FFF's method of forecasting: the more lines there are in the TAF, the more chance there is you'll be spending the day on the ground.
And then there's the method one of the ATC guys at my home airfield uses: he forecasts that tomorrow's weather will be the same as today's. He reckons this gives him something like a 60% success rate, which he says is similar to what the Met Office achieve.
Seriously, though, looking ahead as much as 5 days, I don't know of any forecast which gets it right consistantly. But what normally happens is that they get the general weather right, but the exact speed at which it's moving and the exact direction they might get slightly wrong.
What this means is that if they forecast a front that's going to stretch from the Scottish Highlands down to Devon 4 days from now, there will definitely be a front, but it might only go as far south as Birmingham and it might arrive 3 or 5 days from now (when they have no doubt forecasted good weather).
On the other hand, if the forecast is for three days of high pressure, with no frontal activity, then the chances are there won't be any frontal activity, and there will be a period of high pressure when the weather will be fine. Even if they get the exact arrival date of this high pressure slightly wrong, if you plan your "big flight" for the middle of this period the chances are you'll be ok.
FFF
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