High Surf in Hawaii, December 3 to 4, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST THU DEC 3 2009

.SYNOPSIS...
A COLD FRONT APPROACHING FROM THE NORTHWEST WILL ARRIVE
TONIGHT...PRODUCING INCREASED SHOWERS AND POSSIBLE
THUNDERSTORMS...ALONG WITH SLIGHTLY STRONGER SOUTHWESTERLY WINDS.
WINDS WILL WEAKEN THIS WEEKEND AND INTO NEXT WEEK...WITH SHOWERS
EXPECTED IN INTERIOR SECTIONS DURING THE AFTERNOON...AND CLEAR
NIGHTS.

&&

.DISCUSSION...
CALM WINDS RESULTING FROM A WEAK PRESSURE GRADIENT OVER THE STATE
WILL INCREASE THIS AFTERNOON AS A COLD FRONT APPROACHES THE ISLANDS
FROM THE NORTHWEST...RESULTING IN WINDS BECOMING SOUTHWESTERLY AS
THE FRONT DRAWS UP MOISTURE FROM THE ITCZ. THIS FRONT WILL MOVE
THROUGH THE ISLANDS LATE TONIGHT AND FRIDAY. A BROAD UPPER LEVEL
TROUGH IS EXPECTED TO BRING SOME COLDER 500MB TEMPERATURES DURING
THIS TIME...AND THE MODEL SOUNDINGS SHOW THE LOW LEVEL INVERSION
BEING ERODED IN ADDITION TO THE AFOREMENTIONED ADVECTION OF
MOISTURE. AS A RESULT...HEAVY SHOWERS AND THUNDERSTORMS ARE POSSIBLE
WITH THIS FRONTAL PASSAGE TONIGHT AND FRIDAY.

AFTER THE PASSAGE OF THE FRONT...GFS SHOWS SUBTROPICAL RIDGING
PERSISTING OVER THE STATE PRODUCING LIGHT WINDS ONCE AGAIN...ALONG
WITH INCREASED STABILITY AS SUBSIDENCE AND WARMING LAPSE RATES ARE
EXPECTED WITH THE EMERGENCE OF UPPER LEVEL RIDGING AROUND THE
ISLANDS. THIS SETUP FAVORS A SEA BREEZE-LAND BREEZE WEATHER PATTERN
FOR LATE THIS WEEKEND AND INTO NEXT WEEK...WITH CLOUDY SKIES AND SEA
BREEZE SHOWERS DURING THE AFTERNOONS...AND CLEAR NIGHTS. EARLY NEXT
WEEK...ANOTHER FRONT APPROACHES THE ISLANDS. HOWEVER...AT THIS TIME
IT APPEARS THAT THE FRONT WILL WEAKEN AND STALL ONCE IT REACHES
KAUAI. THUS...HAVE INCREASED THE POPS FOR KAUAI AND THE SURROUNDING
WATERS ON MONDAY.

A VERY LARGE NORTHWEST SWELL IS EXPECTED TO ARRIVE ON SATURDAY WITH
AN EVEN LARGER ONE ON MONDAY...WITH BOTH EVENTS EXPECTED TO PRODUCE
WARNING LEVEL SURF. SEE MARINE SECTION AND SURF PRODUCTS FOR MORE
DETAILS.

IN ADDITION...WINDS ON THE SUMMITS OF THE BIG ISLAND AND HALEAKALA
ARE EXPECTED TO REACH 30 TO 40 MPH THIS AFTERNOON WITH GUSTS
POSSIBLY REACHING 55 MPH. THEREFORE...A WIND ADVISORY HAS BEEN
ISSUED EFFECTIVE AT NOON TODAY.

&&

.MARINE...
FRESH NORTHWEST SWELL WILL PEAK THIS MORNING AND THEN DROP BELOW
ADVISORY LEVELS AGAIN BY FRIDAY.

THE GFS AND ECMWF SOLUTIONS REMAIN IN VERY GOOD AGREEMENT DEVELOPING
A POWERFUL 945-950MB HURRICANE FORCE LOW WITH AN IMPRESSIVE FETCH
AIMED AT HAWAII OVER THE WEEKEND. AS OF NOW...FORERUNNERS COULD
ARRIVE AS EARLY AS LATE SUNDAY AFTERNOON. ALTHOUGH THIS SYSTEM HAS
NOT FORMED YET...PRELIMINARY NWW3 NUMBERS REMAIN IMPRESSIVE FROM
RECENT RUNS. EXTRA LARGE SURF IS EXPECTED EARLY NEXT WEEK.

AS A RESULT OF THE NORTHWEST SWELL REACHING HEIGHTS OF 10 FEET AND
HIGHER TODAY...A SMALL CRAFT ADVISORY IS IN EFFECT UNTIL THIS
EVENING FOR COASTAL WATERS AFFECTED BY THE SWELL.

&&

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

SMALL CRAFT ADVISORY UNTIL 8 PM HST TONIGHT 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
AND BIG ISLAND WINDWARD WATERS.

WIND ADVISORY FROM 12 PM HST TODAY UNTIL 6 AM HST FRIDAY FOR BIG
ISLAND SUMMITS AND HALEAKALA SUMMIT.

&&

HARRISON/BIRCHARD