just wondering if anyone knows...?

is a rising tide north flowing or south flowing for SE Queensland.

cheers...

cheers holgs,

i'm figuring that tides flow south when rising then.

Tidal theory could have been super simple if only the Earth was covered in water only (no land). Then we'll just be 'looking' at the moon and the sun (don't forget that the sun play a role too in the tides generation).

however we've got land and then ocean bassin(not only one big ocean) and also the earth is rotating so we 've got that bloody coriolis force that makes 'things' turn to left in the southern hemisphere (and to the right in the northern hemisphere).


So anyway because the ocean depths are not uniform, we have to relate the tidal forces (moon sun) to a series of inter-connected ocean basins, each with its natural frequency and different frictional characteristics.


and this is when the Amphidromic system arrive:
see
www.seabreeze.com.au/gallery/gallery.asp?imageid=1322&shownew=on
in an idealised bassin (imagine a part of the Indian ocean for example) there is a point where the tidal elevation is zero and the tidal wave rotate around that point. The co-tidal line are the line where the tidal wave go pass at the same time.
see also
www.seabreeze.com.au/gallery/gallery.asp?imageid=1323&shownew=on

so if you are sitting on the edge of this basin ( on a beach somewhere) and you 've got a mate 200km further along the coast, you will get the high tide before him (or vice versa).

this is how it looks like for the whole world (colour are tidal amplitude)
www.seabreeze.com.au/gallery/gallery.asp?imageid=1324

hard to see for SE Queensland (looks to me that it is north to south)
but you could see really well, why there almost no tide in Perth, Perth is just next to an amphidromic point (= zero tidal elevation).

now the thing is that if you are in a little estuary (or bay), the bay will also have its own little way of having the tidal wave coming from one side and leaving from the other side.

After listening to all that science junk, the advice is just to check your local nautical chart, everything is indicated on there!...I'm off to the beach now I've got sore head.

Good stuff leski, I was hoping someone clever would come up with a scientific answer. Can you also tell me why Perth has only one high tide and one low tide in 24 hrs when most places have 2 of each? Thanks.

Thanks leski, never realised that tides were so complex.