260  
FXHW52 PHFO 180109  
SRDHFO  
 
COLLABORATIVE NEARSHORE SWELL AND WIND FORECAST FOR OAHU  
NWS/NCEI HONOLULU HI  
309 PM HST FRI NOV 17 2017  
 
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 4 NNE 13 6 8 UP 9-13 NE DOWN  
11/17 6 NE 9 4 6 DOWN  
1 SSW 17 3 5 UP  
 
SAT 4 NNE 11 5 7 DOWN MED 9-13 N SAME  
11/18 3 NE 9 2 4 DOWN LOW  
2 SSW 14 3 5 SAME LOW  
 
SUN 12 N 13 20 24 UP MED 11-16 NNW SAME  
11/19 1 SSW 14 2 4 DOWN LOW  
 
MON 10 N 12 16 20 SAME LOW 11-16 NNW SAME  
11/20 1 SSW 14 2 4 SAME LOW  
 
TUE 9 N 12 12 16 DOWN LOW 11-16 NNE SAME  
11/21 1 SSW 17 3 4 UP LOW  
 
WED 6 N 10 6 8 DOWN LOW 11-16 NE SAME  
11/22 5 N 17 8 12 UP LOW  
5 NE 6 1 2 UP LOW  
1 SSW 15 2 4 SAME 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...  
N SWELL SPELL.  
 
DETAILED...  
MID FRIDAY ON NORTHERN SHORES HAS BREAKERS FROM 010-030 DEGREES AT  
LEVELS BELOW THE FALL AVERAGE. HEIGHTS SHOULD REMAIN BELOW AVERAGE  
ON SATURDAY FROM THE SAME DIRECTION.  
 
A LONG-LIVED SURFACE LOW PRESSURE IN THE GULF OF ALASKA 11/10-15  
HAS KEPT THE NNE EVENT UP LOCALLY ALL WEEK. NOAA NE BUOY 51000  
SHOWS NNE ENERGY IN THE 12-14 SECOND BAND RISING 11/17. THIS WAS  
DUE TO AN INCREASE TO GALES IN THE LOW OFF OREGON 11/13-15. THE  
SYSTEM WEAKENED AS IT MOVED INTO THE NW USA 11/16.  
 
THE PACIOOS WAIMEA AND MOKAPU, OAHU LATE MORNING 11/17 READINGS  
SHOW AN UPWARD TREND IN THE 12-14 SECONDS. THIS EVENT IS EXPECTED  
TO PEAK LATE FRIDAY AND TREND DOWN THROUGH SATURDAY FROM 010-030  
DEGREES.  
 
THE PERSISTENT NORTH PACIFIC JET STREAM PATTERN SINCE LAST WEEK  
HAS MAINTAINED A BLOCK OVER THE CENTRAL ALEUTIANS AND TROUGHS IN  
THE GULF OF ALASKA. MODELS SHOW IT HOLDING INTO NEXT WEEK. THIS  
IS KEEPING WNW TO NNW SURF AT A SEASONAL MINIMUM AND DOMINANT SWELL  
OUT OF THE N TO NNE.  
 
THE NEXT IN THE SERIES OF SURFACE LOWS DIGGING SSE FROM THE  
EASTERN ALEUTIANS 11/15 WAS ABOUT 20 DEGREES LONGITUDE FURTHER  
WEST THAN PREVIOUS SYSTEMS THAT GAVE NNE SWELL. THUS, MORE  
STRAIGHT N DIRECTION IS EXPECTED.  
 
IT HAD THE LARGEST AREA OF GALES WEDNESDAY NIGHT THROUGH THURSDAY  
NIGHT STRETCHING FROM NEAR THE EASTERN ALEUTIANS TO 40N. THIS  
SOURCE ALONE WOULD GIVE ABOVE AVERAGE SURF FOR SUNDAY WITH  
MODERATE WAVE PERIODS WITHIN 13-15 SECONDS FROM 350-010 DEGREES.  
 
AS OF FRIDAY MORNING THE WIND SPEEDS ARE MOSTLY NEAR GALES AS THE  
CENTER OF LOW PRESSURE CONTINUES TO MOVE SOUTHWARD. MODELS SHOW  
THE HEAD OF THE FETCH TO WITHIN 400 NM OF HAWAII ON SATURDAY WITH  
STRONG TO NEAR-GALE WINDS. THIS WILL ADD SHORT- TO MODERATE-  
PERIOD SWELL OF 9-13 SECONDS ON SUNDAY, ALSO FROM 350-010 DEGREES.  
 
THE COMBINED REMOTE AND NEARBY GENERATED SWELL SHOULD MAKE A LESS  
ORGANIZED BREAKER PATTERN SUNDAY 11/19 UNDER A MODERATE ONSHORE  
WINDS-- ADDING CHOP. SEE THE LATEST NWS STATE WEATHER DISCUSSION  
REGARDING THE TREND AND UNCERTAINTIES IN LOCAL WINDS AND WEATHER  
OVER THE WEEKEND INTO NEXT WEEK.  
 
MODELS SHOW A CUT-OFF UPPER LEVEL LOW ABOVE THE SURFACE LOW  
11/14-16 TO THE IMMEDIATE NORTH OF HAWAII. SUCH PATTERNS CHANGE  
SLOWLY. IT IS MODELLED TO MAINTAIN STRONG TO NEAR GALE WINDS ON  
THE NW TO NE SIDE OF THE SURFACE LOW OVER THE 350-010 DEGREE BAND.  
THIS SHOULD MAINTAIN ABOVE AVERAGE, SHORTER- PERIOD N SWELL  
MONDAY INTO TUESDAY, UNDER A LOCAL GENTLE TO MODERATE, N-COMPONENT,  
CHOP-PRODUCING WIND. THE SURF SHOULD DROP BELOW AVERAGE ON  
WEDNESDAY AS A NEW EVENT FILLS IN.  
 
