pyrotech

Hi Jay, Andy BBC graphics for UK show Snow in South Wales BBC wales shows snow just high ground This will change as we near but could easily be forecast wrong as late as tomorrow morning It could even come down to precipitation rate for evaporative cooling to make the difference or not. Right now it looks like Andy will see snow settle, Jay would see snow at times but not hang about. That could change thou. Lets see what warnings say around 11-12 today Much netter than last winter thou , guys

Certainly enough to watch out for Meto still going for mainly rain for us, the GFS not been the most reliable lately and if anything on catch up with ECM. However its also the latest run with latest data so lets hope that that feature has shifted slightly North as it indicates. Will be a bit of a now cast situation i feel, The Dew points are greatest issue but in heavier precipitation we will see evaporative cooling and if we get a full rotation the cold or colder air would get pulled into the mix with lower associated dew points.

`its only the GFS but looks much better for back edged snow as it moves east at this early stage

The precipitation coming into Wales seems a little further North and east quicker on this run

Thing is Nick, as many long timers on here have seen time and time again its the same story with GFS It showed this cold spell at 15 days, run with it then it dropped it and went for a new route and something completely different only to slowly return to it again late on . How many times have we seen the GFS find the correct trend and drop it when ECM comes into timeframe and the GFS slowly try to catch the ECM up again.

Which is why the Met O have been sensibly cautious and only really today after 4pm did Matt mention "snow for one or two" These set up are notoriously difficult to forecast beyond 5 days and in our little Island even small difference make huge differences in 5 days. Its only fools like me that make a forecast based on synoptic with such shannon entropy involved. however whats the fun in trying to forecast a dead cert when the challenge is to read the models and decipher which is more likely. God i can not wait for ECM tonight

blizzard81 your right in many ways. However in case of gfs I always compare 18z with previous 18z etc rather than 18z to the 06z . short term the output is similar but 3 days plus you find the out put is much better aligned and easier to compare differences. That is one of main reason we see the highs and lows on here when people react to fi on 18z with excitement and then demoralised when wake up next day to see the 06z . Best comparison is same run times . However as you said seen downgrades or corrections too many times over two many years and only occasionally does it revert back to what we hoped for. Does seem to more often be Temps modified upwards

Yes and even where the op's sky high later in fi, the mean is steady with a good majority at very low temps. ECM here is very much a colder outlook, but i think we need to keep our feet firmly on the ground with such difference. Tamara has shown tonight that its quite feasible for what GFS is showing to come true. In my opinion the teleconnections will effect us differently if the Siberian heights become stronger and blocking to our North help to hold the Azores high further West. The same factors could cause the Northerly flow to last longer and sent a Shortwave South over the UK. Unfortunately The Azores high ridging towards Uk and into Europe is more feasible. All options do remain on the table thou. ECM particularly the better option. I would suggest polar maritime incursions with temps rolling from 2-4c then 11c in a rolling basis with wintry showers in the South during the cold spells, but the ECM still offers a pleasant alternative.

i posted them on here for you I think ian reads stuff on here, but does not post, Just a hunch as the second part of his message seemed to answer my post on here. Its a huge loss that we have lost such a respectable professional. May be some common curtesy on the model threads even if a poster says something you don't want to hear or don't agree with. There are many on here that would be severely missed as is Ian. Here they are again Ian Fergusson ‏@fergieweather 42 minutes ago @Floodwarncouk models have been toying for a few runs now with broad idea of a more pronounced NW'ly to N'ly outbreak, but still early days .cont'd... so yes, the likelihood of that has increased, albeit much too early to be deterministic on scope/outcome.

Below is the full reply from ian, posted so he does not get hundreds of posts asking same thing Personally i think thats sounding very positive as it seems maybe they are taking notice of same features we are even at that timescal Ian Fergusson ‏@fergieweather 42 minutes ago @Floodwarncouk models have been toying for a few runs now with broad idea of a more pronounced NW'ly to N'ly outbreak, but still early days .cont'd... so yes, the likelihood of that has increased, albeit much too early to be deterministic on scope/outcome.

Well the GFS, ECM all looking promising Here is a tweet from Ian (bottom of this post in bold) I think basically the met office are also seeing potential of what we are seeing but as Ian says still some uncertainty I read this as maybe not only is there some room for movement away but also maybe initially a fairly dry feed is also possible with costal areas getting highest potential We all know on here that shortwaves and troughs are unlikely to really show up until very late on Anyway Ian's actual reply is below so you can read it as it was said Ian Fergusson @fergieweather Jan 05 @Floodwarncouk models have been toying for a few runs now with broad idea of a more pronounced NW'ly to N'ly outbreak, but still early days

The elephant in the room is the high pressure, In fi there are so many different scenarios for what will happen to it. A nudge west and as the latest run of GFS shows we get cold air and snow possibilities, a little further east we get cold and dry and further east in to a Euro high we get more Atlantic intrusion. There is no consistency yet but the different possibilities make model watching interesting The latest GFS again tries to give a cold intrusion at 12 days, and at least this year there is atmospheric opportunities compared to last year. happy new year all Im just leaving for 15 hour night shift which is why no charts posted to demo what i find interesting

