972
FXHW60 PHFO 031405
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST MON MAR 3 2025
SYNOPSIS
TRADE WINDS WILL STRENGTHEN, BECOMING BREEZY TODAY, AS STRONG
SURFACE HIGH PRESSURE SETS UP FAR NORTH OF THE AREA. RELATIVELY
DRY AFTERNOON CONDITIONS WITH LIMITED RAINFALL PRIMARILY OVER
WINDWARD EXPOSURES AND THE BIG ISLAND KONA REGION. MORE FREQUENT
SHOWERS WILL OCCUR FROM TUESDAY THROUGH THE REMAINDER OF THE
WEEK. RESIDUAL MOISTURE ASSOCIATED WITH THE REMNANTS OF A COLD FRONT
WILL BE DRIFTING SOUTH ACROSS ISLANDS LATER THIS WEEK. HIGHER
MOISTURE WITHIN A LESS STABLE ATMOSPHERE WILL INCREASE AREAWIDE
PRECIPITATION PROBABILITIES THROUGH MID TO LATE WEEK.
DISCUSSION
RELATIVELY DRY TRADE WIND FLOW IS STRENGTHENING ACROSS THE ISLAND
CHAIN. TRADES HAVE RETURNED AND WILL BE STRENGTHENING IN RESPONSE
TO A SURFACE HIGH MOVING IN FROM THE WEST IN THE WAKE OF A DIFFUSE
RIDGE AXIS SLOWLY LIFTING NORTH OF THE ISLANDS EARLY THIS MORNING.
THIS HIGH, CENTERED ABOUT 900 MILES NORTH OF THE ISLAND CHAIN, WILL
PRODUCE A TIGHT ENOUGH DOWNSTREAM PRESSURE GRADIENT TO SUPPORT
SEVERAL DAYS OF GUSTY TRADES. RIDGING ALOFT WILL LIKELY MAINTAIN
A NEAR 5 TO 6K FT INVERSION. LOCALIZED AFTERNOON TO EVENING WINDS
UNDER THIS WEAKENING INVERSION COULD GUST TO 40 MPH OVER AND JUST
DOWNWIND OF HIGHER ELEVATION RIDGE TOPS. THESE STABLE CONDITIONS
AND A NEAR INCH PRECIPITABLE WATER AIR MASS WILL (AND HAS) LIMIT(ED)
RAINFALL WITH THE MAJORITY OF THE SHOWER ACTIVITY REMAINING
FOCUSED OVER MORE WINDWARD-FACING EXPOSURES. RECENT DEW POINTS IN
THE SEASONAL LOWER TO MIDDLE 60S HAS MADE IT FEEL LESS STICKY
THAN COMPARED TO PREVIOUSLY HUMID DAYS. GREATER EASTERN MOISTURE
WILL ADVECT IN THROUGH MID WEEK AND INCREASE HUMIDITY. HAZE WILL BE
LESS OF AN ISSUE AS MODERATE TO FRESH TRADES MORE EFFICIENTLY MIX
OUT THE DOWNSTREAM TRANSPORT OF VOG; HIGHER SO2 CONCENTRATIONS WILL
BE CONFINED TO AREAS JUST DOWNWIND OF THE HALEMAUMAU CRATER.
A FRONT MOVING THROUGH THE NORTHWEST OFFSHORE WATERS IS EXPECTED
TO BECOME MORE PARALLEL TO THE UPPER LEVEL WESTERLY FLOW AS IT
ENCOUNTERS MID TO UPPER RIDDING...DISSIPATING JUST NORTH OF THE
ISLAND CHAIN. THE SURFACE HIGH ROUGHLY A THOUSAND MILES NORTH
NORTHEAST OF THE ISLANDS WILL STRENGTHEN GOING INTO THE MIDDLE OF
THE WEEK. THIS WILL MAINTAIN BREEZY TRADES AND, ALTHOUGH THE
RIDGE ALOFT AND ITS RESULTING INVERSION WILL BEGIN TO ERODE, THE
THREAT FOR LOCALIZED HIGH WIND GUSTS MAY STILL EXIST THE NEXT DAY
OR SO. RESIDUAL MOISTURE TIED TO THE DIFFUSE FRONTAL BOUNDARY
NORTH OF THE STATE WILL SAG SOUTH SOUTHEASTWARD TOWARD THE STATE
AND LIKELY PROVIDE ENOUGH FUEL TO INCREASE SMALLER ISLAND
PRECIPITATION CHANCES TUESDAY. IN ADDITION TO THIS REMNANT
FRONTAL MOISTURE OVER THE NORTHERN NEARSHORE WATERS, RIBBONS OF
HIGHER MID LAYER MOISTURE FROM THE EAST WILL PERIODICALLY ADVECT
IN ON ESTABLISHED TRADES THROUGH MID TO LATE WEEK. THE GREATEST
RAIN WILL LIKELY FALL ACROSS WINDWARD BIG ISLAND AND MAUI WITH
THE HIGHER ACCUMULATIONS OCCURRING FROM WEDNESDAY INTO THE
WEEKEND. THERE WILL BE A TOUCH MORE INSTABILITY IN RESPONSE TO A
MINOR LOWERING OF HEIGHTS SUBTLY COOLING TEMPERATURES ALOFT IN
ASSOCIATION WITH A TROUGH PASSING FAR NORTH OF HAWAII IN TANDEM
WITH THE WEAKER SOUTHERN BRANCH OF THE POLAR JET PASSING OVER THE
STATE. THIS LESS STABLE AND MORE MOIST SCENARIO SHOULD INCREASE
THE PROBABILITIES OF A MORE WET TRADE WIND PATTERN DURING THE
SECOND HALF OF THE WEEK.
