580  
FXHW52 PHFO 240109  
SRDHFO  
 
COLLABORATIVE NEARSHORE SWELL AND WIND FORECAST FOR OAHU  
NWS/NCEI HONOLULU HI  
309 PM HST TUE JAN 23 2018  
 
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 5 WNW 15 8 12 DOWN 17-21 ENE UP  
01/23 7 E 10 6 8 SAME  
2 S 13 3 4 DOWN  
 
WED 3 NW 14 5 7 DOWN LOW 17-21 E SAME  
01/24 7 E 10 6 8 SAME MED  
2 S 12 2 4 DOWN LOW  
 
THU 2 WNW 12 3 4 SAME LOW 13-19 E DOWN  
01/25 2 N 12 3 4 UP LOW  
7 E 10 6 8 DOWN LOW  
1 SW 15 2 3 DOWN LOW  
 
FRI 3 NW 12 4 6 UP LOW 7-10 SE DOWN  
01/26 2 N 11 2 4 SAME LOW  
5 E 10 4 7 DOWN LOW  
 
SAT 2 WNW 18 3 5 UP LOW 4-6 VRB SAME  
01/27 2 N 12 3 4 SAME LOW  
4 E 10 3 5 SAME LOW  
 
SUN 2 WNW 14 3 4 DOWN LOW 7-10 E UP  
01/28 3 N 11 3 5 DOWN LOW  
4 E 10 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... VARIOUS SMALL SOURCES FROM MID LATITUDES OF THE NORTH PACIFIC  
AND STEADY E TRADE WINDSWELL.  
 
DETAILED...  
MID TUESDAY ON NORTHERN SHORES HAS BREAKERS FROM 290-315 DEGREES  
AT LEVELS NEAR THE ACTIVE SEASON, SEP-MAY, AVERAGE. HEIGHTS ARE  
DECLINING.  
 
THE DYING STAGES OF THE LARGE, WINTER-CALIBER LOW PRESSURE SYSTEM  
IN THE FAR NW PACIFIC 1/17-19 THAT PRODUCED THE ABOVE AVERAGE WNW  
EVENT LOCALLY OF 1/22-23 HAD DECREASING GALES IN THE KAMCHATKA  
CORNER BEYOND 2400 NM AWAY 1/19-20. NOAA NW HAWAII BUOY 51101  
SHOWS A DECLINE IN THE 14-17 SECOND WAVE PERIOD BANDS 1/23. THIS  
EVENT IS PREDICTED TO DROP BELOW AVERAGE ON WEDNESDAY FROM 300-320  
DEGREES AND FADE OUT THURSDAY.  
 
SEVERAL SOURCES ARE EXPECTED TO KEEP SMALL SURF INTO THE WEEKEND  
FROM WNW TO N.  
 
A WEAK LOW PRESSURE FORMED NEAR THE DATE LINE 1/22. IT IS DRIFTING  
SLOWLY NE. ASCAT SATELLITE SHOWED THE FETCH AIMED AT HAWAII TO BE  
MOSTLY SUB-GALE AND SHORT. MODELS SUGGEST NEAR GALES LATE 1/23  
INTO EARLY 1/24 OVER THE 305-320 DEGREE BAND BEYOND 1000 NM,  
BEFORE WEAKENING LATER 1/24. THIS SMALL, SHORT-PERIOD EVENT SHOULD  
KEEP SMALL BREAKERS FROM 305-320 DEGREES FRIDAY INTO SATURDAY.  
 
A COMPACT, HURRICANE-FORCE SYSTEM EAST OF JAPAN 1/22 IS TRACKING  
RAPIDLY TOWARD THE SEA OF OKHOTSK WEST OF THE KURIL ISLAND 1/23.  
THE SHORT FETCH WAS NEARLY 3000 NM AWAY. LOW, LONG-PERIOD SWELL  
FROM 300-310 DEGREES IS MODELLED TO FILL IN LOCALLY OVERNIGHT  
FRIDAY AND PEAK ON SATURDAY IN THE SMALL BRACKET. IT SHOULD FADE  
OUT ON SUNDAY.  
 
