Outlook through Saturday October 25: waves produced by hurricane Ana will maintain elevated surf along south facing shores through tonight. Also, an above normal northwest swell has arrived resulting in a high surf advisory for the north and west facing shores that will last through tonight. Expect these two swells to slowly subside through Monday. A new but small north northwest swell is on tap for Thursday, continuing through Friday. Surf heights are forecast heights of the face or front of waves. The surf forecast is based on the significant wave height, the average height of the one third largest waves, in the zone of maximum refraction. Some waves may be more than twice as high as the significant wave height. Expect to encounter rip currents in or near any surf zone.
HIGH SURF ADVISORY FOR NORTH SOUTH AND WEST FACING SHORES
Surf along north facing shores will be 10 to 15 feet through tonight, lowering to 9 to 13 feet Monday. Surf along west facing shores will be 8 to 12 feet through tonight, lowering to 6 to 9 feet Monday. Surf along south facing shores will be 5 to 8 feet through tonight and continue lowering to 3 to 6 feet Monday. Surf along east facing shores will be 3 to 6 feet through tonight, and 2 to 4 feet through Monday.
About Collaborative Surf
This collaborative forecast will be updated Monday through Friday at 300 pm when Pat Caldwell is available.
Collaborative Surf Discussion
SURF HEIGHTS WILL VARY BETWEEN DIFFERENT BEACHES AND AT THE SAME BEACH AT DIFFERENT BREAK AREAS. DISCUSSION: Summary: hurricane Ana making extra-rough surf for SE to S exposures for Saturday into Sunday and an Aleutian extratropical cyclone building north shores late Saturday holding above average Sunday through Monday. Detailed: mid Friday on southern shores has heights typical of October at levels just above flat. A rapid rise is due overnight. See the latest NWS Central Pacific Hurricane Center forecasts concerning hurricane Ana. Stay tuned to the latest predictions of track, location, and intensity. The proximity to Oahu means small errors in these characteristics can make for large errors in local wind, wave.and weather effects. Based on the 11 am HST Friday 10/17 track and intensity, Ana should clear the Big Island shadow mid Friday, arrive at a location south of Oahu on Saturday morning, and move SW of Oahu by Sunday. This should make for a rapid rise and fall of the surf. Surf is expected to build Friday night from 120-140 degrees and continue to rise on Saturday from 120-160 degrees. Proximity means extra-rough conditions with energetic short-period waves of 6-12 second intervals. This would make for a less organized breaking pattern with more waves per set and more frequent sets. In turn.the near shore pile up of water from the frequent arrivals would enhance the near shore currents. Neap tidal conditions are timely coinciding with this event. See specifics on surf-induced flooding expectations in the NWS hurricane Ana local statement. The seas and rough surf off Oahu from Ana are expected to reach a maximum Saturday night from 130-180 degrees. Extra-rough conditions are predicted to continue on Sunday morning, with a steady drop mid Sunday into Sunday night. Southern shores should return to below average surf levels by Monday. No other sources of surf are expected this period. Stay tuned to the latest forecasts in the event of unsuspected changes to the intensity and track. Mid Friday on eastern shores has below average breakers from windswell out of 50-90 degrees. Heights should increase on Saturday. Exposures to northerly swell should remain active through the period as described below for north shores. Enhanced winds from Ana over Oahu Saturday into Sunday are not expected to extend far to the E to NE. Thus.the short fetch should keep the dominant wave periods low. Windswell will likely peak on Saturday from 50-90 degrees and decrease rapidly on Sunday since Oahu would be in the Molokai shadow as the winds veer to SE. Surf from windswell is predicted to be below average Monday to Wednesday. Mid Friday on northern shores has a mix of swell with below October average heights. A new episode is due on Saturday. Low.long-period swell from typhoon Vongfong a week ago S of Japan have been registered by the pacioos near shore buoys off SW and N Oahu. This energy should remain low into Saturday with below average breakers for a few select locations. A broad area of low pressure tracked from the NW Pacific to the gulf of Alaska 10/12-15. The surface winds aimed at Hawaii were strong to near gale and beyond 1600 nm away. Low swell from 315-345 degrees is arriving locally on 10/17. This event is expected to drop on Saturday. A gale low hugging the eastern Aleutians 10/11-12 aimed highest seas east of Oahu. Angular spreading brought surf in locally 10/16 from 350-020 degrees, peaking Thursday night.and dropping on Friday 10/17. Low leftovers are expected on Saturday. The remnant of Vongfong was absorbed into a mid latitude low pressure system and gained eastward track to the SE of Kamchatka on 10/12 with a rapid movement along the central Aleutians. The storm-force system reached the dateline early Thursday with the head of the fetch over the 320-330 degree band about 1600 nm away. On Friday, the system is in the gulf of Alaska with a long, wide fetch over the 330-350 degree band nosing to near 1000 nm away. Models show the system moving east of the Hawaii swell window late Saturday. Long-period forerunners are expected locally Saturday afternoon from 310-320 degrees. Heights should climb above average overnight Saturday and continue to rise on Sunday from 315-330 degrees. Heights should remain above average on Monday from 315-350 degrees. The event should drop off to near average October levels by Tuesday from 340-010 degrees, and drop below average on Wednesday from 350-020 degrees. Into the long range, a compact gale low pressure is modelled to track from Kamchatka along the Aleutians to the dateline 10/18-19. This could make for below to near average October level surf picking up Thursday 10/23 from 315-330 degrees. Models show the system deepening and broadening in the gulf of Alaska by Tuesday, that could lead to above average surf from 350-010 degrees for the weekend of 10/25. Uncertain potential for W to NW surf from Ana will be monitored. From the southern hemisphere, no surf beyond negligible is expected 10/23-25. Long range forecasts are subject to high uncertainty. This collaborative forecast will resume on Monday, October 20. This forecast was produced through the collaborative efforts of NWS and NCDDC. Please send suggestions to email@example.com or call the Warning Coordination Meteorologist at 808-973-5275. Additional resources: see /in lowercase/ http://www.prh.noaa.gov/hnl/pages/marine.php.
Collaborative Surf Table
Collaborative Surf Table 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 OF 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)|
NWS FORECASTER AND NCDDC PAT CALDWELL