788
FXHW60 PHFO 160621
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
821 PM HST SUN MAR 15 2026
SYNOPSIS
PERIODS OF MODERATE TO HEAVY RAIN CONTINUE OVER LEEWARD BIG ISLAND
AND MAUI WHILE CONDITIONS IMPROVE ELSEWHERE. THERE IS A THREAT FOR
HEAVY RAIN DURING THE LATTER HALF OF THIS WEEK AS LOW PRESSURE
DEVELOPS WEST OF THE ISLANDS.
SHORT TERM UPDATE
ISSUED AT 820 PM HST SUN MAR 15 2026
THE KONA LOW HAS MEANDERED WELL NORTH OF THE ISLANDS; HOWEVER,
SHOWERS CONTINUE TO SOCK IN MAUI COUNTY AND THE BIG ISLAND, WHERE
FLASH FLOOD WATCHES REMAIN IN PLACE. IT'S ANTICIPATED THAT SHOWERS
WILL EASE THROUGHOUT THE OVERNIGHT PERIOD, ALLOWING THE
AFOREMENTIONED WATCH TO BE CANCELED BY THE MORNING FORECAST
PACKAGE. MEANWHILE, LATEST OBSERVATIONS CONTINUE TO DEPICT THE
SUMMITS OF BIG ISLAND GUSTING WELL ABOVE HIGH WIND WARNING
THRESHOLD. MODEL GUIDANCE SUGGESTS THESE WINDS WILL FALL BELOW
THRESHOLD AROUND THE TIME OF THE NEXT PACKAGE, WARRANTING THE
DOWNGRADE TO A WIND ADVISORY; HOWEVER, THIS WILL BE REASSESSED
LATER TONIGHT. LARGELY, THE FORECAST REMAINS ON TRACK, SO APART
FROM JUST UPDATING THE WINDS AND TEMPERATURES WITH THE LATEST
TRENDS, NO AMENDMENTS WERE NECESSARY AT THIS TIME.
PREV DISCUSSION
MOISTURE EMBEDDED WITHIN DEEP LAYER SW FLOW EXTENDS WELL UPSTREAM OF
THE BIG ISLAND AND WILL CONTINUE TO DELIVER WAVES OF RAINFALL
THROUGH AT LEAST MONDAY NIGHT AND POTENTIALLY TUESDAY. HOWEVER, THE
LACK OF LARGE SCALE FORCING DURING THIS TIME WILL LIKELY RESULT IN A
TREND TOWARD LOWER INTENSITY RAINFALL COMPARED TO WHAT WAS OBSERVED
YESTERDAY OR EVEN TODAY. AT THE SAME TIME, THE WEAKENING BACKGROUND
WIND FIELD MAY ALLOW THE OVERNIGHT MOUNTAIN BREEZE TO MORE
EFFECTIVELY FOCUS STRONGER CONVECTION OFFSHORE AT NIGHT. RATHER
NONDESCRIPT SURFACE PRESSURE AND WIND FIELDS TAKES SHAPE DURING
TUESDAY WHICH SHOULD FINALLY BRING AN END TO THE STEADY STREAM OF
RAINFALL. AT THIS TIME, THE FLOOD WATCH WILL REMAIN IN EFFECT FOR
THE BIG ISLAND AND MAUI, THOUGH CONFIDENCE IN THE MOISTURE BAND
LIFTING SUFFICIENTLY FAR NORTH TO IMPACT MAUI AGAIN IS LOW AT THIS
TIME. THE WIND ADVISORY WILL END WITH ISSUANCE OF THE AFTERNOON
FORECAST PACKAGE, AND THE HIGH WIND WARNING FOR HALEAKALA AND THE
BIG ISLAND SUMMITS WILL BE EXTENDED THROUGH TONIGHT.
