FXHW60 PHFO 021929
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
930 AM HST WED DEC 2 2009
.SYNOPSIS...
LIGHT WINDS WILL ALLOW FOR A MOSTLY SUNNY WEDNESDAY...AND ANOTHER
COOL CLEAR WEDNESDAY NIGHT. WINDS WILL BECOME SOUTHWESTERLY ON
THURSDAY AHEAD OF THE NEXT APPROACHING COLD FRONT. CLOUDS AND
SHOWERS WILL INCREASE THROUGH THURSDAY AFTERNOON AND PERSIST INTO
FRIDAY AS THE FRONT MOVES ACROSS THE ISLANDS. A PERIOD OF LIGHT AND
VARIABLE WINDS ALONG WITH GENERALLY DRY CONDITIONS WILL FOLLOW FOR
THE WEEKEND. ANOTHER COLD FRONT WILL REACH THE STATE SOMETIME LATE
SUNDAY NIGHT.
&&
.DISCUSSION...
LIGHT WINDS AND RELATIVELY DRY AIR GAVE WAY TO A CRISP MOSTLY CLEAR
NIGHT ACROSS THE ISLANDS. THERE ARE ONLY A FEW ISOLATED LIGHT
SPRINKLES MEANDERING AROUND THE AREA...MOSTLY OVER THE COASTAL
WATERS THIS MORNING. OVERALL ITS A BEAUTIFUL MORNING WITH MOSTLY
CLEAR SKIES. VARIABLE SEA BREEZES WILL LEAD TO SOME SHALLOW
AFTERNOON CLOUD BUILD-UPS...BUT ONLY ISOLATED SHOWERS ARE EXPECTED
WITH LIMITED BOUNDARY LAYER MOISTURE AND STABLE THERMODYNAMIC
PROFILES. THE BOUNDARY N OF KAUAI SAGGING SLOWLY SOUTHWARD DOES NOT
LOOK TO REACH THE AREA AS WINDS CONTINUALLY VEER AND WEAKEN BEHIND
THE FRONT. IT MAY GRAZE THE NORTHWESTERN MOST COASTAL WATERS BEFORE
WASHING OUT AS IT RETREATS NORTHWARD.
SOUTHERLY FLOW INCREASES THU AHEAD OF THE NEXT INCOMING COLD FRONT.
RETURN FLOW WILL INCREASE BOUNDARY LAYER MOISTURE CONTENT AND SHOWER
CHANCES BEGINNING GRADUALLY TOMORROW MORNING. RAIN CHANCES INCREASE
THU NIGHT...GRADUALLY MOVING SE ACROSS THE STATE AS THE FRONT DECAYS
THROUGH SAT MORNING. THIS WILL BRING A SLIGHT CHANCE OF TSTORMS THU
NIGHT WHEN UPPER LEVEL DYNAMIC SUPPORT IS MAXIMIZED...WHICH AT THIS
POINT APPEARS MINIMAL. LINGERING MOISTURE COULD ALLOW FOR A FEW
DIURNALLY FORCED SHOWERS IN THE VICINITY OF THE BIG ISLAND SAT
AFTERNOON.
GFS/ECMWF AND ENSEMBLE SOLUTIONS STILL SHOWING SOLID AGREEMENT INTO
THE LONGER TERM...WHICH IS NICE FOR A CHANGE. TROPICAL STORM NIDA IS
NOW JUST S OF JAPAN AND WILL BEGIN TRANSITIONING TO AN EXTRATROPICAL
CYCLONE OVER THE NEXT 24 HOURS AS BECOMES ABSORBED IN THE NORTH
PACIFIC WESTERLIES. THIS WILL MOVE QUICKLY E DEVELOPING INTO A LARGE
DEEP LAYERED HURRICANE FORCE SURFACE CYCLONE AS IT BECOMES ABSORBED
INTO THE DEEP LAYERED TROUGH ALREADY SITUATED TO OUR N. THIS WILL
SLING ANOTHER WEAK FRONT TOWARDS HAWAII THAT WILL LIKELY BE DECAYING
BY THE TIME IT REACHES KAUAI LATE SUN NIGHT. THIS WILL BE FOLLOWED
BY MODERATE TRADE WINDS DURING THE FIRST HALF OF THE WEEK...ALTHOUGH
GIVEN THE PROXIMITY OF THE WEAK RIDGE/HIGH TO OUR NORTH...ENHANCED
SEA BREEZES ALONG LEEWARD SECTIONS MAY BE POSSIBLE TUE-THU.
