Throw away the iPhone. Who needs internet forecasts to predict when surfs on the way? All you gotto do is check the loo, bru!
Next time the wind is pomping as a cold front is smashing us, go check the water level in your toilet bowl. You'll notice it will have dropped a bit lower than normal. Say hello to the "Toilet barometer". So every morning instead of logging onto your phone to check the forecast, just pop your head over the loo and see what the water level's doing. Gone down? Good - low pressure system is around and there's a chance of waves.
It sounds kinda crazy, but it actually does work. Learnt it way back in the day from Seals legend and weather guru extraordinaire, Eric Stedman.
Here's the low down on the weird loo levels. Basically the water in your loo is in an s-shaped combination of curved tubes. If the far side of the tube develops under-pressure, some of the water will be pulled over into the far side, and water level in your toilet bowl will sink. Where your loo pipe comes out the wall it has a lil chimney pipe coming off of it vertically with a small vent at the top (which gets rid of the pong).
On windy days, this chimney can act like a pump. The wind blowing over it creates a low pressure in the pipe, which then sucks some water out of the toilet and into the pipe. Which is why you see the loo bowl level drop.
There's actually a scientific principle that explains the scenario: Bernoulli’s principle. It's all about fluid dynamics.
Because fluids like air and water tend to move towards area of decreased pressure, lower air pressure results in a suctioning effect throughout the plumbing system, which ultimately lowers the water level in your toilet bowl as the winds start to howl as a cold front moves through. Conversely, calmer weather conditions result in increased air pressure in the toilet and higher water levels as a result.
So go check ya loo during the next cold front. Betcha you'll notice the water level will have dropped a bit.