On Jan 21, 6:09*am, Dawlish wrote:
On Jan 20, 10:15*pm, "Will Hand" wrote:





"Keith(Southend)" wrote in message

...

Will Hand wrote:

"Terry Tibbs" wrote in message
...
cold gone.
sucker gap wider

will?

The ECM is going a tad wild recently with deep low developments popping
up all over the place all depending on how the upper trough in the
western atlantic disrupts. Trough disruption there should tend to build a
Scandi high under normal circumstances, perhaps that's where the problem
lies, the usual difficult trough disruption process. The most consistent
model of late has been UKMO but you only see that to T+144. That model is
basically going for an anticyclonic easterly. A lot of dry weather but
snow showers in east and south. I'm sticking with that for the time being
as it is the simplest and what one would predict from first principles
without models to confuse us.

No sucking from me :-)

Will

GFS has been quite consistent with an easterly as well. Strange how ALL
models have their good and bad points / weather favourites.

It's not so much the models Keith it is the handling of complex situations.
What seems to be happening is that the wavelength has shortened over Canada
this weekend with an upper trough coming east. Just downstream of this (over
western Atlantic) is another upper trough which has a strong SSW flow on its
eastern edge, in other words a confluent but relaxing and eventually
disrupting upper trough. The strong SSW flow causes and helps to reinforce
the downstream Scandi/continental high through ageostrophic effects at the
right exit. Under normal circumstances this disruption process would force
any Atlantic lows to southern or even west of Greenland and build the Scandi
high to the north. Unfortunately the complication of the Canadian shortwave
means that the confluent/disrupting Atlantic trough gets a "kick up the
backside" which crucially alters its orientation to more SW'ly or even
WSW'ly bringing more flow into the Euro high preventing it from building
northwards. Thus it is a fine balance as to how it builds and all depends on
the western Atlantic developments. Interestingly 18Z GFS builds the high in
the short term (rest of run not in yet), but I fancy maybe a strong SW flow
eventually getting into NW Scotland so *could* end up milder there.

Will
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The 00z gfs shows what I was thinking yesterday that it might; a
sinking high and milder, west to north-westerly conditions affecting
us at 10 days around the top of the high. Is the death knell of the
deep cold being tolled? Or is this just another model twist?- Hide quoted text -

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And then when you think you may be seeing something that may be an
actual solution, the ECM doesn't sink the high and suggests, instead,
the northerly that has been hinted at a couple of times in the last 2
days by the ECM and once in a gfs run. Nothing sorted at 10 days
still. Back to the lookout post!