FXHW60 PHFO 021335
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
335 AM HST WED DEC 2 2009
.SYNOPSIS...
LIGHT WINDS AND A STABLE ATMOSPHERE WILL ENSURE LOTS OF SUN TODAY...
AND ANOTHER CLEAR AND COOL NIGHT TONIGHT...BEFORE AN APPROACHING
FRONT BRINGS INCREASING SOUTHWEST WINDS ON THURSDAY. CLOUDS AND
SHOWERS WILL INCREASE THURSDAY AFTERNOON AND PERSIST INTO FRIDAY...
AS THE FRONT MOVES DOWN THE ISLAND CHAIN. THE FRONT WILL STALL AND
DISSIPATE NEAR MAUI AND THE BIG ISLAND FRIDAY NIGHT...WITH LIGHT
WINDS AND A RELATIVELY DRY PATTERN IN PLACE FOR MOST OF THE WEEKEND.
ANOTHER FRONT WILL APPROACH FROM THE NORTHWEST EARLY NEXT WEEK.
&&
.DISCUSSION...
THE QUIET WEATHER PATTERN OVER THE STATE CONTINUES THIS MORNING...
WITH A WEAK SURFACE PRESSURE GRADIENT RESULTING IN LIGHT AND
VARIABLE WINDS. SOLID MID AND UPPER LEVEL RIDGING IS SUPPORTING A
STABLE AIR MASS OVER THE ISLANDS...AND LOW LEVEL MOISTURE IS
LIMITED. THEREFORE...MOSTLY CLEAR AND COOL CONDITIONS THIS MORNING
WILL GIVE WAY TO SEA BREEZES AND A FEW INTERIOR CLOUDS THIS
AFTERNOON...WITH ONLY A SLIGHT CHANCE OF SHOWERS. LITTLE CHANGE
EXPECTED TONIGHT AS WELL...WITH CLEARING SKIES LEADING TO ANOTHER
CRISP MORNING ON THURSDAY.
A FRONT APPROACHING THE ISLANDS FROM THE NW ON THURSDAY WILL LEAD
TO INCREASING SW WINDS THAT WILL BE LOCALLY GUSTY IN WINDWARD
COMMUNITIES...BUT NOT STRONG ENOUGH TO CAUSE MAJOR PROBLEMS. LATEST
MODEL GUIDANCE SHOWS AN EARLIER-ARRIVING FRONT THAT IS MORE
PROGRESSIVE IN IT/S MOVEMENT DOWN THE ISLAND CHAIN THAN PREVIOUS
RUNS...WITH THE FRONT AND A PREFRONTAL CONVERGENCE BAND BRINGING
INCREASING CLOUDS AND SHOWERS AS EARLY AS THURSDAY AFTERNOON. THE
LATEST PHILOSOPHY CALLS FOR FRONT TO MOVE DOWN THE ISLAND CHAIN
THURSDAY NIGHT...REACHING THE BIG ISLAND BY EARLY FRIDAY MORNING.
SOME HEAVY SHOWERS ARE POSSIBLE AS THE FRONT WILL HAVE MODEST MID
LEVEL SUPPORT...AND HAVE ALSO INCLUDED A SLIGHT CHANCE OF
THUNDERSTORMS FOR THURSDAY NIGHT...WHEN DYNAMICS ARE MOST SUPPORTIVE
OF THEIR DEVELOPMENT. THE MOTION OF THE FRONT SHOULD PRECLUDE HEAVY
SHOWERS FROM LINGERING OVER ANY PARTICULAR AREA LONG ENOUGH TO
BRING FLASH FLOODING.
AS THE PARENT LOW RAPIDLY MOVES NE AWAY FROM THE ISLANDS...THE FRONT
WILL DISSIPATE NEAR THE BIG ISLAND ON FRIDAY...BUT SOME OF IT/S
MOISTURE WILL LINGER NEAR MAUI AND THE BIG ISLAND BEFORE DISSIPATING
ON SATURDAY. WINDS WILL SHIFT TO W AND NW AS THE FRONT PASSES...
