Purga

Looks like a good run to me with the high shifting NW to cold incoming...

Still looking like a cold spell is on course for the end of the month. No real changes in the last 24 hrs. The general trend is towards colder weather later this month and the two clusters within the ENS will invariably switch one or two members with each update. Of note is the METO update today. Their choice of words are very wintry for any part of winter. They have been pretty consistent and the as have the ENS. The only inconsistencies are the op runs which is to be expected considering the unprecedented events in the Stratosphere SSW.

The 12z GEFS do show quite a spread! There is a 15C spread as early as day 7, then 2 clusters with a circa 50% split. The cold cluster, shows good depth of cold (a lot below -10). The milder ones include the Op + control 15 of 22 runs of the 12z GEFS go below the -10 line for the South, excl the Op.

Unless it shows a cracking easterly blizzard of course - then it gets the Oscar..

The GFS op shows one of the milder members of the pack this time. There will still be plenty of much colder runs in the ensembles = fear not...

Cracking 06z ENS! BTW don't overlook NAVGEM this morning...

Southerly tracking jet.... Any good?

Strong signal from the GEFS mean run (extended range) for a blocked scenario with cold easterly winds. The blocking then retrogresses to Greenland http://www.meteociel.fr/modeles/gefs_cartes.php?code=21&ech=192&mode=0&carte=0

Indeed Nick et al... 06z GEFS trending colder but still uncertainty evident. The wind spreads (for De Bilt) shows that EPS favours a more solid easterly cluster: The latest GEFS cluster analysis data points to the same: http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=euro&MODELL=gefs&MODELLTYP=2&BASE=-&VAR=cpre&HH=324&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

The way changes in the stratosphere work their way down into the troposphere isn't that well understood For most on here (coldies) a SSW facilitates a series of very complicated events which raise the odds considerably of a decent cold spell - but don;t guarantee it of course. To get 'real cold' (assuming we want sustained very cold air) you need blocking and the jetstream to be deflected. That is precisely what a SSW achieves by reversing the wind direction in the stratosphere and disturbing the jetstream below. As for the model output, we should avoid keep over-reacting to one or more operational runs. The atmosphere around our latitude is a particularly active region and incredibly difficult to model accurately at the best of times. When you have potential impacts from the stratosphere it adds another layer of uncertainty, especially as these are infrequent events.

The SSW does look to be of historic magnitude and we should expect to see some pretty extreme output from the models methinks. Of interest is the broader 45-75N zonal index. It shows the historic reversal of winds. As this is an unknown situation for the models, it'll be fascinating to see how they handle it in the coming weeks! The ride is just beginnig!

Admit it Nick, don't you just luurrvvv the drama ?

Yes ECM ends well whichever way it's presented NH view is a cracker

t's not always a problem though is it Nick

Sorry - must keep positive

Mild sector alert! Seriously though the trend is very good and the potential change looks to be starting much quicker.

Significant blocking showing in the GFS 12z Op run already at day 7

The answer on Wednesday afternoon is a big NO

Reverse psychology Nick? Exeter seduced as well ? PS:

A cold outlook from NOAA for February Greenland and the Balkans anomonously warm - for a change

Split the PV nicely in half...... far reaches of FI looks a peach

A potential lengthly cold spell developing especially for the SE, if GFS 18z is to be believed. A good example of the models underplaying the strength of the developing cold block to out NE / E and the difficulties of brief warm sectors trying to shift a cold boundary layer i.e. indeed FI could turn out quite interesting! keep the faith...

One's Monday & the other's Tuesday

That's done it...... Don't worry, FI to the rescue Feb should be an 'interesting' month and not in the Steve Davis sense

That's snow joke...