For every run there will be less pleasing charts for some A better way to read the charts is to save runs in fi from a time frame like 06z 12z or 18z and compare yesterdays 12z with todays etc. Gives a more accurate idea of model movements in trend. However i do like to give a positive image and so here is my anomaly chart of the day

Merry xmas to you all Spending time with family so my thoughts on models will be brief Opportunities for cold are abundant, This time last year the models indicated very little for opportunity for snow and many people had spent a miserable Christmas outside of their flooded homes. This year snow is in FI, This shows if nothing more that its certain runs, some with minor tweaks that the atmosphere could deliver something wintry. the jet stream diving south and in doing so pushing the Euro high eastwards is certainly a possibility, with that would also see pressure rises towards Greenland. This of course does not mean snow is highly likely here in Uk, but it does give the opportunity for cold air to sink south and then possabilities of shortwaves and for the South its crossed fingers for a undercutting low. Fi will never give you a correct scenario with the complexity of the atmosphere but it can often give trends. i think many forget just how awful it was this time last year, this year is much more interesting at least. anyway enjoy your Christmas evening and lets enjoy these possibilities in deep fi and hope to see some slowly appear in the more reliable period and become consistent which is the best signal of the trend going forward.

Can i just clear up he 10% of snow in 5 days Its like a 10% chance of winning a race on Monday You are 1 of ten runners so 10% chance of winning On the Tuesday your also 1 of 10 running, so still 10% chance Your chance of winning has not changed ( still 10%) If not after 10 days it would mean your 100% guaranteed of winning within the ten days Your not, you could lose every day However If a model predicts a 10% chance of snow over 8 days in january 70% chance over 3 days and 0.1% chance for all other days you can see that for 3 days its predicting a fairly good chance 8 days its a low chance but possible, and just about forget the other days What ever it says thou means very little beyond 5 days but its rolled on not added up If a forecaster said that the storm will hit London, Tuesday 5%, Wednesday 80% or Thursday 15% it means yes 100% a storm will hit but uncertainty of when but you can evaluate most likely Wednesday but if a change that change means likely to be later (Thursday 15%) than earlier (Tuesday 5%) If that all makes sense

Why are people so quick to dismiss the high moving north. Mjo now becoming weak. The likely hood of heights rising in Scandinavia and Siberia increase in this scenario. With 11 to 15 day lag and mjo already in weak phase 1 this is a very likely scenario in around that time frame. Other factors will decide how far north and east but go through my posts and see that this is very much a plausible outcome. Ecm hints that it's heading that way. Gfs shows similar motion at day 10. Scandinavia high after that period is very much a possibility and has been latter part of Autumn for very same reasons. zonal period imminent helped by moderate phase 8 and 1 mjo in mid November. Now back to weak but uncertainty for how long. effects will follow.

Hi Nick The current MJO recently has been against blocking and so until around 15 days from now its dire, but MJO looks to go weak and so maybe after that the scenario changes. We are already in very weak phase 1 and looks to stay weak for at least a week. We then have complete shanon entropy as the spaghetti gets thrown everywhere. For me that means in under 15 days time Scandi or Siberian high looks most likely to start to develop. The North American picture can of course spoil this but its all to play for. I see the MJO effects around 11 to 15 days later.

I follow the MJO quite closely and for me the lag ( that word second time tonight) is around 14,15 days The change to more Zonal conditions is more likely when the MJO is strong and particularly when in phase 1 or 8 A weak MJO appears to be more likely to allow heights to build in Northwest Europe and that is one reason i think in 15 days time we will see hints of that very scenario. The Mjo is looking to become 2 or 3 and that effect will follow through. I mention the other two significant factors - Solar minimum and La Nina These 3 things should allow Height building near where we want and the NAO to become weak to negative The polar Vortex can also be effected but the major effects on that are well known here and i can not see a direct link with MJO. I am quite happy with what the models show today as down stream looks interesting but of course all this is just part of a bigger picture and many triggers need to be put in place for us here in Uk next to what might as well be a warm bath. (Atlantic Ocean) I show below the forecast for MJO

Its the lag effect frosty lol

The models may not be showing anything of interest right now for cold / snow however lets take a good look at the gefs The operational and Control are both Outliers Lets first look towards Scandinavia, we could do with heights building there The run shows the op going for low pressure but the mean is very much in the higher pressure, the control follows this/ Then we look at the 850mb and again control and op both are out on their own so if we take the mean its looking quite a lot better. Finally lets look at London and again 850mb temp, again the mean is a lot better. A disrupted polar vortex Low sunspot count La Nina Huge chance that a Scandi high theme will be the talking point this winter. We have just 4 days of winter so far, the Mountains (Brecon beacons, & Black mountains (still have some snow on them. This time last year Cunbria was facing floods and mild weather was predominant. There is nothing to say GFS and GEFS op is not correct ( at least fairly so) however as most seasoned users know even subtle differences on day 5 make huge differences come day 10 I will say that the mean as always shows the scatter at that period and that technically a Scandi high is most likely to become prominent as it has for much of the Autumn. I would prefer the models to have the milder interludes now than late December onwards when we have the best chance of deep entrenched cold/ I think expectations have been much too high recently, so far this late Autumn and early winter has been full of promise and at least crisp and cold at times. Its still early for full blown winter and this winter has many possibilities ahead. The 18z GFS seems to have everything further Southwards on this run, i suspect no fat lady singing at the end but these slight variations show the complete uncertainty at under 6 days which become huge later on

