High Surf in Hawaii, December 1 to 6, 2007

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST SAT DEC 1 2007

.SYNOPSIS...
A STALLED COLD FRONT WILL WEAKEN NORTH OF THE ISLANDS...BRINGING
SHOWERS MAINLY TO KAUAI AND OAHU TODAY. SOUTHWEST WINDS WILL
INCREASE TONIGHT AND SUNDAY AHEAD OF A STRONGER COLD FRONT...WHICH
WILL MOVE ACROSS KAUAI AND OAHU ON SUNDAY BEFORE STALLING JUST NORTH
OF THE BIG ISLAND SUNDAY NIGHT AND MONDAY. THIS FRONT WILL BRING
WIDESPREAD SHOWERS AND THE POTENTIAL FOR HEAVY RAINFALL TO THE
SMALLER ISLANDS.

&&

.DISCUSSION...
WATER VAPOR IMAGERY SHOWS A SHARP UPPER TROUGH 1000 MILES NORTHEAST
OF HONOLULU...WITH THE NEXT SHORTWAVE OF INTEREST 1200 MILES
NORTHWEST OF HONOLULU. THE SURFACE FRONT NORTH OF KAUAI WILL REMAIN
NEARLY STATIONARY...AS THE BOUNDARY IS NEARLY PARALLEL TO THE
STEERING FLOW. IR SATELLITE SHOWS THE LEADING EDGE OF THE FRONTAL
CLOUD BAND CONTINUES TO BRUSH NIIHAU AND KAUAI. A PREFRONTAL
CONVERGENCE BAND HAS MADE IT AS FAR EAST AS MOLOKAI AND LANAI...BUT
IS EXPECTED TO WEAKEN WITH SUNRISE. REGIONAL RADARS SHOW GENERALLY
LIGHT REFLECTIVITIES IN THE BAND OVER MOLOKAI...WITH LIGHT TO
MODERATE REFLECTIVITIES IN THE MORE SEPARATED SHOWERS BACK ACROSS
OAHU AND KAUAI. 12Z POES AMSU/DMSP SSMI PASSES SHOW AN AXIS OF HIGH
PRECIPITABLE WATERS POOLED NEAR THE SURFACE BOUNDARY...WITH HIGHER
VALUES SPREAD EASTWARD ACROSS THE STATE AS WELL. EVEN THOUGH THE
MAIN CONVERGENCE REMAINS ALONG THE FRONT NORTHWEST OF KAUAI...THERE
IS ENOUGH MOISTURE AND INSTABILITY FOR AT LEAST SCATTERED TO
NUMEROUS SHOWERS ACROSS THE SMALLER ISLANDS TODAY.

THE FIRST SHORTWAVE NORTHEAST OF THE STATE IS ALREADY WORKING TO
BREAK DOWN THE RIDGE NEAR 140W...SETTING UP A FAST ZONAL FLOW ACROSS
THE NORTH PACIFIC. THE NEXT SHORTWAVE TO THE NORTHWEST OF THE STATE
IS ASSOCIATED WITH A +180KT UPPER LEVEL JET PER GOES SATELLITE
DERIVED WINDS...AND IS POISED TO CARVE OUT A BROAD TROUGH ACROSS THE
CENTRAL PACIFIC BY EARLY NEXT WEEK. THIS WILL PROPEL A STRONGER
FRONT DOWN ACROSS THE ISLANDS SUNDAY/MONDAY. SOUTHWESTERLY FLOW WILL
INCREASE TODAY/TONIGHT AHEAD OF THE FRONT. WITH THE MOIST AIRMASS
ALREADY IN PLACE...THE KONA WINDS WILL FAVOR HIGHER POPS ACROSS
TYPICAL LEEWARD AREAS. THE 00Z GFS HAS MORE OF A SOUTHWARD PUSH AND
SHOWS THE FRONT MAKING IT TO THE ALENUIHAHA CHANNEL BEFORE STALLING
SUNDAY NIGHT...WHICH IS ACTUALLY PRETTY SIMILAR TO THE 00Z ECMWF.
THE CURRENT FORECAST HAS CATEGORICAL POPS SUNDAY/SUNDAY NIGHT
SPREADING SOUTHWARD ACROSS THE SMALLER ISLANDS...WHICH LOOKS PRETTY
GOOD. ADDED A SLIGHT CHANCE OF THUNDER TO THE AREAS OF CATEGORICAL
POPS...AS THAT IS WHERE MOISTURE WILL BE HIGHEST...POOLED ALONG THE
BOUNDARY. HOWEVER...THE MAIN THERMAL TROUGH LAGS THE STRONGER
DYNAMICS/MOISTURE ALONG THE FRONT...SO THUNDER IS NOT AS POSSIBLE AS
WOULD OTHERWISE BE THE CASE.

