708
FXHW60 PHFO 041904
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
904 AM HST SAT APR 4 2026
SYNOPSIS
MODERATE TRADES FOCUS SHOWERS WINDWARD AND MAUKA THROUGH THE
WEEKEND. A STRENGTHENING LOW THEN BRINGS POTENTIAL FOR HEAVY RAIN
TO THE ISLANDS FROM TUESDAY NIGHT ONWARD.
SHORT TERM UPDATE
ISSUED AT 905 AM HST SAT APR 4 2026
SHORT TERM FORECAST IN GOOD SHAPE WITH TRADE WINDS AND GENERALLY
DRY WEATHER ANTICIPATED THROUGH AT LEAST MONDAY. ATTENTION REMAINS
FOCUSED ON MID-LATE WEEK FLOOD POTENTIAL. WORTH NOTING THAT WHILE
NEXT WEEK'S SYSTEM IS NOT A KONA LOW, THE DIFFERENCE IS LARGELY
ACADEMIC. IMPACTFUL FLOODING IS POSSIBLE REGARDLESS.
PREV DISCUSSION
A RELATIVELY BENIGN TRADE WIND PATTERN REMAINS IN PLACE ACROSS
THE HAWAIIAN ISLANDS THIS MORNING AND IS EXPECTED TO PERSIST
THROUGH THE WEEKEND INTO MONDAY. MODERATE EASTERLY TRADES WILL
CONTINUE TO FOCUS BRIEF SHOWERS ALONG WINDWARD AND MAUKA SLOPES,
WHILE LEEWARD AREAS REMAIN MOSTLY DRY.
GLOBAL GUIDANCE REMAINS IN DECENT AGREEMENT AND DEPICTS A NOTABLE
AMPLIFICATION OF THE LARGE-SCALE PATTERN ACROSS THE CENTRAL
PACIFIC EARLY NEXT WEEK. A SERIES OF SHORTWAVE TROUGHS DIGGING
SOUTHEASTWARD TOWARD THE STATE WILL TRANSLATE TO LARGE-SCALE
UPPER HEIGHT FALLS ACROSS THE REGION. THE SURFACE RIDGE TO THE
NORTH WILL GRADUALLY ERODE AS AN ATTENDANT SURFACE LOW EVOLVES TO
THE NORTHWEST. THIS WILL DISRUPT THE TYPICAL TRADE WIND FLOW BY
TUESDAY AND ALLOW LOW-LEVEL WINDS TO VEER OUT OF THE SOUTHEAST TO
SOUTH BY WEDNESDAY.
THIS TRANSITION TO SOUTHERLY FLOW WILL DRAW DEEP TROPICAL MOISTURE
NORTHWARD INTO THE ISLANDS BEGINNING TUESDAY NIGHT AND ESPECIALLY
WEDNESDAY INTO THURSDAY. PRECIPITABLE WATER VALUES ARE FORECAST
TO CLIMB TOWARD 2 INCHES OR HIGHER, SIGNALING A MARKED INCREASE IN
MOISTURE.
CONFIDENCE IS INCREASING THAT WEDNESDAY THROUGH THE SECOND HALF
OF THE WEEK MAY PRESENT THE HIGHEST POTENTIAL FOR WIDESPREAD
RAINFALL AND FLOODING IMPACTS. 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 NORTHWEST OF THE ISLANDS. THE
COMBINATION OF DEEP MOISTURE, INCREASING LARGE-SCALE FORCING FOR
ASCENT, AND BREEZY SOUTHERLY WINDS FAVORS A TRANSITION TOWARD A
MORE WIDESPREAD AND ORGANIZED RAINFALL EVENT. IN ADDITION TO THE
RAINFALL CONCERNS DURING THIS PERIOD, A FEW THUNDERSTORMS ALONG
WITH GUSTY DOWNSLOPING WINDS FOR NORTH AND WINDWARD SIDES OF THE
ISLANDS CAN'T BE RULED OUT.
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 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 TO LOCALLY BREEZY TRADE WINDS WILL PREVAIL DURING THE
NEXT 24 HOURS OR SO, WITH ISOLATED LIGHT SHOWERS LIMITED TO
WINDWARD SLOPES AND COASTS, WHERE BRIEF MVFR CIGS ARE POSSIBLE.
ELSEWHERE, VFR CONDITIONS ARE EXPECTED TO PREVAIL.
NO AIRMETS ARE IN EFFECT AND NONE ARE EXPECTED TODAY.
MARINE
MODERATE TO LOCALLY FRESH EAST-NORTHEASTERLY TRADE WINDS WILL
GRADUALLY DECREASE THROUGH SUNDAY AS HIGH PRESSURE TO THE NORTH
MOVES EAST. THE WINDS WILL BEGIN TO VEER OUT OF THE SOUTHEAST TO
SOUTH MONDAY NIGHT INTO MIDWEEK AS BROAD LOW PRESSURE EVOLVES TO
THE NORTHWEST. THE SOUTHERLY WINDS WILL THEN STRENGTHEN TO
LOCALLY STRONG LEVELS TOWARDS THE LATTER HALF OF THE WEEK. THESE
FEATURES WILL BE DRIVEN BY AN UPPER LEVEL TROUGH, WHICH COULD
ALLOW FOR ISOLATED THUNDERSTORMS OVER THE COASTAL WATERS BY THE
MIDDLE TO LATTER HALF OF NEXT WEEK.
SURF ALONG NORTH FACING SHORES WILL REMAIN SMALL TODAY AS SMALL
MEDIUM- PERIOD WEST- NORTHWEST (310 DEGREE) ENERGY FILLS IN.
TONIGHT INTO SUNDAY, SMALL, MEDIUM-PERIOD NORTHWEST (330-340
DEGREE) ENERGY WILL ALSO FILL IN. BOTH OF THESE SMALL SWELLS WILL
BUMP UP SURF SLIGHTLY FOR NORTH AND WEST FACING SHORES. THEN BY
MONDAY NIGHT THROUGH WEDNESDAY, A MODERATE MEDIUM- PERIOD WEST-
NORTHWEST (310 DEGREE) SWELL WILL FILL IN AND INCREASE SURF TO
JUST BELOW ADVISORY LEVELS. THIS SWELL WILL LINGER AND GRADUALLY
DECLINE THROUGH THE LATER HALF OF THE WEEK.
ALONG SOUTH FACING SHORES, EXPECT MINOR PULSES FROM THE SOUTH
PACIFIC TO PROVIDE PERIODS OF SMALL SURF THROUGH THE WEEKEND
UNTIL A LARGER LONG-PERIOD SOUTH SWELL FILLS IN MONDAY AND LASTS
THROUGH THE WEEK. IN ADDITION, STRENGTHENING SOUTHERLY WINDS MAY
LEAD TO INCREASINGLY CHOPPY CONDITIONS BY MIDWEEK.
EAST FACING SHORES WILL DECREASE AS TRADE WINDS EASE AND REMAIN
SMALL AS WINDS VEER SOUTHERLY. BY THE MIDDLE OF NEXT WEEK, A
SMALL MEDIUM PERIOD SWELL COULD ARRIVE AND BUMP UP SURF HEIGHTS.
HFO WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM UPDATE...JVC
DISCUSSION...GIBBS
AVIATION...JELSEMA
MARINE...TSAMOUS
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