438  
FXHW52 PHFO 160103  
SRDHFO  
 
COLLABORATIVE NEARSHORE SWELL AND WIND FORECAST FOR OAHU  
NWS/NCEI HONOLULU HI  
303 PM HST FRI FEB 15 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 10 NE 11 10 14 DOWN 19-23 NE SAME  
02/15 2 NW 13 2 4 DOWN  
 
SAT 12 NE 11 14 18 UP MED 11-16 N DOWN  
02/16 3 WNW 20 6 8 UP LOW  
 
SUN 8 NNE 10 10 12 DOWN LOW 4-6 VRB SAME  
02/17 4 NNE 14 6 8 UP MED  
6 ENE 9 5 7 UP LOW  
5 NW 17 8 12 SAME LOW  
 
MON 5 N 10 5 7 DOWN LOW 4-6 VRB SAME  
02/18 5 ENE 10 5 7 SAME LOW  
4 NW 14 6 8 DOWN LOW  
 
TUE 5 NNW 11 6 10 UP LOW 7-10 E UP  
02/19 5 ENE 10 5 7 SAME LOW  
3 NW 12 4 6 DOWN LOW  
 
WED 3 NNW 10 3 5 DOWN LOW 9-13 NNE UP  
02/20 6 ENE 10 6 8 UP LOW  
2 NW 13 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...  
NW EVENT FOR THE LONG WEEKEND AS N THROUGH E REMAINS ACTIVE.  
 
DETAILED...  
MID FRIDAY ON NORTHERN SHORES HAS BREAKERS FROM A MIX OF  
DIRECTIONS AT LEVELS BELOW THE WINTER AVERAGE. A LOW NW EVENT IS  
DROPPING 2/15 WITH A RISING, LONG-PERIOD WNW EVENT FOR SATURDAY  
PM 2/16.  
 
A HURRICANE-FORCE LOW PRESSURE SYSTEM IN THE FAR NW PACIFIC  
2/12-13 TRACKED SLOWLY NNE. IT WEAKENED AS IT ENTERED THE WESTERN  
BERING SEA 2/14-15.  
 
A LONG-WIDE FETCH SET UP OVER THE 305-320 DEGREE BAND WITH HIGHEST  
SEAS 2/13 TO NEAR 40 FEET BEYOND 2400 NM FROM HAWAII. THE SOURCE  
ZONE STAYED MOSTLY WEST OF 165E. THE LONG TRAVEL DISTANCE LOWERS  
LOCAL SURF POTENTIAL.  
 
LONG-PERIOD FORERUNNERS FROM 305-315 DEGREES ARE EXPECTED LOCALLY  
SATURDAY AFTERNOON 2/16. THE EVENT SHOULD BE FILLED IN BY SUNDAY  
2/17 DAWN FROM 305-320 DEGREES A NOTCH UNDER THE WINTER AVERAGE.  
IT SHOULD SLOWLY DROP SUNDAY NIGHT INTO TUESDAY FROM THE SAME  
DIRECTION. MARGINAL GALES FROM 2/15 OUT NEAR 170E COULD KEEP SMALL  
BREAKERS FROM 305-315 DEGREES ON WEDNESDAY.  
 
NORTHERN EXPOSURES SHOULD ALSO HAVE ACTIVE SURF STARTING OUT NE  
SATURDAY, BACKING TOWARD N BY SUNDAY AND HOLDING INTO WEDNESDAY WITHIN  
NNW TO NNE FROM A NEARBY SOURCE. FURTHER DETAILS ARE GIVEN BELOW.  
 
LONG-PERIOD SWELL ARE ALSO EXPECTED SUNDAY FROM 010-020 DEGREES.  
IT WAS GENERATED BY SEVERE GALES IN THE GULF OF ALASKA 2/14-15  
THAT WERE AIMED HIGHEST AT THE WEST COAST OF THE USA. IT SHOULD  
DROP MONDAY AS IT IS OVERSHADOWED BY THE NEARBY-GENERATED SURF OF  
SIMILAR DIRECTION.  
 
MID FRIDAY ON EASTERN SHORES HAS BREAKERS FROM 20-70 DEGREES WELL  
ABOVE THE TRADE WINDSWELL AVERAGE. HEIGHTS ARE PREDICTED TO  
INCREASE ON SATURDAY.  
 