ATTENTION THEN TURNS TO MID TO LATE WEEK WHEN THE REMNANT FRONTAL
BAND REACTIVATES IN RESPONSE TO RENEWED MID/UPPER FORCING FOLLOWED
BY POTENTIAL DEVELOPMENT OF LOW PRESSURE WEST OF THE ISLANDS
DURING THE SECOND HALF OF THE WEEK. THE FIRST UPPER WAVE ARRIVES
LATE WEDNESDAY. MID- LEVEL FLOW WILL STILL BE SOUTHWESTERLY AT
THIS TIME, THOUGH IT IS UNCERTAIN WHETHER BOUNDARY LAYER FLOW WILL
WILL BE IN A STATE OF WEAK TRADES OF OUT OF THE SOUTH. IN ANY
CASE, AN UPTICK IN SHOWERS IS ANTICIPATED OVER THE ISLANDS BY
WEDNESDAY NIGHT. SURFACE PRESSURE FALLS WILL ALREADY BE TAKING
PLACE UPSTREAM OF THE ISLANDS DURING THIS TIME AS A TRAILING UPPER
WAVE APPROACHES THE ISLANDS FROM THE NORTHWEST. MODEL CONSENSUS
PREVIOUSLY BROKE DOWN AT THIS POINT WITH THE GFS INDICATING A
FLATTER AND MORE PROGRESSIVE SURFACE LOW WHILE THE EC INDICATED A
DEEPER AND SLOWER MOVING LOW. THE MOST RECENT RUN OF THE GFS HAS
MADE A STRONG MOVE TOWARD THE EC INCREASING CONFIDENCE THAT
ORGANIZED LOW PRESSURE WILL DEVELOP OVER OR NEAR THE ISLANDS BY
LATE THIS WEEK. MODERATE TO HEAVY RAIN THEN POTENTIALLY DEVELOPS
OVER THE ISLANDS AS EARLY AS FRIDAY AND WOULD CONTINUE INTO THE
WEEKEND.
AVIATION
ISSUED AT 820 PM HST SUN MAR 15 2026
THE SYSTEM THAT HAS PLAGUED THE AREA CONTINUES TO MOVE NORTHEAST.
LOW CIGS AND SHRA CONTINUE ACROSS THE AREA AND WILL SLOWLY
DECREASE FROM WEST TO EAST TONIGHT INTO TOMORROW. SOME MVFR CONDS
ARE POSSIBLE. THE LONE EXCEPTION IS LANAI WHICH IS LIFR WITH FOG
THATS EXPECTED TO LAST INTO THE MORNING. WINDS HAVE WEAKENED OVER
THE STATE AND WILL CONTINUE THAT TREND INTO TOMORROW. THERE STILL
COULD STILL BE SOME GUSTY WINDS ESPECIALLY OVER MAUI AND THE BIG
ISLAND.
AIRMET SIERRA IS IN EFFECT FOR MTN OBSC FROM MOLOKAI TO THE BIG
ISLAND. OAHU MAY BE ADDED ESPECIALLY OVER WINDWARD LOCATIONS
OVERNIGHT. CONDS IN GENERAL WILL IMP WEST TO EAST AND THIS AIRMET
WILL BE ADJUSTED AS NECESSARY.
AIRMET TANGO REMAINS IN EFFECT FOR MOD MID-UPPER LEVEL TURB
BETWEEN 130 AND FL330. IT IS IS ALSO IN EFFECT FOR TURB DOWNWIND
N THRU E OF TERRAIN STATEWIDE. AS WINDS DIMINISH AND THIS SYSTEM
MOVES FURTHER AWAY FROM THE ISLANDS THIS WILL BE ADJUSTED IN THE
OVERNIGHT HOURS.
LIGHT ICING IS POSSIBLE BETWEEN 130 AND FL260 AS MID-HIGH CLOUDS
CONTINUE MOVING THROUGH THE ISLANDS.
MARINE
THE KONA STORM THAT HAS IMPACTED THE REGION OVER THE PAST FEW DAYS
WILL WEAKEN AS IT MOVES NORTHEAST AND AWAY FROM THE AREA, WITH
CONDITIONS IMPROVING OVER THE COASTAL WATERS. LATEST HI-RES
GUIDANCE SHOWS THAT LOCALLY STRONG WINDS MAY LINGER OVER PORTIONS
OF THE CENTRAL AND EASTERN WATERS TONIGHT. ADDITIONALLY, BUOY
OBSERVATIONS SHOW THAT SEAS REMAIN ELEVATED, WITH BARBER'S POINT
AND HANALEI STILL REPORTING 10FT AND 12FT SIGNIFICANT WAVE
HEIGHTS THIS AFTERNOON, RESPECTIVELY. THEREFORE, THE SMALL CRAFT
ADVISORY (SCA) THAT WAS PREVIOUSLY IN EFFECT HAS BEEN EXTENDED IN
TIME THROUGH TONIGHT TO CAPTURE THE SEAS FOR THE WESTERN WATERS
AND LOCALLY BREEZY WINDS IN THE CENTRAL AND EASTERN WATERS (WITH
THE EXCEPTION OF THE SOUTHEAST BIG ISLAND ZONE WHERE THE SCA HAS
BEEN CANCELLED). BY EARLY MONDAY, BOTH WINDS AND SEAS ARE
EXPECTED TO FALL BELOW ADVISORY CRITERIA. WINDS WILL THEN REMAIN
LIGHT AND VARIABLE THROUGH MID-WEEK. RIDGING IS FORECAST TO
STRENGTHEN NORTH OF THE ISLANDS LATE IN THE WEEK, WHICH SHOULD
BRING A RETURN OF MODERATE TO FRESH TRADE WINDS.
