Surf News

Gary Kewley
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Friday - February 17, 2006
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Surf forecast guru Pat Caldwell
Surf forecast guru Pat Caldwell

Aloha, surfers and beachgoers! Howzit? Last weekend we had it good - up to 10 feet! Thursday (2/16) should find near 8-10 footers before declining into this weekend. Then after this swell we’ll start needing more luck for the really BIG surf. Why? Well, the winter season is just starting to bid us farewell. Nothing lasts forever ... Of course, by April the Southern Hemisphere comes into its winter. This begins to awaken our south shores for summer. But I can’t really be talking about that already, can I?

What I can talk about is the fascinating subject of how we judge (and use) the measure-ment/size of waves. Now this is an extremely delicate issue for many so I’m going to tread lightly. I had the chance to talk with Hawaii’s modern-day surf forecast guru Pat Caldwell. Now, Pat is reluctant regarding his title that surfers gave him. But trust me ... he’s that good. You can log on to Pat’s link at and read his weekly forecast in detail. I’ll also post his published paper on the “Hawaii Scale.” Pat knows how to word his high-tech analysis so regular surfers can understand it. He’s accurate, period. I’m grateful to be a friend and student of his.

Pat is the 45-year-old NOAA Data Center Liaison for Hawaii; married nine years to Diana and proud dad to 5-year-old Cassie (one of the top monkey bar swingers in her kindergarten class). Pat loves the ocean and has geared his entire life around it ... for surfing and windsurfing. Professionally he’s on it. Pat recently published an important paper on the subject of judging waves according to the Hawaii Scale, or better known as the “local scale” in “The Validity of North Shore Oahu Surf Observations” in The Journal of Coastal Research (JRC). In a nutshell: The Hawaii Scale is scientifically valid. Now the hard-core surf crew who have dominated our surf estimations the past 40 years can rest assured they’ve been consistent over time ... Stoked! (But we knew that.)

GQ: Isn’t the theory that the local scale came about by measuring from the “back” of waves untrue? I’ve never ridden there, and if I’m seeing the back I’ve just missed my wave ...

Pat: Right. One of the important points I make is that the observations that have been maintained are in Hawaii Scale, but how it came about I’m not concerned with. I’m only concerned that there’s an important “data set” here ... it has a lot of applications for science and coastal research. So I’m not going to get bogged down with the whole local vs. face value issue. All I see is this as a resource that’s available which can help us better understand climatology, coastal erosion, and better our surf forecasting.

GQ: That’s your job over there, to collect and manage data and determine its quality, right?

Pat: Exactly. Basically I’m an ocean data librarian. I’m 19 years in this job now. We save all measurements from buoys and ships, etc. The surf observations were started as a personal interest back when I arrived in Hawaii in 1987. I met Larry Goddard in the late 1990s and found out he did similarly since 1968. Combining our data sets makes this year our 39th year of daily surf observations.

GQ: And so you’ve collected all this data in Hawaii Scale feet? It’s the scale used by SURF NEWS NETWORK for its 30 years in business.

Pat:Yes. Even today, most surf observers and the coconut wireless communicate in Hawaii Scale. I continue to use Hawaii Scale in the data base for consistency. I have a second publication already accepted by the JRC that derived a translation from Hawaii to face height based on photographic evidence. So the user of the data can change the values to “face,” if desired.

GQ: How did you show that the Hawaii Scale was consistent?

Pat: I computed the daily difference between surf observations and estimated surf heights derived from buoy 51001 (No. 1) northwest of Kauai over 1981-2002 and the Waimea Buoy during 2002. The buoy estimate was based on a standard oceano-graphic formula. The buoy and formula were the same through the period, so if the difference changed, then it would suggest the “human element” changed. However, the difference showed no trend. In other words, 10 Hawaii Scale in 1981 is the same as 10 Hawaii Scale today. Consistency is essential for scientific integrity. In the paper I also provide a surf climatology - one of the products showing how many large to giant days per season revealing many year to year fluctuations, but no long term trend. This suggests the surf observations are also consistent back to 1968.

GQ: What types of studies are being done with the surf data?

Pat: I’ve used these data to derive a formula to estimate surf height given open ocean swell height and period, which can be taken from buoy or wave models. The transformation from deep water to shore is complex, and this formula will greatly improve surf forecasts. This work is being published in JRC this year. Surf is used for a variety of environmental science and engineering applications, such as coastal erosion and coral reef habitat variability.

GQ: What type of error bars do the observations have?

Pat: It ranges from 1-3 feet Hawaii Scale, with the error increasing with height. At 12, the error is 2 Hawaii Scale, meaning the actual height may be in the range of 10 to 14.

GQ: OK ... I like this ... but I’m running out of space and want to know much more! So gang, please be here next issue to cover this issue! Pat Caldwell and I will be here! Will you?

And Pat, a million mahalos for your time, effort and brains!

P.S. Pipe Girls: Get your entries into the T&C Women’s Pipeline Surfing Championships coming up in March! Go to for the scoops. Also, Friends of Kewalo Basin is part of the President’s Day Ho’olaulea ... go to for more.

I’m GQ, dropping in 4 U!

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