High Surf in Hawaii, December 13 to 14, 2014

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
405 PM HST SAT DEC 13 2014

.SYNOPSIS...
A DISSIPATING COLD FRONT WILL MOVE SLOWLY DOWN THE CHAIN TONIGHT
AND SUNDAY WITH A BAND OF CLOUDS AND SHOWERS. THE FRONT WILL MOVE
FROM KAUAI TO OAHU TONIGHT...AND THEN GRADUALLY SPREAD TO MAUI
COUNTY AND THE BIG ISLAND ON SUNDAY AS IT WEAKENS. HIGH PRESSURE
BEHIND THE FRONT WILL BRING STRONG TRADE WINDS WHICH WILL PERSIST
INTO EARLY NEXT WEEK.

&&

.DISCUSSION...
SATELLITE IMAGERY IS SHOWING THE DISSIPATING FRONT OVER THE KAUAI
CHANNEL LATE THIS AFTERNOON. A RAGGED 80-MILE-WIDE BAND OF CLOUDS
AND SHOWERS IS MOVING SOUTHWARD WITH THIS FEATURE...WHICH WILL
REACH OAHU THIS EVENING...AND PUSH FROM OAHU TO MAUI COUNTY AND
THE BIG ISLAND ON SUNDAY. MOST OF THE CLOUDS AND SHOWERS WILL
FOCUS ON WINDWARD SECTIONS...WHICH WILL BE QUITE DAMP...BUT SOME
SHOWERS WILL SPREAD TO NEARBY LEEWARD AREAS AT TIMES DUE TO THE
STRONG TRADES. SOME OF THE MOISTURE WILL GET HUNG UP OVER WINDWARD
SIDES OF MAUI AND THE BIG ISLAND INTO SUNDAY NIGHT AND MONDAY EVEN
AFTER THE BAND BREAKS UP...SO POPS HAVE BEEN INCREASED FOR THESE
TIME PERIODS.

TRADE WINDS HAVE ALREADY REACHED ADVISORY CRITERIA OVER LANAI AND
AROUND WAIMEA AND WAIKOLOA ON THE BIG ISLAND...AND EXPECTING A FEW
MORE LOCATIONS TO SEE ADVISORY LEVEL WINDS AS A RELATIVELY STRONG
HIGH TO OUR NW TAKES UP RESIDENCE NORTH OF THE ISLANDS ALONG 30N
SUNDAY NIGHT AND MONDAY. THE HIGH RESOLUTION GUIDANCE IS SHOWING
THAT WINDS JUST OFF THE SURFACE SHOULD REACH 35-40+ KT IN FAVORED
CHANNELED AND DOWNSLOPE AREAS...WHICH USUALLY TRANSLATES WELL TO
THE HIGHEST SURFACE WIND GUSTS. A VERY DRY AND STABLE AIRMASS WITH
A RELATIVELY LOW INVERSION BEHIND THE FRONT MAY ALSO AID IN LOCAL
TERRAIN-INDUCED ACCELERATION OF THE WINDS.

THE HIGH WILL START TO MOVE AWAY BY TUESDAY...AND THE TRADES WILL
RELAX BACK TO MODERATE TO FRESH LEVELS. THE AIRMASS WILL STAY
RATHER DRY THROUGH MUCH OF NEXT WEEK AND SO RAINFALL IS LIKELY TO
BE RATHER LIGHT. THE GFS MODEL SHOWS A STRONGER TROUGH DEVELOPING
WELL WEST OF THE ISLANDS TOWARD THE MIDDLE OF NEXT WEEK...WHICH
WOULD HAVE LITTLE EFFECT ON OUR WEATHER EXCEPT TO INCREASE HIGH
CLOUDINESS AT TIMES. THE ECMWF IS LESS AMPLIFIED AND FARTHER AWAY
WITH THIS FEATURE.

&&

.AVIATION...
AIRMET FOR BIG ISLAND MOUNTAIN OBSCURATION HAS BEEN CANCELLED AS
CONDITIONS HAVE IMPROVED. THE FRONT MOVING OVER KAUAI IS BRING
CLOUDS AND SHOWERS TO KAUAI...BUT AT THIS TIME DOES NOT APPEAR TO BE
BRINGING SIGNIFICANT IFR CONDITIONS TO THE ISLAND. A MOUNTAIN
OBSCURATION AIRMET IS STILL POSSIBLE PARTICULARLY TONIGHT IF THE
BAND THICKENS UP. THE CLOUDS AND SHOWERS ASSOCIATED WITH THE FRONT
WILL IMPACT OAHU TONIGHT...AND MOVE OVER MAUI COUNTY AND THE BIG
ISLAND SUNDAY...AND MAY LEAD TO FURTHER MOUNTAIN OBSCURATION
AIRMETS.

