FXHW60 PHFO 240132
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 PM HST WED DEC 23 2009
.SYNOPSIS...
A SERIES OF WEAK COLD FRONTS WILL AFFECT THE ISLANDS THROUGH THE
FORECAST PERIOD. BRIEF BOUTS OF LIGHT TO MODERATE TRADES WILL FOLLOW
EACH FRONT...WITH ANY FRONTAL SHOWERS PREDOMINANTLY FOCUSING OVER
WINDWARD AND MAUKA AREAS. LAND AND SEA BREEZES WILL DOMINATE AHEAD
OF EACH FRONT.
&&
.DISCUSSION...
THE WESTERN EDGE OF A RIDGE OF HIGH PRESSURE LIES OVER THE ISLAND OF
KAUAI. THIS PLACES THE ISLANDS IN AN LIGHT WIND REGIME. DAYTIME SEA
BREEZES AND NIGHT TIME LAND BREEZES WILL PREVAIL THROUGH THE DAY
THURSDAY. THE ATMOSPHERE IS RATHER DRY IN THE ISLAND VICINITY WITH
PRECIPITABLE WATER VALUES UNDER 1 INCH AS INDICATED BY THE 00Z
SOUNDINGS FROM LIHUE AND HILO.
A COLD FRONT SEEN ON SATELLITE IMAGERY A FEW HUNDRED NORTHWEST OF
THE STATE IS EXPECTED TO REACH KAUAI LATE THURSDAY AFTERNOON AND
THEN REACH OAHU THURSDAY NIGHT. THE FRONT WILL BRING AN INCREASING
CHANCE OF SHOWERS...BUT SINCE THE SURFACE FRONTAL BOUNDARY LACKS ANY
UPPER LEVEL SUPPORT...ONLY LIGHT RAINFALL ACCUMULATIONS ARE
ANTICIPATED. THE FRONT WILL BECOME SO WEAK AS IT PASSES OAHU THAT IT
BREAKS UP AND DISSIPATES COMPLETELY BEFORE CROSSING MAUI COUNTY ON
CHRISTMAS DAY. LIGHT TO MODERATE TRADE WINDS WILL FILL IN FOR FRIDAY
INTO EARLY SATURDAY WITH CLOUDS AND SHOWERS FAVORING TYPICAL
WINDWARD AND MAUKA AREAS.
BY SUNDAY THE TRADE WIND PRODUCING SURFACE HIGH WILL BE LOCATED FAR
TO THE NORTHEAST OF THE STATE WITH ITS ASSOCIATED SURFACE RIDGE
MOVING SOUTHEASTWARD AND TAKING UP A POSITION JUST NORTH OF KAUAI.
THIS WILL AGAIN PLACE THE ISLANDS IN A LIGHT WIND REGIME THOUGH THE
BACKGROUND WIND FLOW WILL BE FROM THE EAST SOUTHEAST. ANOTHER FRONT
IS FORECAST TO APPROACH THE ISLANDS TOWARD THE MIDDLE OF NEXT WEEK
WHICH WILL PUSH THE SURFACE RIDGE DOWN OVER THE ISLANDS. THUS LIGHT
WINDS AND LOCAL LAND AND SEA BREEZES WILL PREVAIL DURING THAT TIME
FRAME. DETAILS ON OTHER EFFECTS OF THE FRONT REMAIN UNCLEAR THAT FAR
OUT IN TIME SINCE THERE ARE SOME DISAGREEMENTS AMONG THE COMPUTER
MODELS.
&&
.MARINE...
A VERY LARGE NORTHWEST SWELL WILL AFFECT THE NORTH AND WEST FACING
SHORES OVER 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.
&&
$$
BURKE
