tide push
83 views
Skip to first unread message
mjb
Jun 22, 2009, 12:26:26 AM6/22/09
to Surf Forecasting
how can the tide changing from low to high result in bigger or better
waves for a short period of time?
waves for a short period of time?
Nathan Cool
Jun 23, 2009, 11:59:21 AM6/23/09
to surf-for...@googlegroups.com
Good question MJB,
Tide, for the most part, has its effects on the ratio of water depth to wave height, determining where a wave will break. We've all experienced this when we go to some spot, and size is drastically different as the tide changes hour by hour, most notably when there is an extreme tidal swing, like we're seeing this week, where the difference from a low to high tide varies the sea level by as much as 9 feet (7 foot highs with nearly -2 foot lows).
The tidal "push" though is a combination of two things:
1. A change toward the optimal height-to-wave size ratio -- when the water depth reaches its sweet spot for a particular break during the incoming tide (filling the pool with water, so to speak).
2. A push from the incoming tidal flow. Think of tilting a glass of water to and fro, and watch the water slosh to either side. When a radical tidal swing is in play, and the tidal depth will fluctuate by many feet within a short period, the extra "push" from the incoming "rush" of water can add some juice to the incoming waves. An extreme example of this is from what are known as "tidal bores", where a river or other narrow inlet is rushed with water from an incoming tide. You can see a video of a tidal bore here:
http://www.youtube.com/watch?v=B6z3DVZmsnU&feature=related
The primary influence though for SoCal (since we don't deal with tidal bores) is from #1, the height-to-wave size ratio. Still, any incoming rush of water (i.e. from the incoming tide) will provide energy to incoming waves; thus, #2 above does provide a secondary influence to tidal push in SoCal.
-Nathan
Tide, for the most part, has its effects on the ratio of water depth to wave height, determining where a wave will break. We've all experienced this when we go to some spot, and size is drastically different as the tide changes hour by hour, most notably when there is an extreme tidal swing, like we're seeing this week, where the difference from a low to high tide varies the sea level by as much as 9 feet (7 foot highs with nearly -2 foot lows).
The tidal "push" though is a combination of two things:
1. A change toward the optimal height-to-wave size ratio -- when the water depth reaches its sweet spot for a particular break during the incoming tide (filling the pool with water, so to speak).
2. A push from the incoming tidal flow. Think of tilting a glass of water to and fro, and watch the water slosh to either side. When a radical tidal swing is in play, and the tidal depth will fluctuate by many feet within a short period, the extra "push" from the incoming "rush" of water can add some juice to the incoming waves. An extreme example of this is from what are known as "tidal bores", where a river or other narrow inlet is rushed with water from an incoming tide. You can see a video of a tidal bore here:
http://www.youtube.com/watch?v=B6z3DVZmsnU&feature=related
The primary influence though for SoCal (since we don't deal with tidal bores) is from #1, the height-to-wave size ratio. Still, any incoming rush of water (i.e. from the incoming tide) will provide energy to incoming waves; thus, #2 above does provide a secondary influence to tidal push in SoCal.
-Nathan
Reply all
Reply to author
Forward
0 new messages