STRONG AND GUSTY WINDS HAVE BEEN OBSERVED ACROSS THE ISLAND
CHAIN...AND SO AIRMET TANGO HAS BEEN POSTED FOR ALL ISLANDS FOR
TURBULENCE DOWNWIND OF THE MOUNTAINS. THE STRONG AND GUSTY WINDS ARE
EXPECTED TO CONTINUE SUNDAY WITH A HIGH BUILDING IN BEHIND THE FRONT.

AN UPPER LEVEL TROUGH TO THE WEST OF THE ISLANDS IS SPREADING HIGH
CLOUDS OVER THE ISLANDS. THE TROUGH IS EXPECTED TO MOVE CLOSER TO
THE ISLANDS...WHICH SHOULD BRING THICKER HIGH CLOUDS TO THE REGION.
THERE REMAINS THE POTENTIAL FOR ICING AS THE CLOUDS THICKEN.

&&

.MARINE...
BUOY 51001 PEAKED NEAR 14 FT WITH A PERIOD OF 15 SECONDS A FEW
HOURS AGO...AND SWELL LOCALLY CONTIUES TO BUILD. SINCE SOME OF THE
OBSERVATIONS WERE ALREADY STARTING TO APPROACH WARNING CRITERIA...
WE CHANGED THE SURF ADVISORY TO A HIGH SURF WARNING FOR TONIGHT
AND SUNDAY. WE ALSO ISSUED AN ADVISORY FOR WEST FACING SHORES OF
THE BIG ISLAND AS SOME OF THE WNW ENERGY FROM THE SWELL SHOULD GET
INTO THOSE AREAS. SINCE THE ORIGINAL SWELL FETCH AREA WAS NOT
AIMED AT THE ISLANDS FOR VERY LONG...THIS SHOULD BE A RATHER
SHORT-LIVED WARNING EVENT...WITH A NIGHTTIME PEAK. SURF HEIGHTS
WILL ALSO BE LIMITED SOMEWHAT BY THE STRONG TRADES. GUIDANCE SHOWS
THE SWELL DROPPING BELOW WARNING CRITERIA DURING THE DAY ON
SUNDAY. THE INCREASING TRADES WILL ALSO LIKELY RESULT IN ROUGH
SURF FOR EAST FACING SHORES...AND A HIGH SURF ADVISORY WILL
PROBABLY NEED TO BE ISSUED FOR THOSE AREAS BY SUNDAY.

IN ADDITION TO THE LARGE SWELL...THE AFOREMENTIONED HIGH IS
EXPECTED TO BRING WIDESPREAD SMALL CRAFT ADVISORY LEVEL
WINDS...WITH GALES EXPECTED IN SOME OF THE WINDIER CHANNELED AND
DOWNSLOPE AREAS NEAR THE ISLANDS. THE COMBINATION OF STRONG WINDS...
TO GALE FORCE IN THE NORMALLY WINDIEST AREAS...AND THE NORTHWEST
SWELL IS EXPECTED TO RESULT IN HAZARDOUS SEAS THAT WILL PROBABLY
LAST UNTIL TUESDAY.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY UNTIL 6 PM HST SUNDAY FOR KAUAI-OAHU SOUTH SHORE-
WAIANAE COAST-OAHU KOOLAU-OLOMANA-WAIANAE MOUNTAINS-MOLOKAI-
LANAI-MAUI WINDWARD WEST-MAUI LEEWARD WEST-MAUI CENTRAL VALLEY-
SOUTH BIG ISLAND-BIG ISLAND NORTH AND EAST-KOHALA.

HIGH SURF WARNING UNTIL 6 PM HST SUNDAY FOR NORTH AND WEST FACING
SHORES OF NIIHAU KAUAI OAHU AND MOLOKAI AND FOR NORTH FACING
SHORES OF MAUI.

HIGH SURF ADVISORY UNTIL 6 PM HST SUNDAY FOR WEST FACING SHORES OF
THE BIG ISLAND.

GALE WARNING UNTIL 6 PM HST MONDAY FOR MAALAEA BAY-PAILOLO
CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG ISLAND
SOUTHEAST WATERS.

SMALL CRAFT ADVISORY UNTIL 6 PM HST MONDAY FOR KAUAI NORTHWEST
WATERS-KAUAI WINDWARD WATERS-KAUAI LEEWARD WATERS-KAUAI CHANNEL-
OAHU WINDWARD WATERS-OAHU LEEWARD WATERS-KAIWI CHANNEL-MAUI
COUNTY WINDWARD WATERS-MAUI COUNTY LEEWARD WATERS-BIG ISLAND
WINDWARD WATERS.

&&

R BALLARD/M BALLARD