I've seen a rope version of this in the Alps, where it was dubbed 'gypsy forecast'. The only variant was that if the rope was gone, it had been nicked.
There's a big version lying in the Clyde, called the Ailsa Craig.
Girvan aphorism: "If you can't see the Craig its raining. If you can... its going to."
Bit like weather forecasting by cat;
If cat disappears it's foggy
If cat goes white, it's snowing.
If cat disappears downwards it's been snowing
If cat disappears sideways it's windy
etc etc etc