FXHW60 PHFO 240535
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
800 PM HST WED DEC 23 2009
.SYNOPSIS...
A WEAK COLD FRONT WILL AFFECT THE SMALLER ISLANDS THURSDAY AND
CHRISTMAS...BRINGING LIGHT SHOWERS TO MAINLY WINDWARD LOCATIONS.
THIS FRONT WILL DISSIPATE OVER THE STATE BY THE WEEKEND...BUT WILL
USHER IN A PERIOD OF LIGHT TO MODERATE TRADES INTO EARLY NEXT WEEK.
THE AIRMASS WILL REMAIN ON THE DRY SIDE INTO NEXT WEEK...WITH SOME
LIGHT SHOWERS AFFECTING MAINLY THE WINDWARD AREAS.
&&
.DISCUSSION...
A WEAK RIDGE OVER THE STATE TONIGHT WILL BRING CLEARING SKIES AND
CALM CONDITIONS. THIS RIDGE IS DROPPING SOUTH AND PULLING EAST IN
RESPONSE TO THE INCOMING COLD FRONT PUSHING TOWARDS THE STATE FROM
THE NORTHWEST. THE COLD FRONT IS NOW POSITIONED ABOUT 175 MILES
NORTHWEST OF KAUAI AND MOVING EAST SOUTHEAST ABOUT 25 MPH. THE CLOUD
BAND ASSOCIATED WITH THE FRONT IS LOW TOPPED
STRATOCUMULUS...INDICATIVE OF THE STABLE ENVIRONMENT ALOFT. THIS
WEAK COLD FRONT WILL MOVE ACROSS KAUAI LATE THURSDAY AFTERNOON AND
REACH OAHU THURSDAY NIGHT. THE FRONT WILL BE DISSIPATING OVER MAUI
COUNTY BY EARLY CHRISTMAS MORNING. AS THERE WILL BE LITTLE UPPER
LEVEL SUPPORT WITH THIS FRONT...EXPECT ONLY LIGHT PASSING SHOWERS
MAINLY CONFINED TO WINDWARD LOCATIONS. THE TRADES WILL INCREASE TO
MODERATE LEVELS CHRISTMAS DAY BEHIND THE FRONT AS A 1020 MB HIGH
MOVES IN NORTH OF THE STATE.
LIGHT TO MODERATE TRADES WILL CONTINUE OVER THE WEEKEND AND EARLY
NEXT WEEK AS THE RIDGE STAYS NORTH. THE 00Z GFS AND 12Z EC MODELS
HAVE TRENDED AWAY FROM ANOTHER COLD FRONT MOVING INTO THE AREA FOR
THE MIDDLE OF NEXT WEEK. INSTEAD KEEPING THE RIDGE JUST TO THE
NORTH WITH WEAK EAST SOUTHEASTERLY TRADES OVER THE ISLANDS. WILL
TREND THE EXTENDED FORECAST NEXT WEEK IN THIS DIRECTION FOR THE
NEXT FORECAST PACKAGE.
&&
.MARINE...
THE CURRENT NORTHWEST SWELL IS HANGING IN THERE THIS EVENING
BRINGING HIGH SURF ADVISORY LEVEL SURF HEIGHTS TO NORTH AND WEST
FACING SHORES. THESE CONDITIONS WILL CONTINUE OVERNIGHT AND INTO
EARLY THURSDAY AHEAD OF A MUCH LARGER INCOMING NORTHWEST SWELL.
THIS NEXT VERY LARGE NORTHWEST SWELL WILL AFFECT THE NORTH AND WEST
FACING SHORES INTO THE UPCOMING HOLIDAY WEEKEND. THE WAVEWATCH MODEL
PREDICTS OPEN OCEAN SWELL HEIGHTS OF AROUND 20 FEET WITH PERIODS IN
THE 16 TO 18 SECOND RANGE. SURF WILL BUILD RAPIDLY THURSDAY ALONG
NORTH AND WEST FACING SHORES OF NIIHAU AND KAUAI WITH WARNING LEVEL
SURF LIKELY DURING THE AFTERNOON HOURS. THIS SWELL WILL MOVE DOWN
THE ISLAND CHAIN LATER THURSDAY AFTERNOON THROUGH CHRISTMAS DAY.
WAVE HEIGHTS WILL LIKELY BE SIMILAR TO WHAT WE EXPERIENCED DURING
THE SWELL EVENTS FROM A COUPLE OF WEEKS AGO. THIS SWELL WILL THEN
GRADUALLY LOWER SATURDAY AND SUNDAY. RECENT LARGE SWELLS CAUSED
SIGNIFICANT BEACH EROSION AND THIS NEW SWELL WILL LIKELY CAUSE
ADDITIONAL BEACH EROSION AND SIGNIFICANT RUN UP ALONG EXPOSED
SHORELINES.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 AM HST THURSDAY FOR NIIHAU-KAUAI
WINDWARD-KAUAI LEEWARD-WAIANAE COAST-OAHU NORTH SHORE-OAHU
KOOLAU-MOLOKAI-MAUI WINDWARD WEST-MAUI CENTRAL VALLEY-WINDWARD
HALEAKALA.
HIGH SURF WARNING FROM 6 AM THURSDAY TO 6 PM HST SATURDAY FOR
NIIHAU-KAUAI WINDWARD-KAUAI LEEWARD-WAIANAE COAST-OAHU NORTH
SHORE-OAHU KOOLAU-MOLOKAI-MAUI WINDWARD WEST-MAUI CENTRAL VALLEY-
WINDWARD HALEAKALA.
SMALL CRAFT ADVISORY UNTIL 6 AM HST THURSDAY 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-ALENUIHAHA
CHANNEL-BIG ISLAND WINDWARD WATERS-BIG ISLAND LEEWARD WATERS-BIG
ISLAND SOUTHEAST WATERS.
&&
$$
BRENCHLEY