THE FORECAST BECOMES MORE PROBLEMATIC BY THE MIDDLE OF NEXT WEEK.
THE PREVIOUS FORECAST WAS GEARED TOWARD THE 12Z/29 GFS...WHICH WAS
VERY PROGRESSIVE. IT BROUGHT A STRONG COLD FRONT ACROSS THE STATE
MID-WEEK...FOLLOWED BY HIGH PRESSURE AND MUCH DRIER AIR
/PRECIPITABLE WATERS NEAR 0.6 INCHES/. THE SUBSEQUENT 18Z/00Z/06Z
RUNS HAVE ALL JUMPED ONTO A MUCH WETTER SOLUTION SIMILAR TO THE
ECMWF...AND THE 00Z GFS ENSEMBLE MEMBERS FOLLOWED SUIT WITH THE
OPERATIONAL RUN. THE PAST FEW ECMWF RUNS HAVE CUT OFF AN UPPER LOW
IN THE VICINITY OF THE STATE...WITH THE 12Z/30 AND 00Z/01 RUNS
SETTING UP OVER AND SOUTHWEST OF THE STATE...SIMILAR TO THE 00Z GFS.
THIS LEADS TO SURFACE CYCLOGENESIS ALONG THE STALLED FRONTAL
BOUNDARY...WITH THE SOUTHERLY FLOW TAPPING INTO TROPICAL MOISTURE
AGAIN. THE GFS HAS BEEN BACK AND FORTH WITH THIS SYSTEM...AND THE
ECMWF HAS NOT BEEN TOO STABLE EITHER. HOWEVER...THEY DO SEEM TO BE
CONVERGING TOWARD A SOLUTION WHICH...IF IT PANS OUT...COULD BE
ANOTHER SIGNIFICANT AND PROLONGED RAIN PRODUCER FOR PARTS OF THE
STATE. THEREFORE DECIDED TO TREND THE FORECAST TOWARD THE MORE
PESSIMISTIC SOLUTION. IN ADDITION TO HIGHER POPS AND MORE SOUTHERLY
WINDS...ALSO ADDED A SLIGHT CHANCE OF THUNDER TO MANY AREAS DUE TO
THE INCREASING MOISTURE AND INSTABILITY UNDER THE CUTOFF LOW.

&&

.MARINE...
THE NORTHWEST SWELL HAS PEAKED AT BUOY 51001 AT 18FT/15SEC...AND 18
SECOND FORERUNNERS HAVE REACHED THE WAIMEA BAY BUOY. THE PEAK AT
BUOY 001 WAS ABOUT A FOOT HIGHER THAN WAVEWATCH III INDICATED. A
HIGH SURF WARNING IS IN EFFECT FOR NORTH AND WEST FACING SHORES OF
NIIHAU...KAUAI...AND OAHU...WITH A HIGH SURF ADVISORY FOR NORTH AND
WEST SHORES OF MOLOKAI AND NORTH SHORES OF MAUI. IT STILL LOOKS LIKE
ENOUGH ENERGY FROM THE LARGE SWELL WILL MAKE IT THROUGH THE KAUAI
CHANNEL TO WARRANT THE HIGH SURF ADVISORY FOR WEST FACING SHORES OF
THE BIG ISLAND AS WELL. THE SWELL AT BUOY 001 WAS A LITTLE MORE
NORTHERLY /325 DEGREES/ THAN WAVEWATCH INDICATED...WHICH MAY LEAVE
THE NORTH SHORE OF THE BIG ISLAND LESS BLOCKED BY MAUI. THE SAME IS
TRUE OF THE FORERUNNERS AT THE WAIMEA BUOY. THE DIFFERENCE APPEARS
SMALL...BUT IF IT TURNS OUT TO BE SIGNIFICANT WE MAY NEED TO EXPAND
THE ADVISORY TO NORTH FACING SHORES OF THE BIG ISLAND AS WELL.

SMALL CRAFT ADVISORIES ARE ALSO IN EFFECT FOR HAZARDOUS SEAS DUE TO
THE LARGE SWELL. THE CURRENT SCA RUNS THROUGH SUNDAY MORNING...BUT
WILL LIKELY NEED TO BE EXTENDED AS YET ANOTHER LARGER SWELL IS
EXPECTED TO ARRIVE EARLY NEXT WEEK.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF WARNING UNTIL 10 AM HST SUNDAY FOR NORTH AND WEST FACING
SHORES OF NIIHAU KAUAI AND OAHU.

HIGH SURF ADVISORY UNTIL 4 PM HST SUNDAY FOR NORTH AND WEST FACING
SHORES OF MOLOKAI...NORTH FACING SHORES OF MAUI...AND WEST FACING
SHORES OF THE BIG ISLAND.

SMALL CRAFT ADVISORY UNTIL 6 AM HST SUNDAY 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.

SMALL CRAFT ADVISORY UNTIL 10 AM HST SUNDAY FOR ALENUIHAHA
CHANNEL-BIG ISLAND WINDWARD WATERS.

&&

BRAVENDER

CORRECTED DOUBLE WORDING IN THE SYNOPSIS SECTION