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Old February 5th 10, 09:21 AM posted to uk.sci.weather
Dawlish Dawlish is offline
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Default Cold, frosty and wintry on Valentine's Day

On Feb 5, 7:38*am, "Alex Stephens Jr"
wrote:
"Dawlish" wrote in message

...

That's enough for me. 5 gfs runs with agreement from the ECM leads me
to a 10-day forecast.


**At T240, on Valentine's Day, the UK will still be in the grip of a
cold spell. There will be snow lying in some areas of lowland Britain
and that snow will have been on the ground for some time, causing
disruption and travel problems. On the 14th, the wind direction will
be from a continental, or a northern source and temperatures across
much of Britain will be below average.**


Well there you go. That, for me, is the probable outcome of 5 days of
some of the most interesting model watching of recent years. Dig out
the thermals, we've got a week of cold coming, starting at the end of
the weekend.


I think this is the models forecast rather than your own
Alex.


Not really Alex, that's not the way this works. *))

The models show what they will at 10 days. If we took their output at
that distance as a forecast, the accuracy rate would be so low as to
be completely unusable. This past week is evidence enough of that.

The technique that I use recognises the times - and those times are
few, IMO, as a result of model watching for years now - when the
output at 10 days *can* be trusted and that's all I do with these
forecasts. At present, I think it can. Over the last week, you
couldn't believe any of the model output (their "forecasts") at all
really, could you? Hence any forecast, based on this technique, would
only have had a low confidence of it achieving outcome.

Of course the forecast is taken from the models; all my 79 forecasts
have used a very similar technique, but as a result of doing all those
forecasts, I feel that I'm able to say, with 75%+ confidence, that the
UK weather on Valentine's Day will be as in the forecast above. Of
course, that means I'll be wrong about 20-25% of the time, but I'd
take that accuracy. If I had, say, to organise a ad hoc Valentine's
Day speed skating event in the fens, that I needed at least a week to
prepare, I'd now be beginning to put preparations in place, as I think
I would have a 75% chance of cold weather providing the right
conditions. I wouldn't have started those preparations during last
last week, despite the models showing cold conditions at 10 days.