The chances of models showing a Scandinavian / Siberian high are elevated this year due to the Low ice cover, large snow cover and sunspots going into minimum. We also have MJO which has left phase 8 a week ago and weakening as it traverses 1 and 2. most likely to become weak in next few days. The weak la Nina his another factor. over last few months we have seen a prominent Scandi high and steady blocking, which would have been a delight for chartists if had happened in Winter. We seem hung up on this chart or that in Fi but as always its the trend we are looking for not the actual charts. We all know that the chart looks very different at day 8 when it comes around, The polar vortex is always an interesting part of the puzzle, but its difficult to decide where the breakout disruption will occur, it so often happens in the states, when you consider the size of the Uk we have about 1 in 8 chance of being in the sweet spot. The First two weeks of December are ripe for being Zonal and the jet stream normally fires up and brings wet and stormy weather to the Uk, This is as can bee seen by the models a possibility as we enter December, however it takes very little for Scand high to drag cold air in and force low pressure below the Uk bringing what many here would want. The met office extended forecast hints at this scenario ( wetter ) and then a dryer second half of December, High pressure is likely to be in our vicinity but it may well sit to our North east. What we need to look for long term is signs of the Scandal high ( thats been prominent all Autumn) to establish its self again and again as we enter Winter and mean while the models constantly hinting at possible cold incursions show the possibility of something coming out of the blue (excuse the pun) With a moderate warming already having disrupted the vortex and another warming expected the models will struggle to get hold of anything regarding heights and positioning until they are established. The GFS has probably played every card in regards to scenario's over the last few days and ECM has not been overly consistent either, i suspect a cold model run for Fi in GFS for Nov 4th on the 18z tonight. The models predict a jet stream of some potency with us in the firing path early in December, however with Northern Scandi high blocking, which is likely due to reasons mentioned earlier, that jet could be significantly further South and bringing the colder air from Europe more into play. At least its on the cards this December as last December we had no signs of positivity at this stage and the forum was like quiet here

Crew, i agree thats a feature that keeps being forecast, however i still see a great cold possibility with that, , It would most likely become stationary between Greenland and Iceland and then slip South over the Uk bringing a Cold northerly down West Uk and spreading Eastwards, I suspect a Negative NAO by then and we are talking T20 days. So even that can still bring promise. There are just many opportunities here and although non may actually bring the jam, the fact we have opportunities this year is at least a positive IMHO

The common trend in the models is that cold around the pole is likely to push Southwards. The models are seeing many methods of attempting this and the good news is that there is more than one way to get it Southwards. We do not have all our eggs in one basket. Most model runs deep in fi all show cold advancing near the Uk, many just short of the promise. Even with fairly major changes between some runs 12z 18z and 00z we have seen the cold get close to the Uk So what i take from these runs is that although where in Northern Hemisphere we get the flow, is not anywhere near understood, there are many opportunities for the Uk to get close to the action in many different scenarios. So slight alterations and it could become rather interesting. We should not be looking for a single chart at this range but looking for a trend. We can not find a good trend for where heights will be or shortwaves, what we do have thou is a consistent trend of cold coming close to our shores. This is not a guarantee of Cold / Snowy weather, however its a lot better than this time last year. I also see the snow extent charts look very good over Northwest Europe The coldest night in parts of the Uk in November for many years and we have a low dipole index (lowest since 1962) weak La nina and getting close to solar minimum. Those factors alone give Scandi high a very high chance of being a dominant winter feature, Let the trend be your friend not individual charts from different runs

Although the GFS is showing huge differences in FI its interesting that the ECM 00z and GFS 06z had a lot of similarities at around 10 days. We often find huge difference between runs but what we are looking for in my humble opinion is the cross model consistency. It will be very interesting to see the 18Z GFS tonight but i think we will see a lot of inconsistency with this set up. A major issue is the lack of sea ice and along with the cold over Siberia i would expect high pressure to stay further North East over Siberia so perhaps the 06z does have a sliver of reality to it. The Madden Jullian Oscillation is also very interesting and has a lower dipole index seen than for may be 50 years. I am a cold fan in winter so perhaps a little biased but the first half of winter does look interesting, This is also giving a much needed boost for both European and Scottish ski resorts which of course is financially critical for the industry after a poor start last year 10 day similarity between ECM 00z and GFS 06z included

Due to the position of the Euro high the low pressure systems are crossing Atlantic and due to blocking by the high , they are pushed North with the weather fronts trailing in a way that leaves them almost in same position each time. The rainfall is huge in these areas due to orographic rainfall due to the topography. If you watch the movements of the low pressures you will see this and envisage where the weather fronts would sit. Hope that helps.