On 10/25/2015 11:28 AM, wrote:
On Sun, 25 Oct 2015 02:07:43 -0400, wrote:

On Sat, 24 Oct 2015 18:35:50 -0700 (PDT), wrote:

The claim is quite true and I have seen it many times, but I don't think it's as complicated as some make it sound. It can happen in deep water and without wind. In 1992 my eureka moment came one day while heading east on a motor yacht through the Current Rock passage in the Virgin Islands where I had a birds-eye view of whole effect clearly displayed in front of me. I could see that the current causes the waves in the center to travel a little slower than on the outsides, and that this bends the wave train, and now the waves on the left and right were converging towards the center where they added their energy and height. Depending on the location, the effect can be spread over a large or small area I have illustrations here http://www.3dym.com/waves/waves.htm

Where we see it all the time is in a pass or mouth of a river when you
have an onshore wind (from sea to land) smacking into an outgoing tide
or current, the waves will be a washing machine on steroids. If you
can hug the shore and get out of the current it will be reasonable as
long as you don't run aground..

===

Yes, that's very common. The inlets all along the Atlantic coast are
particularly dangerous under those conditions except for the ones with
big breakwaters. We've also seen it in the eastern Caribbean where
the trade winds create big easterly waves but the gaps between the
islands are tidal. You can be going along in the normal 3 to 6 ft
seas and suddenly see a patch of white water ahead where the waves are
breaking and twice as high.



Jupiter Inlet in Florida is notorious for that plus the bottom is
constantly shifting due to wave action shoaling. The Coast Guard
considers the inlet to be "non-navigable" and boating guides advise
to use another inlet north or south of Jupiter. It's ok on calm
days but can still be tricky due to changes in depth. Here's a
link to a video of a guy in a small boat exiting the inlet on a
day that was not as bad as it can get:

https://www.youtube.com/watch?v=yUk055TKLes