SC you are right to be sceptical about SSW.I did a statistical  investigation into winter SSW events and the CET of the following month.half were above average half  below/I suppose a 50% chance of cold isn't bad given that only 1on 3 winters have a -NAO.

However I am not clear how long it takes for a SSW event to propagate down and turn into northern blocking?Is it a couple of weeks or longer?

Also whilst we turn milder by next weekend - I notice the NE USA will turn colder!? SSW or fate?

Another thing where ever on earth did such a low appear from - only a day or so it was hard to find a LP in the Atlantic on the GFS runs. This is so intense not to mention could be exceptionally mild - 12 - 13c widely. Hopefully this will modify and downgrade.

Yes Tally previous runs have shown the Atlantic to be very quiet and so it does make you wonder what has changed to develop this especially as its relatively warm across the pond so should have limited cyclogenesis off Newfoundland .

Tally I assume you missed the smily emoticon there? As has been stated several times today an 'SSW' has not occurred, is maybe forecasted to in a few weeks time and anyway takes several weeks to affect our weather if at all.

If I don't see the term mentioned again in this thread I'll be quite pleased 🤓

Missed it - I did watch Gav's weather videos too showing the warming sequence from Siberia into the polar regions towards end of month.

The sequence - run the chart of Stratosphere temperature 30hpa.

http://www.netweather.tv/index.cgi?action=nwdc;sess=

Doesnt look so sudden or warming anymore (well compared to previous runs) 

6z updates continue to suggest the ZI will increase significantly in the next couple of weeks. It will be interesting to see whether things are toned down as the time approaches.

what does ZI mean ???. or am I being thick

Zone of the Interior ???????? Maybe...

That's something I've been contemplating as well.  The best I can arrive at is that there were signs in the atmosphere of energy in the jetstream being disrupted and some of it dropping onto a more southerly track. That 'space' at mid latitudes across the North Atlantic allowed upper heights to develop.

It started to unravel when signals were picked up that the energy was gong to surge and to surge into the northern arm.  Initially the models toyed with retrogression and the jet diving south over Scandi, which killed any idea of a Scandi high. That was always an iffy evolution.

So, here we are having come round to the usual status quo, with high pressure to the south and the jet to the north, with winds from between SW and NW.

Still at least another 6-8 weeks of potential for cold weather for the south. If it doesn't happen then it will be March and the prospect of some spring warmth.  IMO we can't really lose.

Is ZI the new SSW? ZI is now on P1 since the HLB was DOA. MLB is OK but >96h was always FI so its goodbye to any CAA or low 850s and regardless of dps and 2mTs and your ASL, refs to MJO and QBO at phase1 is JFF - IMO. SSW at 10HPa - no way.

I hope that clarifies the current position we're in.

No disrespect but that's one hell of a statement to make on 16th January......

The light wind just moving to ESE here  in Winchester .METO fax shows cold front making some reasonable progress NE for $4 hours (then reverses back south aest)

http://www.meteociel.fr/modeles/ukmo2.php?ech=0&carte=2000

http://www.meteociel.fr/modeles/ukmo2.php?ech=24&carte=2000

http://www.meteociel.fr/modeles/ukmo2.php?ech=36&carte=2000

http://www.meteociel.fr/modeles/ukmo2.php?ech=48&carte=2000

CWF is Phil Neale to Shropshire's Graham Taylor. Best just to ignore.

I don't fully agree with this notion that once the model output shows zonal it stays like it for weeks on end. Yes, that has happened in the past and we've even had whole winters of it. But on the other hand it does very often bring in a completely new pattern of events and let's face it the one we've had this winter hasn't done us much good so far. While the Continent may temporarily warm up a bit it has still been a very cold underlying theme from early in the winter and I feel this is an advantage over recent winters. So with over six weeks to go I feel there is a good chance of a decent cold spell, if not spectacularly so.

A post from the other side which is interesting,

I would keep an eye out for a mention of a possible easterly bringing snow in the 16/30 dayer. 

That's been exeters traditional way of covering a potential SSW showing in glosea - of course if they see it being certain they will publish their blog 

enough uncertainty at the moment re timing and also if any reversal looks to affect further down in the short term. 

The models seem to displace 10hpa toward nw scandi but too soon to see if  further down follows. Only watching the end of the ens members and op will show if there is a quick trop response 

these may begin to show within a couple days at day 16 (if at all)

You may recall that back in early December when the models first began to move away from the idea of a cold spell later in December as had been suggested previously, we had claims at that time from one or two members that once zonality got going last month, it would likely last until well into the New Year. In the end, it only last for about a week.

As the events of the past then or so days have demonstrated pretty well in my opinion, the model output can sometimes be just as unpredictable and as volatile as the weather itself. Last winter's model output was, rather like the weather at the time, constantly awful and a total bore for coldies, but that cannot be said of either the weather we have experienced or the model output we have witnessed so far this season.

The model runs at the moment are genuinely fascinating. It seems like the atlantic is really trying to establish itself but everything is so lethargic that despite the pattern being westerly, the winds are so light the cold air is not being blown away. Real chance of some surprise evap cooling snow!