when is it a tide

[2BonC]

During our trip through the Adriatic Sea we were mooring at Osor a small village on the Island of Cres. The water was very flat there but we raised all pannels and felt fine directly at the pier. It was nice to step on land keeping the feet dry .The weather was bad but the sea was calm by that time.
During the night when we were sleeping some knocking was to be heard. As it already had started to rain haevyly I decided that I must have had just a bad dream After a while when I tried to fell asleep again the knocking came up again changing more and more from lite to heavy bumps . I couldn´t stick any longer to my idea of the dream and decided it would be better to peel out of the sleeping back and look for the source of this disturbances.
After you have read the subject for sure you emediately will know what the reason was.
We moored during the high tide and the low tide had left only little water below the boat. In adition the weather had deteriorated and the watersurface was in quite heavy motion than. In spite of that the boat bumped on the ground from time to time. If the sea had remained calm we probably would have noticed the problem only at the next morning. However finally everything went out good (except I became completely wet ), I just pulled the boat back into the sea along the side of another boat which was tightened there.

What I have learned:

As everybody knows a tide is the differance in waterlevel of at least 4 meter (about 13ft). There is no tide in the Medeteranian sea
However I experienced that a decrease in waterlevel of less than 0.5 meter (about 1.5 ft) can be of paramount concern to your boat even this levelchange is not called "tide"



What me got most, my buddy didn´t even notice the whole thing during the night, he was just wondering the next morning



- but on the other hand he steers the boat without using his hands

[pokerrick1]

When one is in San Felipe (21 foot tide swings)

Rick

[2BonC]

..which San Felipe are you talking about, Google Earth is offering me the choice between about seven S Fs but no one in Mexico.

[Hamin' X]

..which San Felipe are you talking about, Google Earth is offering me the choice between about seven S Fs but no one in Mexico.

San Felipe, BC, Mexico

~Rich

[pokerrick1]

Correct - - Google Earth - - - San Felipe, BC, Mexcio. Third largest tide swing in the world.

Rick

[2BonC]

Rick, did you find it via Google Earth, I didn´t. That´s what is offered to me by GE:



Could I have made a mistake during my search or do the Europeans have a different GE?

Rainer

[Hamin' X]

Rainer,

I'm not sure what is going wrong with your Google Earth. Mine shows San Felipe just fine when I enter "San Felipe, BC, Mexico, or San Felipe, Baja California" in the search window.

The Lat/Lon is:

31º 01' 48.51" N
114º 50' 17.83" W

~Rich

[Oskar 26M]

Thanks for posting the Lat/Lon Rich.

When I typed in "San Felipe, BC, Mexico" my GE centred me on San Felipe, Mexico which was a mountain range. The town was about half a degree further north so it was outside the default map size on my laptop's small screen.
Now I can see the marina. Nice spot!

[Hamin' X]

My pleasure.

~Rich

[2BonC]

thank you Rich, now I got it, I just entered San Filipe, missed Mexico! Must be nice there, I have been in Mexicali around x-mas in 1994. It was quite cold at this time but by mistake we went swimming in the Pacific! However by that time I never thought about sailing at all.
I think I will never be there with a Mac, it´s to far for Car and Trailer

[Dimitri-2000X-Tampa]

There are tides in the Med, they are just quite small compared to other places. What you likely experienced was a storm tide which is when the water level is moved due to the wind and not the gravitational forces (although the gravitaional tide may also have contributed). So if you are in the Northern part of the Adriatic and the water level goes down dramatically, this is probably due to a North wind. I see it in Florida all the time, a NE wind of 15 knots could easily lower the water level in Tampa Bay by .5 meter, maybe even more if it cumulates over time. I have never heard this definition of a tide being a 4m difference in water level. Try this definition:

http://en.wikipedia.org/wiki/Tide

[2BonC]

..it was my definition!!!! , and I also know I can not go by car from GE to Mexico!

[Kelly Hanson East]

Didnt click on that link, but I would define a tide as a change in the height of water which is cyclical with a period of the Moons motion- regardless of the actual change in water depth.

Incidentally, the Hudson "River" near us, 130 miles upstream from NYC, is technically a tidal estuary, with about a 1.1 meter tidal change in depth.

[Frank C]

I first learned of the seiche when reading The White Hurricane (Amazon), a book about a vast winter gale across the Great Lakes in November of 1913. Winds of 90 mph and 35-foot waves sank a dozen large lake ships, ore carriers, during the 3-day storm, taking 248 lives.

A seiche (pronounced saysh) is a standing wave in an enclosed or partially enclosed body of water. Seiches and seiche-related phenomena have been observed on lakes, reservoirs, bays and seas. The key requirement for formation of a seiche is that the body of water be at least partially bounded, allowing natural phenomena to form a standing wave ...

On the North American Great Lakes, seiche is often called slosh. It is always present, but is usually unnoticeable, except during periods of unusual calm ... The National Weather Service issues low water advisories for portions of the Great Lakes when seiches of 2 feet or greater are likely to occur.

Lake Erie is particularly prone to wind-caused seiches because of its shallowness and elongation. These can lead to extreme seiches of up to 5 m (16 feet) between the ends of the lake ...

The effect is similar to a storm surge like that caused by hurricanes along ocean coasts, but the seiche effect can cause oscillation back and forth across the lake for some time. In 1954, Hurricane Hazel piled up water along the northwestern Lake Ontario shoreline near Toronto, causing extensive flooding, and established a seiche that subsequently caused flooding along the south shore ...

Lake seiches can occur very quickly: on July 13, 1995, a big seiche on Lake Superior caused the water level to fall and then rise again by three feet (one meter) within fifteen minutes, leaving some boats hanging from the docks on their mooring lines when the water retreated. On Lake Michigan, eight fishermen were swept away and drowned when a 10-foot seiche hit the Chicago waterfront on June 26, 1954.

[Hamin' X]

Very interesting, Frank. I was not aware of this phenomenon in the Great Lakes.

~Rich