Only two tides per day in WA?

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bgreen
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Only two tides per day in WA?

Post by bgreen » Sat Sep 26, 2020 6:39 pm

A mate asked me about this and I don't have a clue.

Mandurah is reported having only two tides for September 26 and 27, but 3 times for the 28th and 4 for 29th and 30th.

https://tides.willyweather.com.au/wa/peel/mandurah.html

I checked another site and it also reported only 2 tides for the 26th.

On the 26th Margaret River was shown as having 4 tides, but 3 were of the same height:

https://tides.willyweather.com.au/wa/so ... mouth.html

Recent coverage of the Tasmanian whale beachings, had a ranger say tide was difficult to predict there because it was subject to barometric tides.

Any idea why WA would only have 2 tides per day in some places.

Thanks

Bob

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Cranked
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Re: Only two tides per day in WA?

Post by Cranked » Sat Sep 26, 2020 6:59 pm

Here you go:

https://scijinks.gov/tidal-curiosities/

We'll just have to wait until boo gets on board and explains it in layman's terms though.
“I don’t necessarily agree with everything I say ”— Marshall McLuhan

bgreen
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Re: Only two tides per day in WA?

Post by bgreen » Sat Sep 26, 2020 8:21 pm

Thanks Cranked. An argument for not making assumptions about tide times.

channels
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Re: Only two tides per day in WA?

Post by channels » Sat Sep 26, 2020 9:26 pm

Never noticed it when I lived there. I moved away and went back to visit and realised that the tides in WA were different.

Only a few places in the world that it occurs.

alakaboo
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Re: Only two tides per day in WA?

Post by alakaboo » Sat Sep 26, 2020 11:02 pm

The short answer for SW WA is that during neap tides the tidal influence of the sun and the tidal influence of the moon can almost perfectly cancel each other out at high latitudes. In Australia it's not common but it's pretty standard in the NW Pacific.

Image

The long answer is much longer and mathematical, and has to do with local geography, bathymetry, the movement of the lunar and solar tidal bulges across the ocean surfaces and how that is disrupted by the location of the continental land masses, the coriolis effect and barometric influences.
There's also very long period standing wave oscillations in some water bodies.

CoastalWiki gives a pretty good explanation
http://www.coastalwiki.org/wiki/Ocean_and_shelf_tides

bgreen
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Re: Only two tides per day in WA?

Post by bgreen » Sun Sep 27, 2020 1:39 pm

Thanks Alakaboo. The map was useful, for when travels may again be a possibility.

Beanpole
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Re: Only two tides per day in WA?

Post by Beanpole » Sun Sep 27, 2020 3:32 pm

No tides in the Meditteranian.

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No Pants Lance
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Re: Only two tides per day in WA?

Post by No Pants Lance » Sun Sep 27, 2020 3:53 pm

yes there are. as there is only one t, 2 r's and one i in it too.

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Wyre
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Re: Only two tides per day in WA?

Post by Wyre » Sun Sep 27, 2020 3:55 pm

nainaret-tide-M
godsavethequeen wrote:I wonder if reg is still thrashing the neighbour's elderly poodle with his wattle branch.

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Cranked
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Re: Only two tides per day in WA?

Post by Cranked » Sun Sep 27, 2020 4:02 pm

The 6 hour 2m tides in Indo are a treat, gradually subsiding into nearly 12 hours of less than half a meter. Its a killer walking 300m over bare reef with no booties too.
“I don’t necessarily agree with everything I say ”— Marshall McLuhan

Beanpole
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Re: Only two tides per day in WA?

Post by Beanpole » Mon Sep 28, 2020 12:21 pm

No Pants Lance wrote:
Sun Sep 27, 2020 3:53 pm
yes there are. as there is only one t, 2 r's and one i in it too.
I know. Predictive text doesn't though. Teach me not to proof read before posting.
Okay Skip, shall we say a small tidal variation then?

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