159
FXHW60 PHFO 100657
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
857 PM HST WED SEP 9 2026
SYNOPSIS
A PLUME OF MOISTURE REMAINS OVER THE EASTERN END OF THE STATE,
BRINGING CLOUDS AND SHOWERS TO THE BIG ISLAND THIS EVENING. WINDS
REMAIN LIGHT, WITH LAND BREEZES EXPECTED IN MOST AREAS OF THE
STATE, WITH A RETURN TO TRADE WINDS THURSDAY. DRIER TRADE WIND
WEATHER IS EXPECTED TO DEVELOP THURSDAY NIGHT INTO EARLY NEXT
WEEK.
DISCUSSION
SATELLITE DERIVED PRECIPITABLE WATER (PW) SHOWS 2
INCHES OF PW OVER THE SOUTHEASTERN COAST OF THE BIG ISLAND, WHICH
MATCHES WELL WITH THE AFTERNOON SOUNDING FROM HILO. ALTHOUGH
RAINFALL RATES ARE UNDER AN INCH PER HOUR, THE GROUND REMAINS VERY
SATURATED, AND THE RAIN HAS CAUSED SOME FLOODING OF ROADWAYS.
WITH THE LIGHT WINDS, WE ANTICIPATE LAND BREEZES KICKING IN THIS
EVENING, WHICH SHOULD HELP TO MOVE THE RAIN OFFSHORE.
A SURFACE TROUGH OVER THE CENTRAL ISLANDS IS MOVING TO THE WEST,
AND IS HELPING TO PROVIDE SOME OF THE INSTABILITY NEAR THE
ISLANDS. COMBINED WITH THE HIGH PW VALUES, THERE ARE A FEW MORE
SHOWERS STATEWIDE. HOWEVER AS THE TROUGH MOVES TO THE WEST, WE CAN
EXPECT TRADE WINDS TO SLOWLY BUILD IN FROM EAST TO WEST. MOISTURE
WILL LINGER, BUT THE FOCUS OF SHOWERS SHOULD RETURN TO MORE
TYPICAL WINDWARD SIDES OF THE ISLANDS. EXPECT THE TRADE WIND
PATTERN TO PERSIST INTO NEXT WEEK.
AN UPPER LEVEL LOW IS EXPECTED TO REMAIN FAR TO THE NORTHEAST OF
THE STATE HEADING INTO THE WEEKEND AND THEN LIFT NORTHWARD.
DEWPOINTS REMAIN IN THE LOW 70S ACROSS THE STATE, AND WHEN
COMBINED WITH THE LIGHT WINDS, IT MAKES IT FEEL WARM AND MUGGY.
MODELS SUGGEST DEWPOINTS WILL DROP BACK INTO THE UPPER 60S
THURSDAY NIGHT, PROVIDING SOME RELIEF FROM THE MUGGY CONDITIONS.
AVIATION
OBSERVATIONS SHOW THE TRADE WINDS HAVE SET UP ACROSS THE ISLANDS
TONIGHT, WITH RADAR SHOWING SHOWERS ACROSS THE REGION. CEILINGS
AND VISIBILITY WILL LIKELY BE REDUCED TO MVFR TO IFR CONDITIONS
DUE TO THESE SHOWERS. AS A RESULT, AIRMET SIERRA REMAINS FOR THE
BIG ISLAND, MAUI, LANAI, AND MOLOKAI THROUGH AT LEAST 10Z. SHOWERS
SHOULD WRAP UP BETWEEN 10-14Z FOR MOST SITES, WITH THE FORECAST
SHOWING DRIER TRADE WIND CONDITIONS FOR THURSDAY.
FOR SITES PMDY AND NSTU, THE FORECAST SHOWS AN INCREASE IN
EASTERLY WINDS BETWEEN 18-21Z. STARTED TO TREND WINDS UP AS A
RESULT, BUT THESE MAY NEED TO BE ADJUSTED WITH THE NEXT FORECAST
UPDATE.
MARINE
ISSUED AT 519 PM HST WED SEP 9 2026
A SURFACE TROUGH OVER THE STATE WILL GRADUALLY MOVE WESTWARD
TONIGHT. AS THE TROUGH MOVES WEST, MODERATE TO LOCALLY FRESH
TRADE WINDS WILL GRADUALLY RETURN FROM EAST TO WEST ACROSS THE
ISLAND CHAIN THROUGH THROUGH THURSDAY AND THEN PERSIST INTO THE
WEEKEND. THE SURFACE TROUGH WILL BRING SOME SCATTERED SHOWERS
ACROSS THE AREA THROUGH THURSDAY.
THE CURRENT MODERATE MID-PERIOD SOUTH SWELL CONTINUES TO DECLINE
THIS AFTERNOON AND SURF HAS DROPPED BELOW ADVISORY THRESHOLDS FOR
SOUTH FACING SHORES. THIS SWELL WILL CONTINUE TO STEADILY DECLINE
OVER THE NEXT FEW DAYS WITH BELOW AVERAGE SURF EXPECTED BY THE
WEEKEND.
SURF ALONG EAST FACING SHORES WILL GRADUALLY DECREASE TONIGHT AND
WILL REMAIN NEAR SEASONAL AVERAGES THROUGH AROUND SATURDAY DUE TO
EAST AND NORTHEAST SWELLS GENERATE BY FORMER TROPICAL CYCLONES.
SURF ALONG NORTH FACING SHORES CONTINUES TO RECEIVE A SMALL BUMP
DUE TO LOWELL. THIS SHORT-PERIOD NORTHWEST SWELL WILL QUICKLY
FADE, ALLOWING SURF TO BECOME TINY ALONG NORTH FACING SHORES ON
THURSDAY AS LOWELL WEAKENS AND TRACKS AWAY FROM THE ISLANDS.
FIRE WEATHER
FIRE WEATHER RISK WILL REMAIN LOW THE NEXT SEVERAL DAYS DUE LIGHT
WINDS AND LINGERING MOISTURE. EXPECT A SLIGHT CHANCE OF
THUNDERSTORMS OVER THE BIG ISLAND THURSDAY AFTERNOON. TEMPERATURE
INVERSION HEIGHTS ARE EXPECTED TO REMAIN ELEVATED OR WEAK.
HFO WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION/FIRE WEATHER...M BALLARD
AVIATION...KR
MARINE...KINO
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