416
FXHW60 PHFO 180241
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
441 PM HST TUE MAR 17 2026
SYNOPSIS
A WEATHER PATTERN FEATURING LIGHT WINDS, MOSTLY CLOUDY SKIES, AND
SCATTERED TO NUMEROUS SHOWERS WILL CHARACTERIZE CONDITIONS THROUGH
THURSDAY. DEEP MOISTURE FROM THE TROPICS REMAINS ENTRENCHED,
PARTICULARLY OVER THE BIG ISLAND AND MAUI COUNTY. THE FORECAST CALLS
FOR A INCREASE IN ADVERSE WEATHER BY FRIDAY AS A NEW UPPER-LEVEL LOW
AND SURFACE SYSTEM APPROACH FROM THE WEST, BRINGING THE POTENTIAL
FOR HEAVY RAIN AND RENEWED MODERATE SOUTHWEST WINDS. GIVEN THE
EXTREME SOIL SATURATION FROM THE RECENT STORM, EVEN MODERATE
ADDITIONAL RAINFALL POSES A RISK FOR RAPID RUNOFF AND FLOODING.
DISCUSSION
THE STATE CONTINUES TO RESIDE BENEATH THE LINGERING EFFECTS OF A
LARGE, ENTRENCHED UPPER-LEVEL TROUGH, THE REMNANT SIGNATURE OF THE
POWERFUL KONA LOW THAT RECENTLY MOVED AWAY. DESPITE THE DISSIPATION
OF THE LOW'S CORE, THE LARGER ATMOSPHERIC FLOW CONTINUES TO
TRANSPORT MOISTURE-LADEN TROPICAL AIR ACROSS THE ISLAND CHAIN.
ATMOSPHERIC MEASUREMENTS CONFIRM A PERSISTENT, UNUSUALLY HIGH AMOUNT
OF WATER VAPOR (PWAT VALUES) SATURATING THE AIR MASS THIS AFTERNOON.
NEAR-TERM MODEL PROJECTIONS SUGGEST A BRIEF REPRIEVE FROM THE
HEAVIEST, MOST WIDESPREAD RAIN OVER THE NEXT 36 TO 48 HOURS, WITH
THE WESTERN ISLANDS OF KAUAI AND OAHU SEEING THE MOST NOTICEABLE
SLACKENING. NEVERTHELESS, THE ATMOSPHERE REMAINS UNSTABLE, AND
SHOWERS WILL BE A CONSISTENT FEATURE. THE HIGHEST CONCENTRATION OF
SHOWERS, INCLUDING THE POTENTIAL FOR LOCALIZED HEAVY BURSTS, IS
EXPECTED TO REMAIN FOCUSED ALONG THE AXIS OF DEEPEST MOISTURE OVER
THE EASTERN ISLANDS—MAUI COUNTY AND THE BIG ISLAND—THROUGH
WEDNESDAY. SHIFTING FOCUS TO THE LATTER PART OF THE WEEK, THE UPPER-
LEVEL FLOW IS PREDICTED TO AMPLIFY, WITH THE TROUGH DEEPENING AGAIN
JUST WEST OF HAWAII. THIS DEVELOPMENT IS EXPECTED TO DRAW THE RICH
PLUME OF TROPICAL MOISTURE BACK ACROSS THE ENTIRE ARCHIPELAGO WHILE
GENERATING STRONGER LARGE-SCALE LIFT NECESSARY FOR PRECIPITATION.
NEAR THE SURFACE, MODELS INDICATE A LOW-PRESSURE AREA FORMING AND
ADVANCING TOWARD THE ISLANDS, WHICH WILL HERALD THE RETURN OF
MODERATE SOUTH-TO-SOUTHWEST (KONA) WINDS AND CAUSE COASTAL DEWPOINTS
TO CLIMB BACK TOWARD 70 DEGREES FAHRENHEIT. THIS EVOLVING SETUP
STRONGLY SUPPORTS A MAJOR RESURGENCE OF RAIN COVERAGE AND INTENSITY,
LIKELY STARTING LATE THURSDAY AND CONTINUING INTO THE WEEKEND.
CURRENT FORECASTS SUGGEST SEVERAL ADDITIONAL INCHES OF RAINFALL
COULD ACCUMULATE ACROSS VARIOUS PORTIONS OF THE STATE DURING THIS
EVENT. WHILE THIS APPROACHING SYSTEM IS NOT FORECAST TO MATCH THE
MAGNITUDE OF THE RECENT INTENSE STORM, ITS IMPACT WILL BE AMPLIFIED
BY THE CURRENT, SEVERELY SATURATED GROUND CONDITIONS. DUE TO THE PRE-
EXISTING ENVIRONMENT—INCLUDING FULL STREAM BEDS, ELEVATED
RESERVOIRS, AND WATERLOGGED SOILS—EVEN MODEST RAINFALL RATES WILL
LIKELY EXCEED THE GROUND'S INFILTRATION CAPACITY, LEADING TO
IMMEDIATE RUNOFF PROBLEMS. CONSEQUENTLY, THE FLASH FLOOD THREAT IS
EXPECTED TO BECOME A PRIMARY CONCERN ACROSS ALL ISLANDS STARTING
FRIDAY AFTERNOON, WITH SIGNIFICANT POTENTIAL FOR IMPACTS LASTING
THROUGH THE WEEKEND.
