Tidal Flow

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whatthe
whatthe
WA
186 posts
WA, 186 posts
8 Oct 2008 1:28pm
Can someone tell me which direction the current flows for ebb or flood tides off Fremantle? I can't find reference to it anywhere but know it is pretty simple.

Am interested if this has any effect on people's kiting experiences? Is is better to kite with current and wind in the same direction? I have been told that tide against wind makes for steeper chop.


Cheers
Kitehard
Kitehard
WA
2782 posts
WA, 2782 posts
8 Oct 2008 2:35pm
Hi Whatthe,

The current along the whole coast runs from South to North and is also helped along a bit by the waves which are generated by the wind. So most of the time the current will run with the wind.

When the current opposes the wind it does indeed make for biger and steeper chop.

I don't know if there are any local peculiarities around the Freo area apart from the tidal flow that comes out with the ebb and in with the Flood through the port and river mouth.

Hope this helps a little.

Good winds,

whatthe
whatthe
WA
186 posts
WA, 186 posts
8 Oct 2008 3:57pm
When I was sailing in the Whitsundays, the current would flow North or South depending on whether it was an Ebb tide or Flood tide (can't remember which one!). Hence it was better to navigate through channels at the turn of the tide when current flow was the lowest.

Is this a universal effect or just local??? The tide comes in at different times for different latitudes. For example low tide for today in Geraldton is 1319, Freo is 1415 and Albany is 1534. The water has to come from somewhere, so if it comes from due East or West, then is there a Coriolis effect?

I guess what I am asking is if you kite at some beach in Perth, what direction will the current flow if you are in a Ebb tide?

Smedg
Smedg
NSW
836 posts
NSW, 836 posts
8 Oct 2008 9:44pm
too complicated for me but i wouldn't expect too many swells or tides coming from the east if you're in WA..
lotofwind
lotofwind
NSW
6451 posts
NSW, 6451 posts
8 Oct 2008 9:47pm
^^^^^^unless a sunami hits the east coast
Danger Mouse
Danger Mouse
WA
592 posts
WA, 592 posts
9 Oct 2008 2:20am
If the water from the tide is flowing in the same direction as the wind and the flow of water is fast enough, it will have the same effect as the wind being lighter than it actually is. Needless to say that if they oppose each other it will have the same effect as if there was more wind.

I haven't really experienced it in Aus so much, but have here in a couple of places. This would be concentrated in a situation where a tidal lake or estuary has water flowing to it through a narrow inlet from the ocean as this would increase the flow of water.

D
vader
vader
NSW
418 posts
NSW, 418 posts
9 Oct 2008 7:09am
Kite Republic

D_Meredith79 is correct.

you want the wind and tide going in opposite directions.
it make huge difference. for example
16-18 wind and tide going same way could mean that the effect would actually be 12-14knt.

16-18 wind and tide opposite could mean 20-24knts. effectively

we have to take this into concideration every time we kite at dolls point .
cheers
echostorm
echostorm
QLD
1245 posts
QLD, 1245 posts
9 Oct 2008 8:01am
Simple answer, flood flows from the north, ebb flows from the south. Flood is high tide, ebb is low tide.
vertigo
vertigo
NSW
34 posts
NSW, 34 posts
9 Oct 2008 10:55am
I think you'll find your confusing 2 completely different things Whatthe. "Ocean currents" and "Tidal flow" are 2 very different things. You will normally have a current that flows through an ocean in a steady direction, and WA is no different, it even has a name.

Heres a quote from http://www.srfme.org.au/news/mar04.htm :
"The Leeuwin originates near North West Cape in Western Australia and flows southward towards Cape Leeuwin before turning eastwards into the Great Australian Bight. From south-eastern South Australia it was known as the South Australian Current and flowed to north western Tasmania. It then turned south again down the Tasmanian west coast to become the Zeehan Current, reaching as far as South Cape - and in winter flows north as far as the Freycinet Peninsula."

Everyone is right though in regards to tidal flow. Same theory as crossing a bar:
Cross while the tide is flowing in the same direction as the wind = Smooth rolling waves
Cross while the tide is flowing against the wind = Rough as guts, steep chop
whatthe
whatthe
WA
186 posts
WA, 186 posts
9 Oct 2008 10:55am
Echostorm: Thanks, that was what I was looking for So, I guess that means that in a seabreeze (SSW in Perth) you would feel more apparent wind when kiting after low tide as the flood is flowing from North to South. But the chop is steeper!

Vertigo: Agree, that there are two different flows going on, Ocean currents which are relatively constant and large scale, and tidal flow which is more localised and quite complex as it is influenced by the coastal geometry and ocean floor. Kinda similar to gradient breeze and thermal breeze. I know the Leeuwin current goes past Rotto, hence the coral at Parker Point due to the warmer water. Am wondering tho if it has much effect within 200m of shore where we kite?
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