BEFORE BECOMING NRLY MOST AREAS ON FRIDAY. A BUBBLE HIGH FOLLOWING
THE FRONT IS RESPONSIBLE FOR DRIVING THESE WINDS...BUT IT WILL MOVE
QUICKLY E AND WEAKEN...AND LIGHT WINDS WILL VEER TO THE E ON
SATURDAY BEFORE BECOMING LIGHT AND VARIABLE LATE SATURDAY AS THE
HIGH COLLAPSES TO THE NE. LATE SATURDAY AND SUNDAY ANOTHER FRONT
APPROACHING FROM THE NW WILL TURN WINDS TO THE SW AGAIN...WITH THIS
WEAK FRONT NEARING KAUAI MONDAY MORNING. LONGER RANGE WAVE MODEL
GUIDANCE CONTINUES TO INDICATE THAT A VERY LARGE NW SWELL WILL BE
STIRRED UP BY THE LOW THAT DRIVES THIS FRONT TOWARD THE ISLANDS.
ALTHOUGH FORECAST CONFIDENCE IS GREATLY DIMINISHED FOR THIS TIME
PERIOD...THIS FRONT IS ANTICIPATED TO STALL OUT NEAR KAUAI AND OAHU
INTO TUESDAY...AND DISSIPATE ON WEDNESDAY...AS IT/S FOLLOWING HIGH
WILL MOVE RAPIDLY E ALONG 27N. INTO THE MIDDLE OF NEXT WEEK...TRADE
WINDS SUPPORTED BY THIS HIGH WILL BE ON THE LIGHTER SIDE...WITH IT/S
ASSOCIATED RIDGE JUST N OF KAUAI.
GIVEN THE RAPID ZONAL FLOW ALOFT DRIVING THESE LOWS AND ASSOCIATED
FRONTS...IT IS WITHOUT QUESTION THAT TIMING OF THESE FEATURES...AND
THEIR POTENTIAL EFFECTS ON THE ISLANDS...WILL NEED TO BE FINE TUNED
AS TIME GOES BY.
&&
.MARINE...
THE FIRST OF SEVERAL SOLID NW SWELLS IS EXPECTED TO BUILD LATER
TODAY...AND JUST STARTED TO SHOW UP AT BUOY 51101 TO THE NW OF KAUAI
AT 2 AM. THIS SWELL IS EXPECTED TO RESULT IN ADVISORY LEVEL SURF
ALONG N AND W FACING SHORES OF MOST ISLANDS LATER TODAY AND
THURSDAY...AND HAVE JUST ISSUED AN ADVISORY...WITH AN EFFECTIVE
TIME OF NOON TODAY. OPEN OCEAN SWELL HEIGHTS ARE EXPECTED TO PEAK
AROUND 10 TO 12 FEET TONIGHT...WHICH IS NOT AS LARGE AS THE SWELL
THAT CAME IN ABOUT A WEEK AGO. HOWEVER...THE TIMING OF THE PEAK
WILL COINCIDE WITH A VERY HIGH HIGH TIDE EARLY THURSDAY...INCREASING
THE POTENTIAL FOR WAVE RUNUP AND MINOR BEACH EROSION. A WARNING IS
NOT EXPECTED TO BE NECESSARY.
ANOTHER NW SWELL SLATED FOR FRIDAY NIGHT AND SATURDAY WILL BRING
SURF TO WARNING LEVELS ALONG N AND W FACING SHORES OF MOST ISLANDS.
A THIRD NW SWELL IS EXPECTED TO BE EVEN LARGER AND QUITE LONG-
LIVED...ARRIVING SUNDAY NIGHT AND PERSISTING THROUGH TUESDAY WITH
WARNING LEVEL SURF.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY FOR NORTH AND WEST FACING SHORES OF NIIHAU
KAUAI OAHU AND MOLOKAI AND FOR NORTH FACING SHORES OF MAUI FROM
NOON TODAY TO 6 AM FRIDAY.
&&
$$
BIRCHARD
