# So where do 70 foot freak waves come from. Other ships sunk? **URL:** \ **Category:** Factual Questions\ **Created:** [April 18, 2005, 3:39am UTC](https://boards.straightdope.com/t/so-where-do-70-foot-freak-waves-come-from-other-ships-sunk/299843 "2005-04-18T03:39:52Z")\ **Posts on this page:** 15\ **Page:** 3
**Author:** ![wevets](https://avatars.discourse-cdn.com/v4/letter/w/e9a140/32.png) [@wevets](https://boards.straightdope.com/u/wevets)\ **Post date:** [December 14, 2016, 3:43pm UTC](https://boards.straightdope.com/t/so-where-do-70-foot-freak-waves-come-from-other-ships-sunk/299843/41 "2016-12-14T15:43:21Z")
Buoys are generally tethered to the bottom - letting them float freely could be a hazard to navigation. There are some that do, but most buoys need to stay in pretty much the same location over time. Even those that are anchored may move, depending on the type of anchor - a large concrete weight is common, although if the depth and sea floor type permits, a buoy may be bolted to the bottom. The tether may have some give, but in extremely high wave conditions, the buoy may run out of tether and wind up submerged. Buoys (at least National Oceanic and Atmospheric Administration buoys in the U.S.) measure wave height through internal accelerometers and inclinometers. GPS can sometimes give sufficiently accurate elevation information, but does not work at all when the buoy is submerged. > [@National Buoy Data Center](#): > > NDBC-reported wave measurements are not directly measured by sensors on board the buoys. Instead, the accelerometers or inclinometers on board the buoys measure the heave acceleration or the vertical displacement of the buoy hull during the wave acquisition time. A Fast Fourier Transform (FFT) is applied to the data by the processor on board the buoy to transform the data from the temporal domain into the frequency domain. Note that the raw acceleration or displacement measurements are not transmitted shore-side. Response amplitude operator (RAO) processing is then performed on the transformed data to account for both hull and electronic noise. It is from this transformation that non-directional spectral wave measurements (i.e., wave energies with their associated frequencies) are derived. Along with the spectral energies, measurements such as significant wave height (WVHGT), average wave period (AVGPD), and dominant period (DOMPD) are also derived from the transformation. [http://www.ndbc.noaa.gov/wave.shtml](http://www.ndbc.noaa.gov/wave.shtml) Here’s a good diagram showing how buoys are commonly anchored to the sea floor depending on depth: [![](https://www.weather.gov/images/tae/mooring.gif) ](https://www.weather.gov/images/tae/mooring.gif) ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [December 14, 2016, 3:53pm UTC](https://boards.straightdope.com/t/so-where-do-70-foot-freak-waves-come-from-other-ships-sunk/299843/42 "2016-12-14T15:53:30Z")
Apparently some are drifting: I imagine that they are fairly small and made of plastic, so they would not be a navigation hazard. > [@](#): > > “Despite the huge strides in satellite technology, the sustained observations and data records from moored and drifting buoys and ships still play a major role in this respect.” > > [62.3ft wave between UK and Iceland sets a world record](http://www.telegraph.co.uk/news/2016/12/13/six-storey-high-wave-inbetween-uk-iceland-sets-world-record/) And 19 metres (62’4") is the new world record so 70’ seems an exaggeration. ---
**Author:** ![TroutMan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/troutman/32/6721_2.png) [@TroutMan](https://boards.straightdope.com/u/TroutMan)\ **Post date:** [December 14, 2016, 4:19pm UTC](https://boards.straightdope.com/t/so-where-do-70-foot-freak-waves-come-from-other-ships-sunk/299843/43 "2016-12-14T16:19:13Z")
> [@bob\_2](#): > > And 19 metres (62’4") is the new world record so 70’ seems an exaggeration. This was the record for largest wave measured by a buoy. In the same article, it mentions a surfer who rode a 78’ wave, so 70’ is certainly possible. Of course, that doesn’t preclude the possibility that the height of the waves from the OP were exaggerated, which is very likely. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [December 14, 2016, 4:23pm UTC](https://boards.straightdope.com/t/so-where-do-70-foot-freak-waves-come-from-other-ships-sunk/299843/44 "2016-12-14T16:23:38Z")
nm - Ninja’d by **wevets**. Good stuff at that site. I use it to watch hurricanes and such. ---
**Author:** ![notfrommensa](https://avatars.discourse-cdn.com/v4/letter/n/f14d63/32.png) [@notfrommensa](https://boards.straightdope.com/u/notfrommensa)\ **Post date:** [December 14, 2016, 5:17pm UTC](https://boards.straightdope.com/t/so-where-do-70-foot-freak-waves-come-from-other-ships-sunk/299843/45 "2016-12-14T17:17:10Z")
The wave in the article was measured in Feb-2013. Why is this news now, almost 4 years later? ---
