Surf reports are typically made several times per day at select locations around Oahu, primarily by Honolulu City and County lifeguards and the Surf News Network, Inc. Wave heights are reported in Hawaii Scale Feet, which systematically underestimates breaker size by as much as one-half. Although exactly when and why this tendency originated is highly disputed, it became the primary means of communicating surf size by the late 1960s. From publicly available surf reports and other notes from reputable surfers, Mr. Larry Goddard logged heights from 1968 through September 1987 and Mr. Patrick Caldwell has done similarly from September 1987 to 2004. The caretakers of the dataset typically cross-check observations among the various reporters for quality control. The daily value in the GC set represents the upper end of the reported height range, which is roughly equivalent to H1/10, for the observing time and location with the highest breakers along a given coast facing a similar direction. For the north shore, most observations are taken at Sunset Point, which is usually one of the areas of highest surf under the dominant northwest swells. For days of extreme surf with heights greater than 15 HSF, visual observations are reported from Waimea Bay, where breakers are closer to shore. For the south shores, Ala Moana is usually the reporting site. Observations from the west and east side of Oahu have also been recorded although these reports are of lower quality. Comparisons of the GC database to 1981-2002 data from NOAA buoy 51001, which is located roughly 400 km west-northwest of Oahu, show the north shore surf observations are temporally consistent with the shoaling-only, buoy-estimated breaker heights and have an uncertainty of 10 to 15% of the surf height.
To better understand wave height variability
NOAASupplemental: Entry_ID: Unknown Sensor_Name: visual observations Originating_Center: NOAA/NESDIS/NODC/NCDDC Storage_Medium: ASCII text files Online_size: 868 kbyte Resource Description: NODC Accession Number 0001754
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Dept. of Oceanography
University of Hawaii at Manoa
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Surf Observations ================= With the growth of surfing in the 1960s on the north shore, Oahu, came routine observations made by surfers, and later in the 1970s, by lifeguards and commercial surf report ventures. Observations were reported in Hawaii Scale Feet (HSF). Observations are reported as a height range. Observers ignore the smaller waves. As a simplified example, assume a given day has dominant wave energy in the 14-17 second wave period range with negligible energy outside this band. Assume five waves catch the eye of an observer every four minutes, or 100 waves every 80 minutes. This takes into account the time periods of varying length without waves arriving. The upper end of the reporting range is approximately equivalent to the H1/10, the average of the highest 10 waves, which if evenly distributed in time, would occur every 8 minutes. The lower end of the observing range is near the H1/3, or the average of the highest 1/3 waves, which if evenly distributed in time, would occur every 3 minutes. The highest wave over this nominal 80-minute period with 100 waves, or H1/100, would be equivalent to the observer's use of "occasional" heights in their reports. A digital database of surf observations, referred to as the Goddard-Caldwell (GC) set, dates back to August 1968 for the north shore, and to March 1972 for the south shore of Oahu. It is described in more detail in Caldwell (2005). Data are recorded in HSF. The daily values in the GC database refer to the surfing location along the given coast with the highest reported breakers. For the north shore, most observations are taken at Sunset Point, which is usually one of the highest surf spots along the coast under the dominant northwest swell direction. Under north swell, if reports were available from Laniakea, which can be bigger than Sunset, then those were used in the GC set. For days of extreme surf with heights greater than roughly 15 HSF, visual observations are reported at Waimea Bay, where breakers are much closer to shore relative to most of the north shore, which is fringed with offshore reefs. The surf reports are typically made several times per day. The daily value in the GC set represents the upper end of the reported height range for the observing time with the highest breakers. This number aims to be equivalent to H1/10. Comparisons of the GC database to 1981-2002 data from NOAA buoy 51001, which is located roughly 400 km west-northwest of Oahu, show the surf observations are temporally consistent with the shoaling-only, buoy-estimated breaker heights and have an uncertainty of 10 to 15% of the surf height (Caldwell, 2005). Mr. Larry Goddard maintained the database for the North Shore from 1968-9/1987 and the south shore (Ala Moana) from 1972-7/1987. Many observations were his own, but he also received help from reputable surfers such as Randy Rarick, Peter Coles, Bernie Baker, and Lt. Benson. Mr. Goddard assumed the lifeguards underestimate the surf by roughly 15% when the surf is roughly double the size of a surfer up to the levels when Sunset Beach is no longer surfable (15 Hsf). Thus the following back adjustment was made to the Goddard years (1968-8/1987): for surf observations between 5 and 9', 1' was subtracted and for values between 10 and 15', 2' was subtracted. For south shore observations, if a report was not available from Ala Moana, and Mr. Goddard was at home near Maili Point on the west side of Oahu, then Maili was used as a proxy for Ala Moana, which has similar swell exposure and refractive characteristics. Mr. Caldwell began a digital archive of surf observations, coincidently, when Mr. Goddard moved to the mainland and discontinued his set. The Caldwell set from 1987 onward considers the primary source as the Oahu lifeguard and the Surf News