kold weather

By the way as I mentioned on the other thread, ECM ensembles actually do seem like they are honing in on a possible snow set-up between the 29-31st of the month, that maybe a time period just to keep an eye on and see if other models start to clock the same thing.

The GFS based models (such as NMM, WRF, obviously the GFS) are quite keen on doing something with the trough, other models are basically showing nothing there at all. I suspect given the cyclonic nature of the airflow and low pressures that the GFS idea is correct and there will be troughing heading west. I see the fax charts also suggest this. Given time of day, probably not much will settle but it will be nice to get a heavy snow shower come through, and could get a brief dusting before it all melts again.

ECM ensembles are certainly not as good down the line with more and more Atlantic lows powering up in the central Atlantic in early Feb. I'm not convinced about that trend but we will see. I've not seen what the Arctic is doing yet so I won't comment on that. Also still a very wide range of options on the table to be fair! The other more positive thing is there does seem to be strengthening agreement for a possible larger snow event around the 29-31st, indeed that is reflected in the ECM ensemble mean having an area of lower heights over the UK for the 31st. There is going to be a fair amount of uncertainty with locations, some give just a small load locally, others give a country wide snow set-up. So in terms of the ECM, a mixed bag, potential in the medium term but not as good further on.

I think a lot of the differing views are based on where people live, EG those in the north and west are broadly ok with the set-up as it gives them repeated snow attempts. Those in the south and to a degree east are not too keen as this set-up offers little, especially compared to the snowy easterly they were seeing just a few short days ago! The truth is probably inbetween, but sometimes its hard to not let your biases seek in.

Lets have some fun: 3.9C, 105mm. Cool and cyclonic overall. blocking to the north/north-east keeping us in a broadly cyclonic flow for a fair chunk of the month. Some of that 105mm may come as snow.

I would think high evelations such as the lake district mountions, Snowdon, W.Scotland Highlands, etc are probably going to be getting some big falls, Ii'd suggest probably not the day to go hiking as conditions could go down very rapidly and the models are all suggesting quite an aggressive flow with regards to instability so they may be near constant in those favoured locations. I'm betting some lucky person scores 6 inches tomorrow at higher elevation in a favoured spot. Totals lower down will depend on just how much 'melt' time there wil lbe between any showers and just how warm the surface still is, as sadly this winter has been on the mild side thus far bar the odd frosty night.

Its certainly been a very lagged response, but perhaps that shouldn't be a surprise given the QBO we have at the moment. If I recall 2013 had a similar base state and that one took the best part of 2 months to get going. Of course once it did, it pretty much tanked the whole way through March, with locations Midlands north cashing in. Could quite easily still see a long period of -ve AO but that doesn't mean all that much. I seem to recall a strong -ve AO happening in Jan 1998 and that was hardly inspiring either for us, unfortunately sometimes despite getting decent blocking in the Arctic, it just doesn't have an impact on us if other factors are dominating even more, such as that PV lobe over Canada.

The other thing to note is that there IS some ridging, indeed 48hrs chart from the model shows quite a plump ridge from, but the PV lobe has been pretty unrelenting thus far and there energy flattens it out and indeed forces a NW airflow pretty quickly. Also the SSW may be a bust for US but if you take a look at the N.Hemisphere profile by 240hrs there is a pretty large and strong Arctic High in place...its just that unfortunately for us its literally on the other side of the world and so is of only minimal use for us IF the PV lobe does ease off. Ensembles still are trying to develop some northern blocking, or a block of some description to our N/NE but a large chunk are instead dominated by that UGLY Atlantic upper low that sits and rotates milder LPs onto our shores...man I really hate that upper low in that position, with a passion! May still be ok for the north but if that happens, game over for the south.

What is worrying is the fact alot of the GFS ensembles are also throwing out that rounded Atlantic low and it's been getting more and more support each run. Trend is not our friend On the face of it this has got potential still but I really worry that there just won't be the cold to tap into, especially further south and that we could end up with cracking northern blocking and STILL get shafted because of overly bloated Atlantic troughing that may not disrupt enough. On the positive side, we would be hugely unlucky not get one decent countrywide snow opportunity, surely the upper trough won't be quite that circular. Plus the AO does look like it's heading into the cellar so the SSW looks like it's finally having a decent impact.

ECM truly is awful for sustained cold. It may well evolve a decent block eventually but the Atlantic tracking LP's would suggest that even if a block does get into place there would be a real lack of any cold to tap into, especially if we do go into a Scandi based pattern, the LPs will just rotate and disrupt SE drawing in too mild air from Europe. Worst run I've seen for a long time in terms of potential for cold in the longer term. Maybe that's too negative, but this run really would put any sustained cold spell another 15-20 days away IMO...though could argue that the NW part of the country wouldn't be too bothered after this week.

Try living down here, the 12z ECM is VERY boring run! For you guys up in the NW its certainly good, though even then the 12z ECM really isn't *that* great, its 24hrs of snow showers followed by heavy rain, followed by 24hrs of wintry showers, followed by rain, etc...

True, there is still plenty of time, though odds are looking more likely that the pieces may not quite line up the way we need them to for us to benefit. Anyway 12z ECM forms a little polar vortex lobe to our NNE which in its place completely screws over the NW pattern we had been developing. Even IF northern blocking did develop, the 12z ECM would still be a poor run from 240hrs onwards as there would be no cold to tap into due to the placement of the Atlantic lows...that's just about as bad as it gets as northern blocking would just lock in a broadly average temperature distribution. PS, NW dominated weather isn't that uncommon, you can get those sorts of PM set-ups even in the most zonal of winters with a raging +ve AO. The ECm in particular id basic about as standard as you can get for the UK after 144hrs.

