300
FXHW60 PHFO 061409
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
409 AM HST FRI MAR 6 2026
SYNOPSIS
TRADE WIND WEATHER WILL CONTINUE THROUGH THE WEEKEND WITH BRIEF
PASSING SHOWERS FAVORING WINDWARD AND MOUNTAIN AREAS OF ALL
ISLANDS. WINDS BEGIN TO SHIFT OUT OF THE SOUTH FROM SUNDAY NIGHT
INTO MONDAY AS A STRONG CUTOFF LOW PRESSURE SYSTEM APPROACHES FROM
THE NORTHWEST. STRONG SOUTHERLY WINDS WILL DRAW DEEP TROPICAL
MOISTURE NORTHWARD INCREASING THE THREAT FOR WIDESPREAD HEAVY
RAINFALL AND SEVERE WEATHER THROUGH MUCH OF NEXT WEEK.
DISCUSSION
IN THE BIG PICTURE, A COLD FRONT APPROACHING THE STATE FROM THE
NORTHWEST HAS STALLED ROUGHLY 400 MILES NORTHWEST OF KAUAI THIS
MORNING. THE HIGH PRESSURE RIDGE NORTH OF THE STATE WILL REMAIN IN
PLACE AND CONTINUE TO PRODUCE EASTERLY TO EAST-SOUTHEASTERLY
TRADE WINDS THROUGH THE WEEKEND. BANDS OF CLOUDS DEVELOPING ACROSS
THE REGION WILL PRODUCE BRIEF PERIODS OF SHOWERS ALONG WINDWARD
SLOPES OF ALL ISLANDS. THESE SHOWERS WILL FAVOR WINDWARD AND
MOUNTAIN AREAS, MAINLY DURING THE OVERNIGHT TO EARLY MORNING
HOURS. SUBSIDENCE TEMPERATURE INVERSION HEIGHTS WILL RANGE FROM
5,000 TO 7,000 FEET THROUGH SUNDAY, SUPPORTING THIS PASSING SHOWER
REGIME.
THE NEXT STORM SYSTEM CONTINUES TO PROWL ACROSS THE NORTHWEST
PACIFIC ON ITS JOURNEY TOWARD THE HAWAIIAN ISLANDS. THE LATEST
FORECAST MODEL GUIDANCE SHOWS INCREASING POTENTIAL FOR SEVERAL
DAYS OF WIDESPREAD HEAVY RAINFALL ALONG WITH A FEW STRONG TO
POTENTIALLY SEVERE THUNDERSTORMS BEGINNING EARLY NEXT WEEK.
ON MONDAY, THE WEATHER PATTERN WILL TRANSITION FROM TRADE WIND
CONDITIONS TO SOUTHERLY KONA WIND FLOW AS A STRONG CUTOFF LOW
DEEPENS AND MEANDERS ROUGHLY 800 MILES NORTHWEST OF KAUAI.
ALTHOUGH THE CENTER OF THIS SYSTEM WILL REMAIN WELL NORTHWEST OF
THE STATE, ITS INFLUENCE WILL EXTEND ACROSS THE ISLAND CHAIN. THIS
STRONG UPPER LOW IS EXPECTED TO SUPPORT THE DEVELOPMENT OF A DEEP
SURFACE LOW OF AROUND 990 MB.
FROM MONDAY NIGHT INTO TUESDAY, STRONG SOUTHERLY WINDS WILL
DEVELOP ACROSS THE STATE, DRAWING ABUNDANT MOISTURE NORTHWARD
FROM THE DEEP TROPICS. THIS LOW LEVEL MOISTURE PLUME WILL MOVE
BENEATH MUCH COLDER TEMPERATURES ALOFT, WITH THE LATEST GLOBAL
MODEL GUIDANCE SUGGESTING 500 MB TEMPERATURES AROUND -10 TO -12
CELSIUS. TWO ADDITIONAL TROUGHS ASSOCIATED WITH THIS STORM WILL
PROVIDE THE FORCING MECHANISM FOR SEVERE WEATHER POTENTIAL. THE
COMBINATION OF A LOW LEVEL TROUGH MOVING FROM WEST TO EAST DOWN
THE ISLAND CHAIN AND AN UPPER LEVEL NEGATIVELY TILTED TROUGH ALOFT
WILL LIKELY TRIGGER PERIODS OF HEAVY SHOWERS AND THUNDERSTORMS.