A LARGE AREA OF LOW PRESSURE IN THE GULF OF ALASKA 1/21-23 HAS HAD  
GALES HUGGING THE EASTERN ALEUTIANS AND NEAR GALES STRETCHING  
FURTHER TOWARDS HAWAII. SMALL SURF IS EXPECTED TO HOLD THURSDAY  
INTO THE WEEKEND FROM 350-010 DEGREES.  
 
MID TUESDAY ON EASTERN SHORES HAS BREAKERS FROM 70-90 DEGREES AT  
LEVELS ABOVE THE TRADE WINDSWELL AVERAGE. SIMILAR SURF IS EXPECTED  
FOR WEDNESDAY.  
 
FRESH TO STRONG TRADES E OF HAWAII TO 135W HAVE HELD OVER THE PAST  
5 DAYS EVEN THOUGH THE LOCAL TRADES DIPPED TO MODERATE LEVELS  
1/21-22. THE UPSTREAM SOURCE HAS KEPT THE DOMINANT WAVE PERIOD  
NEAR 10 SECONDS, WHICH ALLOWS FOR GREATER BREAKER SIZE. MODELS  
KEEP THE ELEVATED WAVE PERIOD THROUGH THE PERIOD, WITH THE SURF  
SLOWLY TRENDING DOWN FRIDAY TO SUNDAY.  
 
THE PACIOOS MOKAPU BUOY OFF EAST OAHU SHOWS A RISE IN THE 4-8  
SECOND BAND ASSOCIATED WITH THE INCREASING TRADES 1/23. THIS IS  
ADDING LOCAL ROUGHNESS TO THE SURF. SIMILAR CONDITIONS ARE  
EXPECTED INTO THURSDAY MORNING.  
 
SEE THE LATEST NWS STATE FORECAST DISCUSSION REGARDING THE MIX IN  
MODEL GUIDANCE OF LOCAL WINDS THURSDAY INTO THE WEEKEND.  
 
MID TUESDAY ON SOUTHERN SHORES HAS SMALL BREAKERS FROM 170-220  
DEGREES. HEIGHTS ARE EXPECTED TO DROP ON WEDNESDAY.  
 
A STATIONARY BROAD AREA OF WEAK LOW PRESSURE EAST OF NEW ZEALAND  
1/13-15 GENERATED THE OUT-OF-SEASON SOUTH SWELL LOCALLY OF  
1/22-23. THIS EVENT SHOULD SLOWLY DROP 1/24.  
 
A NARROW FETCH OF STORM-FORCE WINDS IN THE TASMAN SEA 1/15-16  
COULD ADD LOW, LONG-PERIOD SURF FROM 208-220 DEGREES 1/23-25.  
 
INTO THE LONG RANGE, LOW ODDS FOR A SMIDGEN OF LONG-PERIOD SURF  
OUT OF 180-200 DEGREES LOCALLY 1/29-30 FROM A FAST-MOVING, STORM-  
FORCE SYSTEM THAT TRACKED EAST WELL S TO SE OF NEW ZEALAND  
1/21-22.  
 
ANOTHER LOW IN THE GULF OF ALASKA 1/26-28 IS MODELLED TO SET UP  
GALES BEYOND 1500 NM AWAY. IT SHOULD TREND THE LOCAL SURF UP 1/30  
FROM 350-010 DEGREES AND HOLD 1/31 WITH A PEAK NEAR THE ACTIVE  
SEASON AVERAGE. LOW, LONG-PERIOD SURF FROM WNW TO NW IS ALSO  
EXPECTED LOCALLY WITHIN 1/29-31.  
 
EASTERLY TRADE WINDSWELL IS EXPECTED NEAR THE AVERAGE 1/29-31.  
 
LONG RANGE FORECASTS ARE SUBJECT TO LOW CONFIDENCE.  
 
THIS COLLABORATIVE FORECAST WILL RESUME ON THURSDAY, JANUARY 25.  
 
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  
 

 
 
NWS FORECASTER AND NCEI PAT CALDWELL  
 
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