413
FXHW60 PHFO 071358
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
358 AM HST TUE OCT 7 2025
SYNOPSIS
THE REMNANTS OF AN OLD FRONTAL BOUNDARY LAY ACROSS THE STATE
TODAY. THIS WILL MAINTAIN LIGHT AND VARIABLE BREEZES AS LOCALIZED
SEA AND LAND BREEZES PLAY MORE A ROLE THE NEXT FEW DAYS. MOISTURE
POOLING UP ALONG THE BOUNDARY WILL KEEP RAIN CHANCES HIGH AS
INTERMITTENT RAIN WILL AFFECT MOST OF THE STATE. TRADES WILL
RETURN BY THE WEEKEND AS THE WEAK BOUNDARY WASHES OUT AND SURFACE
HIGH PRESSURE NORTHEAST OF THE ISLANDS RE-ESTABLISHES A TIGHTER
DOWNSTREAM GRADIENT OVER THE REGION.
DISCUSSION
THIS MORE UNSETTLED WEATHER PATTERN WILL HANG WITH US THE NEXT
FEW DAYS AS LOWER HEIGHTS REMAINS OVER THE AREA THROUGH FRIDAY. A
PAIR OF UPPER LOWS POSITIONED NEAR SYMMETRICAL NORTH OF THE ISLAND
CHAIN, ONE APPROXIMATELY 900 MILES NORTHEAST OF THE STATE WITH AN
WEAKER LOW ABOUT 800 MILES NORTHWEST, ARE INDIRECTLY IN CONTROL
OF OUR WEATHER AS UPPER RIDGING REMAINS SOUTH OF HAWAII. THE MID
LEVEL REFLECTION OF THESE LOWS, ALONG WITH MOISTURE POOLING ALONG
A DIFFUSE TROUGH DRAPED ACROSS THE CENTRAL ISLANDS THIS MORNING,
WILL BE THE IMPETUS TO RECURRING PERIODS OF THICKER, LOWER LAYER
CLOUDS AND SHOWERY CONDITIONS. 12Z SOUNDINGS CONFIRM THAT A
FAIRLY MOIST BOUNDARY LAYER EXTENDS UP TO AROUND 700 MB (~9 K
FT). THIS IS A DEPTH THAT IS CERTAINLY CAPABLE OF PROVIDING
ENOUGH MOISTURE TO SUPPORT THICKER CLOUDS AND HIGHER SHOWER
PROBABILITIES THE NEXT SEVERAL DAYS. THIS BOUNDARY HAS DISRUPTED
TRADE FLOW AND THE BENIGN GRADIENT CREATED OVER THE STATE WILL
ALLOW MORE LOCALIZED BREEZES TO PLAY A MORE DOMINANT ROLE. THUS,
PEAKS OF SUNSHINE WILL ENHANCE EARLY AFTERNOON SEA BREEZES AND
ASSIST IN BUILDING CLOUDS AND GENERATING MORE PRECIPITATION WITHIN
WIND-SHELTERED LEEWARD AREAS. AS THE BOUNDARY BECOMES MORE
DIFFUSE AND LIFTS A TOUCH NORTH THROUGH THE DAY, THE GENERAL FLOW
WILL VEER MORE SOUTHEAST-SOUTH AND TAP INTO A MORE MOISTURE RICH
EQUATORIAL AIR MASS. THIS WILL LIKELY INCREASE KEEP RAIN CHANCES
ON THE HIGHER SIDE OF LOWER-END MODERATE PROBABILITIES (30-40%).
