In article ,
John Hall writes:
In article 20140103111029.77cd8e04@home-1,
Graham P Davis writes:
On Fri, 3 Jan 2014 02:01:17 -0800 (PST)
exmetman wrote:

Hi

The latest midnight run of the GFS model shows the first signs at
T+312 (16 January) of a change in type from the current seemingly
unending cyclonic SWl'y to a more of a blocked E'ly with high
pressure building to the NE of Iceland and low pressure belt being
pushed further south into central France. Colder air will obviously
follow if this scenario pans out...



Again? Will it be 2nd time lucky for an easterly forecast from GFS this
winter?

Since Christmas Eve, Matt Hugo has been pointing out that ECMWF was
hinting at a splitting of the stratospheric vortex - not an SSW - and
that this might produce a change of type.



I don't normally put much faith out as far as T+312 - or indeed in the
06Z and 18Z GFS runs, which I understand don't have such a full data set
as the 00Z and 12Z - but for once the 06Z is consistent with the 00Z in
what it's showing. As early as T+192 the zonal train is shown as slowing
down. However beyond T+240 the operational run is very much towards the
cold end of the ensemble.
snip

The operational 12Z GFS run has reverted to keeping things zonal, which
doesn't come as a great surprise.
--
John Hall "He crams with cans of poisoned meat
The subjects of the King,
And when they die by thousands G.K.Chesterton:
Why, he laughs like anything." from "Song Against Grocers"