTAIN OBSCURATIONS/AIRMET SIERRA WILL BE POSSIBLE FOR
THIS AREA AS THIS MOISTURE TRACKS IN.
MARINE
MODERATE TRADES ARE FORECAST TO INCREASE TO FRESH TO LOCALLY
STRONG BY THIS AFTERNOON AS SURFACE TROUGHING TO THE NORTHEAST
WEAKENS TODAY AND AN APPROACHING TROUGH TO THE SOUTHEAST ENHANCES
THE LOCAL PRESSURE GRADIENT. A SMALL CRAFT ADVISORY HAS BEEN
ISSUED BEGINNING 2 PM THIS AFTERNOON FOR LOCALLY STRONG TRADES
THROUGH THE TYPICAL WINDY AREAS AROUND MAUI COUNTY AND THE BIG
ISLAND. DISSIPATION OF THE TROUGH TO THE NORTHEAST COMBINED WITH
RENEWED TROUGH DEVELOPMENT SOUTH OF THE ISLANDS AND STRENGTHENING
HIGH PRESSURE TO THE NORTHEAST WILL KEEP FRESH TO LOCALLY STRONG
TRADES IN PLACE THROUGH AT LEAST THE WEEKEND. SOME WEAKENING OF
THE TRADES IS POSSIBLE EARLY NEXT WEEK ASSOCIATED WITH TRANSIENT
MID-LATITUDE TROUGHING.
BACKGROUND MEDIUM AND LONG PERIOD ENERGY WILL PRODUCE SMALL
SURF FOR SOUTH FACING SHORES TODAY. A SERIES OF LARGER, MEDIUM TO
LONG PERIOD SOUTH SWELLS ARRIVE BEGINNING ON SATURDAY, CAUSING SURF TO
TREND UP FOR SOUTH AND WEST FACING SHORES THIS WEEKEND INTO EARLY
NEXT WEEK. A MODERATE, LONG PERIOD SOUTH SWELL WILL PEAK NEAR THE HIGH
SURF ADVISORY THRESHOLD BY THE MIDDLE OF NEXT WEEK.
ALONG EAST FACING SHORES, TRADE WIND SWELL AND MODERATE TRADES
WILL SUPPORT SURF SLIGHTLY BELOW SEASONAL AVERAGES. SURF WILL BUILD
THIS WEEKEND IN RESPONSE TO STRENGTHENING TRADE WINDS. SURF ALONG
NORTH SHORES REMAINS FLAT TO TINY THROUGH THE PERIOD, WITH A SLIGHT
BUMP POSSIBLE ON SUNDAY FROM A SMALL, MEDIUM-PERIOD NORTH SWELL.
HFO WATCHES/WARNINGS/ADVISORIES
SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 6 PM HST
SATURDAY FOR MAALAEA BAY-PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG
ISLAND LEEWARD WATERS-BIG ISLAND SOUTHEAST WATERS.
DISCUSSION...THOMAS
AVIATION...FOSTER
MARINE...QUESADA
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