THE TIMING OF THESE ISLAND BY ISLAND IMPACTS MAY EVOLVE AS THE
TRACK OF THIS SYSTEM BECOMES BETTER DEFINED.
EXPECT SEVERAL DAYS OF IMPACTFUL WEATHER WITH THIS NEXT SIGNIFICANT
STORM SYSTEM. POTENTIAL IMPACTS INCLUDE STRONG GUSTY SOUTHERLY
WINDS OVER AND ALONG STEEP NORTHERN AND EASTERN SLOPES OF ISLAND
MOUNTAINS. THESE GUSTY WINDS MAY EXCEED WIND ADVISORY THRESHOLDS
AS SOUTHERLY WINDS STRENGTHEN FROM TUESDAY THROUGH FRIDAY. HEAVY
RAINFALL IN THIS UNSTABLE ENVIRONMENT, COMBINED WITH SURFACE
CONVERGENT AND UPPER LEVEL DIVERGENT FORCING, WILL LEAD TO A
SIGNIFICANT FLASH FLOODING THREAT. THESE FLOODING CONCERNS WILL
BEGIN ACROSS THE WESTERN HALF OF THE STATE EARLY NEXT WEEK, THEN
SPREAD STATEWIDE FROM WEDNESDAY INTO FRIDAY. A HYDROLOGIC OUTLOOK
MAY BE ISSUED TO HIGHLIGHT THESE FLOODING THREATS, AND A FLOOD
WATCH MAY ALSO BE REQUIRED BY EARLY NEXT WEEK.
HIGH ELEVATION ICE AND SNOW, ALONG WITH INCREASING SUMMIT LEVEL
WINDS, WERE INCLUDED IN THE LATEST EXTENDED FORECAST FOR THE
HIGHEST SUMMITS OF MAUNA KEA AND MAUNA LOA ON THE BIG ISLAND ABOVE
12,000 FEET ELEVATION BEGINNING WEDNESDAY AS THE DEEPEST SHOWERS
MOVE INTO THE EASTERN HALF OF THE STATE. WINTER WEATHER AND WIND
ADVISORIES OR WARNINGS MAY BE NEEDED TO ADDRESS THESE HIGH
ELEVATION WINTER HAZARDS.
THE UPPER LEVEL NEGATIVELY TILTED TROUGH WILL PROVIDE AN
EFFICIENT ATMOSPHERIC LIFTING MECHANISM WITHIN THIS UNSTABLE
ENVIRONMENT CHARACTERIZED BY AMPLE WIND SHEAR. OVERALL, THESE
CONDITIONS MAY SUPPORT THE DEVELOPMENT OF DEVIANT-MOVING SEVERE
THUNDERSTORMS DURING THIS EVENT. STRONG DAMAGING WINDS, LIGHTNING,
AND EXTREMELY HEAVY RAINFALL WILL BE THE PRIMARY THREATS WITH THE
STRONGER THUNDERSTORMS ACROSS THE HAWAIIAN ISLANDS.
PLEASE PREPARE NOW FOR THE POTENTIAL FOR SEVERE WEATHER IMPACTS
ACROSS THE STATE OF HAWAII LASTING SEVERAL DAYS NEXT WEEK. THE
PRIMARY FORECAST CHALLENGE THIS FAR OUT IN TIME WILL BE
PINNING DOWN THE DAY TO DAY IMPACTS FOR EACH ISLAND. MANY OF
THESE ISLAND BY ISLAND HAZARDS WILL DEVELOP ON SMALLER SCALES
AND MAY EVOLVE RAPIDLY OVER SHORTER FORECAST TIME PERIODS.
AVIATION
TRADES WILL WEAKEN SLIGHTLY TODAY, ALLOWING FOR MORE OF A LAND-
SEA BREEZE PATTERN THROUGH THE FIRST HALF OF THE PERIOD FOR MOST
SITES, BEFORE TRADES PREVAIL ONCE AGAIN BY THE AFTERNOON INTO
EARLY EVENING HOURS. VFR IS EXPECTED TO PREVAIL, HOWEVER
INTERMITTENT MVFR REMAINS POSSIBLE ALONG WINDWARD SITES DUE TO LOW
CLOUDS AND PERIOD LIGHT RAIN SHOWERS.