That is a bit of a grim ECM on the face of it at 216hrs, in terms of where the atlantic low is going. I really don't want to see any low in that position its on at 216hrs, any cold is going to get washed away from Europe and its going to need a great fetch to being it back...and judging by this winter...

Also with the showers your going to see the snow level come down somewhat anyway thorough evaporative cooling. The snow shouldn't be marginal bar maybe right at the coast. Settling snow should happen BUT whether or not they have staying power, especially given how warm the surface still is given how relatively mild December was and also given the fact the low level will be moderate quite a lot by the Irish Sea, a lot is going to depend on the frequency of the showers, because there will certainly be melting inbetween the showers. Also GFS para is again a tale of two halves. NW half of the country (plus Wales!) look snowy and cold, the SE half (though E.Midlands probably joins in with the snow) broadly more changeable temps and *mainly* rain (can't rule out a well placed LP/trough like the 12z GFS op had). If things really do get as cyclonic as the GFS 12z op wants, possible flooding issues may arise for some to the south of the snow line, though the dry first half of Jan will probably limit that somewhat.

Plenty of cyclonic activity within the constant NW airflows we get, with the caveat being the GFS is nearly always a solid 1-2C too cold on this sort of flow, hence why the GFS had backend snow for tonight whilst all the others models showed nothing of the sort. Looks to be a very frustrating pattern for us in the south, little to look forward to other than copious amount of rain and maybe the odd wintry trough working through. As has been said, everything sets up a little too far NE and flabby, so whilst we do get a brief, much needed shot of deep cold into our area, its soon forced away. The ECM ensembles that I looked through earlier broadly did the same thing.

End of the run sees the pattern resetting back towards what we are going to see this week as the upper blocking shifts eastwards. Overall this run is: 1: Cold for a majority of the time. 2: Snowy for Midlands north. some exposed parts in NW England, Scotland, Ireland, etc could see very large falls of snow simplat due to how stubborn this NW airflow becomes, regardless of fronts. 3: South is very wet, maybe the odd transient snow event but get the rowing boats out because all the good stuff is to the north!

Unfortunately this is going to be what kills us down here in the south, without any deep cold we are at the mercy of the LP track to come down far enough EAST so we don't have an onshore flow which in marginal set-ups is a major problem. All but one of the snow set-ups so far on the 12z GFS will be rain for the south. Heck, could have a flooding issue based on this run!

Very interesting GFS run between 240-276hrs, the upper low JUST stays far enough east so that there isn't too much warm wrapping into the flow. The north keeps the colder air, the south enters less cold air but should join the party. ANOTHER snow event for the Midlands as well on this run, that's lime the 4/5th shot of snow?

This looks like the one that is going to stop the rinse/repeat type pattern, at least for a little while. A lot depends on where that lobe goes, too far west and we may end up dragging in southerly type airflow, especially for the south. The further north you go though the more leeway you have with that happening. If it stays in a goos spot though could develop another very snowy period.

EVen the south gets involved by 216hrs with a nice little embedded low pressure coming down from the NW, along with a decent number of showers coming in on that NW thanks to the highly cyclonic nature of the flow, looks like a very snowy run for a lot of people.

Agreed northwest, for a large part of the country this is actually quite an interesting, if very marginal, set-up. 192hrs is a better flow for the south to get involved, longer fetch as well, should mean warm sectors become less of an issue.

Would be a small area of quite decent snowfall on Sunday if the GFS came off, and a larger area of front edge snow which transitions to rain as the warm sector comes through, room for adjustments there. Main story for south is a lot of rain, fortunately its been quite dry otherwise there would ve flooding concerns with this sort of repeating pattern. Its really not a good pattern for us down here UNLESS an area of cold can actually establish at some point without getting flushed away 12hrs later and rinse and repeat. Midlands, especially west Midlands and areas north/west of that main story is probable frontal snow chances and heavy snow showers behind the fronts which may dig into the south to give some wintry stuff for us lot down here! So going to be a mix of reactions on here I suspect, for those further north/west, solid pattern. For those in south, its basically average winter fare in every way over the next 7 days.

First little LP at 120hrs is a pure rain event on the 12z ICON. However there are several interesting features running down the north sea on the 27th and also decent event for central/eastern England, Scotland and a fair part of Wales from a front on the following day. That is followed by snow showers. Anyway not a bad ICON in terms of snow chances, nothing that looks real solid, but decent enough opportunities.

Anyway doesn't matter, the 12z ICON has rain whole way through on the latest run, so the 00z ICON was probably just on the colder side of what is possible. Indeed most models make a lot more of that LP and have it way further north.

I was looking at the 06z run which does have dew points at 10C in the far SW at 120hrs, but to be fair it does cool down quickly after that. Looking now at the 00z run, still predominantly rain, but it DOES show some back end snow which does give a small settling amount east Devon. Anyway I hope that run comes off because that's a great shot at getting snow in my location as well, which isn't exactly a favoured area in the set-uo shown! ps, here was the 06z at 120hrs with the 10C in the far SW, more general temps of 7-8C, still way too high for any snow.