432
FXHW60 PHFO 050100
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
300 PM 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 BEGINNING TUESDAY OR WEDNESDAY. GIVEN RECENT FLOOD
EVENTS AND SOILS THAT REMAIN ONLY PARTIALLY RECOVERED, THE POTENTIAL
FOR RUNOFF AND FLASH FLOODING IMPACTS MAY INCREASE RAPIDLY.
DISCUSSION
TODAY THROUGH MONDAY. MODERATE TRADES FOCUS SHOWERS WINDWARD AND
MAUKA. A ZONALLY ORIENTED SUBTROPICAL JET HAS SAGGED SOUTH ALLOWING
HIGH CLOUDS TO CLEAR. THE STJ WILL GET A SLIGHT BUMP NORTH AGAIN
TOMORROW ALLOWING HIGH CLOUDS TO RETURN. BENIGN STABLE TRADE WIND
WEATHER THROUGH MONDAY.
TUESDAY. POTENT SHORTWAVE OF INTEREST IS SEEN OVER JAPAN ON THIS
MORNING'S WATER VAPOR IMAGERY. THE EXISTING LONGWAVE PATTERN WILL
SERVE AS A WAVEGUIDE ALLOWING THIS FAST-MOVING WAVE TO DEEPEN THE
EXISTING TROUGH NORTHWEST OF THE ISLANDS EARLY NEXT WEEK. THE FIRST
SIGN OF ITS ARRIVAL WILL BE UPSTREAM SURFACE PRESSURE FALLS THAT
WILL CAUSE WINDS TO WEAKEN AND VEER TO SOUTHEASTERLY MONDAY NIGHT
INTO TUESDAY. COMBINED WITH BLOCKED FLOW IN THE SHADOW OF THE BIG
ISLANDS, TUESDAY WILL BE FAVORABLE FOR SEA BREEZE DEVELOPMENT.
STEADILY RISING PWAT VALUES DURING THIS TIME AS TROPICAL MOISTURE IS
DRAWN NORTH COMBINED WITH AMPLE MID-LEVEL FORCING DURING MIDDAY WILL
SET THE STAGE FOR POTENTIALLY HEAVY AFTERNOON SHOWERS OVER ISLAND
INTERIORS. THERE WILL BE MORE CLARITY ON THIS POTENTIAL AS THIS
PERIOD ENTERS THE HIGH RES MODELING WINDOW DURING DURING THE NEXT
COUPLE OF DAYS. THIS FIRST WAVE WILL BE ON ITS WAY OUT BY LATE
TUESDAY, ITS PRIMARY ROLE SERVING TO PRIME THE LOCAL ATMOSPHERE BY
DRAWING PWATS APPROACHING 2" NORTHWARD. ANY RAIN WITH THIS INITIAL
PUSH OF MOISTURE IS MOST LIKELY TO BE STRATIFORM IN NATURE AND NOT
PARTICULARLY HEAVY.
WEDNESDAY THROUGH THURSDAY NIGHT. SIMILAR EVOLUTION OF A TRAILING
WAVE IS EXPECTED, THIS TIME ACHIEVING BETTER PHASING WITH MID-
LATITUDE ENERGY ALLOWING PRESSURE FALLS TO EVOLVE INTO ORGANIZED LOW
PRESSURE CENTERED NW OF THE ISLANDS. WITH DEEP MOISTURE IN PLACE AND
CONTINUING TO INCREASE, MID-LEVEL FORCING STEADILY INCREASES
WEDNESDAY INTO LATE THURSDAY. SUPERPOSITIONED WITH OUTSTANDING JET
SUPPORT BY WEDNESDAY NIGHT, THE WED-THURS TIME PERIOD STILL APPEARS
TO BE THE THE TARGET PERIOD FOR GREATEST FLOODING POTENTIAL. AT THIS
TIME, GUIDANCE GENERALLY FAVORS THE WESTERN END OF THE STATE, BUT
THE ENTIRE STATE IS WITHIN THE MARGIN OF ERROR AT THIS LEAD TIME AND
FLOODING MAY STILL IMPACT ANY/MULTIPLE ISLANDS. OF NOTE, RECENT
SOLUTIONS HAVE CONVERGED ON A CONSENSUS FOR A STRONGER LOW
DEVELOPING IN CLOSER PROXIMITY TO THE ISLANDS. THIS WILL RESULT IN
ELEVATED POTENTIAL FOR DOWNSLOPING WINDS MOST LIKELY ON THURSDAY.