Network, Inc. reports, unless more reliable information was provided via a network of surfing friends. The data quality should be higher starting in 1999 due to the availability of Internet cameras at key surf locations. The cameras also provided late day reports under rising swell conditions. The wave direction data began in 1990 based on personal knowledge of Mr. Patrick Caldwell, who has studied the daily weather maps in preparation of surf forecasts. Another technique used was noting the swell sizes on the various sides of the island. For instance, if Makaha is 8', Sunset is 10', and N.Beach is 2', then the direction is obviously dominated by NW component. Since 12/2001, a directional buoy near Waimea, Oahu has improved the wave direction information. For the Windward Surf Index, reports from North Beach on the Kaneohe Marine Corp Base Hawaii were used until 1995 until it was discontinued by the Oahu lifeguard reporting system. Since then, Makapuu has been the primary reporting site, although Mr. Caldwell lives in Kailua Hawaii and has been able to fine tune the estimates personally. The windward index includes both trade wind energy as well as any long period swell from North Pacific sources. Due to potential for large gradients in size along the windward coast during the arrival of long period energy, especially if the direction requires refraction around Kahuku Point, the Windward Surf Index is of less quality. Less confidence is also given to reports from Makaha on the west side. For those wanting to research windswell for Windward Oahu, the historic buoy at Makapuu is the best option. These datasets are archived at NODC under Accession Numbers: 9400105, 950087, 9600143, 9600154, and 9700155. Wind data are a ballpark estimate of open ocean areas, independent of island influence. Usually, the Bellows or Kahuku anemometers are used as a reference during trade wind events, and Honolulu airport under S to SW wind conditions. Use at your discretion. It is highly recommended that research not be performed on these wind data. High quality wind data sets from select locations in Hawaii can be obtained from the National Climatic Data Center. Translation from Hawaii Scale to Trough-to-Crest Heights. A breaker or surf is defined at the moment in time when some portion of the front face of a wave becomes vertical and unstable due to a decrease in water depth. The trough to crest surf height is defined as the vertical distance between the crest and the preceding trough at the moment and location along the wave front of highest cresting, which has been shown in models and observations to be at the time and location of breaking. For locations with high refraction, such as Sunset Point, where most of the visual observations are made, the breaker often forms an A-shape. The trough to crest height refers to the center of the A, i.e., the point along the wave front with the highest height. The translation (Caldwell and Aucan, 2004) of HSF to trough-to-crest heights is a factor of two within the 10-20% margin of error for the full range of breaker sizes encountered in Hawaii. This assumes the height is defined as the highest height reached in the vertical from the trough to crest at any point along the wave front during breaking and zones of high refraction (outer reefs) are included for extreme days when Waimea Bay was the reporting location. The HSF, or simply dividing trough to crest height by two, has been adopted by other big wave enthusiasts around the globe as seen in pictures and dialogue from extreme surf contests in California, Peru, and South Africa. It is important for scientists and the general public to understand this relationship for utilizing surf observations reported in HSF. Note, the Goddard-Caldwell database remains in HSF. Acknowledgements Thanks are given to the surf observers-- lifeguards of the City and County of Honolulu and employees of the Surf News Network. Deep appreciation is given to Mr. Larry Goddard for sharing his digital database of surf observations. For his set of data, thanks go out to the various lifeguard reporters and reputable surfers: Randy Rarick, Peter Cole, Bernie Baker, and Albert Benson. For the Caldwell set, thanks are given to Garret McNamara, Ian Masterson, Kaleo Ahina, Robert Yonover, and Clark Abbey for surf information which was used in cross checking the lifeguard reports. While the author was away from the island, various students and staff at the University of Hawaii and Windward Community College Surf Science and Technology class have logged daily reports, a few of which include: Ian Masterson, Kaleo Ahina, Shaun Johnston, Eric Grossman, Jerome Aucan, Yvonne Firing, Kimball Millikan, and Robert Burke. Great thanks go out to all these individuals. For access to the digital cameras, appreciation is given to Surfline, Inc. (www.surfline.com), and for daily surf notes and pictures, thanks are extended to Jamie Ballenger (www.hawaiianwatershots.com) and Claudia Ferrari (www.claudiaferrari.com/news.htm).
Files are stored in directory ../../data File names: oahuyyyy.dat, where yyyy = year Surf Heights given in Hawaii Scale Feet. Trough-to-Crest heights are double the Hawaii Scale Feet heights within the 10-20% margin of error. format layout, columns as: yyyy mm dd nshor wshor almo dh winw wspd wdir nsd ssd 2000 1 1 8 4 1 2 3 2 17 15 999 2000 1 2 5 2 1 2 2 2 17 15 999 2000 1 3 4 2 1 2 2 2 17 15 999 nshor (North Shore, Oahu, mostly Sunset until > 15', then Waimea) wshor (Makaha) almo (South Shore, Oahu, Ala Moana Bowls) dh (Diamond Head) winw (Windward Oahu (east side) index) wspd (wind speed in beaufort for open waters) wdir (wind direction, coded 1=N 2=NNE 3=NE, etc ... 16=NNW 17:light and variable) nsd (north shore wave direction as above) ssd (south shore direction) note for swell directions, 18:mixed usually only the dominant direction is given, ignoring mixed conditions, which happen commonly missing data flag for all fields: 999
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