Surviving Weather Men 2

Let us speak of ships and sealing wax. Or more properly weather and probability. Everyone hears the probabilities from the weather beavers but they never bother to tell you what they mean by it, so it’s almost a useless thing.

What is amazing is how dumbfounding it is for nerds who know – at least intellectually – about probability and find out what weather beavers mean.

There are basically two definitions of probability: temporal and spatial.(Time and Space) 

If you stand in one spot and observe from second to second (or minute to minute….) whether that spot is sunny or shadowed and write that down, at the end of an hour or a day the fraction of time that the spot is shaded (ratio of time shaded to total time spent observing) is the probability of being shaded. That’s temporal probability.

If you run about from spot to spot and observe whether that spot is shaded or sunny, and write it down, then after you have run to many spots, the ratio of shaded spots to the total number of spots is the probability of being shaded. That’s spatial probability.

Now what about weather? Well, it’s a combination of spatial and temporal. If a weather beaver says there is (e.g.,) a 60% probability of rain then what that means is that over a day’s time and the total area of the forecast (which is usually the “viewing area” for television weather forecasts,) there are six chances out of ten of rain falling somewhere and somewhen. 

What it doesn’t mean is that there’s a 60% chance you will get rain. It doesn’t work that way. Nor does it mean that 60% of the people in the “viewing area” are going to get rain. It just means that there is a 60% chance that somewhere in the viewing area will get rain. 

It’s maths, folks, and the weather beavers figure you are incapable of understanding maths and if they try to explain it to you in a meaningful manner you will get bored and do the channel flip thing. And then they lose money. 

Incidentally, the bored thing doesn’t depend on whether you get maths or not. Because talking about maths simply bores those who don’t get maths because it’s blah blah and bores those who do get maths because what is being said is too simple.