**Author:** ![TroutMan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/troutman/32/6721_2.png) [@TroutMan](https://boards.straightdope.com/u/TroutMan)\ **Post date:** [December 14, 2016, 5:36pm UTC](https://boards.straightdope.com/t/so-where-do-70-foot-freak-waves-come-from-other-ships-sunk/299843/46 "2016-12-14T17:36:30Z")
“The organization said the delay in confirming the new record was due to the time it took to analyze, cross-check and verify the data.” ---
**Author:** ![Robot\_Arm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robot_arm/32/18280_2.png) [@Robot\_Arm](https://boards.straightdope.com/u/Robot_Arm)\ **Post date:** [December 14, 2016, 5:55pm UTC](https://boards.straightdope.com/t/so-where-do-70-foot-freak-waves-come-from-other-ships-sunk/299843/47 "2016-12-14T17:55:58Z")
> [@wevets](#): > > Here’s a good diagram showing how buoys are commonly anchored to the sea floor depending on depth: > [http://www.weather.gov/images/tae/mooring.gif](http://www.weather.gov/images/tae/mooring.gif) Interesting. I didn’t realize there were moored buoys in such deep water (and, presumably, very far from the nearest shore). I assume that skilled mariners know to look out for them so they don’t get run over by a supertanker or something. > [@TroutMan](#): > > This was the record for largest wave measured by a buoy. In the same article, it mentions a surfer who rode a 78’ wave, so 70’ is certainly possible. Of course, that doesn’t preclude the possibility that the height of the waves from the OP were exaggerated, which is very likely. Waves build up and break as they get to shallower water where the surfers hang out. Comparing a mid-ocean swell to a breaking wave at a beach is not really the same thing. ---
**Author:** ![notfrommensa](https://avatars.discourse-cdn.com/v4/letter/n/f14d63/32.png) [@notfrommensa](https://boards.straightdope.com/u/notfrommensa)\ **Post date:** [December 14, 2016, 6:09pm UTC](https://boards.straightdope.com/t/so-where-do-70-foot-freak-waves-come-from-other-ships-sunk/299843/48 "2016-12-14T18:09:47Z")
> [@TroutMan](#): > > “The organization said the delay in confirming the new record was due to the time it took to analyze, cross-check and verify the data.” Nearly 4 years? Maybe I’ll use this as an excuse to delay paying my taxes. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [December 14, 2016, 6:39pm UTC](https://boards.straightdope.com/t/so-where-do-70-foot-freak-waves-come-from-other-ships-sunk/299843/49 "2016-12-14T18:39:56Z")
I once saw a Lake Michigan weather buoy report a 255-foot wave, followed by a zero wave height. Since a wave that large, if it came ashore, would have inundated my house with 200 ft of water, and that didn’t happen, I’m inclined to think this was a single byte digital sensor that went nuts, and reported all binary ones for an instant. Which won’t stop me from looking out the window if it happens again. ---
**Author:** ![Gray\_Ghost](https://avatars.discourse-cdn.com/v4/letter/g/c0e974/32.png) [@Gray\_Ghost](https://boards.straightdope.com/u/Gray_Ghost)\ **Post date:** [December 14, 2016, 10:41pm UTC](https://boards.straightdope.com/t/so-where-do-70-foot-freak-waves-come-from-other-ships-sunk/299843/50 "2016-12-14T22:41:33Z")
Other large waves reliably measured: [ul] [li][The rogue wave that struck the Draupner Platform](https://en.wikipedia.org/wiki/Draupner_wave) on 1 January 1995, and was measured at 84 feet high with a laser heightfinder. That platform is roughly 90 miles off the shore of Norway, in about 230 feet of water.[/li][li]Depending on your belief in the crew’s trigonometry abilities, [the wave that SS Ramapo encountered in a massive storm in the Pacific Ocean on 7 February 1933.](http://hyperphysics.phy-astr.gsu.edu/hbase/watwav.html) A bridge officer calculated, based on sightlines from the stern and crows’ nest, that the waves the ship was enduring were over 110 feet high.[/li][/ul] Edit, and though not the same as a wind wave, the [gigantic landslide-caused waves in Lituya Bay](https://en.wikipedia.org/wiki/1958_Lituya_Bay_megatsunami), Alaska, are probably of interest. Washing away trees that are 1600 feet plus above the water is a whole lot of splash. I’d heard before of the 1958 wave I’ve linked to, but didn’t realize that such waves there are, on a geologic time scale, rather common. ---
**Author:** ![Chefguy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chefguy/32/138_2.png) [@Chefguy](https://boards.straightdope.com/u/Chefguy)\ **Post date:** [December 15, 2016, 12:22am UTC](https://boards.straightdope.com/t/so-where-do-70-foot-freak-waves-come-from-other-ships-sunk/299843/51 "2016-12-15T00:22:29Z")
I’m thinking they come from 70-foot freaks. Don’t know if that was pointed out back in 2005. ---
