Sunday evening we were walking along a beach when waves suddenly began rolling in and breaking, from a previously calm surface, first near the inside of a point and then moving farther down. This went on for many minutes. I checked time and it was precisely the moment of predicted maximum ebb flow. However, the actual flow speed that evening was not especially high. Upon looking out to the water, we saw exactly one ship that had passed by earlier, in the shipping channel; no other boats were in sight. There was no wind to speak of, nor had there been swell that day or the previous day.
Curious, Monday evening we set off again to see if the event would repeat itself. My reasoning was that Monday's max ebb was slightly faster and coming off a higher high tide also. There was a light wind but other than that, weather was similar. No ships present. Nothing unusual happened this time. So there must've been some other variable creating the sudden wave activity on Sunday night.
I've seen many, many ships pass by in the same location before, yet I never saw any of them generate that kind of wake/wave. While I still wouldn't rule that out, what other kinds of things would cause unusual wave activity? Would a submarine do it?
The barometric pressure in the area was dropping all day both days. Someone told me a few small earthquakes had occurred not far away, but I don't know the timing of them in relation to what we saw.
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if not ship may very long period swell|
Posted by: jcbikeski on Jun-25-13 4:30 PM (EST)
With swell around 22 seconds or more I've seen lulls last twenty minutes or more then a set of several big waves before another long lull. So not sure if later after your waves it happened again but one possibility. The ebb tide could further jack up whatever was coming in.
It was an isolated event|
Posted by: pikabike on Jun-26-13 12:47 PM (EST)
We watched to see if it would happen again but it didn't. Good advice, though--22 sec is a long stretch, much longer than I'd expect. Something to keep in mind when paddling. Thanks for the heads-up.
only will see that period in open ocean|
Posted by: jcbikeski on Jun-26-13 1:08 PM (EST)
These long lulls start to be a minor issue closer to around 18 seconds and a big issue by 22. But you only see that in places like the open Pacific coast where you have many miles for the far storms to organize into fewer but larger waves. I'm guessing the ship -- maybe loaded but moving fast or it made a sudden slow down.
Location Location Location|
Posted by: yatipope on Jun-25-13 5:41 PM (EST)
Its always frustrating when someone posts a highly detailed report of an unusual occurance but neglects to include WHERE THEY ARE AT!
Posted by: pikabike on Jun-26-13 12:41 PM (EST)
Between Point Wilson and Hudson Point, with the movement starting at PW and progressing down the beach. We've seen submarines nearby before, but always with a tender (I think that's what they call them).
Posted by: jackl on Jun-25-13 7:27 PM (EST)
Was this in the ocean ?
Yes and no|
Posted by: pikabike on Jun-26-13 12:39 PM (EST)
It was in the ocean (or sea, if you get picky...).
variation in ships|
Posted by: Peter-CA on Jun-25-13 8:16 PM (EST)
I've seen wide variations in ship wakes in my years of paddling SF Bay. The vast majority I have seen put out just about no wake. But I guess if they are loaded just right (or maybe just wrong is a better way to say it), they kick up huge wakes.
Maybe it was perfect timing|
Posted by: pikabike on Jun-26-13 12:55 PM (EST)
The one ship that had passed might have gone by some "triggering" location at precisely the right time to create big wakes.
east coast tsunami reported|
Posted by: Andy_Szymczak on Jun-25-13 9:13 PM (EST)
Didn't think east coast got them|
Posted by: pikabike on Jun-26-13 12:43 PM (EST)
The article stated that weather, not seismic activity, might have caused it. Interesting stuff.
Seas vs. swell|
Posted by: rjd9999 on Jun-26-13 2:04 PM (EST)
There are seas and there are swells - essentially, local events and conditions which were created distantly, but which arrive at your location.
When we were in Johnstone Straight, BC|
Posted by: jackl on Jun-26-13 3:28 PM (EST)
Long after a Cruise ship went by, (it was almost out of sight) we got the swells from it, but we fully expected it.
As above ..|
Posted by: seadart on Jun-26-13 3:30 PM (EST)
My first guess would be a shipwake; a ship can pass a long way off shore and waves can be fairly large, the shape of the ship determines what kind of waves you will get, some smaller boats can actually throw very impressive wakes. But as mentioned forerunners of a long period swell, start to show up as rogue sets that may be spaced quite a bit a part like 20 minutes or so. There have been several nice south swells in the last few weeks of long period coming up from New Zealand area ... also this week there was a little bit of a Freak North west swell that was long period (unusual this time of year). The long period swells of course come from huge storms that blow for days with very high winds.
Posted by: ppine on Jun-27-13 4:22 PM (EST)
Wakes from shipping seems logical. People often forget about wind driven waves from a long distance away doing some strange things. A shoreline with lots of irregularities can deflect waves and surf. Sometimes harmonics are involved. Opposing wind and tides do unusual things. The ocean is more dynamic than many realize.