629  
FXHW52 PHFO 161517 CCA  
SRDHFO  
 
COLLABORATIVE NEARSHORE SWELL AND WIND FORECAST FOR OAHU...CORRECTED  
NWS/NCEI HONOLULU HI  
517 AM HST TUE JUL 16 2019  
 
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 SSW 17 8 12 DOWN 11-16 E DOWN  
07/15  
 
TUE 4 NNE 8 1 3 UP LOW 13-19 E UP  
07/16 4 SSW 14 6 8 DOWN MED  
 
WED 4 NNE 8 1 3 DOWN LOW 17-21 E UP  
07/17 6 E 6 2 4 UP LOW  
3 S 13 4 6 DOWN LOW  
 
THU 7 E 7 3 5 UP LOW 17-21 E SAME  
07/18 2 S 12 2 4 DOWN LOW  
 
FRI 8 E 8 4 6 UP LOW 17-21 E SAME  
07/19 2 SE 9 1 2 SAME LOW  
 
SAT 6 E 9 4 6 DOWN LOW 13-19 E DOWN  
07/20 2 SE 9 1 2 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...  
NEW ZEALAND SWELL WINDING DOWN INTO MID WEEK AS TRADE WINDSWELL BUILDS.  
 
DETAILED...  
MID MONDAY ON SOUTHERN SHORES HAS BREAKERS FROM 180-200 DEGREES  
WELL ABOVE THE SEASONAL AVERAGE. HEIGHTS SHOULD REMAIN ABOVE  
AVERAGE ON TUESDAY.  
 
THE PACIOOS/CDIP NEARSHORE BUOYS OFF BARBERS PT, OAHU AND  
KAUMALAPAU, LANAI 7/15 CONTINUE TO SHOW SELECT ENERGETIC ENVELOPES  
WELL ABOVE AVERAGE. THIS SOURCE SEEMED TO HAVE A DIRECT AIM AT THE  
HAWAII ISLANDS LAST WEEK 7/6-8, THOUGH THE NEARSHORE BUOYS AS WELL  
AS THE NOAA SOUTHERN BUOYS 51002 AND 51004 7/14-15 SHOW THAT THE  
SWELL ENERGY WAS HIGHEST TOWARDS THE EAST.  
 
JUST FROM THE PRIMARY SOURCE WINDS OF 7/6-8 THAT GREW SEAS TO  
WITHIN 30-40 FEET OVER A LARGE AREAS SE TO E OF NEW ZEALAND,  
DISPERSION SHOULD KEEP THIS EVENT ACTIVE INTO TUESDAY AS THE  
DOMINANT WAVE PERIOD SLOWLY SHIFTS DOWNWARD. WITH THE SOURCE SO  
FAR AWAY, THE 18-22S ENERGY ARRIVES A DAY AHEAD OF THE DOMINANT  
15-17S ENERGY, WHICH IN TURN ARRIVES ABOUT A DAY AHEAD OF THE  
13-15S DOMINANT PEAK, SINCE THE LONGER THE WAVE PERIOD, THE FASTER  
THE GROUP SPEED OF THE SWELL TRAINS. THIS MAKES FOR SLOW CHANGES  
TO THE LARGER SOUTH SWELL EVENTS IN HAWAII.  
 
THE LARGE LOW PRESSURE PATTERN REMAINED ACTIVE 7/8-10 THOUGH WITH  
LESS DIRECT AIM AT HAWAII AND WINDS SUBSIDING TO LOW-END GALES.  
SURF IS EXPECTED TO TREND DOWN WEDNESDAY INTO THURSDAY TO LEVELS  
BELOW AVERAGE FROM 180-200 DEGREES.  
 
BACKGROUND SHORTER-PERIOD TRADE WINDSWELL FROM THE SOUTHERN  
HEMISPHERE WILL LIKELY TOP THE HEIGHTS FROM 140-160 DEGREES FRIDAY  
INTO THE WEEKEND.  
 
MID MONDAY ON EASTERN SHORES HAS BREAKERS AT AN EAST SIDE MINIMUM.  
AN INCREASE IS PREDICTED FOR TUESDAY.  
 
SEE THE LATEST NWS STATE FORECAST DISCUSSION FOR AN EXPLANATION OF  
THE REGIONAL WEATHER PATTERN DRIVING THE UPWARD TRENDING TRADE  
WINDS.  
 
ASCAT SATELLITE 7/14-15 SHOWS AN AREA OF FRESH TO STRONG BREEZES  
OVER THE 10-30 DEGREE BAND NEAR 28-32N, 152-60W THAT COULD GIVE  
SLIGHTLY MORE SURF SIZE TO THE WINDSWELL ON TUESDAY INTO WEDNESDAY  
7/16-17 FROM THE NNE. THIS TINY EVENT COULD ALSO AFFECT SELECT  
NORTH SHORE LOCATIONS.  
 
A WIDE AREA OF FRESH TRADES WITH POCKETS TO STRONG BREEZES E TO NE  
OF HAWAII OUT 1000 NM IS MODELLED TO SET UP 7/16-20. THIS SHOULD  
TREND THE WINDSWELL UP ABOVE AVERAGE BY THURSDAY FROM 70-90  
DEGREES HOLDING INTO SATURDAY.  
 
INTO THE LONG RANGE, TRADE WINDSWELL SHOULD HOVER NEAR THE AVERAGE  
7/21-23 FROM 70-90 DEGREES.  
 
THE TASMAN SEA BECAME THE FOCUS OF LOW PRESSURE PATTERNS STARTING  
7/13. THIS PATTERN IS EXPECTED TO HOLD OFF AND ON OUT A WEEK. THIS  
SHOULD BRING A LONG SPELL WITH DOMINANT BACKGROUND LEVEL SURF FROM  
208-220 DEGREES STARTING ROUGHLY 7/22 OUT A WEEK. PEAK DAYS TO  
NEAR THE AVERAGE.  
 
LONG RANGE FORECASTS ARE SUBJECT TO MAJOR REVISIONS.  
 
THIS COLLABORATIVE FORECAST WILL RESUME ON WEDNESDAY, JULY 17.  
 
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  
 
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