425
FXHW60 PHFO 061341
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
341 AM HST MON APR 6 2026
SYNOPSIS
MOSTLY DRY AND PLEASANT TRADE WIND WEATHER WILL CONTINUE TODAY,
WITH BRIEF PASSING SHOWERS FAVORING WINDWARD AND MAUKA AREAS. A
SIGNIFICANT PATTERN CHANGE IS THEN EXPECTED BY TUESDAY AS AN UPPER
DISTURBANCE AND SURFACE LOW PRESSURE EVOLVE NORTHWEST OF THE
ISLANDS. THIS SYSTEM IS EXPECTED TO DRAW DEEP TROPICAL MOISTURE
NORTHWARD OVER THE STATE, LEADING TO AN EXTENDED PERIOD OF
SOUTHERLY WINDS, INCREASED CHANCES FOR WIDESPREAD RAINFALL, AND
RENEWED FLOODING CONCERNS FROM THE MIDDLE OF THE WEEK THROUGH THE
WEEKEND.
DISCUSSION
THE FORECAST HAS BEEN NUDGED CLOSER TO THE NATIONAL BLEND OF
MODELS, WITH SOME FINE TUNING OF THINGS LIKE THE QPF FOR THE
WEDNESDAY THROUGH FRIDAY TIME SPAN.
A DIGGING SHORTWAVE TROUGH EAST OF MIDWAY WILL PUSH RAPIDLY TO THE
EAST-SOUTHEAST DOWN THE NORTHWEST HAWAIIAN ISLANDS TODAY. THE
HIGH RESOLUTION ENSEMBLES SHOW THE TROUGH ALOFT SHOULD BE CLOSE
ENOUGH TO BEGIN LOCALLY ENHANCING SHOWERS OVER AND NEAR KAUAI
TONIGHT IN THE SOUTHEAST FLOW. A FEW OF THESE MIGHT BECOME
BRIEFLY HEAVY AS THIS LEADING SHORTWAVE GETS CLOSE AND MID-LEVEL
TEMPERATURES COOL FOR A WHILE, BUT INSTABILITY WILL STILL BE
LIMITED AT THIS POINT.
HIGH PRESSURE TO THE NORTH WILL CONTINUE TO BRING SOME MODERATE
TRADES TO THE ISLANDS TODAY, BUT A COLD FRONT NORTHWEST OF THE
ISLANDS THAT IS MOVING TO THE EAST WILL HELP TO PUSH THE RIDGE
CLOSER TO THE ISLANDS. THE RESULT WILL BE WEAKENING WINDS THAT
WILL BEGIN TO VEER TO A SOUTHERLY DIRECTION. TONIGHT OR TOMORROW
MORNING, A BROAD SURFACE TROUGH IS EXPECTED TO DEVELOPS NORTHWEST
OF THE ISLANDS, HELPING TO REINFORCE THE BACKGROUND SOUTHEAST TO
SOUTH WINDS FROM TUESDAY THROUGH WEDNESDAY.
THIS IS ABOUT THE TIME A SERIES OF SHORTWAVE TROUGHS, LIKE THE ONE
MENTIONED ABOVE, WILL BEGIN TO DIG TOWARDS THE ISLANDS. AS
BACKGROUND FLOW BECOMES MORE SOUTHERLY, MODELS REMAIN IN GOOD
AGREEMENT THAT DEEP TROPICAL MOISTURE WILL BE DRAWN NORTHWARD ONCE
AGAIN OVER THE ISLANDS AS EARLY AS TUESDAY BUT ESPECIALLY BY
WEDNESDAY. THE INCREASED MOISTURE, COMBINED WITH DAYTIME HEATING,
SEA BREEZES, AND A POTENT SHORTWAVE TROUGH MOVING THROUGH, MAY
EVEN TRIGGER SOME HEAVY SHOWERS OVER INTERIOR AREAS ON TUESDAY.
FROM WEDNESDAY THROUGH THE END OF THE WEEK, THERE REMAINS THE
POTENTIAL FOR MORE WIDESPREAD RAINFALL AND FLOODING. UPPER-LEVEL
FORCING IS EXPECTED TO STRENGTHEN AS A STRONG SHORTWAVE ROUNDS THE
BASE OF THE TROUGH, POTENTIALLY ENHANCING LIFT OVER THE REGION
WHILE LOW PRESSURE ORGANIZES WEST OF THE ISLANDS. THE COMBINATION
OF DEEP MOISTURE, INCREASING LARGE-SCALE FORCING FOR ASCENT, AND
SOUTHERLY WINDS (WHICH COULD BE GUSTY AT TIMES) ALL POINT TOWARDS
YET ANOTHER WIDESPREAD AND ORGANIZED RAINFALL EVENT FOR THE STATE.
IN ADDITION TO THE RAINFALL CONCERNS DURING THIS PERIOD, SOME
STRONG TO SEVERE THUNDERSTORMS ALONG WITH GUSTY DOWNSLOPING WINDS
FOR NORTH AND WINDWARD SIDES OF THE ISLANDS CAN'T BE RULED OUT.
