Originally Posted by mushymanrob:
“but it isnt.... thats the point... the noaa anomaly charts are very good at predicting the mean upper flow for upto 2 weeks ahead. they are predicting pressure to rise over france and southern europe with low pressure to our near northwest.
from that you can deduce the flow will be southwesterly, so its more likely to be muggy with cloud especially in the northwest, with rain too. warm in the southeast even hot..
the anomaly charts predicted the up coming cool spell with northwesterlies, again they were right.
so it isnt guesswork, although the detail cannot be predicted, the general pattern can.”
Predicting the general pattern does sometimes work beyond 5 days though it doesn't allow for reliable weather forecasts, for the man in the street, the devil is in the detail. Comments like "looking like a rerun of the last heatwave" at 7 to 10 days range are little more than guesswork - we can't usually be that precise at that range.
Sometimes, of course, guesswork guesses right (even Piers Corbyn!) but even then it's often for the "wrong" part of the country... which doesn't help Joe Bloggs much at all. I tend to think of the huge number of times that e.g. winter model runs suggest an incursion of bitterly cold air... and the almost equal number of times it remains a week away or fails to cross the Channel or North Sea.
Translating an approximate general pattern (approximate is what we tend to get) into a useful weather forecast for the man in the street, well that's what we can't do very well beyond 5 days, sometimes less. Not even the experts can do it reliably and I noticed that tonight's BBC 1 forecast "for the week ahead" pointedly stopped at Monday... which is only 4 or 5 days away. Two nights ago, Rob McElwee was talking about a "small chance of a shot of heat from the south" next week, which was a pointless comment if it was only a small chance. Last night he downgraded it to "a very small chance" and tonight, it wasn't even mentioned!