765
FXHW52 PHFO 310051
SRDHFO
COLLABORATIVE NEARSHORE SWELL AND WIND FORECAST FOR OAHU
NWS/NCEI HONOLULU HI
251 PM HST WED DEC 30 2020
THIS COLLABORATIVE FORECAST WILL BE UPDATED MONDAY THROUGH FRIDAY AT
300 PM WHEN PAT CALDWELL IS AVAILABLE.
FORECAST SWL DMNT DMNT H H HGT WIND WIND SPD
DATE HGT DIR PD 1/3 1/10 TEND PROB SPD DIR TEND
1 PM 10 NW 17 21 27 SAME 11-16 E SAME
12/30 6 E 8 4 6 SAME
THU 9 NW 15 16 22 DOWN MED 17-21 NE UP
12/31 15 NNW 17 33 42 UP MED
7 E 8 4 7 UP LOW
FRI 13 NNW 15 27 34 DOWN LOW 19-23 ENE UP
01/01 9 ENE 7 5 8 UP LOW
SAT 7 NNW 13 10 14 DOWN LOW 17-21 ENE DOWN
01/02 9 ENE 8 6 8 DOWN LOW
SUN 4 NNW 11 6 8 DOWN LOW 13-19 ENE DOWN
01/03 6 NNW 18 10 14 UP LOW
7 ENE 8 4 7 DOWN LOW
MON 8 NNW 17 16 20 UP LOW 11-16 E DOWN
01/04 6 ENE 7 3 5 DOWN LOW
LEGEND:
SWL HGT OPEN OCEAN SWELL HEIGHT MEASURED FROM TROUGH TO CREST
IN FEET LOCATED 20 NAUTICAL MILES OFFSHORE
DMNT DIR DOMINANT DIRECTION TYPICALLY +/-10 DEGREES IN 16 COMPASS
POINTS
DMNT PD DOMINANT PERIOD IN SECONDS
H1/3 SIGNIFICANT WAVE HEIGHT IN THE SURF ZONE
H1/10 AVERAGE HEIGHT IN THE HIGHEST ONE-TENTH WAVES IN THE SURF
ZONE
HGT TEND HEIGHT TENDENCY OF SWELL (VALID VALUES: UP/DOWN/SAME)
PROB PROBABILITY OF OCCURRENCE (VALID VALUES: HIGH/MED/LOW)
WIND SPD OPEN WATER WIND SPEED MEASURED IN KNOTS LOCATED
20 NAUTICAL MILES OFFSHORE
WIND DIR WIND DIRECTION IN 16 COMPASS POINTS
SPD TEND WIND SPEED TENDENCY (VALID VALUES: UP/DOWN/SAME)
SURF HEIGHTS WILL VARY BETWEEN DIFFERENT BEACHES AND AT THE SAME
BEACH AT DIFFERENT BREAK AREAS.
DISCUSSION:
SUMMARY....
FIREWORKS IN SKY AND OCEAN TO BRING IN THE NEW YEAR.
DETAILED...
MID WEDNESDAY ON NORTHERN SHORES HAS STEADY, ABOVE-SEASONAL-AVERAGE
BREAKERS SPREAD FROM 12-18 SECONDS, DOMINANT IN THE 15-17 SECOND
BAND, AND RANGING DIRECTIONALLY FROM 300-340 DEGREES, DOMINANT FROM
320 DEGREES. HEIGHTS ARE EXTRA-LARGE, DEFINED BY SIZE HIGH ENOUGH TO
TRIGGER OUTER REEFS. HEIGHTS SHOULD REMAIN ABOVE THE SEASONAL AVERAGE
THURSDAY MORNING, THOUGH SUB-EXTRA-LARGE, THEN RAMP UP SHARPLY
MIDAFTERNOON INTO THE EVENING.
A BROAD AREA OF WINTER-CALIBER LOW PRESSURE FILLED THE NW TO CENTRAL
N PACIFIC 12/25-28, COMMONLY REFERRED TO AS THE ALEUTIAN LOW, WHICH
IS PLENTIFUL FOR MOST DAYS OF WINTER TO DEFINE THE AVERAGE SURFACE
PRESSURE PATTERN. THE PARENT LOW FOR THIS PRESENT EVENT SENT
EXTRA-LONG-PERIOD ENERGY TO HAWAII FROM HURRICANE-FORCE WINDS WEST OF
THE DATE LINE BEYOND 1800 NM THAT TOOK SURF ABOVE AVERAGE LOCALLY
MONDAY NIGHT INTO TUESDAY FROM 305-325 DEGREES. AN OFFSPRING LOW
ADDED A NEW FETCH OF UPPER GALES NOSING SEAS TO NEAR 25 FEET ABOUT
1000 NM AWAY BY 12/28. SURF FROM THIS CLOSER SOURCE FILLED IN
OVERNIGHT TUESDAY AND IS PEAKING WEDNESDAY 12/30 ON OAHU. THIS EVENT
SHOULD SLOWLY TREND DOWN IN THE WEE HOURS THURSDAY TO MIDDAY, THOUGH
REMAIN ABOVE AVERAGE FROM 300-340 DEGREES. A LARGER EVENT IS IMMINENT
IN THE PM.
