Cheshire Freeze

Remember, we were undone by continental heights last winter. Never underestimate them...the issue is the modelling often does (or has at least seemed to in recent years). I can't get the EC output out of my head from last winter where it constantly progged Euro heights falling...wrongly!

It doesn't look like the logical progression to me...but what do I know. The jet will follow the path of least resistance, which means that heading into Europe is out of the equation as there is a displaced 1025 mb wedge of heights there! Best case scenario from that chart is WAA gets far enough N around the UK to allow HP to replace that Scandi troughing. From there we, in theory, could see HP stretched from Scandi to Greenland with the jet being deflected underneath. It's a complicated route for all that to fall into place without other spoilers popping up though!

Perhaps I'm just being impatient It is a good chart from a NH perspective but we all know that these 'fly in the ointments' can come thick and fast for the UK until the overall background picture is no longer conducive to tapping any cold! Then we all sit here long faced, scratching our heads and picking the bones of what went wrong. 9 times out of 10 this is simply how it works for the UK unfortunately.

It's not bad at all hemispherically but for the UK it's trash...as ever. Over the past few years whenever the AO has gone negative we've found ourselves in the path of the WAA so that other areas of the hemisphere get the cold.

Yes I was somewhat encouraged when looking at the 30hpa level on this run. That's the sort of stuff we need to see more of in upcoming runs.

My main concern Nick in reply to your earlier question. It looks like we're heading towards a period of trop vortex disruption, but looks to be just a couple of weeks too soon...which is why I'm a bit dismayed that it doesn't look like it will be 'sustained'. We got pretty lucky at the end of November 2010 with the depth of cold available and I'm not sure that we have the luck to push this time. However we'll see. It'd be nice to see something pop up in the strat forecasts to add another attempt to the pipeline for mid-late December.

Sometimes you just 'know' Nick. Call it years of hard earned experience! By sustained I mean something that sees us into winter proper. Had we had decent strat and long range modelling support, I'd be a hell of a lot more optimistic.

Exactly. I can't see any support at all for any sustained high latitude blocking going forward.

This is why I warned people not to get too excited... The pretty hemispheric patterns are quickly fading on the GFS...that's two runs in a row now. Compare that to the 12z ECM of yesterday for same timeframe- We're now back at day 10 before we start to see manifestations of interest once again History shows we've been here many many times before and history also shows us that any promise is likely to be held in FI before being snuffed out altogether once this trend starts. P.S @bluearmy The EC46 proved itself to be about as useful as the morning after pill in a nunnery last winter!

Hmmmmm it was a very very tenuous one! I believe the strat guys gave a reasonable analysis as to why it didn't quite cut the mustard

Usually with the sort of charts on offer in the circa day 10 timeframe, I'd be getting a bit giddy. That is one huge Siberian HP and is usually a harbinger of all things winter. However, I have a nagging feeling we'll see the 'pretty patterns' of the progged shredded vortex dry up pretty sharpish as we head towards December. We need to see warmings of the strat if we're to prevent the upper strat uniting with the trop to bring the usual December dirge. Unfortunately there is little sign of this at the moment. So those getting carried away may want to keep their excitement in check. It's pertinent to note that most of the 'legendary' years kicked of with a Canadian warming early doors... Last year served as a lesson to us all just how quickly the trop vortex can ramp up once zonal winds increase.

Looks good, but on top of it all there is this for the same timeframe Vortex looks to be tightening

I was just about to say the same thing. It went downhill rapidly after that point.

@northwestsnow You can clearly see the NE Pacific HP here Omni present it seems. It's always there or there abouts in the model output. I think some have attributed it to the +PDO. I guess until this flips, we're stuck with it.

It's having the effect of repeatedly sending cold down across Canada and the USA which is helping to form lows and firing up the jet stream as it heads out into the Atlantic sector. This in turn is preventing pressure rises where we need them and promoting pressure to rise across the continent. It's text book stuff and has been happening every winter for the past few years now.

Most probably the Pacific temperatures just off the west coast of USA/Canada. HP has been semi permanent there for the past few winters and is forecast there again this winter.

Quite. As I understand it, the MJO has less effect when there is a strong ENSO event as it is somewhat 'drowned out'. Saying that, last winter was fairly ENSO neutral and we were stuck in the doldrums somewhat. As for the longer range modelling, I don't think we can attribute the output to a strong nina forecast as the CFS seems to be at around the -1 figure. Historically, a value between -0.5 and -1 has been seen to be the magic value in terms of getting a cold winter.

I'm correct in thinking a long range forecasting model is still a forecasting model? Moreover, the longer term NWP is interlinked with the nearer range so it's all fair game as far as I can comprehend. Maybe the thread should be renamed 'Short to medium range model output discussion'?

Absolutely. Christmas Day 2004 is a good example of what can happen even in a generally +NAO set up. Couple of inches of snow here from an Irish Sea streamer that day. Perhaps worth noting that even with the +NAO signal, there are some runs which bring mean uppers a couple of degrees below average from the W/NW which perhaps hints at the potential for a colder version of zonality than we might usually expect. Higher ground of the N could do very well for snow even with a +NAO.

High pressure was never even close to getting a foothold to our N. There was a mean mid latitude HP signature hauled up below a very strong circum- polar flow.

The ECM seasonal went for a strongly -NAO winter last year. That's all I'm saying. I'm not being 'down- spirited' at all. I'm merely pointing out where we are at right now and where we are *most likely* to be headed as we approach winter proper. People have had digs at me for being negative in recent years but looking back in hindsight, the negativity was very very justified...

All aligned wrong for us. Early cold pouring into NE USA as per usual which will only serve to fire the jet stream up. This is a recurrent theme of recent winters with an antagonistic response of pressure rising downstream across mainland Europe. About as flat as you can get across the N Atlantic sector.

One such case sticks out in my mind (and it was the last genuinely cold and snowy period)....March 2013. The CFS saw that coming from two months away. Nailed it. Not sure whether the GLOSEA saw the same signals as wasn't really checking that model at the time. These sort of charts were being churned out regularly leading up to the event, with HP shown somewhere between Scandi and Greenland At the moment we're seeing no such inclination from any long range model and it has been this way for months. Averaged CFS output produces this over D-J-F Strongly +NAO and mirrors the GLOSEA almost down to a tee. Extrapolating from that modelling...best hopes are lee NW'lys if depressions track favourably to our E/NE.

Long range modelling has always seemingly had a good handle on default 'zonal patterns' so confidence in this outcome should be higher. They tend to struggle more picking out patterns against the normal climatological mean. In a broad sense, the CFS and GLOSEA have been rock solid behind a +NAO winter for months. I struggle to see what will alter to change their prognosis.

I looked last night. Looked horrendous with +NAO right through to Feb. I'm not feeling too optimistic at present but you never know with the weather!