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wave_basics [2024/02/19 15:40] preavley |
wave_basics [2026/01/12 00:56] (current) pstureavley |
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| - | **Waves and Boat Wakes for Paddlers** | + | **Understanding Waves and Boat Wakes for Paddlers** |
| {{youtube>qjtnza-LOWY?large}} | {{youtube>qjtnza-LOWY?large}} | ||
| + | |||
| + | This video has a good section on surfing boat wakes | ||
| </WRAP> | </WRAP> | ||
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| <WRAP indent> | <WRAP indent> | ||
| + | |||
| + | ---- | ||
| ==== Swell and Wind Waves ==== | ==== Swell and Wind Waves ==== | ||
| <WRAP indent> | <WRAP indent> | ||
| + | |||
| + | ---- | ||
| are both primarily generated by wind or wind events like storms. | are both primarily generated by wind or wind events like storms. | ||
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| **Swell** refers to waves that have moved beyond the area of wind that generated them, sometimes traveling great distances and not "affected" by the local wind (the swell retains its size and speed - although it can be masked or made less visually obvious by large local wind waves). Swell waves tend to be longer and faster than local wind waves. "**Groundswell"**or** "ground swell**" refers to swell that has traveled 1000's of miles and is often identified by a period (time between waves) of more than 15 seconds. | **Swell** refers to waves that have moved beyond the area of wind that generated them, sometimes traveling great distances and not "affected" by the local wind (the swell retains its size and speed - although it can be masked or made less visually obvious by large local wind waves). Swell waves tend to be longer and faster than local wind waves. "**Groundswell"**or** "ground swell**" refers to swell that has traveled 1000's of miles and is often identified by a period (time between waves) of more than 15 seconds. | ||
| - | **Larger Waves ** (including [[https://www.sciencealert.com/a-rogue-wave-four-stories-high-is-the-largest-on-record|Freak Waves]], and [[https://www.nps.gov/articles/coastal-geohazards-seiches.htm|Seiches]]) - wave size increase happens when: | + | * **[[:wavedynamics|Swell Dynamics in Downwinding]]** |
| + | **Larger Waves ** (including [[https://www.sciencealert.com/a-rogue-wave-four-stories-high-is-the-largest-on-record|Freak Waves]], and [[https://www.nps.gov/articles/coastal-geohazards-seiches.htm|Seiches]]) - wave size increase happens when: | ||
| * Wind puts pressure against strong ocean current | * Wind puts pressure against strong ocean current | ||
| * Ocean depth change is dramatic | * Ocean depth change is dramatic | ||
| * Two close storms cause overlapping waves | * Two close storms cause overlapping waves | ||
| + | * … | ||
| </WRAP> | </WRAP> | ||
| + | |||
| + | ---- | ||
| ==== Breaking Waves ==== | ==== Breaking Waves ==== | ||
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| <WRAP indent> | <WRAP indent> | ||
| - | when waves roll over shallower areas such as shorelines (**Shore Break) **the deeper part of the wave slows due to friction from the underlying shallows while the tops of waves keep their speed and eventually topple over (break). This process can occur anywhere (not just close to shore) there are shallows due to features such as underwater reefs, shallow bottom shelves, and sand bars. Very shallow water will cause all waves to break which is usually easy to notice, while deeper shallows will cause only bigger waves (**Boomers**) to break sometimes with periods of 30 minutes or more between breaking waves. Such breaking waves can be surprising (particularly for paddlers unfamiliar with the underlying shallows) and have to be watched out for carefully by folks in smaller vessels. The indigenous Australian term for areas with large offshore breaking seas due to reefs and shallows is **Bombora**. [[:nautical_charts|Nautical charts]] are available online (view or download) for coastal waters around the world to allow anticipation of shallows and potential boomers, although online viewers may not have sufficient resolution to show all smaller shallow areas. Water depth and resultant occurence of breaking waves can also vary with the tide. | + | ---- |
| + | |||