THE NEXT IN THE SERIES OF LOWS IN THE GULF OF ALASKA IS EXPECTED  
TO SHIFT EASTWARD TO SOUTH OF ANCHORAGE, ALASKA WITH A SSE TRACK.  
SINCE IT IS EXPECTED TO BE FURTHER EAST, THE LOCAL SWELL DIRECTION  
SHOULD RETURN TO DOMINANT NNE. THE SURFACE WINDS ARE MODELLED TO  
BE MUCH STRONGER THAN THE PRECEDING SYSTEM. SEVERE GALES WITH  
POCKETS OF STORM- FORCE WINDS ARE EXPECTED TO AIM HIGHEST SLIGHTLY  
EAST OF HAWAII NORTH OF 40N, THOUGH A LARGE, WIND FETCH OF GALES  
AIMED DIRECTLY AT HAWAII WITH THE HEAD OF THE FETCH ABOUT 700 NM  
AWAY ON TUESDAY. LONG-PERIOD FORERUNNERS FROM 000-020 DEGREES  
SHOULD FILL IN LOCALLY WEDNESDAY MID DAY, WITH SURF CLIMBING  
ABOVE AVERAGE LATE WEDNESDAY. MORE COMMENTS BELOW.  
 
MID FRIDAY ON EASTERN SHORES HAS DECLINING SHORTER-PERIOD SWELL OF  
8-10 SECONDS FROM 30-50 DEGREES AT LEVELS NEAR THE TRADE WINDSWELL  
AVERAGE. IT SHOULD DROP BELOW AVERAGE ON SATURDAY.  
 
THE AFOREMENTIONED N TO NNE EVENTS SHOULD KEEP ACTIVE SURF FOR  
MORE NORTHERLY EXPOSURES OF THE EAST SIDE THROUGH THE PERIOD.  
 
MODERATE NE TRADES WEDNESDAY SHOULD SLOWLY RETURN TRADE WINDSWELL  
FROM 40-60 DEGREES 11/22.  
 
MID FRIDAY ON SOUTHERN SHORES HAS INCONSISTENT, LOW, LONG-PERIOD  
SWELL FROM WITHIN 180-220 DEGREES AT LEVELS. SIMILAR SURF IS  
PREDICTED FOR SATURDAY.  
 
THE AUSTRAL SPRING IN THE MID LATITUDES SW TO SE OF NEW ZEALAND  
HAVE BEEN ACTIVE OVER THE PAST 10 DAYS. GIVEN THE NEAR NIL TYPICAL  
SIZE FOR THIS TIME OF YEAR, SURF HAS BEEN HIGHER THAN NORMAL. MORE  
OF THE SAME IS EXPECTED INTO THE LONG RANGE.  
 
NOAA SOUTHERN HAWAII BUOYS SHOW AN UPWARD TREND IN THE 15-17  
SECOND BANDS INTO 11/17. THIS LONG-PERIOD ENERGY WAS GENERATED IN  
THE TASMAN SEA AND JUST TO THE EAST OF THE NEW ZEALAND SHADOW  
11/8-9. AS THE ASSOCIATED LOW PRESSURE MOVED EAST, THE SURFACE  
WINDS WEAKENED TO MARGINAL GALES. A WIDE, LONG FETCH OVER THE  
180-200 DEGREE BAND HELD 11/10-15 THAT SHOULD KEEP A BACKGROUND  
SURF PATTERN FOR THE REST OF THE PERIOD. ANOTHER STRONG LOW IN THE  
TASMAN 11/13-14 COULD ADD ADDITIONAL LOW, LONG-PERIOD SWELL FROM  
208-220 DEGREES LOCALLY 11/21-22.  
 
INTO THE LONG RANGE, MORE OF THE SAME FROM THE SSW WITH SMALL  
BREAKERS FOR ZONES OF HIGH REFRACTION ALONG SOUTHERN EXPOSURES  
11/23-27.  
 
NORTH SHORES ON 11/23 SHOULD CLIMB FROM 000-020 DEGREES INTO  
EXTRA- LARGE LEVELS, MEANING HIGH ENOUGH FOR BREAKERS ON OUTER  
REEFS. WITH PROXIMITY, THERE SHOULD BE SHORT- TO MODERATE-PERIOD  
SWELL ARRIVING SIMULTANEOUSLY, MAKING FOR LESS ORGANIZED BREAKERS.  
IT SHOULD SLOWLY TREND DOWN TO NEAR AVERAGE BY LATE 11/24.  
 
A COMPACT SEVERE GALE IN THE KAMCHATKA CORNER IS MODELED FOR  
11/21-22. IT COULD MAKE BELOW AVERAGE, LONG-PERIOD SWELL FROM  
310-320 DEGREES ROUGHLY 11/25. ANOTHER GULF OF ALASKA LOW IS DUE  
ROUGHLY 11/23-25 TRENDING N TO NNE SURF UP AROUND 11/26-27.  
 
FRESH TO STRONG ENE TRADES 11/24 SHOULD BUILD BREAKER ABOVE THE  
TRADE WINDSWELL AVERAGE BY 11/25 FROM 50-80 DEGREES.  
 
LONG RANGE FORECASTS ARE SUBJECT TO LOW CONFIDENCE.  
 
THIS COLLABORATIVE FORECAST WILL RESUME ON MONDAY, NOVEMBER 20.  
 
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 HTTP://WWW.PRH.NOAA.GOV/HNL/PAGES/MARINE.PHP  
 

 
 
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