927
FXHW60 PHFO 170140
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
340 PM HST WED APR 16 2025
SYNOPSIS
AN APPROACHING FRONT FROM THE NORTHWEST IS PUSHING A RIDGE OVER
THE ISLANDS, RESULTING IN LIGHT WINDS OVER THE ISLANDS. THIS
AFTERNOON'S SEA BREEZES WILL BECOME OVERNIGHT LAND BREEZES. SOME
CLEARING OF CLOUDS IS POSSIBLE OVERNIGHT, PARTICULARLY OVER MAUI
COUNTY AND THE BIG ISLAND. AN UPPER LEVEL DISTURBANCE WILL BRING
CLOUDS AND SHOWERS TO THE ISLAND TONIGHT THROUGH FRIDAY WITH THE
POSSIBILITY FOR HEAVIER SHOWERS AND THUNDERSTORMS.
DISCUSSION
AS EXPECTED, THERE HAVE BEEN TWEAKS TO THE FORECAST WITH THE
AFTERNOON PACKAGE. THE OVERALL FORECAST PHILOSOPHY REMAINS THE
SAME WITH SHOWERS INCREASING IN COVERAGE TONIGHT. THUNDERSTORMS
ARE POSSIBLE MAINLY WEST OF MOLOKAI STARTING TONIGHT, AND
SPREADING STATEWIDE TOMORROW. BY FRIDAY NIGHT, THE CHANCE OF
THUNDERSTORMS IS SHIFTED TO MAUI COUNTY AND THE BIG ISLAND. HAVE
IN GENERAL INCREASED QPF, LEANING INTO THE NATIONAL BLEND OF
MODELS (NBM) VALUES.
THE FRONT TO THE NORTHWEST OF KAUAI CONTINUES TO WEAKEN, AND
CONTINUES TO KEEP A RIDGE NEARBY, RESULTING IN THE LIGHT WINDS
OVER THE ISLANDS. THE FRONT IS EXPECTED TO CONTINUE TO STAY TO THE
WEST OF KAUAI AND WEAKEN OVER THE NEXT 12 TO 24 HOURS. THE SURFACE
RIDGE NEARBY WILL CONTINUE TO BRING THE LIGHT WINDS TO THE REGION.
MEANWHILE, AN UPPER LEVEL TROUGH OVER THE ISLANDS WILL DIG IN,
BRINGING COLDER UPPER LEVEL TEMPERATURES. THIS COUPLED WITH AN
INCREASE IN PRECIPITABLE WATER WILL PROVIDE SUFFICIENT INSTABILITY
OVER THE ISLANDS THAT WILL RESULT IN AN INCREASE IN SHOWERS, AND
BRING THE POSSIBILITY FOR HEAVIER SHOWERS AND THUNDERSTORMS.
MODELS ARE IN GOOD AGREEMENT WITH 500 MB TEMPERATURES REACHING
AROUND -13C, AND WITH PRECIPITABLE WATER VALUES REACHING AROUND
1.5 INCHES, BOTH OF WHICH ARE BELOW NORMAL FOR APRIL. WITH NO
ORGANIZED SURFACE FEATURE MOVING OVER THE ISLANDS TO FOCUS THE
SHOWERS, CONFIDENCE REMAINS LOW FOR ANY WIDESPREAD FLOODING. AS A
RESULT, WE ARE NOT ISSUING A FLOOD WATCH, BUT CANNOT RULE OUT
LOCALIZED FLOODING DURING THE EVENT.
THE UPPER LEVEL TROUGH MOVES TO THE EAST SATURDAY, WITH A MORE
TYPICAL TRADE WIND PATTERN SETTING UP AT THE SURFACE FOR THE
WEEKEND AND INTO MONDAY. HEADING INTO TUESDAY, THE GLOBAL MODELS
ARE DEPICTING ANOTHER UPPER LEVEL LOW SINKING SOUTHWARD AS A FRONT
ONCE AGAIN APPROACHES FROM THE NORTHWEST. THIS COULD LEAD TO
ANOTHER ROUND OF WET WEATHER FOR THE MIDDLE OF THE NEW WEEK.
AVIATION
WIND SPEEDS ARE ON THE DECLINE AS AN APPROACHING FRONT STALLS NW
OF THE ISLANDS. LIGHT AND VARIABLE WINDS WILL PREVAIL OVER KAUAI
AND OAHU WHILE LIGHT TO MODERATE ESE FLOW WILL LIKELY PERSIST OVER
MAUI AND THE BIG ISLAND. VFR CONDITIONS WILL PREVAIL, 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 IFR CIG/VIS IN +TSRA/+SHRA, AS WELL AS MODERATE TO
SEVERE TURBULENCE ALOFT.
MARINE
THE SLOW APPROACH OF A WEAKENING COLD FRONT INTO THE FAR
NORTHWEST OFFSHORE WATERS TODAY HAS WEAKENED NEARSHORE EAST-
SOUTHEAST WINDS. AS THIS FRONT STALLS JUST WEST OF THE ISLANDS
THURSDAY, 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 THROUGH THE DAY THURSDAY AS A NEWLY-
ARRIVING MODERATE SIZE, MEDIUM PERIOD NORTH NORTHWEST SWELL
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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