| + | when waves roll over shallower areas such as shorelines (**Shore Break) **the deeper part of the wave slows due to friction from the underlying shallows while the tops of waves keep their speed and eventually topple over (break). This process can occur anywhere (not just close to shore) there are shallows due to features such as underwater reefs, shallow bottom shelves, and sand bars. Very shallow water will cause all waves to break which is usually easy to notice, while deeper shallows will cause only bigger waves (**Boomers**) to break sometimes with periods of 30 minutes or more between breaking waves. Such breaking waves can be surprising (particularly for paddlers unfamiliar with the underlying shallows) and have to be watched out for carefully by folks in smaller vessels. The indigenous Australian term for areas with large offshore breaking seas due to reefs and shallows is **Bombora**. [[:nautical_charts|Nautical charts]] are available online (view or download) for coastal waters around the world to allow anticipation of shallows and potential boomers, although online viewers may not have sufficient resolution to show all smaller shallow areas. Water depth and resultant occurrence of breaking waves can also vary with the tide. Working on and around surf breaks, surfskiers are typically looking: | ||
| + | |||
| + | - to catch and ride swell early, peeling off before arriving at the break zone | ||
| + | - or sometimes catch waves on days when they are mushy (which board surfers typically do not like as much) with no hollow curl or pronounced break | ||
| + | - or to catch waves on the wave shoulders away from the breaking part of the waves and peeling off before the breaking part of the waves peels to the point of the wave where the paddler is, although this can be tricky because waves move around and their break and shoulders do not stay consistently placed relative to the beach. | ||
| + | - … | ||
| </WRAP> | </WRAP> | ||
| + | |||
| + | ---- | ||
| ==== Rebound (aka Reflection) ==== | ==== Rebound (aka Reflection) ==== | ||
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| <WRAP indent> | <WRAP indent> | ||
| - | flat shorelines usually absorb most wave energy while steep shorelines can cause waves to bounce off and rebound back out into deeper water causing turbulence and waves working at odd angles to the prevailing wave patterns. This can create more challenging paddling. It also can contradict the usual wisdom of staying closer to shore for safety or easier paddling when rebound makes for more difficult paddling conditions closer to shore. Transient rebound can quickly cause more turbulence when larger waves from passing boats or ships bounce off of the shore. Abrupt barriers at the water's edge can cause pronounced rebound referred to as "[[https://en.wikipedia.org/wiki/Clapotis|clapotis]]" | + | ---- |
| + | |||
| + | flat shorelines usually absorb most wave energy while steep shorelines and barriers in the water can cause waves to bounce off and rebound with the rebounding waves working at odd angles to the prevailing wave patterns and causing greater turbulence. This can create more challenging paddling. It also can contradict the usual wisdom of staying closer to shore for safety or easier paddling when rebound makes for more difficult paddling conditions closer to shore. Transient rebound can quickly cause more turbulence when larger waves from passing boats or ships bounce off of the shore. Abrupt barriers in the water can cause pronounced rebound which interacts with the prevailing waves to for wave patterns referred to as "[[https://en.wikipedia.org/wiki/Clapotis|clapotis]]". If a steep shoreline is shallow enough to expose flat shore at lower tide levels then wave energy will be better absorbed and rebound can be mitigated during lower tide. | ||
| [[:rebound_videos|Rebound Videos]] | [[:rebound_videos|Rebound Videos]] | ||
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| ---- | ---- | ||
| - | **Tom Mason & friends negotiate clapotis at mouth of the river Arun** | + | **Tom Mason & friends negotiate clapotis at mouth of the River Arun** |
| {{youtube>EiAwYZBXpGE?large&start=50}} | {{youtube>EiAwYZBXpGE?large&start=50}} | ||
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| </WRAP> | </WRAP> | ||
| - | ==== Boat Wakes ==== | + | ---- |
| + | |||
| + | ==== Boat Wake Waves ==== | ||
| <WRAP indent> | <WRAP indent> | ||
| - | If you have access to a shipping channel or some water where there is large boat or ship traffic, be aware of the interaction between water depth and boat wakes (refer to "breaking waves" above) and where it is better to position yourself. Shallower water can cause boat wakes (like all waves) to steepen and possibly break. This may be good for surfing where it allows you to more easily catch boat wakes (particularly from smaller boats) if they get somewhat bigger and steeper, or it can make already good size wakes too big, too steep, breaking, and more dangerous than you want to deal with. | + | ---- |
| <WRAP centeralign> | <WRAP centeralign> | ||
| - | |||
| - | ---- | ||
