High Surf in Hawaii, April 4 to 6, 2013

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HONOLULU HI
1008 PM HST WED APR 3 2013

.UPDATE...
WINDS OVER THE BIG ISLAND SUMMITS HAVE DIMINISHED...AND THE WIND
ADVISORY HAS BEEN CANCELLED. FORECASTS HAVE BEEN UPDATED TO REMOVE
THIS HEADLINE...AND TO FINE TUNE THE OVERNIGHT FORECAST TO ACCOUNT
FOR LATEST SATELLITE AND RADAR OBSERVATIONS.

&&

.SYNOPSIS...
LIGHT TRADE WINDS WILL CONTINUE THROUGH THURSDAY...THEN INCREASE
FRIDAY AND SATURDAY. WINDS WILL WEAKEN AGAIN SUNDAY...AND TURN TO
THE SOUTHEAST...BEFORE BECOMING LIGHT AND VARIABLE EARLY NEXT WEEK.
WITH LIGHT WINDS...CLOUDS WILL TEND TO DEVELOP OVER LEEWARD AND
INTERIOR AREAS DURING AFTERNOONS AND EVENINGS. WITH THE TRADE
WINDS...CLOUDS WILL FAVOR WINDWARD AREAS DURING NIGHTS AND MORNINGS.
THE ATMOSPHERE WILL BE STABLE...SO ANY SHOWERS THAT DEVELOP WILL BE
BRIEF. A LARGE NORTHWEST SWELL WILL BRING HAZARDOUS SURF TO NORTH
AND WEST FACING SHORES THURSDAY AND FRIDAY.

&&

.DISCUSSION...
CURRENTLY...LIGHT TRADE WINDS PREVAIL ON THE LARGE SCALE...SUPPORTED
BY A WEAK 1021 MB HIGH CENTERED ABOUT 600 MILES NE OF THE ISLANDS.
WINDS ARE LIGHT ENOUGH HOWEVER TO ALLOW ISLAND-SCALE LAND AND SEA
BREEZE CIRCULATIONS TO OVERRIDE THE SYNOPTIC FLOW...ESPECIALLY IN
SHELTERED AREAS. THE TRADES ARE PUSHING LIMITED LOW-LEVEL MOISTURE
OVER THE WINDWARD SLOPES OF THE ISLANDS...BUT MOST AREAS ARE DRY
THIS EVENING. RADAR DOES SHOW A MODEST INCREASE IN LIGHT SHOWERS
OVER OAHU/S KOOLAU RANGE...ALONG A NARROW CLOUD LINE OVER OAHU
WINDWARD WATERS...AND MOVING INTO WINDWARD EAST MAUI...BUT LITTLE IN
THE WAY OF RETURNS ELSEWHERE. SKIES OVER THE ISLANDS AND NEAR SHORE
WATERS ARE FAIRLY CLOUDY THOUGH...DUE TO LINGERING BROKEN LOW CLOUDS
THAT FORMED OVER THE SLOPES IN RESPONSE TO DAYTIME HEATING AND THE
CONVERGENCE OF WIDESPREAD SEA BREEZES. MOST OF THESE LOW CLOUDS WILL
DISSIPATE OVER THE NEXT FEW HOURS...LEAVING DRY AND CLEAR SKIES OVER
LEEWARD AREAS THROUGH TOMORROW MORNING. THE LIGHT TRADES WILL BRING
A FEW CLOUDS AND ISOLATED SHOWERS TO WINDWARD SLOPES AND COASTS
OVERNIGHT...EXCEPT FOR CLOUDIER SKIES OVER WINDWARD BIG ISLAND.

