678
FXHW60 PHFO 141949
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
949 AM HST MON APR 14 2025
SYNOPSIS
BREEZY TRADE WINDS WILL CONTINUE TODAY AND GRADUALLY EASE
TOMORROW, WITH PASSING CLOUDS AND SHOWERS FAVORING WINDWARD AND
MAUKA AREAS. LIGHTER WINDS ARE EXPECTED BY THE MIDDLE OF THE WEEK
WITH FEWER WINDWARD SHOWERS AND A GREATER CHANCE FOR AFTERNOON
INTERIOR SHOWERS THROUGH THE WEEKEND. AN UPPER LEVEL TROUGH AND
DEEP ATMOSPHERIC MOISTURE WILL ENHANCE SHOWER ACTIVITY ON THURSDAY
AND FRIDAY AND BRING THE POTENTIAL FOR THUNDERSTORMS AND HEAVY
RAINFALL.
DISCUSSION
HIGH PRESSURE CENTERED TO THE NORTHEAST OF THE STATE WILL
MAINTAIN BREEZY TRADE WINDS ACROSS THE REGION THROUGH TONIGHT,
CONTINUING TO FOCUS CLOUDS AND SHOWERS OVER WINDWARD AND MAUKA
AREAS. WATER VAPOR IMAGERY SHOWS A WEAK UPPER-LEVEL LOW SPINNING
OVER THE STATE. THIS LOW WILL GRADUALLY MOVE EAST THROUGH TUESDAY
CONTRIBUTING TO A SLOW EASTWARD PROGRESSION OF WEAK INSTABILITY,
WHICH MAY ALLOW FOR THE ENHANCEMENT OF WINDWARD SHOWERS MOVING IN
ON THE BREEZY TRADES. SOME OF THESE SHOWERS COULD DELIVER BRIEF
DOWNPOURS THAT WILL OCCASIONALLY SPILL OVER INTO LEEWARD AREAS.
MID-LEVEL RIDGING WILL BRIEFLY BUILD OVERHEAD TUESDAY NIGHT INTO
EARLY WEDNESDAY IN ADVANCE OF A MID-LEVEL SHORTWAVE TROUGH THAT
WILL DIVE SOUTHEAST ACROSS THE CENTRAL PACIFIC AND BEGIN TO EDGE
OVER HAWAII BY WEDNESDAY NIGHT. AT THE SURFACE, A STRONG LOW
PRESSURE SYSTEM TO THE FAR NORTH WILL DISPLACE THE RIDGE THAT'S
BEEN ANCHORED TO OUR NORTHEAST TO BRING IT CLOSER TO, OR OVER, THE
ISLAND CHAIN. THE PROXIMITY OF THIS RIDGE AXIS AND THE APPROACH
OF A COLD FRONT FROM THE NORTHWEST WILL BRING LIGHTER SOUTHEAST
WINDS ACROSS THE AREA, ALLOWING LAND AND SEA BREEZES TO EXPAND IN
COVERAGE BEGINNING ON WEDNESDAY.
THE SHORTWAVE TROUGH WILL DIVE DOWN THE ISLAND CHAIN THROUGH THE
LATTER PART OF THE WEEK BEFORE IT OPENS UP AND WEAKENS AS IT
TRACKS EASTWARD THIS WEEKEND. THE MOST FAVORABLE UPPER- LEVEL
DYNAMICS ASSOCIATED WITH THE ORIENTATION OF THE SHORTWAVE TROUGH,
THE COOLEST TEMPERATURES ALOFT (500 MB AROUND -12C), AND THE
DEEPEST ATMOSPHERIC MOISTURE (PRECIPITABLE WATER AROUND 1.6
INCHES) ALL SEEM TO LINE UP BEST ON THURSDAY AND FRIDAY. AS SUCH,
HEAVY SHOWERS AND A SLIGHT CHANCE OF THUNDERSTORMS HAVE BEEN ADDED
TO THE FORECAST ACROSS THE STATE FOR THURSDAY AND FRIDAY (MORE OF
THE FOCUS WILL BE ON BIG ISLAND FRIDAY).
LIGHT WINDS WILL CONTINUE INTO THE WEEKEND AS THE MID-LEVEL
SHORTWAVE WEAKENS RESULTING IN EITHER A LAND/SEA BREEZE PATTERN
WITH MORE MUTED DIURNAL CONVECTION OR A HYBRID SEA BREEZE PATTERN
WHICH WILL TEND TO FOCUS SHOWERS OVER WESTERN SLOPES OF EACH
ISLAND. GENTLE TO MODERATE TRADES WILL MOVE IN AROUND SUNDAY OR
EARLY NEXT WEEK.