| {{youtube>95sQcSulRFM}} | {{youtube>95sQcSulRFM}} | ||
| + | |||
| + | </WRAP> | ||
| ---- | ---- | ||
| - | </WRAP> | + | * [[:surf#surfing_boat_wakes_wash|Boat Wake Finding & Surfing]] |
| + | * … | ||
| - | * [[:surfable_boat_wakes|Where to Find Boat Wakes]] | + | </WRAP></WRAP> |
| - | * [[https://www.surfski.info/forum/15-tips/19197-paddling-close-to-small-and-big-ships.html|Surfski.info Discussion On Riding Boat Wakes 4/2018]] | + | |
| - | </WRAP> | + | ---- |
| - | ==== Waves for Downwinding ==== | + | ===== Measuring Wave Heights ===== |
| - | * **[[:wavedynamics|Wave Dynamics for Downwinding]]** | + | (and why it is problematic) |
| - | ==== Longest Waves for Surfing ==== | + | |
| - | * [[https://youtu.be/am9mH0sLGfg|Longest Waves Video]] | + | <WRAP indent> |
| - | * ... | + | |
| ---- | ---- | ||
| + | |||
| + | [[https://www.ombe.co/guides/how-to-measure-wave-height|How to Measure Wave Height]] | ||
| </WRAP> | </WRAP> | ||
| + | |||
| + | ---- | ||
| ===== Wave Heights in Weather Forecasts ===== | ===== Wave Heights in Weather Forecasts ===== | ||
| - | * [[http://www.weather.gov/dlh/WaveHeightExplanation|NOAA Wave Heights]] Wave height predictions in NOAA forecasts are the significant wave heights (average of the top 1/3 of wave heights). About 1 in 7 waves is higher than the significant wave height. NOAA also reports occasional wave heights which is the average of the top 10% of wave heights being observed. A wave twice the significant wave height is expected to happen about 3 times in 24 hours. | + | * [[http://www.weather.gov/dlh/WaveHeightExplanation|NOAA Wave Height Measurement]] Wave height predictions in NOAA forecasts are the significant wave heights (average of the top 1/3 of wave heights). About 1 in 7 waves is higher than the significant wave height. NOAA also reports occasional wave heights which is the average of the top 10% of wave heights being observed. A wave twice the significant wave height is expected to happen about 3 times in 24 hours. |
| * **Sneaker Waves **- This has to do with the occurrence and risk of sporadic larger waves when they reach shore. NOAA: "Sneaker waves are potentially deadly waves that surge further up the beach than expected, overtaking the unaware." [[https://www.weather.gov/safety/sneaker-waves|More from NOAA]]. Weather services where sneaker waves tend to be more dangerous now frequently include alerts for expected more frequent occurrence of sneaker waves. | * **Sneaker Waves **- This has to do with the occurrence and risk of sporadic larger waves when they reach shore. NOAA: "Sneaker waves are potentially deadly waves that surge further up the beach than expected, overtaking the unaware." [[https://www.weather.gov/safety/sneaker-waves|More from NOAA]]. Weather services where sneaker waves tend to be more dangerous now frequently include alerts for expected more frequent occurrence of sneaker waves. | ||
| * … | * … | ||
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| * [[https://www.swellnet.com/news/swellnet-analysis/2019/06/11/waves-youve-never-heard|Infra-gravity Waves]] aka [[https://www.metocean.co.nz/long-waves|Long Waves]] | * [[https://www.swellnet.com/news/swellnet-analysis/2019/06/11/waves-youve-never-heard|Infra-gravity Waves]] aka [[https://www.metocean.co.nz/long-waves|Long Waves]] | ||
| + | * [[https://www.amazon.com/Science-Ocean-Waves-Ripples-Tsunamis/dp/1421410788/ref=tmm_hrd_swatch_0?_encoding=UTF8&qid=&sr=|The Science of Ocean Waves]] J.B. Zirker | ||
| * [[http://media.bom.gov.au/social/blog/870/ruling-the-waves-how-a-simple-wave-height-concept-can-help-you-judge-the-size-of-the-sea/|Wave Size]] | * [[http://media.bom.gov.au/social/blog/870/ruling-the-waves-how-a-simple-wave-height-concept-can-help-you-judge-the-size-of-the-sea/|Wave Size]] | ||
| * **Rogue Waves** | * **Rogue Waves** | ||
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| * [[https://www.surfline.com/surf-news/why-do-waves-come-in-sets/1156|Wave Sets]] | * [[https://www.surfline.com/surf-news/why-do-waves-come-in-sets/1156|Wave Sets]] | ||
| * [[https://www.facebook.com/sportscene/videos/10153337488756525/|Dancing wave video]] | * [[https://www.facebook.com/sportscene/videos/10153337488756525/|Dancing wave video]] | ||
| + | * [[:finding_waves_anyway_can|Finding Other Waves]] | ||
| * [[https://thescienceofpaddling.net/part-35-waves-linear-and-nonlinear|Wave Math]] | * [[https://thescienceofpaddling.net/part-35-waves-linear-and-nonlinear|Wave Math]] | ||
| * [[https://www.youtube.com/watch?v=pir_muTzYM8&ab_channel=Veritasium|US Naval Indoor Ocean]] | * [[https://www.youtube.com/watch?v=pir_muTzYM8&ab_channel=Veritasium|US Naval Indoor Ocean]] | ||
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