AVIATION
MODERATE TO BREEZY EASTERLY TRADES WILL STRENGTHEN THROUGH THE
AFTERNOON HOURS, AS A HIGH PRESSURE SYSTEM BUILDS IN AND PASSES
BY JUST NORTH OF THE HAWAIIAN ISLANDS. PERIODS OF CLOUDS AND BRIEF
SHOWERS WILL FAVOR WINDWARD AND MOUNTAIN SLOPES DURING THE
OVERNIGHT TO EARLY MORNING HOURS.
AIRMET TANGO FOR LOW-LEVEL TURBULENCE OVER AND DOWNSTREAM OF
ISLAND TERRAIN WILL LIKELY BE ISSUED LATER TODAY DUE TO THE
STRENGTHENING TRADE WINDS.
MARINE
HIGH PRESSURE BUILDING TO NEAR 1037 MB N OF THE ISLANDS WILL LEAD
TO STRENGTHENING TRADE WINDS TODAY AND TONIGHT, WITH FRESH TO
NEAR GALE-FORCE WINDS LIKELY REMAINING INTO NEXT WEEKEND. A SMALL
CRAFT ADVISORY (SCA) IS CURRENTLY SLATED TO START AT NOON TODAY
FOR ALL WATERS.
A NEW NW SWELL WILL LEAD TO ADVISORY-LEVEL SURF ALONG EXPOSED N AD
W FACING SHORES AS IT PEAKS LATER TODAY/EARLY TUESDAY. INCREASING
SWELL ENERGY HAS BEEN REPORTED IN THE 15-17 SECOND BANDS AT NDBC
BUOYS NW OF KAUAI OVERNIGHT, AND WHILE CURRENT WAVE HEIGHTS WILL
NOT RESULT IN HIGH SURF, THE SWELL IS EXPECTED TO CONTINUE TO
BUILD THROUGH THE DAY, AND A HIGH SURF ADVISORY WILL GO INTO
EFFECT AT NOON TODAY. THIS SWELL WILL DIMINISH LATER TUESDAY INTO
WEDNESDAY, WITH ANOTHER NW SWELL AROUND FRIDAY POTENTIALLY
LEADING TO ADVISORY-LEVEL SURF AGAIN. ANOTHER PULSE OF NW SWELL IS
POSSIBLE NEXT WEEKEND. A SMALL S SWELL IS POSSIBLE TODAY. CHOPPY
SURF ALONG E FACING SHORES WILL INCREASE IN RESPONSE TO THE
BUILDING TRADE WINDS.
HFO WATCHES/WARNINGS/ADVISORIES
HIGH SURF ADVISORY FROM NOON TODAY TO 6 PM HST TUESDAY FOR
NIIHAU-KAUAI LEEWARD-WAIANAE COAST-OAHU NORTH SHORE-MAUI
WINDWARD WEST-KAUAI NORTH-MOLOKAI WINDWARD-MOLOKAI NORTH-MOLOKAI
WEST-MAUI CENTRAL VALLEY NORTH-WINDWARD HALEAKALA.
SMALL CRAFT ADVISORY FROM NOON TODAY TO 6 PM HST WEDNESDAY FOR
KAUAI NORTHWEST WATERS-KAUAI WINDWARD WATERS-KAUAI LEEWARD
WATERS-KAUAI CHANNEL-OAHU WINDWARD WATERS-OAHU LEEWARD WATERS-
MAUI COUNTY WINDWARD WATERS-MAUI COUNTY LEEWARD WATERS-BIG
ISLAND WINDWARD WATERS.
SMALL CRAFT ADVISORY UNTIL 6 PM HST WEDNESDAY FOR KAIWI CHANNEL-
MAALAEA BAY-PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND
LEEWARD WATERS-BIG ISLAND SOUTHEAST WATERS.
DISCUSSION...BLOOD
AVIATION...BOHLIN
MARINE...BIRCHARD
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