LARGE, ROUGH SURF ALONG SOUTH-FACING SHORES THAT HAS BEEN
OBSERVED OVER THE PAST FEW DAYS WILL TREND LOWER TONIGHT AND
MONDAY AS WIND SPEEDS SUBSIDE. A NEW LONG-PERIOD SOUTH SWELL WILL
ARRIVE LATE MONDAY NIGHT AND TUESDAY, GIVING AN EXTENDED BOOST TO
SOUTH SHORE SURF THROUGH LATE THIS WEEK.
A MODERATE SIZED, SHORT-PERIOD WEST-NORTHWEST SWELL WILL CONTINUE
TO AFFECT NORTH AND WEST FACING SHORES THROUGH MONDAY, BUT SURF
WILL REMAIN BELOW ADVISORY LEVELS. THE ONE EXCEPTION IS FOR WEST
FACING SHORES OF THE BIG ISLAND, WHERE A HIGH SURF ADVISORY
REMAINS IN EFFECT THROUGH 6 AM HST. THIS SHORT-PERIOD SWELL WILL
LOWER MONDAY NIGHT AND TUESDAY, WHILE A NEW MEDIUM-PERIOD NORTH-
NORTHWEST SWELL FILLS IN. THIS NORTH-NORTHWEST SWELL COULD BRING
SURF UP TO ADVISORY LEVELS TUESDAY NIGHT AND WEDNESDAY, WITH THE
SWELL THEN SHIFTING MORE NORTHERLY AND LOWERING BELOW ADVISORY
LEVELS THURSDAY INTO NEXT WEEKEND.
SURF ALONG EAST FACING SHORES WILL REMAIN WELL BELOW NORMAL LEVELS
THROUGH THE MIDDLE OF THE WEEK, BEFORE TRENDING UPWARD THURSDAY
INTO NEXT WEEKEND AS TRADE WINDS RETURN OVER AND UPSTREAM OF THE
ISLANDS.
HFO WATCHES/WARNINGS/ADVISORIES
FLOOD WATCH UNTIL 6 AM HST MONDAY FOR BIG ISLAND EAST-BIG ISLAND
INTERIOR-BIG ISLAND NORTH-BIG ISLAND SOUTH-BIG ISLAND SOUTHEAST-
HALEAKALA SUMMIT-KAHOOLAWE-KIPAHULU-KOHALA-KONA-LANAI LEEWARD-
LANAI MAUKA-LANAI SOUTH-LANAI WINDWARD-MAUI CENTRAL VALLEY NORTH-
MAUI CENTRAL VALLEY SOUTH-MAUI LEEWARD WEST-MAUI WINDWARD WEST-
MOLOKAI LEEWARD SOUTH-MOLOKAI NORTH-MOLOKAI SOUTHEAST-MOLOKAI
WEST-MOLOKAI WINDWARD-SOUTH HALEAKALA-SOUTH MAUI/UPCOUNTRY-
WINDWARD HALEAKALA.
HIGH WIND WARNING UNTIL 6 AM HST MONDAY FOR BIG ISLAND SUMMITS-
HALEAKALA SUMMIT.
HIGH SURF ADVISORY UNTIL 6 AM HST MONDAY FOR KOHALA-KONA.
SMALL CRAFT ADVISORY UNTIL 6 AM HST MONDAY FOR ALENUIHAHA
CHANNEL-BIG ISLAND LEEWARD WATERS-BIG ISLAND WINDWARD WATERS-
KAIWI CHANNEL-KAUAI CHANNEL-KAUAI LEEWARD WATERS-KAUAI NORTHWEST
WATERS-KAUAI WINDWARD WATERS-MAALAEA BAY-MAUI COUNTY LEEWARD
WATERS-MAUI COUNTY WINDWARD WATERS-OAHU LEEWARD WATERS-OAHU
WINDWARD WATERS-PAILOLO CHANNEL.
SHORT TERM UPDATE...PIERCE
DISCUSSION...JVC
AVIATION...WALSH
MARINE...VAUGHAN
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