HIGHER RAIN CHANCES WILL LIKELY OCCUR ALONG THE WESTERN HALF OF
THE ARCHIPELAGO AND FOCUS ALONG MORE SOUTHERN COASTS AND UPSLOPE
(LEEWARD) MAUKA THROUGH THURSDAY. TROUGHING OVER THE STATE WILL
PERSIST INTO LATE WEEK BUT WILL FADE WAY BY FRIDAY. ONCE THIS
OCCURS, SURFACE HIGH PRESSURE OFF THE U.S. WEST COAST WILL EXERT
MORE OF AN INFLUENCE AND RE-ESTABLISH A GRADIENT BETTER SUPPORTING
LIGHT TO MODERATE TRADE WINDS THIS WEEKEND. MORE OVERCAST AND
RAIN WILL KEEP AFTERNOON MAXIMUM TEMPERATURES A DEGREE OR TWO
LOWER THAN EARLY OCTOBER MID 80 NORMS WHILE OVERNIGHT DRAINAGE
BREEZES WILL COMPENSATE FOR INSULATING CLOUDS AS NEAR SUNRISE
TEMPERATURES DIP TO NEAR CLIMATE LOW TO MID 70 STANDARDS.
MID TO UPPER LEVEL RIDGING, AS WELL AS AN ASSOCIATED DRIER AIR
MASS, WILL BEGIN TO EXPAND UP FROM THE SOUTHEAST AND ENVELOPE THE
STATE LATER THIS WEEK. THIS WILL PROVIDE A BIT MORE REGIONAL
STABILITY AND POSSIBLY DESIGNATE FRIDAY AND SATURDAY AS THE
DRIEST DAYS OF THE WEEK. LOBES OF MORE HUMID AIR MAY ROTATE IN
AROUND THE SOUTHERN PERIPHERY OF MID-LEVEL RIDGING POSITIONED
NORTHEAST OF THE STATE EARLY NEXT WEEK. THE SECOND WEEK OF
OCTOBER MAY NOT BE AS UNSETTLED AS THIS WEEK BUT IT APPEARS THAT A
MORE WET TRADE PATTERN SETS UP SUNDAY THROUGH TUESDAY AS ROUNDS
OF SHOWERS MOVE IN FROM THE EAST ON THIS RE-ESTABLISHED TRADE
FLOW.
AVIATION
A LINGERING DIFFUSE OLD FRONTAL BOUNDARY DRAPED ACROSS THE STATE
HAS WEAKENED REGIONAL WINDS AND ALLOWED POOLED UP MOISTURE TO
INITIATE MORE FREQUENT SHOWERS. VERY LIGHT AND, AT TIMES, VARIABLE
WINDS WILL BE DEPENDENT UPON THE LOCATION OF THE BOUNDARY WAFTING
OVER THE REGION. DUE TO THIS WEAK SYNOPTIC WIND REGIME, DAYTIME
SEA BREEZES AND NOCTURNAL LAND BREEZES WILL BECOME THE DOMINANT
WIND PATTERN ACROSS MANY ISLAND TERMINALS. AIR FIELDS NORTH OF
THE BOUNDARY WILL EXPERIENCE MORE EASTERLY BREEZES WHILE SITES
SOUTH OF THE BOUNDARY WILL HAVE A MORE SOUTHERLY COMPONENT. THE
BOUNDARY IS FORECAST TO LIFT NORTH THROUGH MID WEEK AND THIS WILL
ALIGN STATEWIDE WINDS MORE SOUTHEASTERLY LATER IN THE PERIOD. A
BAND OF MOISTURE ASSOCIATED WITH THE BOUNDARY WILL OCCASIONALLY
PRODUCE TEMPO MVFR DECKS AND VISIBILITIES WITHIN MORE MODERATE
SHOWERS. SHORT-LIVED, ISOLATED IFR CONDITIONS ARE POSSIBLE WITHIN
POCKETS OF HEAVIER RAIN.
IN THE SHORT TERM, DRIER AIR WILL GRADUALLY FILL IN BEHIND THE
EXITING BOUNDARY AND CONDITIONS WILL GENERALLY FAVOR VFR.
