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# Thread: forcast time plot??

1. Senior Member
Join Date
Feb 2008
Posts
501
No... just read the surfline article i posted at the beginning of this thread, it has most all of the answers

"Wave speed: The speed of a swell or a wave train can be calculated by multiplying the swell period times 1.5. For example, a swell or a wave train with a period of 20 seconds will be traveling at 30 knots in deep water. (Knots are nautical miles per hour. One knot equals 1.2 mph on land.) A swell with a period of 10 seconds will travel at 15 knots. The individual waves actually move twice as fast as the wave train or the swell, and a single wave's speed can be calculated by multiplying the swell period times three. So individual waves with a period of 20 seconds travel at 60 knots in deep water. Again, think of the wave train like a rotating conveyor belt that is also moving forward."
- from surfline.com

Remember, most of this stuff applies to waves in DEEP water... once the waves start "feeling" the bottom of your local bathymetry, they slow down, steepen, ext.

2. Senior Member
Join Date
Feb 2008
Posts
501
Your thinking of of swell period as a measurement of wave speed via seconds over distance.

When in fact....the swell period is just a way of measuring wavelength. The higher wavelengths (of ocean waves) equals higher amounts of energy, thus they can move faster.

3. Senior Member
Join Date
Feb 2008
Posts
501
btw...
Does anyone else here find it strange that longer wavelengths in the electromagnetic spectrum are at the lower end of the energy spectrum? while longer wavelength ocean waves have more energy??

My physics is a little rusty, but all i can think of is that maybe physicists look at the entire collection of waves, while surfers and oceanographers are more concerned about the energy in any one particular wave, Thus: short period ocean waves actually do have more total energy per volume of ocean than longer period waves, and one gamma ray actually has less energy than one radio wave.... Does anyone understand what i am thinking about?

4. ## food for thought

Originally Posted by epidemicepic
btw...
Does anyone else here find it strange that longer wavelengths in the electromagnetic spectrum are at the lower end of the energy spectrum? while longer wavelength ocean waves have more energy??

interesting

5. Originally Posted by epidemicepic
My physics is a little rusty, but all i can think of is that maybe physicists look at the entire collection of waves, while surfers and oceanographers are more concerned about the energy in any one particular wave, Thus: short period ocean waves actually do have more total energy per volume of ocean than longer period waves, and one gamma ray actually has less energy than one radio wave.... Does anyone understand what i am thinking about?
sounds about right.

6. Long period waves do have more energy than short period waves. But remember... they all start out as short period waves. So big short period waves turn into big long period waves only through distance. With distance traveled, the energy is organized into long period waves which have the collective energy from the combination and organization of the short period waves they were formed from. Electromagnetic energy does not change wavelength or frequency over distance.