GFS Op 00z: HP moving up from the SW and after a couple of false starts (troughs embedded in SW-lies affecting mainly W districts Sun 2nd and Tue 4th) is well established 1045mb N England Thu 6th. It's mobile and soon moves on to the Baltic where it settles until Tue 11th with not-very-cold SE-lies for Britain. After the 11th it extends a broad ridge W-wards which covers Britain but all swept away in the circulation of LP 960mb situated near Iceland.

ECM: similar to GFS but manages to bring the cold pool which has been lurking on the Continent to Britain on Mon 10th.

GEM: like the above but various small cold pools are floating around, Fri 7th assisted by small LP 995mb off Biscay and Mon 10th as ECM but mostly affecting eastern districts.

GEFS : rain now for the SE, and matching GFS, small amounts Sun 2nd N England and Tue 4th NW Scotland. Op  then dry throughout and control mostly so,  but an increasing number of other ens members have rain from Sun 9th onwards with typically 1/3 chances of snow widely. Temps mild at first, mean back to norm or a little below from Tue 4th (the main cluster of ens members is below norm by 2 or 3 C but the mean is sustained by a few very mild outliers.)

I guess it's the kind of pattern that a tweak in atlantic energy/angle could make it more widely cold or more atlantic flavoured with any cold being kept over Scandinavia. Currently though as Ally mentions, cool and fairly bland looks favoured once the HP does establish post day 5 or so. 

In some ways I'm rooting for the bland HP nothingness to last a fair chunk of the month. Not because it'll be particularly enjoyable weather but because the MetO three monther had a strong signal for milder than normal, wetter than normal and windier than normal and if month one is the opposite I'll find it amusing. (Obviously March/April could then be uber unsettled and compensate but still). 

So much potential….

If the block stays in place and retrogresses towards Greenland, then of course we could be in business. But that is probably another 2 weeks away

The problem is, that big chunk of Vortex seems to have dug in over Greenland. It doesn't look like moving anywhere.

This may change, but blocks with energy going over the top always seem to topple under the pressure ('scuse the pun)

Was ever the situation (apparently) 😉😂

Yes but the energy isn't going west to east. It seems to be cyclonically moving around the Greenland/Canada vortex such that western progression has completely stopped by the time we get to the UK, instead we seem to have south to north motion of large scale systems at this longitude. So this chunk of vortex isn't really impeding the development of a scandanavian high at all, other than we really do need a chunk of that vortex to undercut a bit more such that the scandi high develops in the right place.

If it propagates down we are looking at the first week of March before it does anything for us on the surface. By then the mood in here has firmly switched to spring yearning. Arguably the cold rampers lose their majority in here in about 2 weeks (with 2018 being an exception ofc).

Still on the plus side MJO could be in phase 7 by mid month, so the best case scenario could be a continuation of a cold spell that becomes more severe and peaks around mid month.

I think the retrogression towards Greenland will be needed to get proper cold air in as the air to the East is nowhere near cold enough and it looks like any retrogression would be at least 2 weeks away.

The good news is, this is a very common and natural progression from a scandi high. The deep high is going to cause alot of deep WAA on its western side which should raise heights westward. 'Faux cold' where a chilly but impressive scandi high preceds the real event with a greenland high is such a textbook sequence.

Like the 00z the 06x splits the PV at the end:

Long range ECMWF zonal doesn't reflect any reversal of zonal flow but if this run verifies we would see an SSW and a reversal of zonal winds as well as a split of the PV. - Interesting how this SSW (if comes off) is occurring around the same time as the BFTE in Feb 2018).

Which is close to what the GFS 6z shows in the furthest reaches of FI. The details of the evolution wouldn't lead to a great spell for the UK - but the detail (hell, maybe the whole broad evolution) will be very different come the time anyway.

Concur. A skeg of GEFS shows very few Atlantic dominated solutions. Instead we see a range from a cool tug to decent CAA with -12 uppers. It’s a slow, almost tortuous move towards a decent cold spell but it might just get there.

https://www.wetterzentrale.de/en/topkarten.php?map=1&model=gfs&var=2&run=6&time=204&lid=OP&h=0&mv=0&tr=12#mapref 

Would be happy to be proved wrong though!

In terms of the op run, I thought it was a decent run albeit it takes until deep FI to usher any cold uppers our way. I suspect it'd be pretty cold at the surface for many though before that point (even if the current T2M don't show it - GFS has been poor for MBY in factoring in low level continental cold). The retrogression signal towards the end is also nice to see if a reboot/prolonged cold spell is what you want to see and would be welcomed by some of those Scottish types who inhabit the eastern coastal areas😉

I definitely wouldn't want to call the mid to long term at the moment, outside of saying it's looking potentially dry for most. I think the evolution to upper cold if the pattern persists is reasonably plausible, the issue most of the time is getting the pattern to stick around long enough rather than the atlantic pushing it away before it can get interesting. 

Yes, although the height of the 0c isotherm is something I look at when there are cold scenarios in the offing.  For my patch the 06z keeps the median value for the 0c isotherm mostly below 500-600 metres from 7th to 14th. A very few mild outliers, as you have noted, drag the mean above the median: the distribution is very much skewed towards the colder options.

If this is the cold pool we are tapping into then its strength will be determined by the strength of the cold core low. The stronger it ends up being, the more divergence, the more expansional cooling and decrease in the uppers. So not really so much dependent on how cold the continent is?

Yeah with a much colder continent we could have been looking at ice days rather than 5c maxes which is frustrating.

 What does this mean?  Doesnt the increase in solar heating also have an effect now?

It's the same as adiabatic cooling - the principle that an expanding gas cools. 

The effect of increasing solar radiation as the sun moves back north is different.

If you notice how severely bland temps as in the past we get below 0 to -5 daytime to high of 13 or 14 in winter to now 3 to 5 while mild temps no change otherwise we should be getting 15 to 17 maxes.  UK climate getting very worst with severe temperate levels between winter and summer now.