WHILE THE AMBIENT WIND FIELD IS NOT OVERLY STRONG, SOUTHERLY 925MB
WINDS IN EXCESS OF 30 KTS MAY BE SUFFICIENT TO GENERATE WIND
ADVISORY LEVEL GUSTS IN FAVORED LOCALES LOCATED N/NE OF STEEP
TERRAIN.
FRIDAY ONWARD. THE NORTH CENTRAL PACIFIC WILL REMAIN A FAVORED AREA
FOR DEEP TROUGHING THROUGH MID-APRIL. AT THE SAME TIME, THE MOISTURE
BAND ASSOCIATED WITH NEXT WEEK'S LOW WILL LIKELY REMAIN IN PLACE
OVER THE ISLANDS FOR SOME TIME. THIS RAISES THE POTENTIAL FOR
ADDITIONAL WAVES OF HEAVY RAIN TO DEVELOP NEXT WEEKEND OR BEYOND.
THE DURATION/ENDING TIME OF THIS PARTICULAR EVENT IS THEREFORE MUCH
LESS CERTAIN THAN USUAL.
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. ALSO WORTH NOTING THAT WHILE NOT
NOT A KONA LOW, THE DIFFERENCE IS LARGELY ACADEMIC AND DOES NOT
CHANGE THE EXPECTATION FOR FLOODING IMPACTS.
A HYDROLOGIC OUTLOOK SUMMARIZING CURRENT INFORMATION HAS BEEN ISSUED.
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 ENE TRADES EASE THROUGH SUNDAY AS HIGH
PRESSURE NORTH OF THE AREA ADVANCES EAST. BY MONDAY A FRONT WILL
APPROACH THE REGION FROM THE NW AND A TROUGH WILL MOVE UP FROM
THE S. AS A RESULT, WINDS WILL VEER TO ESE. TUESDAY THROUGH THE
REMAINDER OF THE WEEK, SE TO S WINDS WILL PREVAIL AND COULD
BECOME STRONG TOWARD THE LATER HALF OF THE WEEK. THESE FEATURES
WILL BE DRIVEN BY AN UPPER LEVEL TROUGH WHICH MAY GENERATE
ISOLATED THUNDERSTORMS OVER THE COASTAL WATERS BY THE MIDDLE TO
LATTER HALF OF NEXT WEEK.
SURF ALONG N SHORES REMAINS SMALL INTO THIS EVENING AS SMALL
MEDIUM PERIOD WNW (310 DEGREE) ENERGY FILLS IN. TONIGHT INTO
SUNDAY, SMALL, MEDIUM- PERIOD NW (330-340 DEGREE) ENERGY WILL
ALSO BUILD. THESE SWELLS WILL BUMP SURF SLIGHTLY UPWARD FOR N AND
W SHORES. MONDAY NIGHT THROUGH WEDNESDAY, A MODERATE MEDIUM-
PERIOD WNW (310 DEGREE) SWELL WILL FILL IN AND INCREASE SURF TO
JUST BELOW THE ADVISORY THRESHOLD. THIS SWELL WILL LINGER AND
GRADUALLY DECLINE THROUGH THE LATTER HALF OF THE WEEK.
ALONG S SHORES, EXPECT MINOR PULSES FROM THE SOUTH PACIFIC TO
PROVIDE PERIODS OF SMALL SURF THROUGH THE WEEKEND UNTIL A LARGER
LONG-PERIOD S SWELL FILLS IN MONDAY AND LASTS THROUGH THE WEEK.
STRENGTHENING SOUTHERLY WINDS WILL LEAD TO CHOPPY CONDITIONS BY
MIDWEEK.
E SHORES WILL SUBSIDE AS TRADES WEAKEN AND WILL REMAIN SMALL AS
WINDS VEER TO SE. BY THE MIDDLE OF NEXT WEEK, A SMALL MEDIUM
PERIOD SWELL WILL PROVIDE A BUMP TO SURF.
HFO WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...JVC
AVIATION...M BALLARD
MARINE...JVC
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