026
FXHW60 PHFO 050700
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
900 PM HST SAT APR 4 2026
SYNOPSIS
MOSTLY DRY AND PLEASANT TRADE WIND WEATHER WILL CONTINUE INTO
MONDAY, WITH BRIEF PASSING SHOWERS FAVORING WINDWARD AND MAUKA
AREAS. A SIGNIFICANT PATTERN CHANGE IS THEN EXPECTED BY TUESDAY
INTO MIDWEEK AS AN UPPER DISTURBANCE AND SURFACE LOW PRESSURE
EVOLVE NORTHWEST OF THE ISLANDS. THIS SETUP IS EXPECTED TO DRAW
DEEP TROPICAL MOISTURE NORTHWARD OVER THE STATE, LEADING TO AN
EXTENDED PERIOD OF SOUTHERLY WINDS, INCREASING CHANCES FOR
WIDESPREAD RAINFALL, AND RENEWED FLOODING CONCERNS FROM TUESDAY
THROUGH NEXT WEEKEND. GIVEN RECENT FLOOD EVENTS AND SOILS THAT
REMAIN ONLY PARTIALLY RECOVERED, THE POTENTIAL FOR RUNOFF AND
FLASH FLOODING IMPACTS MAY INCREASE RAPIDLY.
DISCUSSION
A RELATIVELY BENIGN TRADE WIND PATTERN REMAINS IN PLACE ACROSS
THE HAWAIIAN ISLANDS THIS EVENING AND IS EXPECTED TO PERSIST INTO
MONDAY. MODERATE EASTERLY TRADES WILL CONTINUE TO FOCUS MAINLY
LIGHT SHOWERS ALONG WINDWARD AND MAUKA SLOPES, WHILE LEEWARD AREAS
REMAIN DRY.
GLOBAL GUIDANCE REMAINS IN GOOD AGREEMENT AND DEPICTS A NOTABLE
AMPLIFICATION OF THE LARGE-SCALE PATTERN ACROSS THE CENTRAL
PACIFIC BY MONDAY. A SERIES OF SHORTWAVE TROUGHS DIGGING
SOUTHEASTWARD TOWARD THE STATE WILL TRANSLATE TO LARGE-SCALE
UPPER HEIGHT FALLS A CROSS THE REGION. THE SURFACE RIDGE TO THE
NORTH WILL GRADUALLY ERODE AS AN ATTENDANT BROAD SURFACE TROUGH
EVOLVES TO THE WEST. THIS WILL DISRUPT THE TYPICAL TRADE WIND FLOW
BY MONDAY NIGHT AND ALLOW LOW-LEVEL WINDS TO GRADUALLY VEER OUT
OF THE SOUTHEAST TO SOUTH TUESDAY THROUGH WEDNESDAY.
THIS TRANSITION TO SOUTHERLY FLOW WILL DRAW DEEP TROPICAL MOISTURE
NORTHWARD INTO THE ISLANDS BEGINNING TUESDAY AND ESPECIALLY BY
WEDNESDAY. PRECIPITABLE WATER VALUES ARE FORECAST TO CLIMB TOWARD
2 INCHES OR HIGHER, SIGNALING A MARKED INCREASE IN MOISTURE. THIS
INCREASING 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.
CONFIDENCE IS INCREASING THAT THE SECOND HALF OF THE WEEK MAY
PRESENT THE HIGHEST POTENTIAL FOR WIDESPREAD RAINFALL AND FLOODING
IMPACTS ACROSS THE STATE. DURING THIS TIME, 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 GUSTY
SOUTHERLY WINDS FAVORS A TRANSITION TOWARD A MORE WIDESPREAD AND
ORGANIZED RAINFALL EVENT. 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, ESPECIALLY BY THURSDAY AND INTO
FRIDAY.
