Nouska

A wee touch north again on the 12Z AROME and a more south westerly angle of approach. I might just dodge the worst of this bullet. Dry slot appearing on water vapour satellite - they must be reckoning on a sting jet with the forecast wind speeds. AROME ARPEGE Source. http://brunnur.vedur.is/myndir/seviri/2017/02/03/seviri_eurnat_wv6-2.html

Hi, yes, you too. It is looking like an exceptionally rough night and morning in your specific area. We've been chatting on a status update. The internet playing up badly now but don't know if it is weather related or something else - a bit temperamental like all utilities in rural France!

I hope you guys realise I'm sacrificing my roof in order to set up your easterly.

I think it is better to use the one with climatology - in this instance, they are all below climatology from the 8th.

Horrible forecast! http://www.meteofrance.com/accueil How long without power this time? Update with the 12Z models. Nasty squall line modelled before the wind comes in with full force. Strongest winds reaching your area Spike.

Comparing the latest ensembles for SW Holland to the 12Zrun I posted last night. There is still the 'shadow' of the previous run but much of the scatter afterwards has been resolved. There may be six clusters but a good percentage of them go easterly as early as the 7th. Looking at the extended EPS means - cold 850 temperatures right the way to the end of the run. eg. Edit to say - loving the up to the top button!

The wind direction from SW Holland (closer to SE UK than De bilt) sector tells that story. Rapid swings as the storms rush through, hit the block, then the flatlining in an easterly. Too much scatter for complete confidence but I don't see any other definitive cluster apart from the easterly one.

In view of current modelling, thought I would repost this again. Will this be another success for the NCAR CESM and will the cold get as far as it forecasts it to - I have more confidence this time - in both the model and what it shows.

This mornings ECM 360 hour ensemble mean still looking good - sees the Scandinavian high pressure still present at a good latitude, Atlantic kept at bay and indications of very southerly jet stream. The mean 850 temps not very low but do not need to be with a continental feed. Probabilities for T850 < -8C coming in from the east, starting to make an appearance.

A risk of a 'so near, yet so far' scenario when two of the stations are west and only one east - based on what has gone before, I'll opt for same figure as January as that seems to have been quite accurate. 3,9C.

The ECM 360 hour MSLP ensemble mean is an interesting chart as in there appears to be no connector to the Atlantic on the isobars - if I'm reading correctly, the east is the player and the spread for the south is quite low at fifteen days in the future.

Well, there are some historic cold February months in the NOAA upstream analogues derived from the GFS 06Z run! http://www.cpc.ncep.noaa.gov/products/predictions/short_range/tools/model_guidance.php?dayin=11 Why do those conundrums always feature on the last day of the month - when CET competition requires an entry.....decisions, decisions.... the ECM not buying it as yet and remembering sudden swing on cusp of the last two months.

It's interesting to note that the last two major SSWs coincided with that MJO phasing in a high amplitude. Jan '09 Jan '13 There's maybe something in the theory you were reading about in that paper - difficult to identify the chicken or the egg as the jump coincides with SSW commencement on 6th January 2013 but MJO leads well ahead of SSW date 24th January 2009. http://ds.data.jma.go.jp/gmd/tcc/tcc/products/clisys/mjo/monitor.html

OK ... here they are - if same time frames you are thinking of. Dec 09 Nov 10

January 2009 split had heights centred over Greenland. Compare GFS 06Z forecast split with heights focused on eastern Siberia. Would the end result not be similar or is there a risk of the two lows rejoining over the Atlantic when the core heights are not in that sector?

I don't know if it is mentioned in the first page or not but this question asked many times over the years. There is a good explanation in a specific thread in the learners section. Unfortunately some of the visuals are missing. Maybe an idea to link this in the opening post of the strat thread.

There are more promising signs of a wave2 development on the 06Z GFS - that would be the first step to get a better pattern above and then rely on this being reflected further down. from this to this At first glance, it may seem as if the core vortex is setting up in the worst possible location but there are plenty of historical situations where this has worked out well if a proper split occurs - simply because of the suggestion from Ed (I think) that the jet does not cross the split.

Thanks Ruben. The forecast penetration of a very cold strat over the UK was overdone on the first phase but looking better for the weekend with -84C overhead - should verify at such close range. Question - will there be clear enough skies to view and are there other missing factors to consider in the formation of nacreous clouds?

Agreed - just as an example, I'll include the SSW reanalysis charts for 2006 that I posted in the winter thread. pre 2006 SSW - almost identical to the current displacement. Afterwards the vortex moved over the Eurasian land mass and led to a colder pattern for the UK. This is the type of response Cohen is looking for in his recent report and what @Singularity was describing, either here or in the model thread. I'm not seeing that yet as the tendency this time is to want to move back polewards after each wave of warming. The QBO was east phase back in 2006 - the fact we are in a strongly west phase may be what is preventing the final push. Looking at the temperature chart does not help here - need to look at the geopotential heights charts that go with it. http://www.instantweathermaps.com/GFS-php/strat.php

A Bartlett, you say .... "not exactly the same as 1988 version" ..... damned right - nothing at all like the '88 orange monster. I've never seen a 'blue Bartlett' before ... maybe it's been affected by all the European cold. What you are seeing is mostly returning polar maritime air - a Bartlett has very warm upper air, centred over France, and feeds a constant train of tropical maritime air into the UK. Compare the 18Z animation to a typical Bartlett type chart.

Interesting to note that the SSW of January 21st 2006 was preceded by an almost identical pattern of warming and geopotential heights as are forecast for this one. The pattern that followed was different to what is being modelled in the far reaches of GFS. Back then the vortex buried itself deep over the landmass of Eurasia but on this occasion it is forecast to keep more over the N.Scandinavian sector.

Hmm... see references to SSW January 2013 similarity in model thread. Yes, immediate response to initial warming might be similar but a split vortex followed very rapidly. Nothing like this currently showing in stratospheric levels but that's not to say it will not occur, should there be a technical reversal of zonal winds as was the case back then. Edit for @Allseasons-si to show projected day 12 forecast. No signs of a split on GFS and not on ECM at day 10 either. The problem with the displacement is there is still the tail going back to NE Canada - not allowing the separation for heights to build in the gap. It's a strange year of disconnects - could still allow for something different to evolve from tropospheric up rather than strat down.

I posted the week 5 T850 chart on the strat thread - cold southern UK and down here.

We go from this ... to this .... The models will be playing around with what the effects are at the surface but the current move to a southerly jet stream looks like a fairly quick response to the strat picture or am I missing something?

I'm surprised that nobody picked up on his follow up to an earlier SSW tweet. Just guessing, as he says or are there signs in the longer range products they use. Late February on the EC46 has suggestion of negative T850 to the south and heights raised over N. Scandinavia.