AVIATION
SHOWERS CONTINUE TO MOVE THROUGH THE ISLANDS FROM OAHU TO BIG
ISLAND. SHOWERS CURRENTLY OVER OAHU ARE EXPECTED TO MOVE THROUGH
MAUI COUNTY AND THE BIG ISLAND TONIGHT. A SURFACE TROUGH POSITIONED
NEAR THE BIG ISLAND HAS ALLOWED AFTERNOON CONVECTION TO PRODUCE
SHOWERS AND ISOLATED THUNDERSTORMS OVER WINDWARD BIG ISLAND. THESE
AFTERNOON SHOWERS ARE EXPECTED TO WEAKEN TONIGHT. VFR TO MVFR
CONDITIONS ARE EXPECTED FOR KAUAI AND OAHU TONIGHT, WHILE MVFR TO
ISOLATED IFR CONDITIONS ARE POSSIBLE FOR MAUI COUNTY AND BIG ISLAND.
SHOWERS ARE ALSO POSSIBLE TOMORROW OVER ISLAND INTERIORS, AND
WINDWARD BIG ISLAND. WINDS WILL REMAIN LIGHT AND VARIABLE TONIGHT,
WITH LIGHT EAST WINDS TOMORROW. AIRMET SIERRA IS IN EFFECT FOR MTN
OBSC. OVER OAHU, MAUI COUNTY, AND THE BIG ISLAND. OAHU WILL LIKELY
HAVE CONDITIONS IMPROVE TONIGHT AFTER THE SHOWERS HAVE MOVED
THROUGH. MAUI COUNTY AND BIG ISLAND WILL LIKELY CONTINUE TO HAVE MTN
OBSC. THROUGH TONIGHT. LIGHT ICING IS ALSO POSSIBLE FROM 130-FL260
DUE TO MID-UPPER LEVEL CLOUDS MOVING THROUGH.
MARINE
LIGHT AND VARIABLE WINDS PREVAIL THROUGH MIDWEEK, WITH DAYTIME SEA
BREEZES AND OVERNIGHT LAND BREEZES NEAR THE COASTS. A RIDGE BUILDING
TO THE NORTH OF THE STATE WILL LEAD TO STRENGTHENING EASTERLY TRADE
WINDS FOR NORTHERN PORTIONS OF THE OFFSHORE WATERS LATE THIS WEEK,
THOUGH THE STRONGEST WINDS LOOK TO REMAIN OUTSIDE THE FORECAST AREA.
BY THIS WEEKEND, A WEAK LOW APPROACHING FROM THE WEST TRAVERSES
ACROSS THE STATE AND BEGINS TO LIFT NORTH ON SATURDAY, WHICH APPEARS
LIKELY TO INDUCE LIGHT TO MODERATE SOUTHERLY WINDS FOR THE AREA.
SURF ALONG EXPOSED NORTH AND WEST FACING SHORES WILL PEAK TONIGHT
JUST BELOW ADVISORY THRESHOLDS AS A NORTH-NORTHWEST SWELL BUILDS
DOWN THE ISLAND CHAIN. THIS SOURCE SHOULD BEGIN TO SUBSIDE WEDNESDAY
AND CONTINUE TO EASE INTO THE SECOND HALF OF THE WEEK AS IT SHIFTS
OUT OF THE NORTH-NORTHEAST WITH THE DEVELOPMENT OF FRESH TO STRONG
WINDS JUST OUTSIDE OF THE OFFSHORE WATERS. A NEW NORTHWEST SWELL IS
EXPECTED TO ARRIVE FRIDAY NIGHT INTO THIS WEEKEND AND PROVIDE FRESH
MEDIUM- TO LONG- PERIOD SWELL ENERGY FOR CONTINUED SMALL TO MODERATE
SURF. SURF ALONG SOUTH SHORES WILL ALSO TREND UP THROUGH MID-WEEK AS
A FRESH LONG PERIOD SOUTH SWELL ARRIVES. THIS SWELL WILL PEAK
WEDNESDAY THROUGH THURSDAY, THEN EASE INTO THE WEEKEND. SURF ALONG
EAST FACING SHORES WILL REMAIN WELL BELOW AVERAGE DUE TO THE LACK OF
TRADES LOCALLY AND UPSTREAM. THE EXCEPTION WILL BE FOR EAST FACING
SHORES EXPOSED TO NORTH-NORTHEAST SWELLS EXPECTED LATER THIS WEEK.
HFO WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...PARKER AVIATION...DT MARINE...QUESADA
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