On Jan 6, 9:15*am, John Hall wrote:
In article ,
*Eskimo Will writes:

Apparently this has been written in consultation with very senior
"suits" and not just by the forecasters. Shows the increasing
concern for the weather in the second half of January. At some
stage commitment is required one way or the other.

I see that, with the 00Z runs, the GFS operational run has fallen into
line with the ECMWF in bringing in a spell of easterlies. The two models
diverge thereafter. GFS brings back "normal" conditions after a few days
whereas the ECM is still keen to follow the easterly with a northerly
(though perhaps not quite as quickly or quite as strong as the 12Z was
indicating).

The GFS operational run is at the cold "end" of its ensemble, though the
cold spell does show up in the mean solution. There an unusually wide
spread of ensemble temperatures from as early as six days out, with
850mb values of anything between -8C and +3C possible.

The UKMO operational run seems to be out on its own, with no sign of
anything cold developing up to T+144.
--
John Hall

* * * * * "Whenever people agree with me I always feel I must be wrong."
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *Oscar Wilde

'anything between -8C and +3C possible'

That is consistent with the original forecast which stated 'great
uncertainty'.

I have often wondered about these wordings.

I guess in terms of unusual cold, great uncertainty means 25%
probability.
Uncertainty means 50% probability.

75% probabilty or more would lead to a statement about confidence in
it happening.

I am right?

Len
Wembury