Cheshire Freeze

Just looked at the mean pressure anomalies of the ECM ensembles...note the retrogressive signature between 216-240 hours.

I wish we could see pre 72 hr UKMO... All we have to go on pre 72 is the ECM and GFS...and the latter doesn't seem to be covering itself in glory just at the moment.

It did. You can see the flow straightens up far too quickly overnight Thurs to allow a proper Cheshire gap streamer to develop Already pretty N'ly by midnight

Takes until 6pm Thurs to clear the legacy of that wave feature to the S. jaffa cakes poor from ECM in the closer timeframes it has to be said (compared to what it was showing a day or so ago).

Agree, late Thurs through into Fri AM looks best bet down here. Before then, showers concentrated N Cheshire, Gtr Manchester as you say.

Yep, that wave feature needs to do one...it has a knock on effect for us as it delays the cold flow and veers winds more w'ly ahead of it for a time. Without the coldest uppers earlier, you delay triggering convection.

Someone call an ambulance, I'm overdosing on blocking

Yep as I said last night to Nick, get enough amplification initially and you stand a chance of some retrogression as continued signals suggest vortex movement away from the Canadian side. What we don't want a half a job Annie situation where we get a trapped Euro ridge. High risk!

192 hours. Lovely stuff.

And, more importantly, look at the vertical advection on western flank!

The window for us is being cut short by little shortwaves in the flow- one to south Thursday which halts the NW flow somewhat and one from north on Friday. However, Thurs eve still looks interesting here...this is Cheshire's best chance

UKMO nigh on perfect wind flow for us in S of region Thursday night ECM not bad 25th Dec 2004 kinda direction

Cold uppers, light winds, continental drift, snow on the ground?....-15 easily possible in places

192- Snow possibly pushing slowly W across England...bitterly cold

Are you going to be snowed in Knocker

Indeed, prolongs the cold to 144 and we'll find out in the next few mins whether 168 is a real stunner....

Oh my Stays very cold for the majority too

GFS has us in a westerly at 120 ECM and UKMO N'ly

ECM & UKMO virtually identical at 96...GFS less so. 120 ECM should tell us more... EDIT: perhaps even a tad sharper than the UKMO, still very cold across the UK with -8 uppers relatively widespread

Not too bad is an understatement! Deepish troughing to E and strong ridge going up over the top. As good as earlier ECM...

Yep, another quite significant backtrack from GFS on the 0z

''The control is just the same starting conditions as the Op but run at a lower resolution. If there is something dodgy about the initial phase of the Op then that carries over to the Control too'' If it was as simple as this then whatever was causing the op to be too flat at 12z would be initialised with the control. Therefore the chances of finding that highly amplified pattern would have been slim. By your logic. I'll just maintain, the ensembles are generally useless IMO. If the OP can't stumble on the correct way forward in X amount of runs then pray tell how the 20 ensembles +control of GEFS will?

If it was that simple, the 12z op should have been a stunner too like the 12z control!

It's clear to see what the GFS wants to do in FI...which is lift low heights right out of the western half of the Arctic, more especially the Canadian sector. It's an awkward progression as upstream we see a clear move towards what you have described, but downstream we seem to be in some sort of hangover from the easterly attempt. As you say it's one or the other which is favoured or both ONLY if we can get that block to be a true Scandi high rather than more of a N Euro one.

But supported by the control....which is a downgrade on its 12z run. All finely balanced i'm afraid.