AIRMET SIERRA REMAINS IN EFFECT FOR EAST THROUGH SOUTH KAUAI AND
OAHU. THIS IS EXPECTED TO PREVAIL THROUGH THE PERIOD.
MARINE
FRESH TO STRONG EAST TO SOUTHEAST WINDS ASSOCIATED WITH A SURFACE
RIDGE EXTENDING SOUTHWEST INTO THE REGION WILL REMAIN IN PLACE
THROUGH THE WEEKEND. EXPECT THE STRONGEST WINDS AND ROUGHEST
CONDITIONS WITHIN THE CHANNELS, ALONG THE HAMAKUA COAST OF THE BIG
ISLAND, WINDWARD WATERS, AND SOUTH OF THE BIG ISLAND. THE SURFACE
RIDGE WILL BEGIN TO WEAKEN EARLY NEXT WEEK AS BROAD LOW PRESSURE
DEVELOPS NEARBY TO THE WEST. THIS PATTERN WILL CAUSE WINDS TO VEER
OUT OF THE SOUTH TO SOUTH-SOUTHEAST, POTENTIALLY REMAINING IN THE
FRESH TO STRONG RANGE NEXT WEEK.
SURF ALONG EAST-FACING SHORES WILL REMAIN NEAR SEASONAL AVERAGE
INTO EARLY NEXT WEEK DUE TO A LARGE UPSTREAM FETCH OF FRESH TO
STRONG BREEZES EXTENDING ACROSS THE NORTHEAST PACIFIC. A DOWNWARD
TREND IS EXPECTED NEXT WEEK AS THIS PATTERN WEAKENS AND LOCAL
WINDS VEER SOUTHERLY.
SURF ALONG NORTH- AND WEST-FACING SHORES WILL REMAIN RELATIVELY
SMALL THROUGH THE PERIOD, WITH ONLY A FEW WEST-NORTHWEST PULSES
EXPECTED OVER THE WEEKEND. A GRADUAL INCREASE IS EXPECTED THROUGH
THE WEEKEND, WITH SUNDAY POTENTIALLY THE LARGEST DAY, REACHING
AROUND HEAD-HIGH LEVELS. A LONG-PERIOD WESTERLY SWELL ASSOCIATED
WITH A SLOW-MOVING STORM-FORCE LOW TRACKING EASTWARD TOWARD THE
DATE LINE FROM THE FAR NORTHWEST PACIFIC IS EXPECTED EARLY NEXT
WEEK. HOWEVER, THE WESTERLY WINDS ASSOCIATED WITH THIS SYSTEM NEAR
THE ISLANDS ARE FORECAST TO WEAKEN BY THE WEEKEND, WHICH WILL
LIMIT THE AMOUNT OF SWELL GENERATED TOWARD THE STATE. ADDITIONALLY,
KAUAI WILL BLOCK SOME OF THIS ENERGY FROM REACHING OTHER COASTS
ACROSS THE ISLAND CHAIN.
SURF ALONG SOUTH-FACING SHORES EXPOSED TO SOUTHEAST TRADE-WIND
SEAS WILL GRADUALLY INCREASE THROUGH THE WEEKEND. CONDITIONS COULD
BECOME ROUGH EARLY NEXT WEEK AS WINDS VEER SOUTHERLY AND
STRENGTHEN. A LONG-PERIOD SOUTH-SOUTHWEST SWELL ASSOCIATED WITH A
RECENT SYSTEM PASSING THROUGH OUR SWELL WINDOW NEAR NEW ZEALAND
IS EXPECTED TO ARRIVE TUESDAY AND PERSIST THROUGH MIDWEEK.
HFO WATCHES/WARNINGS/ADVISORIES
SMALL CRAFT ADVISORY UNTIL 6 PM HST SATURDAY FOR ALL EASTERN
COASTAL WATERS AND CHANNELS.
DISCUSSION...BOHLIN
AVIATION...EVANS
MARINE...GIBBS
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