ALTHOUGH FORECAST CONFIDENCE BEGINS TO LOWER BY NEXT WEEKEND DUE
TO MODEL DIFFERENCES, THE GENERAL LARGE-SCALE PATTERN COULD
LINGER. THIS SCENARIO SUGGESTS THE POTENTIAL FOR RAIN MAY PERSIST
THROUGH NEXT WEEKEND AND BEYOND FOR AT LEAST PARTS OF THE STATE
OR WHERE THE DEEP MOISTURE AXIS ANCHORS.
REGARDLESS OF THE PRECISE EVOLUTION, ANTECEDENT CONDITIONS REMAIN
A SIGNIFICANT CONCERN. THE ISLANDS HAVE 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 PERIOD OF HEAVY RAINFALL NEXT WEEK MAY QUICKLY
LEAD TO ENHANCED RUNOFF, RENEWED RISES IN STREAMS AND RESERVOIRS,
AND LOCALIZED FLASH FLOODING CONCERNS.
THIS SYSTEM WILL CONTINUE TO BE MONITORED CLOSELY OVER THE COMING
DAYS, AS ADDITIONAL ADJUSTMENTS TO TIMING, DURATION, AND IMPACT
MESSAGING ARE LIKELY AS THIS CHANGE IN THE PATTERN EVOLVES.
AVIATION
MODERATE TRADE WINDS WILL SLOWLY WEAKEN OVER THE NEXT 24 HOURS.
ISOLATED LIGHT SHOWERS WILL CONTINUE TO BE CARRIED IN TO THE
WINDWARD SLOPES, WITH BRIEF MVFR CONDITIONS ARE POSSIBLE.
OTHERWISE, VFR CONDITIONS ARE EXPECTED TO PREVAIL.
NO AIRMETS ARE IN EFFECT AND NONE ARE EXPECTED OVERNIGHT.
MARINE
MODERATE TO LOCALLY FRESH TRADES WILL PERSIST DURING THE NEXT
COUPLE DAYS AS HIGH PRESSURE NORTH OF THE ISLANDS MOVES SLOWLY
EASTWARD. WINDS WILL EASE AND SHIFT SOUTHEASTERLY MONDAY NIGHT
THROUGH WEDNESDAY AS A FRONT STALLS OUT AND MERGES WITH A TROUGH
JUST WEST OF THE ISLANDS. THE WINDS WILL TURN MORE SOUTHERLY AND
INCREASE TO MODERATE AND STRONG LEVELS ON THURSDAY AS A STORM
SYSTEM DEVELOPS ALONG THE TROUGH WEST OF THE STATE.
A SERIES OF OVERLAPPING SMALL NORTHWEST SWELLS WILL KEEP SOME
SMALL SURF IN PLACE ALONG NORTH FACING SHORES THROUGH MONDAY. A
NEW LONG-PERIOD NORTHWEST SWELL WILL FILL IN MONDAY NIGHT AND
TUESDAY, GIVING A MORE NOTICEABLE BOOST TO NORTH SHORE SURF LATE
TUESDAY THROUGH WEDNESDAY, FOLLOWED BY A GRADUAL DECLINE THURSDAY
INTO NEXT WEEKEND.
OVERLAPPING SOUTHERLY SWELLS WILL KEEP SOME SMALL SURF IN PLACE
ALONG SOUTH FACING SHORES THROUGH MONDAY. A NEW LONG DURATION,
AND SLIGHTLY LARGER LONG-PERIOD SOUTH SWELL, WILL FILL IN MONDAY
NIGHT. THIS SWELL WILL GIVE A MORE NOTICEABLE BOOST TO SOUTH
SHORE SURF TUESDAY INTO NEXT WEEKEND. STRENGTHENING SOUTHERLY
WINDS COULD LEAD TO CHOPPY CONDITIONS BY LATE NEXT WEEK.
EAST SHORE SURF WILL REMAIN SMALL AND BELOW CLIMATOLOGICAL LEVELS
DURING THE NEXT 7 DAYS DUE TO A LACK OF STRONG TRADE WINDS OVER
AND UPSTREAM OF THE ISLANDS.
HFO WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...GIBBS
AVIATION...M BALLARD
MARINE...JELSEMA
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