Joe Levy

I know I've been bleating on about this for days, but the consistency of this warming on the GFS is getting rather impressive, I just hope it stays that way. I know that stratospheric forecasts are often more accurate than tropospheric ones, not 100% sure why.

Writing an essay at the moment as is the life of a student, so using my breaks to have a look at the models, and the inter-run variability is still keeping me on the edge of my seat! At 96hours the GFS 0z corrects westwards to give a more continental flow, extending the potential for wintry weather a little bit. Nothing major, but on our small island, small changes count And on the UKMO 0z the situation is roughly the same, with quite cold uppers as well At 120hours on the GFS the block is several hundred miles further west as well - small in hemispheric terms, but significant for our region UKMO broadly the same but a smidge further east than the GFS and the jet angle isn't as favourable, but still better than earlier. I am going to stop at 144hours as even that is beyond the reliable in such a difficult situation as this. The GFS 0z is much better than previous output, with a better angle to the jet, a westward correction and greater trough disruption. However, this only increases the uncertainty if this run was so different to the last! It was hard not to resist posting this chart from the GFS at 168hours and it is really just for fun as it is a little way away, but just one more, I promise very similar to the JMA that appeared yesterday evening - cold and low thicknesses so wintry showers possible just about anywhere. But not to be taken too seriously yet!

I think you should make that you profile picture on here! People seem to like it I just wish that the chart shown on the screen was part of a model consensus!

Well the full ENS are out and the links from my previous post on the short ENS at the top of the page should now have converted to the full timescale. It is interesting how few members rise above the 0 degree line, suggesting that cool or cold is more likely at the moment. Nothing extremely cold, but we don't need deep cold, and again, it's the overall pattern that's crucial rather than the specifics. Currently, the pattern is not yielding cold weather for us in the visible time frames, but we shall see what the models look like in a few days time and whether that is still the case.

It is odd, but it means that there is more than one solution to a fairly similar outcome on the ground. Different paths, same destination

The short ENS for the 18z are interesting, as there is quite a bit of uncertainty between the 24th and the 26th, yet strangely, no matter what each ensemble shows in that time period, they all descend back down to -4/-5, which is rather comforting! http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=188&y=173 (South West England) http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=307&y=141 (South-East England) http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=278&y=1 (Northern England)

It's pretty much identical to be honest. It starts at almost exactly the same time just perhaps one frame's difference in terms of the peak of the warming. The important thing is that it's there and it's very strong, stronger than any warmings I have noticed so far

The warming is still there on the 18z, which is promising

Nearing the end of hi-res on the GFS 18z and a cool north-westerly flow has established in a set up that is very different to what was shown on the 12z, hence the uncertainty ahead!

I am not sure I fully understand the dynamics of warmings, but the warming we are referring to is a lot higher up in the atmosphere than is being shown in that chart. That is 850hpa, which is the troposphere I think, whereas the warming we refer to is in the stratosphere. The very high temperature anomalies on the chart you have posted are likely to do with the very strong Pacific ridge/Alaskan high which Nick mentioned, as it will be pulling in very warm air on its western flank into the Arctic.

What on earth would I do without the experts ey? the 12z ensembles are coming out everyone, and guess what... there are lots of different options available at 138 hours and what does that mean? It means we don't know what will happen in 5 days time, so no one should pretend that we do!

Well even if it isn't sudden, it is still a warming and it is one of many smaller warmings that have been eroding and continue to erode the vortex. It may be that this warming is the final straw. Tamara had a great post explaining it and I am not really capable of explaining it as clearly as her! EDIT bluearmy has expressed what I am trying to say a little more clearly in the post above!

I couldn't agree more! It's frustrating that so many people have not paid attention to the trends being shown in the NH pattern, such as the persistent evidence of stratospheric warming shown in pretty much every op for days now! Don't worry, some of us are still paying attention

To those who say that Winter is over (no names mentioned) which is a silly thing to say itself given that we're only half way through and that we can still get cold weather in March and April, I present this chart to you - the SSW is still in the output and is gradually getting closer as the GFS maintains it. If it continues to do so, then I'm sitting firmly in the camp who think that February, traditionally one of the coldest months anyway, has the most potential.

It arrived in December it just hasn't been the sort of Winter most of us enjoy!

You may well be right, and I would love that to be the case, but be careful about speaking in absolutes! There is no certainty to this situation and dramatic changes either way could take place. There is evidence for a shift westward and we should hope that it continues, but there is no guarantee to this, so unlike you, I expect nothing, I only hope!

Very interesting FI on the ECM at 240 hours. Fairly similar to some of the output on the GFS and GEFS, but to be taken with a pinch of salt for the time being.

If Shannon really had any empathy then there would be a lot less entropy haha being pedantic of course...

Yes, this chart at the end of the run is rather intriguing

It has been shown to be this strong in the last couple of days, and its strength varies from run to run, but its appearance has been consistent and is in line with hints from those at the Met Office. In terms of timescale, it is fairly difficult to know for certain. If there is rapid downwelling from the stratosphere into the troposphere, then it will be much quicker. However, between a week and two weeks is the best rough timescale I can give you with my limited knowledge. I would say that the second week of February is one to watch, should this come to fruition.

The stratospheric warming is still there in the latter stages of the GFS 6z, beginning on around the 26th through to the end of the run

The SSW shown on the 12z GFS is still there and perhaps even more powerful on the 18z. This chart is from right at the end of the run, however it actually starts to appear slightly earlier than on the 12z, I am just demonstrating it at its peak which so happens to be at 384hours.

It's hard to tell, since we can't see the temperature profile after this point. It is obviously easier if the warming occurs just to our north, but if it weakens the vortex enough, then its position isn't the most important factor, its existence in the first place is more significant.

Yes I agree, but that wasn't my point. My point is that we need the building blocks to be in place and at the moment, they aren't. That chart may be two weeks away, but the weather doesn't have to follow the model output! The weather controls the output not the other way round. The Met Office have probably been expecting an SSW for a while now based on hints dropped by various members, so looking at a stratospheric chart two weeks away is not as futile as you might think!

SSW anyone? I think that before we get excited about snowy synoptics and when they might appear, or equally get hung up on what seems to be eternal zonality, it is these sorts of charts we want to see repeated. The building blocks are more important than the specifics first and foremost. These can completely alter the model output over time so take nothing for granted beyond high resolution charts.