071
FXHW60 PHFO 291322
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
322 AM HST THU MAY 29 2025
SYNOPSIS
THE HIGH PRESSURE RIDGE NORTH OF THE HAWAIIAN ISLANDS WILL REMAIN
WEAKENED DUE TO A PASSING COLD FRONT FARTHER TO THE NORTH. EXPECT
ANOTHER DAY OF LIGHT TO MODERATE TRADE WINDS WITH HYBRID SEA
BREEZES ALONG TERRAIN SHELTERED WESTERN SLOPES OF EACH ISLAND. A
BRIEF INCREASE IN TRADE WIND SPEEDS MAY DEVELOP BY FRIDAY
AFTERNOON WITH LIGHTER EAST TO SOUTHEAST WINDS FROM SUNDAY
THROUGH MONDAY. OVERALL FAIRLY STABLE CONDITIONS REMAIN IN THE
FORECAST TODAY, BRIEF PASSING SHOWERS WILL RETURN FROM FRIDAY INTO
EARLY NEXT WEEK.
DISCUSSION
SATELLITE IMAGERY THIS MORNING SHOWS FAIRLY STABLE CLOUDS ARE
DRIFTING IN ON THE EASTERLY TRADE WINDS. AN UPPER LEVEL LOW JUST
NORTH OF THE ISLANDS WILL SLOWLY DRIFT NORTHWARD OVER THE NEXT FEW
DAYS. A LONG NARROW WEST TO EAST ORIENTED TROUGH WILL PERSIST OVER
THE HAWAII REGION, IN THE SHORT RANGE ADDING TO THE STABILITY OVER
THE ISLANDS. THIS TROUGH WILL SHIFT FARTHER NORTHWARD BY THIS
WEEKEND ALLOWING THE SUBTROPICAL JET STREAM TO MOVE UP INTO THE
ISLANDS FROM SATURDAY INTO EARLY NEXT WEEK. THE UPPER AIR BALLOON
SOUNDINGS LAUNCHED AT 2 AM HST (12Z) FROM LIHUE AND HILO SHOW
TEMPERATURE INVERSION HEIGHTS NEAR 6,000 FEET, INDICATING A FAIRLY
STABLE LIMITED SHOWER ENVIRONMENT.
THE SUBTROPICAL RIDGE NORTH OF HAWAII WILL CONTINUE TO BE WEAKENED
BY PASSING COLD FRONTS ROAMING FROM WEST TO EAST ACROSS THE
NORTHERN PACIFIC BASIN. THIS TRANSLATES TO MODERATE TRADE WINDS
THROUGH SATURDAY, WITH A BRIEF INCREASE INTO LOCALLY MODERATE
TRADE WINDS BY FRIDAY AFTERNOON. ON SUNDAY ANOTHER LOW PRESSURE
SYSTEM DROPS INTO THE REGION, SETTING UP NORTHWEST OF KAUAI. THIS
LOW PRESSURE SYSTEM WILL WEAKEN AND LIFT THE RIDGE AXIS NEAR THE
ISLANDS NORTHWARD, PLACING THE STATE IN A LIGHTER SOUTHEASTERLY
WIND PATTERN FROM SUNDAY INTO MONDAY. EXPECT VOG (VOLCANIC SMOG)
TO MOVE UP AND IMPACT AIR QUALITY CONDITIONS OVER THE SMALLER
ISLANDS DURING THIS TIME PERIOD. DURING THESE LIGHTER WIND
PATTERNS EXPECT SEA BREEZES TO EXPAND ALONG TERRAIN SHELTERED
WESTERN SLOPES OF EACH ISLAND.