NOT PLANNING ANY BIG CHANGES TO THE FORECAST DURING TODAYS DAY
SHIFT...PROBABLY JUST THE USUAL FINE TUNING AND SOME MINOR
ADJUSTMENTS TO CLEAN UP AND SMOOTH OUT THE LONG TERM GRIDS.
&&
.PREVIOUS DISCUSSION.../ISSUED 335 AM HST WED MORNING/
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.
EARLY MORNING SURF WILL START OUT ON THE SMALLER SIDE HITTING MAYBE
HEAD HIGH OR JUST OVERHEAD FOR THE TOP NORTH FACING FOCAL AREAS. A
HIGH SURF ADVISORY HAS BEEN ISSUED AND BEGINS AT NOON TODAY...UNTIL
6 AM HST FRI MORNING. SURF WILL BUILD TODAY REACHING THE 15 FOOT
RANGE THIS AFTERNOON...THEN PEAK OVER 20 FEET TOMORROW. THIS WILL
SUBSIDE...CLOSELY FOLLOWED BY ANOTHER NW SWELL THAT WILL BUILD FRI
NIGHT WITH THE POTENTIAL TO PEAK SAT ABOVE THE WARNING LEVEL OF 25
FEET.
AS MENTIONED IN THE PUBLIC DISCUSSION ABOVE...TROPICAL STORM NIDA
WILL BE UNDERGOING EXTRATROPICAL TRANSITION OVER THE NEXT DAY OR SO.
IT WILL BE CARRIED QUICKLY EASTWARD ADDING SUBSTANTIAL ENERGY TO AN
ALREADY DEEP LAYERED TROUGH N OF THE ISLANDS. 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 SUN AFTERNOON. ALTHOUGH THIS SYSTEM HAS NOT FORMED
YET...PRELIMINARY NWW3 NUMBERS ARE IMPRESSIVE WITH ANYWHERE FROM 18
TO 20 FEET OF SWELL WITH PERIODS OF 17 TO 19 SECONDS WHICH SUGGESTS
WAVE HEIGHTS APPROACHING 40 FEET ON THE FACE...PERHAPS GREATER ON
THE BIGGEST SETS SNEAKING THROUGH. THIS WILL LIKELY FLUCTUATE OVER
THE NEXT FEW DAYS...BUT EITHER WAY CONFIDENCE IS PRETTY HIGH IN
EXTRA LARGE SURF FOR EARLY NEXT WEEK. WE WILL MONITOR THE EVOLUTION
OF THE ASSOCIATED LOW PRESSURE SYSTEM OVER THE NEXT FEW DAYS.
&&
.AVIATION...
VFR CONDITIONS WILL BE THE RULE FOR THE TERMINALS AND MOST OF THE
AREA TODAY. SOME LOCATIONS MAY SEE AN MVFR CIG THIS AFTERNOON FROM
00-03Z. NEXT CHANCE FOR WIDESPREAD FLIGHT RESTRICTIONS COMES
TOMORROW AFTERNOON INTO FRI MORNING WITH THE NEXT FRONTAL PASSAGE.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY FROM NOON TODAY TO 6 AM HST FRIDAY FOR NIIHAU-
KAUAI WINDWARD-KAUAI LEEWARD-WAIANAE COAST-OAHU NORTH SHORE-OAHU
KOOLAU-MOLOKAI-MAUI WINDWARD WEST-WINDWARD HALEAKALA.
&&
$$
PUBLIC/AVIATION...DEJESUS
MARINE...DEJESUS/BIRCHARD
PREVIOUS...BIRCHARD
