JGS wrote:
On Sun, 19 Dec 2004 18:29:14 GMT, WaIIy wrote:


On Sun, 19 Dec 2004 17:56:54 GMT, "Roger Long"
wrote:


I've been kind of interested in some of the posts about Lake Erie conditions
to see references to 12 foot waves. I know the waves are shorter and steeper
there due to the lighter water and shallow depths. Twelve footers would
considered pretty big however, even on the ocean.

I've been pretty involved in past years with marine safety and accident
investigation projects and this gave me a chance to look into wave height
reports. There is a pretty consistent tendency for even experienced seaman
to over estimate wave heights by about 100 percent.

I lived on Lake Erie (near Cleveland) for 6 years and near the lake for
50 years and have never see or reliably heard of 12 footers.

The highest I have been in are 7- 8 footers and wouldn't like to do that
again.

Lake Erie is notorious due to the closeness of the waves. Everything
is a chop 1ft-2ft-6ft chop.

Of course, when it is rolling or fairly flat, it's wonderful (if quite
brown).


See:
http://www.ndbc.noaa.gov/station_page.php?station=45005

Look at the data significant wave height:
http://www.ndbc.noaa.gov/images/climplot/45005_wh.jpg

Looks like it came close to a 12 footer at least on one occasion. Perhaps in
the Central Basin it may have reached 12'.

But you're right, a 12 footer seems quite rare if it ever did quite make it.


If you look at the text data you'll see that that the "significant wave
height" only reached 4 meters (13 feet) once in a 20 year period.
However, it did get over 3 meters several times a year, and over 2
meters numerous times. Of course, the worst weather is in the Spring
and Fall (and the the buoy is pulled in the Winter) so the Summer sailor
will not likely see these conditions.

"Significant wave height" is the average of the higher third of all
waves, measured over the course of an hour. If that is 3 meters, then
the average of the highest tenth of all waves would be about 4 meters.
Thus, many individual 12 foot waves have happened, though usually no one
was there to witness them.

Anyone who goes out when the wave height is 6 feet (as it was the last
time I was on Lake Ontario) will likely see some 8 footers and maybe, if
they're out all day, a few 10 footers.

BTW, in a hurricane significant wave height will get much larger - 10
meters would easily be possible.