THE NEXT OFFSPRING IN THIS EXTRA-TROPICAL CYCLONE FAMILY FORMED NEAR
35N, 160E 12/28, RACED ENE AND REACHED THE DATE LINE EARLY TUESDAY
WITH HURRICANE-FORCE WINDS. THE TRACK THEN TURNED MORE NE AS IT
CONTINUED TO DEEPEN TO 960 MB, REACHING NEAR 42N, 168W EARLY
WEDNESDAY. THE REDUCTION IN SURF POTENTIAL DUE TO THE FAST TRACK WAS
WELL OFFSET BY THE EXTREME WINDS ACTING UPON EXISTING HIGH SWELL OVER
THE 310-330 DEGREE BAND. LARGEST SEAS TO 40 FEET 12/30 ARE AIMED NE
OF HAWAII, THOUGH 12/30 MORNING JASON SATELLITE REGISTERED SEAS OF
32-36 FEET WITH A MORE DIRECT AIM AT HAWAII IN AN AREA ABOUT 1000 NM
AWAY. GIVEN THE WAVE TRAVEL DECAY RULE OF THUMB OF HALF OF THE HEIGHT
REDUCED FOR EACH 1000 NM TRAVEL, THAT PLACES DEEP WATER SWELL OFF
OAHU LATE THURSDAY OF LONG PERIODS OF 15-19 SECONDS, THAT WOULD
MANIFEST AT THE PEAK OF THE EVENT TO GIANT LEVELS, DEFINED BY THE
COMMON LARGER, THOUGH LESS FREQUENT, SETS SURPASSING 40 FEET ON OUTER
REEFS IN ZONES OF HIGH REFRACTION. WITH A CLOSE SOURCE, EVENTS
TYPICALLY RISE AND FALL FASTER, WITH THE EXTREME HEIGHTS LIKELY
CENTERED OVERNIGHT THURSDAY AS THE NEW YEAR RINGS IN. IT SHOULD BE
FROM 310-340 DEGREES, THOUGH DOMINANT NEAR 325-330 DEGREES. HEIGHTS
SHOULD SLOWLY SETTLE DOWN FRIDAY THOUGH REMAIN EXTRA-LARGE THROUGH
THE DAY. HEIGHTS SHOULD FALL SHARPLY SATURDAY TO LEVELS BELOW THE
SEASONAL AVERAGE BY THE AFTERNOON FROM 310-360 DEGREES. REMNANT
SHORTER-PERIOD SURF IS EXPECTED FOR SUNDAY MORNING AS A NEW EVENT
SLOWLY FILLS IN.
KEEP ABREAST TO NATIONAL WEATHER SERVICE UPDATES 12/31 FOR
FINE-TUNING OF THE TIMING AND MAGNITUDE OF THE POTENTIAL,
SHORT-LIVED, GIANT EPISODE AS THE SWELL TRAINS ROLL UNDER THE NOAA NW
HAWAII BUOYS. NOTE THE NWS STATEMENT REGARDING THE COINCIDING SPRING
HIGH TIDE AND UPPER-LEVEL WINTER SURF, GIVING WAY TO POTENTIALLY
WELL-ABOVE AVERAGE COASTAL WAVE RUN-UP 1/1 IN THE WEE HOURS TO NEAR
DAWN.
THE PARENT LOW AFOREMENTIONED WEAKENED IN THE BERING SEA 12/28-29. A
NEW PARENT LOW IS MODELLED TO REPLACE IT BY 12/31 OVER THE WESTERN
ALEUTIANS WITH THE CENTER OF LOW PRESSURE DROPPING TO NEAR 928 MB
THURSDAY. HURRICANE-FORCE WINDS ABOUT 2400 NM AWAY SHOULD SEND LOW,
EXTRA-LONG-PERIOD FORERUNNERS ARRIVING IN HAWAII SATURDAY EVENING
FROM 320 DEGREES. THE PRIMARY EVENT IS EXPECTED TO BE GENERATED BY A
LONG, WIDE FETCH OF GALES TO STORM-FORCE WINDS BEYOND 1800 NM AWAY
12/31-1/1. THIS EVENT SHOULD HAVE A SLOW RISE SUNDAY REACHING LEVELS
ABOVE AVERAGE MIDDAY FROM 300-325 DEGREES.
