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.
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.
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.
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.
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