chionomaniac

Following on from my last post, I was hoping I would be totally wrong in my reading of post day 6. Depressingly I am not on the GFS and ECM fronts. Though it is a good exercise for anyone wanting to improve their forecasting skills. I will try and do the same tomorrow, subject to football and vaccination delays

So, yet again, for the 12Z’s I have refrained from looking past T+144, and in fact I haven’t looked at any models today. So what do the big three show at day 6 and not knowing what the models show further down the line, what impression do they make. As the ECM is still unfolding I will strat with the GFS. Looking at the day 6 chart we see another weak Greenland high with a large depression centred to the NE of the UK. A negatively tilted trough looks to be heading across the Atlantic under the block. The 850 temps at this time suggest cold air circulating around the circular UK low - but no straight Arctic flow here Whereas it is pretty straightforward to suggest that the Atlantic low heads east, when we look at the jet stream things are more complex This suggests that the jet stream is on course for a more southerly flow, which suggests that the lows trajectory may be more south than initially thought. So I expect another north/south battleground scenario across the UK - possibly with a snowline from the north of England Northwards. I don’t think that from these charts I can deduce anything further down the line. So a possible battleground scenario then all options are still on the table with the GFS. And I hate sitting on the fence. We have less info to go on with the UKMO, but the main difference compared to the GFS is a far stronger Greenland high and a more negatively tilted Atlantic trough. It appears that the block is still too north and weak to prevent the Low crossing the Atlantic in a position where it would leave the UK in a colder airmass, but the split energies of the divergent jet stream do leave optimism that colder scenarios longer term could occur. Everything to play for from this chart. Uk Now, I can look at the ECM. Again we see another large circular depression centred over the UK, with no straight flow northerly, so another cool but not cold. Again we see a stronger Greenland block than the GFS, but this is west based so it is very likely that any low crossing the Atlantic will have a strong milder SW maritime influence to it, for all except the very north. Normally any block in this position mores west further, so I would expect wet average conditions following this set up. Now I am posting this I can go and look once again as to what actually the models predict post day 6!

Cold rain yuk

Right this topic is derailed and I will be removing all the off topic posts

Right with 18ZGFS running I am going to look at this one right to the end and keep my block on past T+144 limited to the 12Z. It’s very difficult not to look when the info is available but I reckon I can manage it for the 12z until I have seen them and commented on them

Temp at benson was -3°c earlier. Now 0°C so temps are rising. Lower than expected temps earlier were very shallow

Lol. I don’t forecast for myself, but I do look at the models with an Imby attitude. Who doesn’t? It’s only natural

Hmmm. Barely below freezing. For best chances you would want to see closer to -5°C over France before the channel modifies the air.

No. I live a little further south in Hayward’s Heath now

To be fair, with the southerly wind forecast tomorrow morning, we need it to be brass monkeys in Norther France tonight

Below freezing here. Was 1°c when I got home around 5pm. Gatwick showing -1°c and do-2°c. That’s 2°c colder than forecast

So, I said earlier that I would just look at the big three upto T+144 following the 12zs this afternoon and see how I felt about the runs without looking further past this time or reading the forum to garner ideas. It has been far more difficult than I thought. Here are the 3 T+144 charts GFS Ukmo ECM So here are my thoughts. All 3 suggest a weak Greenland block with a deep depression centred to the east of Scotland. Any cold northerly flow, would be dependent on the block holding and being reinforced, otherwise the Atlantic will creep under the back door and put a stop to a proper cold northerly. Out of the three, it looks like the UKMO has the best chance to have a quick return to the Atlantic under the block, and any cold northerly looks short lived and not reaching the south of the UK. There is little suggestion here that the Greenland block would be reinforced. Conversely, the GFS looks like it has the best chance of reinforcing the Greenland block, at least for a while, due to the negative angle of the low towards the SW of Greenland. This may allow colder 850,s to reach more southern areas and the strong arm of the southern jet stream may allow a frontal snow event over the uk depending on exactly how delayed the Atlantic passage takes. And the ECM is a halfway house between them. Due to the weakness of the Greenland high and lack of reinforcement from all three models, my likely opinion would be a typical north/ south divide between colder and more mild conditions, with the GFS giving the best chance that the cold would extend further south. There are no indications from any of the models that a prolonged cold spell is on the cards. I will try and repeat this exercise with tomorrow’s 12z runs, but in the meantime I will have a look at the extended outlooks to see how well I have done!

I think I may conduct an experiment for a week, and not look further than T+144 on any output and see what my thoughts are based on runs up to that point. Obviously I will read this thread but only after looking at the models and commenting on them . Ill start with the 12Z's after the ECM this evening. Will be interesting to see how right or wrong I will be.

Neutralisation reversed lol

Yep looks like those small gains have been neutralised lol

And better orientation of Atlantic block at T+126. All good. The rest of the run is just for fun now

Early days but this latest Gfs run is ever so slightly more amplified than previous and weaker Iceland low. Small earlier differences can be magnified later

I think the thing to realise is that the SSW is still in its infancy to how it affects us at the surface level. So, the models will still be variable as to ascertaining what the correct trop response will be for a while yet. So past day 6 small differences in how the SSW affects the trop can make big differences here - from a mild Southwesterly to a cold northerly. It all depends on how and where a block sets up and orientates

I would describe this winter so far as Synoptic Heaven but Surface Hell.

Yep, I think too many may be guilty of looking too far ahead, rather than concentrating on the short term building blocks that we see currently modelled. I mean how many people would be fretting if they couldn’t see what was modelled past day 6?

Well, another interesting day model watching. The main thing I see is that we have fairly similar patterns between the main three at day 6. If we were to pause at this point, and not know what was modelled after this point, then I think most of us would agree that this is a pretty promising position. And that’s what I see too. I think there are a number of directions the models can go after this point, including the west based -ve NAO. But if we were to stop there and imagine a slightly different direction than we already know the models are taking then the promise is great. And with the SSW downwelling and it’s influence displaying a range of different output and ensemble outcomes after this, I think that we should be very careful writing off any particular scenario. One thing we know is that following an SSW, the models can change direction very quickly - both the ensembles and the operationals. So still a lot to look forward to over the coming days.

Blimey, and I thought it was wet here.

Whatever they flip flop, when it comes down to it, it will be no snow

It certainly wont help, but would need to see what is happening lower down the strat towards the trop. LOL whatever happens following a SSW there always seems to be some arm of vorticity or positional daughter in the mix to thwart us.

Plenty of time for that to improve Mucka, nearer the time as I am sure you know. As ever let’s get the right 500hPa pattern first, despite knowing it has already failed us once this winter. Surely we can’t hit tails twice on the run. Lol and I know the probability reply so don’t say it!