MEDIUM RANGE FORECAST GUIDANCE SHOWS THIS LOW MOVING WESTWARD
AWAY FROM THE ISLANDS FROM LATE MONDAY INTO TUESDAY, ALLOWING
MODERATE TO LOCALLY BREEZY EASTERLY TRADE WINDS TO BLOW ACROSS THE
STATE THROUGH MUCH OF NEXT WEEK. BRIEF PASSING SHOWERS WILL
REMAIN IN THE FORECAST FROM TUESDAY ONWARD, FAVORING THE WINDWARD
AND MOUNTAIN AREAS IN THE TYPICAL OVERNIGHT TO EARLY MORNING
HOURS.
AVIATION
A HYBRID MODERATE TRADE WIND PATTERN WILL CONTINUE TODAY WITH
DAY TIME SEA BREEZES DEVELOPING ALONG TERRAIN SHELTERED WESTERN
SLOPES OF EACH ISLAND. A BRIEF INCREASE IN TRADE WIND SPEEDS INTO
THE LOCALLY BREEZY RANGE MAY DEVELOP BY FRIDAY AFTERNOON. OVERALL
VFR CONDITIONS WILL PREVAIL WITH LIMITED SHOWER POTENTIAL.
NO AIRMETS IN EFFECT AND NONE ARE EXPECTED.
MARINE
LIGHT TO MODERATE NORTHEAST TO EAST WINDS WILL PERSIST TODAY,
THEN STRENGTHEN TO FRESH TO STRONG LEVELS FRIDAY AS THE SURFACE
RIDGE BUILDS NORTH OF THE ISLANDS. THIS WILL INCREASE THE
POTENTIAL FOR SMALL CRAFT ADVISORY CONDITIONS, ESPECIALLY ACROSS
THE TYPICALLY WINDIER CHANNELS AND WATERS AROUND MAUI COUNTY AND
THE BIG ISLAND THROUGH THE DAY FRIDAY. FORECAST GUIDANCE SUGGESTS
THE RIDGE WILL WEAKEN AGAIN OVER THE WEEKEND AND INTO EARLY NEXT
WEEK AS A BROAD SURFACE TROUGH DEVELOPS FAR NORTHWEST OF THE AREA.
IF THIS SCENARIO UNFOLDS, THE TRADES WILL VEER OUT OF THE EAST-
SOUTHEAST BY SUNDAY, WITH LIGHTER WINDS OVER THE WESTERN END OF
THE STATE AND FRESH TRADES CONTINUING OVER THE EASTERN END.
SURF ALONG SOUTH-FACING SHORES WILL TREND UP TODAY AS A LONG-
PERIOD SOUTH-SOUTHWEST SWELL FILLS IN. HEIGHTS SHOULD REACH NEAR
AVERAGE LEVELS BY THIS AFTERNOON AND HOLD THROUGH FRIDAY AS THE
SWELL PEAKS. A GRADUAL DECLINE IS EXPECTED OVER THE WEEKEND INTO
EARLY NEXT WEEK. THROUGH MUCH OF NEXT WEEK, EXPECT A MIX OF
LONG-PERIOD BACKGROUND SOUTH-SOUTHWEST AND SHORTER-PERIOD
SOUTHEAST SWELL.
SURF ALONG NORTH- AND WEST-FACING SHORES WILL RISE TODAY AND HOLD
THROUGH THE WEEKEND AS OVERLAPPING NORTH-NORTHWEST SWELLS MOVE
THROUGH. THE FIRST SWELL ARRIVING TODAY WILL PUSH SURF TO AROUND
AVERAGE LEVELS INTO FRIDAY, FOLLOWED BY A SECOND SWELL THAT WILL
DRIVE HEIGHTS ABOVE AVERAGE SATURDAY. SURF WILL GRADUALLY LOWER
TO SEASONAL LEVELS SUNDAY THROUGH EARLY NEXT WEEK.
SURF ALONG EAST-FACING SHORES WILL GRADUALLY BUILD OVER THE
WEEKEND AND INTO EARLY NEXT WEEK AS TRADE WINDS RETURN.
HFO WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...BOHLIN
AVIATION...BOHLIN
MARINE...GIBBS
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