**Author:** ![Sunny\_Daze](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunny_daze/32/438_2.png) [@Sunny\_Daze](https://boards.straightdope.com/u/Sunny_Daze)\ **Post date:** [December 15, 2016, 2:24am UTC](https://boards.straightdope.com/t/so-where-do-70-foot-freak-waves-come-from-other-ships-sunk/299843/52 "2016-12-15T02:24:17Z")
If you do a little digging, a number of other, taller waves have been recorded. Perhaps what is significant about this one is the location and the buoy? For example, during the infamous “Perfect Storm”, > [@](#): > > A buoy off the coast of Nova Scotia reported a wave height of 100.7 feet (30.7 m), the highest ever recorded in the province’s offshore waters. [cite](https://en.wikipedia.org/wiki/1991_Perfect_Storm) The Alaska earthquake in 1964 generated several tsunamis, one of which was 219 feet. In Lituya Bay, in 1958, a tsunami reached over 1,700 feet (not a rogue wave and thankfully a very confined phenomenon). [cite](http://qz.com/193139/the-biggest-tsunami-recorded-was-1720-feet-tall-and-chances-are-good-it-will-happen-again/) Hurricane Ivan proved that hurricanes can generate very large waves that are not rogues, but are simply a function of the storm. Ivan went over an array of Naval Research Laboratory equipment in the Gulf of Mexico and revealed that 90 foot waves were common. [cite](http://www.livescience.com/364-hurricane-waves-soared-100-feet.html) There’s more out there if you look for it. TL;DR not sure why this wave is a story. There are well documented cases of bigger waves. Given the right conditions (hurricanes, for example), very big waves appear to be relatively common. ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [December 16, 2016, 2:03pm UTC](https://boards.straightdope.com/t/so-where-do-70-foot-freak-waves-come-from-other-ships-sunk/299843/53 "2016-12-16T14:03:55Z")
> [@NurseCarmen](#): > > I’d say 70 is a little extreme for 30 foot seas, but I’d venture to guess it would be more possible with 40 foot seas. > > One thing for sure, It’d suck to be on the boat. I sail, and heavy seas can occasionaly get me feeling queasy if I can’t see the horizon. It’s hard to see the horizon in a big floating hotel. Swells are long wave length and have the sinusoidal shape and travel the ocean. Seas are caused by local wind and have a more triangular shape… the approaching front is steeper because the water is being pushed along rather then pushed down. In the storm the seas and swells usually are at different times, but if a sea wave can add to the swell… now you can get multiple swells or multiple sea hit in all the combinations. A shallow lake could have a wave formed by storm surge… because the storm surge is significant amount of water compared to the depth… the energy of the surge is not going to dissipate into the depths, its going to remain a surface wave. ---
**Author:** ![Fubaya](https://avatars.discourse-cdn.com/v4/letter/f/c2a13f/32.png) [@Fubaya](https://boards.straightdope.com/u/Fubaya)\ **Post date:** [December 17, 2016, 12:12am UTC](https://boards.straightdope.com/t/so-where-do-70-foot-freak-waves-come-from-other-ships-sunk/299843/54 "2016-12-17T00:12:51Z")
The article is wrong. It says “Wave height is defined as the distance from the crest of one wave to the trough of the next.” Ok, that’s true, but the buoy actually measured “ **significant wave height** ,” which is different. It’s the average of the highest 1/3 of waves measured by an instrument, usually considered to be about 15-20 waves. So this 62.3 feet record is the average of the tallest 15-20 waves that were passing the buoy at the time. Actual wave heights can be estimated to be from 60-200% of that number, and in fact, the buoy actually recorded one wave that looks to have been about 27 meters: [World Meteorological Organization's World Weather & Climate Extremes Archive](https://wmo.asu.edu/content/World-Highest-Wave-Buoy) EDIT: I’m slightly off in that last sentence. That graph is hourly significant wave heights covering several months. The 27 meter wave doesn’t appear to be on the same date as the record breaker. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [December 17, 2016, 1:52pm UTC](https://boards.straightdope.com/t/so-where-do-70-foot-freak-waves-come-from-other-ships-sunk/299843/55 "2016-12-17T13:52:39Z")
> [@Fubaya](#): > > The article is wrong. It says “Wave height is defined as the distance from the crest of one wave to the trough of the next.” > … I agree with all you’ve said. Although I’d go a bit further than that. Absent any qualifier, “distance” means in the horizontal direction, not vertical. Also, “trough of the next” is the trough following the crest following the crest they’re referencing. Far better had they said “Wave height is defined as the [del]distance[/del] \*height difference \*from the crest of one wave to the _following_ trough [del]of the next[/del].” It’s not that hard to write a minimally ambiguous sentence. But they have to bother to try. Idjits. [Previous page](https://boards.straightdope.com/t/so-where-do-70-foot-freak-waves-come-from-other-ships-sunk/299843.md?page=2)