AVIATION
MODERATE TO BREEZY TRADE WINDS GRADUALLY EASE TONIGHT AND
TUESDAY. AIRMET TANGO FOR TURBULENCE BELOW 8,000 FEET OVER AND
DOWNWIND OF TERRAIN REMAINS IN EFFECT. CONDITIONS ARE BORDERLINE,
AND THE AIRMET WILL LIKELY BE DROPPED LATER TODAY. THE TRADES WILL
PRODUCE BRIEF PERIODS OF MVFR CONDITIONS OVER WINDWARD TERRAIN,
AND ASIDE FROM SPOTTY AFTERNOON SHOWERS ON LEEWARD SLOPES OF THE
BIG ISLAND, VFR WILL PREVAIL ACROSS LEEWARD AREAS. A MID-LEVEL
RIDGE WILL MAINTAIN OVERALL STABLE CONDITIONS, THOUGH A LINGERING
WEAK UPPER-LEVEL TROUGH MAY TRIGGER AN ISOLATED HEAVY SHOWER ON
BIG ISLAND SLOPES THIS AFTERNOON.
MARINE
HIGH PRESSURE NORTHEAST OF THE STATE WILL MAINTAIN MODERATE TO
LOCALLY STRONG EAST TO SOUTHEASTERLY WINDS. A SMALL CRAFT ADVISORY
IS IN EFFECT THROUGH 6 AM TUESDAY FOR THE EASTERN HALF MARINE
ZONES TO ACCOUNT FOR THE TYPICALLY WINDIER AREAS SURROUNDING MAUI
COUNTY AND BIG ISLAND WITHIN THIS EAST SOUTHEAST FLOW PATTERN.
WINDS WILL BEGIN TO WEAKEN ON TUESDAY, THEN BECOME MORE LIGHT AND
VARIABLE ACROSS MORE WESTERN WATERS MID TO LATE WEEK, WHILE REMAIN
LIGHT TO MODERATE EAST SOUTHEAST ACROSS THE EASTERN WATERS. THIS
WILL BE IN RESPONSE TO THE APPROACH AND EVENTUAL STALLING OF A
FRONT NORTHWEST OF THE ISLANDS LATER THIS WEEK.
AS OBSERVED BY THE CDIP HANALEI NEARSHORE BUOY THIS MORNING, A
SMALL TO MODERATE SIZE, MEDIUM PERIOD NORTHWEST SWELL IS PASSING
AROUND KAUAI AND WILL REACH OAHU LATE THIS MORNING. THIS 5 TO 6
FOOT SWELL WILL RESULT IN SLIGHTLY OVER HEAD TO DOUBLE HEAD HIGH
SURF ALONG MANY NORTH AND WEST-FACING SHORES THROUGH TONIGHT. THIS
SWELL WILL DECLINE FROM TUESDAY MORNING INTO WEDNESDAY. A LARGER
MODERATE SIZE NORTH NORTHWEST SWELL WILL ARRIVE THURSDAY. THIS
SWELL MAY POTENTIALLY LIFT SURF TO HIGH SURF ADVISORY HEIGHTS
ALONG NORTH AND WEST-FACING SHORES OF THE SMALLER ISLANDS
THURSDAY NIGHT AND FRIDAY.
EAST-FACING SHORE SURF WILL REMAIN SOMEWHAT ROUGH DUE TO RECENT
STRONG EAST TRADES. AS THE WINDS DIMINISH DURING THE SECOND HALF
OF THE WEEK, EAST CHOP WILL SIGNIFICANTLY FALL OFF.
SURF ALONG SOUTH-FACING SHORES WILL REMAIN SMALL AND MOSTLY AT
BACKGROUND LEVELS THROUGH THURSDAY. A SERIES OF SMALL OVERLAPPING
SOUTH SWELLS COULD INCREASE SURF UP TO SEASONAL LEVELS FROM FRIDAY
THROUGH THE WEEKEND.
HFO WATCHES/WARNINGS/ADVISORIES
SMALL CRAFT ADVISORY UNTIL 6 AM HST TUESDAY FOR KAIWI CHANNEL-
MAUI COUNTY WINDWARD WATERS-MAUI COUNTY LEEWARD WATERS-MAALAEA
BAY-PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND WINDWARD
WATERS-BIG ISLAND LEEWARD WATERS-BIG ISLAND SOUTHEAST WATERS.
DISCUSSION...FOSTER
AVIATION...WROE
MARINE...BLOOD
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