Posted by: cworthy | September 4, 2010

The wind is cooking at nearly 40 mph at the weather buoy. I’d say that no one will be fishing in the morning.

Hurricane Earl is getting all the media attention as it races up the east coast, but the wind with no name is getting our attention here. Tropical storm winds are 30- 40 mph and that is what the weather buoy is reading now!  They don’t call it a tropical storm around here and I’m not sure what they call it other than the first storm of fall in Michigan.

Here is a question for you. The NOAA buoy is showing waves of 9 feet tonight. Do they measure from the middle of the wave or do they measure from the bottom of the trough to the crest like most locals do.  If they measure from the middle that would mean that the waves are 18 feet by local standards. Could that be true? If you know the real answer  please post the answer here as a comment. Or, if you don’t know but have the time to sit at your computer, dig and find out, then many of us would like to know.

Good luck fishing whenever that happens to be.

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Responses

  1. Bill try this URL from NOAA

    http://www.ndbc.noaa.gov/educate/waves.shtml

  2. from a surfers website:

    “Wave height is the distance from a wave’s trough to its crest (i.e. amplitude). The crest is the top of an unbroken wave, the trough is at the bottom of the front of the wave…….On average, about 15% of waves will equal or exceed the significant wave height. The highest 10% of waves could be 25-30% higher than the significant wave height. And on occasion (about one per hour) one can expect to see a wave nearly twice the significant wave height. And then there are rogue waves”.

    From Oceanworld…….the satellite altimeter method……”The altimeter technique works as follows. Radio pulse from a satellite altimeter reflect first from the wave crests, later from the wave troughs. The reflection stretches the altimeter pulse in time, and the stretching is measured and used to calculate wave-height (Figure 16.12). Accuracy is ±10%.

    NOAA’s explanation requires some advanced math and a better keyboard than I have to even write the formulas.

    The CDIP (Coastal Data Information Program) is most concise:

    Wave Anatomy:

    •Still-Water Line – The level of the sea surface if it were perfectly calm and flat.

    •Crest – The highest point on the wave above the still-water line.

    •Trough – The lowest point on the wave below the still-water line.

    •Wave Height – The vertical distance between crest and trough.

    •Wavelength – The horizontal distance between successive crests or troughs.

    •Wave Period – The time it takes for one complete wave to pass a particular point.

    •Wave Frequency – The number of waves that pass a particular point in a given time period.

    •Amplitude – One-half the wave height or the distance from either the crest or the trough to the still-water line.

    •Depth – the distance from the ocean bottom to the still-water line.

    •Direction of Propagation – the direction in which a wave is travelling.

    DARN WIND!

  3. Bill, I was going to let you know that back when I had classes that included such topics as ocean wave height, we always calculated amplitude as crest-top to trough-bottom. Then I saw steve’s post, which I think captured everything I ever learned and then some.

    Dad and I went out on the this evening (Sep-4) around Lee Point… it was some of the craziest weather I’ve seen. Lots of low cloud cells with rain and super gusts. Couldn’t keep the boat on the bank. We caught a couple lakers for our trouble but mostly watched the ever changing rainbows on the lake and tried not to lose our hats.

    Enjoy the woods.


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