THE HIGH TO THE NE WILL MOVE E THROUGH THURSDAY WITH LITTLE CHANGE
IN CENTRAL PRESSURE...AND TRADE WINDS WILL REMAIN LIGHT ENOUGH THAT
LAND AND SEA BREEZES WILL PREVAIL OVER THE ISLANDS THROUGH THURSDAY
NIGHT. THIS MEANS CLOUDS AND A CHANCE OF A SHOWER OVER LEEWARD AND
INTERIOR AREAS IN THE AFTERNOON AND EVENING...AND THE SAME FOR
WINDWARD AREAS DURING NIGHTS AND MORNINGS. THE HIGH WILL STRENGTHEN
TO NEAR 1030 MB FAR NE OF THE ISLANDS ON FRIDAY AND SATURDAY...AND
THEN REMAIN NEARLY STATIONARY WITH LITTLE CHANGE IN CENTRAL PRESSURE
THROUGH THE MIDDLE OF NEXT WEEK. TRADE WINDS OVER THE ISLANDS WILL
RESPOND BY INCREASING TO MODERATE TO FRESH SPEEDS FRIDAY...AND
REMAINING THAT WAY THROUGH SATURDAY. THE TRADES WILL BE FROM NEARLY
DUE E INITIALLY...BUT WILL BE VEERING TO THE SE BY SUNDAY...AS AN
APPROACHING FRONT FORCES THE SURFACE RIDGE SOUTHWARD TOWARD THE
ISLANDS.

THE FRONT IS CURRENTLY EXPECTED TO STALL NW OF KAUAI ON MONDAY AND
TUESDAY...AND REMAIN IN PLACE FOR MOST OF NEXT WEEK. IN THIS
SCENARIO...THE SURFACE RIDGE WILL BE OVER THE ISLANDS...MAINTAINING
LIGHT WINDS AND MOSTLY DRY WEATHER. THERE IS POTENTIAL FOR VOG FROM
THE BIG ISLAND TO SPREAD OVER KAUAI AND POSSIBLY OAHU IN THIS REGIME
AS WELL.

&&

.AVIATION...
VFR CONDITIONS EXPECTED TO PREVAIL AT THE TERMINALS THROUGH THE TAF
PERIOD...WITH PHTO SEEING ISOL MVFR CIG IN -SHRA OVERNIGHT...AND
PHNY WITH MVFR CIG THURSDAY MIDDAY. CLOUDS AND -SHRA WILL FAVOR
WINDWARD SLOPES OVERNIGHT...WITH ISOL MVFR CIG EXPECTED. THE FOCUS
FOR ISOL POCKETS OF MVFR CIG WILL SHIFT TO INTERIOR/LEEWARD AREAS
THURSDAY AFTERNOON. NO AIRMETS ARE IN EFFECT.

&&

.MARINE...
LONG-PERIOD FORERUNNERS OF A POWERFUL NW SWELL ARE EXPECTED TO
ARRIVE OVERNIGHT...WITH THE SWELL BUILDING THURSDAY AND THURSDAY
NIGHT BEFORE PEAKING FRIDAY AND DIMINISHING OVER THE WEEKEND. BUOY
51101 HAS DETECTED SOME OF THESE FORERUNNERS IN THE 24 SECOND BAND
THE LAST 2 HOURS. A HIGH SURF ADVISORY IS IN EFFECT FOR EXPOSED N
AND W SHORES DUE TO THE RISING SURF...AND MAY NEED TO BE UPGRADED TO
A WARNING FOR THE PEAK ON FRIDAY. AN UPDATED COLLABORATIVE NEARSHORE
SWELL AND WIND FORECAST FOR OAHU /SRDHFO/ WAS ISSUED THIS
AFTERNOON...AND HAS FURTHER DETAILS THAT CAN BE LOOSELY APPLIED
STATEWIDE. ANOTHER NW SWELL ARRIVING SUNDAY NIGHT WILL APPROACH
ADVISORY LEVELS ON MONDAY.

COMBINED SEAS ARE EXPECTED TO EXCEED 10 FEET THURSDAY NIGHT THROUGH
FRIDAY NIGHT...PRIMARILY DUE TO THE NW SWELL. THIS WILL NECESSITATE
THE ISSUANCE OF A SMALL CRAFT ADVISORY /SCA/ SOMETIME ON THURSDAY
FOR MANY MARINE ZONES. INCREASING TRADE WINDS MAY EXCEED 25 KT IN
THE WINDIER MARINE ZONES AROUND MAUI AND THE BIG ISLAND THIS
WEEKEND...WHICH WOULD ALSO REQUIRE THE ISSUANCE OF A SCA.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 PM HST SATURDAY FOR NORTH AND WEST FACING
SHORES OF NIIHAU KAUAI OAHU AND MOLOKAI AND NORTH FACING SHORES OF
MAUI.

&&

BIRCHARD