SEE THE LATEST NWS STATE FORECAST DISCUSSION REGARDING THE  
UNSETTLED WEATHER AND CHANGING WINDS ASSOCIATED WITH UPPER LEVEL  
DISTURBANCES IN THE VICINITY THROUGH THE PERIOD.  
 
SURFACE HIGH PRESSURE ALONG 40 N TO THE N TO NE OF HAWAII HAS HELD  
ALL WEEK AND IS MODELLED TO HOLD THROUGH THE PERIOD. TIGHT  
PRESSURE GRADIENT BETWEEN THE STRONG HIGH AND THE SURFACE LOW  
PRESSURE AREAS NEAR HAWAII AND STRETCHING TOWARD CALIFORNIA HAVE  
ALLOWED A LARGE AREA OF STRONG TO MARGINAL GALES WINDS AIMED AT  
HAWAII. THIS HAD KEPT THE SURF UP ALL WEEK FROM NNE TO ENE.  
 
ASCAT SATELLITE FRIDAY MORNING 2/15 SHOWS A LARGE AREA OF 30 KNOT  
WINDS ON THE NORTH SIDE OF THE SURFACE LOW TO THE IMMEDIATE ENE  
OF HAWAII. WAVE MODEL OUTPUT INCREASES THE LOCAL COMBINED SEAS  
AND SWELL FROM THIS SOURCE ON SATURDAY, WITH SURF EXPECTED TO  
CLIMB FROM 20-70 DEGREES.  
 
WITH THE WESTWARD SHIFT OF THE NEARBY LOW PRESSURE AREA, MODELS  
SHOW ADDITIONAL SHORT- TO MODERATE-PERIOD SWELL PICKING UP ON OAHU  
SUNDAY AND HOLDING INTO WEDNESDAY WITHIN NNW TO NNE.  
 
A FETCH OVER THE 50-70 DEGREE BAND E OF HAWAII HAS SET UP 2/15 AND  
EXPECTED TO HOLD INTO MID NEXT WEEK. THIS SHOULD ADD MORE  
E-COMPONENT WINDSWELL STARTING LATE SATURDAY AND HOLDING INTO NEXT  
WEDNESDAY AT LEVELS ABOVE AVERAGE.  
 
GIVEN THE OVERLAPPING EVENTS DESCRIBED ABOVE, THE EASTERN SIDE IS  
EXPECTED TO REMAIN ABOVE AVERAGE THROUGH THE PERIOD FROM A WIDE  
DIRECTIONAL SPREAD. WAXING SPRING TIDES SHOULD ENHANCE WAVE RUN-  
UP DURING THE HIGHER HIGH TIDES NEAR DAWN THROUGH THE PERIOD.  
 
MID FRIDAY ON SOUTHERN SHORES HAS NEAR NIL CONDITIONS. HEIGHTS  
SHOULD REMAIN LOW ON SATURDAY.  
 
THE INCREASING E-COMPONENT TO THE WINDSWELL SHOULD TREND SELECT  
MORE EASTERLY EXPOSURES UP OVER THE WEEKEND AND HOLD NEXT WEEK.  
 
TROPICAL CYCLONIC ACTIVITY NEAR VANUATU 2/11-15 IS EXPECTED TO  
ADD LOW, MODERATE PERIOD SWELL WITHIN 13-15S FROM 220-240 DEGREES  
SUNDAY 2/17 INTO MID WEEK WITH TINY TO SMALL BREAKERS.  
 
INTO THE LONG RANGE, NO SURF BEYOND TINY TO SMALL IS EXPECTED  
FROM THE SOUTHERN HEMISPHERE 2/21-23.  
 
NW SHORES ARE EXPECTED TO REMAIN BELOW AVERAGE 2/21-23. N TO E  
SHORES SHOULD TOP THE HEIGHTS WITH ABOVE AVERAGE SHORTER-PERIOD  
BREAKERS 2/21-23.  
 
LONG RANGE FORECASTS ARE SUBJECT TO HIGH UNCERTAINTY.  
 
THIS COLLABORATIVE FORECAST WILL RESUME ON TUESDAY, FEBRUARY 19.  
 
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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