DIFFERENCES REMAIN IN THE GLOBAL MODELS FOR NEXT WEEKEND, BUT THE
GENERAL CONSENSUS IS THAT THE ACTIVE PATTERN COULD LINGER IN THE
AREA. THE ECMWF CLEARS OUT MUCH OF THE STATE OF THE BULK OF THE
RAIN, BUT THE GFS CONTINUES THE POTENTIAL FOR RAIN ACROSS AT
LEAST PORTIONS OF THE STATE THROUGH THE WEEKEND AND BEYOND, WHERE
THE DEEP MOISTURE AXIS ANCHORS.
AS PREVIOUS DISCUSSIONS HAVE MENTIONED, ONE IMPORTANT CONSIDERATION
WITH THIS WEEK'S RAINFALL IS ANTECEDENT CONDITIONS. THE ISLANDS
EXPERIENCED SIGNIFICANT FLASH FLOOD EVENTS IN RECENT WEEKS, AND
DESPITE SEVERAL DAYS OF DRIER TRADE WIND WEATHER, SOILS REMAIN
VULNERABLE IN MANY AREAS. AS A RESULT, ANY TIME PERIOD OF HIGHER
RAINFALL RATES COULD QUICKLY LEAD TO ENHANCED RUNOFF, RENEWED
RISES IN STREAMS AND RESERVOIRS, AND LOCALIZED FLASH FLOODING
CONCERNS.
THIS SYSTEM WILL CONTINUE TO BE CLOSELY MONITORED OVER THE COMING
DAYS, AND ADDITIONAL ADJUSTMENTS TO TIMING, DURATION, AND IMPACT
MESSAGING ARE POSSIBLE AS DETAILS BECOME MORE CLEAR.
AVIATION
A RIDGE NORTH OF THE ISLANDS CONTINUES TO BRING MODERATE TRADES TO
THE ISLANDS. AS THE RIDGE SLOWLY SINKS SOUTHWARD, IN RESPONSE TO
A FRONT FAR TO THE NORTHWEST PUSHING TO THE EAST, TRADES WILL
WEAKEN AND VEER TO A MORE SOUTHERLY DIRECTION. PASSING SHOWERS
BEING CARRIED IN ON THE TRADE WIND FLOW COULD BRING BRIEF MVFR
CONDITIONS, HOWEVER VFR CONDITIONS ARE GENERALLY EXPECTED
AIRMET SIERRA IS IN EFFECT FOR CLOUDS AND SHOWERS IMPACTING THE
EAST SIDE OF OAHU, BUT ANTICIPATE THIS TO BE DROPPED SHORTLY AFTER
DAYBREAK. AIRMET TANGO IS IN EFFECT FOR UPPER LEVEL TURBULENCE
OVER THE ISLANDS.
MARINE
MODERATE TO LOCALLY FRESH TRADES WILL HOLD THROUGH THIS AFTERNOON
AS HIGH PRESSURE FAR NORTH OF THE ISLANDS MOVES SLOWLY EASTWARD.
WINDS WILL EASE AND SHIFT SOUTHEASTERLY TONIGHT THROUGH WEDNESDAY
AS A FRONT STALLS JUST WEST OF THE ISLANDS. THE WINDS WILL TURN
MORE SOUTHERLY AND INCREASE TO MODERATE AND STRONG LEVELS ON
THURSDAY AS A LOW PRESSURE SYSTEM DEVELOPS ALONG THE STALLED
FRONTAL BOUNDARY.
SMALL NORTHWEST SWELLS WILL KEEP SOME SMALL SURF ALONG NORTH
FACING SHORES THROUGH TODAY. A MODERATE LONG-PERIOD NORTHWEST
SWELL WILL FILL IN TONIGHT AND TUESDAY, GIVING MORE OF A BOOST TO
NORTH SHORE SURF LATE TUESDAY THROUGH WEDNESDAY. A SMALL, SHORT
PERIOD NORTH NORTHEAST SWELL WILL FILL IN DURING THE DAY TUESDAY
BEFORE PEAKING WEDNESDAY AND SUBSIDING THURSDAY. THIS OVERLAP WILL
MAKE FOR SOME ROUGH CHOPPY CONDITIONS.
A SMALL SOUTHERLY SWELL WILL KEEP SOME SMALL SURF IN PLACE ALONG
SOUTH FACING SHORES THROUGH TODAY. A SLIGHTLY LARGER, LONG-PERIOD
SOUTH SWELL, WILL FILL IN TONIGHT. THIS SWELL WILL GIVE A MORE
NOTICEABLE INCREASE TO SOUTH SHORE SURF TUESDAY AND POSSIBLY
REACHING ADVISORY LEVELS BY WEDNESDAY BEFORE SLOWLY EASING
THURSDAY INTO THE WEEKEND. STRENGTHENING SOUTHERLY WINDS COULD
MAKE FOR ROUGH CHOPPY SURF BY LATE NEXT WEEK.
EAST SHORE SURF WILL REMAIN SMALL AND BELOW THE SEASONAL AVERAGE
DURING THE NEXT 7 DAYS DUE TO A LACK OF STRONG TRADE WINDS OVER AND
UPSTREAM OF THE ISLANDS, EXCEPT FOR SOME WRAP FROM THE NORTHERLY
SWELLS.
HFO WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...M BALLARD
AVIATION...M BALLARD
MARINE...ALMANZA
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page