MODELS SHOW THE JET SOUTH OF THE PARENT LOW BECOMING ZONAL 1/1-3, AND
SENDING A NEW OFFSPRING OF GALES ON A TRACK FROM THE FAR NW PACIFIC
TO EAST OF THE DATE LINE BY 1/2. THIS CLOSER SOURCE SHOULD BRING
LARGER SURF, WITH HEIGHTS GROWING ABOVE AVERAGE EARLY MONDAY AND
PEAKING LATE MONDAY FROM 310-330 DEGREES.
MID WEDNESDAY ON EASTERN SHORES HAS ABOVE AVERAGE SURF FROM THE TRADE
WIND BELT OF 70-90 DEGREES. HEIGHTS SHOULD BE SIMILAR ON THURSDAY.
SEE THE LATEST NWS STATE FORECAST DISCUSSION REGARDING THE TREND IN
LOCAL WINDS AND SKIES.
SURFACE HIGH PRESSURE HAS HELD BETWEEN HAWAII AND CALIFORNIA SINCE
LAST WEEKEND WITH A LARGE FETCH OF FRESH TO STRONG BREEZES, AND
POCKETS TO SEVERE GALES, EAST OF HAWAII MOSTLY WITHIN 135-150W. THIS
UPSTREAM SOURCE HAS THE PACIOOS/CDIP HILO, HAWAII AND MOKAPU, EAST
OAHU, BUOYS HOLDING 7-10 SECOND WAVE PERIOD ENERGY, WHICH IS ON THE
LONGER SIDE OF THE WIND SWELL SPECTRUM. LONGER WAVE PERIODS ALLOW
MORE HEIGHT TRANSFORMATION UPON SHOALING, AND LEADS TO MORE ACTIVE
SURF. THIS UPSTREAM SOURCE SHOULD HOLD THROUGH THURSDAY, AS A NEW
FRESH TO STRONG TRADE EVENT LOCALLY OF 12/31-1/2 MAINTAINS THE ABOVE
AVERAGE BREAKER HEIGHTS UNDER ROUGH CONDITIONS FROM 70-90 DEGREES
INTO THE WEEKEND. HEIGHTS ARE MODELLED TO SLOWLY TREND DOWN 1/3-4 TO
NEAR AVERAGE.
MID WEDNESDAY ON SOUTHERN SHORES HAS BREAKERS NEAR NIL AS COMMON IN
WINTER. MORE OF THE SAME IS LIKELY ON THURSDAY.
AUSTRAL SUMMER MODE BECAME ESTABLISHED LAST WEEK INTO THIS WEEK IN
THE MIDLATITUDES FOR LONGITUDES FROM TASMANIA TO SOUTH OF FRENCH
POLYNESIA, WHICH SPELLS MORE OF THE SAME NIL-NESS LOCALLY. FROM LATE
DECEMBER TO EARLY MARCH, ODDS ARE HIGHER FOR SURF ON SOUTH SHORES
FROM EAST OR WEST THAN FROM SOUTH.
INTO THE LONG RANGE, WIND SWELL FROM THE TRADE WIND BELT SHOULD DROP
BELOW AVERAGE OUT OF 70-90 DEGREES BY LATE MONDAY AND HOLD BELOW
AVERAGE INTO WEDNESDAY 1/4-6.
THE NORTH SIDE SHOULD HOLD ABOVE AVERAGE 1/5 AND SLOWLY TREND DOWN
INTO 1/7 FROM 310-340 DEGREES.
LONG RANGE FORECASTS ARE SUBJECT TO LOW CONFIDENCE.
THIS IS THE LAST COLLABORATIVE FORECAST. THANKS FOR SUPPORT FROM THE
NWS HNL TEAM AND KIND WORDS RECEIVED FROM THE PUBLIC.
THIS FORECAST WAS PRODUCED THROUGH THE COLLABORATIVE EFFORTS OF
NWS AND NCEI. PLEASE SEND SUGGESTIONS TO W-HFO.WEBMASTER@NOAA.GOV
OR CALL THE WARNING COORDINATION METEOROLOGIST AT 808-973-5275.
ADDITIONAL RESOURCES:
SEE HTTPS://WWW.WEATHER.GOV/HFO/MARINE
NWS FORECASTER AND NCEI PAT CALDWELL
PLEASE SEE
WEATHER.GOV/MEDIA/NOTIFICATION/PDF2/PNS20-87SRD_DISCONTINUATION.PDF
FOR MORE DETAILS ON THE DISCONTINUATION OF THIS PRODUCT.
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