412
FXHW60 PHFO 162009
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1009 AM HST WED APR 16 2025
SYNOPSIS
AN APPROACHING FRONT FROM THE NORTHWEST IS PUSHING A RIDGE OVER
THE ISLANDS. THIS IS RESULTING IN LIGHT WINDS OVER THE ISLANDS,
LEADING TO AFTERNOON SEA BREEZES AND OVERNIGHT LAND BREEZES. AS A
RESULT, EXPECT TO SEE MORE CLOUDS AND SOME SHOWERS THIS AFTERNOON.
THE APPROACHING FRONT WILL BRING MORE CLOUDS AND SHOWERS TO THE
REGION STARTING TONIGHT, AND THE INSTABILITY ASSOCIATED WITH THE
SYSTEM WILL BRING THE POSSIBILITY FOR HEAVIER SHOWERS AND
THUNDERSTORMS THROUGH FRIDAY.
DISCUSSION
NO CHANGES TO THE FORECAST AT THE MOMENT, BUT ANTICIPATE MAKING
SOME TWEAKS TO VARIOUS FIELDS WITH THE AFTERNOON PACKAGE TO FINE
TUNE SOME ASPECTS FOR THE FIRST 36 HOURS. SPECIFICALLY WILL BE
LOOKING AT AREAS OF HEAVY RAIN AND ADJUSTMENTS TO QPF.
A WEAKENING COLD FRONT NORTHWEST OF KAUAI IS MOVING TOWARDS THE
ISLANDS, PUSHING A RIDGE OVER THE ISLANDS. THIS IN TURN IS
BRINGING LIGHT WINDS TO THE REGION, RESULTING IN AFTERNOON SEA
BREEZES THAT WILL BRING AN INCREASE IN CLOUDS AND SHOWERS TO THE
INTERIOR OF THE ISLANDS TODAY. THE FRONT IS EXPECTED TO CONTINUE
TO WEAKEN OVER THE NEXT 24 HOURS, WHILE STAYING JUST NORTHWEST OF
KAUAI. SURFACE WINDS ARE EXPECTED TO REMAIN LIGHT THROUGH FRIDAY.
MEANWHILE, AN UPPER LEVEL TROUGH MOVING OVER THE ISLANDS WILL
BRING COLDER THAN NORMAL TEMPERATURES TO 500 MB. MODELS, BOTH
GLOBALLY AND HIGHER RESOLUTION, SHOW GOOD AGREEMENT WITH 500 MB
TEMPERATURES GETTING TO -13C. THE MODELS ARE ALSO IN GOOD
AGREEMENT WITH PRECIPITABLE WATER VALUES REACHING 1.5 INCHES,
WHICH IS ABOVE NORMAL FOR APRIL. THIS UNSTABLE AIRMASS WILL
LIKELY PRODUCE SOME HEAVY SHOWERS AND THUNDERSTORMS. THESE ARE NOT
EXPECTED TO BE A LINE OF STORMS THAT WILL BE TRACKED DOWN THE
ISLAND CHAIN, BUT RATHER MORE POP-UP STORMS. AT THIS TIME, WE ARE
NOT EXPECTING WIDESPREAD FLOODING ISSUES, SO NO FLOOD WATCH IS
BEING ISSUED. WE CAN EXPECT THE POSSIBILITY FOR SOME LOCALIZED
FLOODING IN HEAVIER SHOWERS.
THE UPPER LEVEL TROUGH MOVES TO THE EAST SATURDAY, WITH A MORE
TRADE WIND PATTERN SETTING UP AT THE SURFACE FOR THE WEEKEND AND
EARLY NEXT WEEK. HEADING INTO THE MIDDLE OF NEXT WEEK, ANOTHER WET
PATTERN IS BEING SUGGESTED BY THE GLOBAL MODELS.
AVIATION
WIND SPEEDS ARE ON THE DECLINE AS AN APPROACHING FRONT STALLS NW
OF THE ISLANDS. LIGHT AND VARIABLE WINDS WILL DEVELOP OVER KAUAI
AND OAHU WHILE LIGHT TO MODERATE ESE FLOW WILL LIKELY PERSIST OVER
MAUI AND THE BIG ISLAND. VFR CONDITIONS WILL PREVAIL IN THE SHORT
TERM, AND NO AIRMETS ARE CURRENTLY POSTED, BUT THE ISLAND
ATMOSPHERE WILL BECOME INCREASINGLY UNSTABLE OVER THE NEXT 12-24
HOURS AS A SHARP TROUGH ALOFT PASSES OVERHEAD. THE TROUGH WILL
BRING THE POTENTIAL FOR LOCALIZED HEAVY SHOWERS/IFR VIS CIG AND A
SLIGHT CHANCE OF THUNDERSTORMS, AS WELL AS INCREASED POTENTIAL
FOR MODERATE TO SEVERE TURBULENCE ALOFT.
MARINE
THE SLOW APPROACH OF A COLD FRONT JUST ENTERING OUR NORTHWEST
OFFSHORE WATERS HAS WEAKENED NEARSHORE EAST-SOUTHEAST WINDS. AS
THIS FRONT STALLS JUST WEST OF THE ISLANDS TODAY, WESTERN WATER
LIGHT AND VARIABLE BREEZES AROUND KAUAI WILL BECOME MORE LOCALIZED
DAYTIME ONSHORE AND OVERNIGHT OFFSHORE BREEZES. ELSEWHERE, GENTLE
TO MODERATE EAST SOUTHEAST WINDS WILL PERSIST OVER SMALLER ISLAND
WINDWARD WATERS AND AROUND BIG ISLAND THE NEXT FEW DAYS. AS
SURFACE HIGH PRESSURE STRENGTHENS FAR NORTHEAST OF THE STATE, A
BRIEF RETURN TO FRESH TO LOCALLY STRONG EASTERLY TRADES IS
POSSIBLE THIS WEEKEND. THERE WILL BE AN INCREASED CHANCE FOR
WIDESPREAD HEAVY SHOWERS AND THUNDERSTORMS FROM TONIGHT THROUGH
FRIDAY IN RESPONSE TO THE PASSAGE OF AN UPPER LEVEL TROUGH OVER
THE STATE.
SURF ALONG EXPOSED NORTH AND WEST-FACING SHORES WILL CONTINUE TO
DIMINISH TODAY AS THE LATEST NORTHWEST SWELL FADES AWAY. AN UPWARD
TREND IN SURF IS EXPECTED THURSDAY AS A MODERATE SIZE NORTH
NORTHWEST SWELL ARRIVES AND BUILDS DOWN THE ISLAND CHAIN. NORTH
AND WEST SHORE SURF MAY NEAR ADVISORY LEVELS THURSDAY NIGHT INTO
FRIDAY DURING THE PEAK OF THIS SWELL. A DOWNWARD TREND IS EXPECTED
AS THE SWELL TURNS OUT OF THE NORTH THIS WEEKEND.
EAST-FACING SHORE CHOP WILL REMAIN LOW INTO SATURDAY. A SLIGHT
UPTICK IN TRADES WILL RESULT IN A STEADY RISE OF EASTERN WIND
WAVES EARLY NEXT WEEK.
SURF ALONG SOUTH-FACING SHORES WILL REMAIN SMALL THROUGH THE
WEEK WITH THE PASSING OF OVERLAPPING BACKGROUND SOUTH SWELLS.
A LARGER SOUTH SOUTHWEST SWELL MAY ARRIVE NEXT TUESDAY.
HFO WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...M BALLARD
AVIATION...BIRCHARD
MARINE...BLOOD
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