LOCALIZED BREEZES WILL STILL HOLD ON THROUGH THE MAJORITY OF THE
WEEK. THUS, DAYTIME SEA BREEZES WILL BUILD INTERIOR CLOUDS AND
PRODUCE SCATTERED (LEEWARD) SHOWERS WHILE OVERNIGHT LAND BREEZES
WILL SCOUR OUT DECKS.
THERE ARE CURRENTLY NO AIRMETS IN EFFECT. TUESDAY'S AIRMET SIERRA
OVER OAHU, MAUI, LANAI AND MOLOKAI WAS CANCELLED LAST NIGHT DUE
TO LIFTING CLOUDS AND IMPROVED MOUNTAIN VISIBILITIES.
MARINE
A TROUGH DRAPED OVER THE COASTAL WATERS WILL SLOWLY DRIFT WEST
OVER THE NEXT SEVERAL DAYS AND BRING LIGHT TO GENTLE SOUTH OR
SOUTHEAST FLOW ACROSS ALL ZONES. THIS FLOW SHOULD ALSO GIVE WAY TO
LOCALIZED LAND AND SEA BREEZES. MODERATE EASTERLY TRADES ARE
FORECAST TO FILL BACK IN BY THIS WEEKEND AS HIGH PRESSURE BUILDS
FAR NORTHEAST OF THE STATE.
THE CURRENT SMALL, MEDIUM PERIOD, NORTH NORTHWEST (330-340 DEG)
SWELL HAS BEEN COMING IN SLIGHTLY ABOVE GUIDANCE, AS NOTED ON THIS
MORNINGS WAIMEA BAY BUOY OBSERVATIONS. HOWEVER, THIS SWELL HAS
ALREADY PEAKED AND SHOULD CONTINUE TO SLOWLY DECLINE THROUGH LATE
THIS WEEK. FORERUNNERS FROM THE NEXT, MORE SIGNIFICANT MODERATE,
LONG PERIOD, NORTHWEST SWELL ARE PROGGED TO ARRIVE BY LATE THIS
WEEKEND. DURING THE PEAK OF THE EVENT, EARLY NEXT WEEK, SURF ALONG
NORTH FACING SHORES MAY APPROACH HIGH SURF ADVISORY CRITERIA.
BACKGROUND SOUTH SOUTHWEST SWELL ENERGY WILL BRING TINY TO SMALL
SURF ALONG SOUTH FACING SHORES THROUGH LATE WEDNESDAY. A SMALL,
LONG PERIOD, SOUTH SOUTHWEST (190-200 DEG) SWELL WILL FILL IN
THURSDAY MORNING AND BRING A SLIGHT BUMP UP TO SURF ALONG SOUTH
FACING SHORES THROUGH LATE FRIDAY. EXPECT BELOW AVERAGE SURF ALONG
EAST FACING SHORES THIS WEEK AS WEAK FLOW PREVAILS.
PEAK HIGH TIDES ASSOCIATED WITH THE LUNAR CYCLE WILL LEAD TO
MINOR COASTAL FLOODING ALONG SHORELINES AND LOW LYING COASTAL
AREAS THROUGH THIS WEEKEND. COASTAL FLOODING WILL COINCIDE WITH
THE DAILY PEAK TIDE EACH MORNING. A COASTAL FLOOD STATEMENT
REMAINS IN EFFECT FOR ALL COASTAL AREAS THROUGH FRIDAY, BUT MAY
NEED TO BE EXTENDED.
FIRE WEATHER
WEAK LOCALIZED AND/OR VARIABLE BREEZES AND A HIGHER FREQUENCY OF
SHOWERS WILL HELP MAINTAIN BELOW CRITICAL FIRE WEATHER THRESHOLDS
THE NEXT SEVERAL DAYS. INVERSION HEIGHTS ACROSS THE STATE WILL
RANGE FROM AS LOW AS 4,000 TO AS HIGH AS 9,000 FEET THROUGH MID
WEEK.
HFO WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...BLOOD
AVIATION...BLOOD
MARINE...THOMAS
FIRE WEATHER...BLOOD
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