# Thread: forcast time plot??

1. ## forcast time plot??

how do i interprit the meaning of '' @sec '' as in the swell is 9.2 feet@10 sec ..............what do seconds have to do with it ? how does it affect the way the wave is ? for better and worse

2. Senior Member
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Feb 2008
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the seconds measure the amount of time it takes for 1 wave to pass from crest to crest

A longer period means the wave has more energy, and also means it has probably come from much further away (aka groundswell)

A shorter period has less energy, and comes from a more local source... aka windswell.

Generally, we want groundswell over windswell, because its more organized and has more power and "oomph" when your riding it. But it also just depends on your local break and how different periods and directions effect it.

there are numerous other posts about this.... also check out http://www.surfline.com/surfology/su..._forecast2.cfm
Last edited by epidemicepic; Mar 9, 2010 at 10:57 PM.

3. ## Tnks

,thankss!!

4. The seconds (wave period) also relates to the size of the wave face height.

For example, at an average beach break:
4 ft @ 6 seconds might be 2-4ft wave face.
4 ft @ 12 seconds might be 4-5ft wave face.

So, when you see the surf timeline shows around chest high, you can scroll over to find out the swell height and swell period in which that chest high calculation was made from.

5. ## what determins time period from set to set

if there is less seconds does that mean a shorter wait inbetween set ?

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Originally Posted by staystoked
if there is less seconds does that mean a shorter wait inbetween set ?
yeah, shorter period usually equals less time between sets, but i believe there are other factors too

7. ## ??

what would the ocean look like at 5ft@ 2 sec and 5ft @ 35 sec

???

8. Originally Posted by staystoked
if there is less seconds does that mean a shorter wait inbetween set ?
yes, the wave period is the time between sets.

But, keep in mind, the period that is reported is the dominant period of a particular swell or of the overall significant wave height. So, if the swell period is 12 seconds, that doesn't mean there isn't other swells in the water with different swell periods. At any time, there are waves approaching a particular location from all over the Ocean. We use statistical approaches to categorize the waves into dominant swells groups, which we report - such as 3.5 ft ESE swell @ 10 seconds. I hope that makes sense.

9. 5ft at 2 seconds is not waves, its just repeated windchop breaking on top of itself with no organization whatsoever... they really start recording ridable windswell at about 6-7 seconds, if I remember correctly. 5ft at 35 seconds, that is a good question, I have never seen conditions like that. Usually the best groundswells that are huge are like 10-15ft at 18 seconds or something along those lines...
During the Tsunami, I heard reports of 4ft at @ 3 minute intervals...... I guess that fact that tsunami water can reach upwards of 400MPH, that what the 3 minutes means.... The size was still 4 feet, but when each wave arrived at certain points, it was a traveling 4 ft wall of disaster... I think anyway...

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if you think about it.... our tides are really just 4-6 foot waves circling the earth with a 6 hour period