weatherguy

ECM well on its way here at +120h! Enough to drag me out of my slumber, that's for sure.

Will this saga ever end? Fully expecting them to both agree on a slider low by Christmas Eve, only for them to throw up a Bartlett out of nowhere at this rate... Major differences are apparent even at +96h, so surely something has to give soon?

Seen it countless times over the years that whenever there has been a SSW (or any real disruption to the SPV), the models go a bit haywire with regards to the placement of the TPV lobes. I haven't posted yet this winter though I have been lurking...Seems to me there was a major adjustment west of the pattern this morning, and now there has been a major adjustment east. This chaos is to be expected. COULD be a sinker here at 240h but it's pretty irrelevant at such a timeframe. Main takeaway is we have a lovely NH profile for the medium term and, prior to that, we have a couple of shots of snow for the UK, with the main event in the short-term yet to be decided.

There is very little evidence to suggest that this virus is susceptible to warm weather, despite the tentative early suggestions. There are simply too many variables at play determining the rate of observed infection spread (international travel [particularly in the early seeding stages], extent of social distancing measures, cultural factors such as face mask usage, population density, extent and efficacy of testing to name but a few). I feel it is reasonable to believe warmer weather does have an impact on reducing the rates of infection, but this thing is so infectious by way of it being novel in nature, that this is a relatively minor factor. On the contrary, warmer weather may increase the temptation for those thinking of flouting social distancing advice, therefore encouraging the spread further. That being said, the current enforced lockdown is working as it has stopped the exponential expansion of cases here. In my opinion, this should continue until the number of active cases falls down to a level at which we have about 4 weeks of leeway in terms of correcting any easing of social distancing measures (and assuming that any easing of lockdown measures MAY trigger a renewal of the 3-4 day doubling times). For example, in simple terms, if we were to ease lockdown measures today, it would not be known what impact this would have on the rates of infection for about 3 weeks (roughly 2 weeks for the first "new" cases to show up, a further week to get data about the general direction of infectivity). If the spread is shown to be exponentially rising again and a renewed lockdown is required, this would not have any effect for a further 1-2 weeks. Leave the cases too high, and it becomes fairly obvious that we COULD be overwhelmed. It is crucial that we are cautious and have the breathing room to make gradual changes as necessary, lest we end up with an outbreak which would effectively destroy the NHS' care capacity. I am, however, not optimistic that the government will take this approach, owing to the economic damage that is being sustained.

Got about 1-2cm here...pretty pathetic, but after the complete deprivation of snow this winter I'll take it!

Greatly appreciated, thanks!

This may well get deleted, but here goes it! Could anyone explain, or direct me towards an explanation of, what the MJO actually is please? I know that we want to see "it" in high amplitude 6/7/8 as this aids in the development of HLB...but what do the the phase numbers mean, what is "it", and what are the mechanisms by which this promotes HLB? Thanks in advance

It's anyone's guess really! I have always wondered whether something along the lines suggested below is plausible: 1) Mild winter=(usually) a +AO with cold bottled up in the northern latitudes 2) Feb-March=natural breakdown of the sPV/tPV as we head into Spring 3) Breakdown of the sPV/tPV causes a cold start to Spring as there's an unusual amount of deep cold lingering, which is forced to more southerly latitudes in one last hurrah by pressure rises at northern latitudes Makes sense in my mind at least, though I have no evidence to back this up, and I imagine the other scenario is simply that as the sPV/tPV breaks down, the cold dissipates too rapidly for many places to benefit. Would be interested to see if any correlation exists for +AO winters and cold Springs in our neck of the woods? But alas, my prior rant was centred around the forecast zonal wind speeds remaining above the average seen for Dec-Jan, even heading towards March...which would be funny if it wasn't so horrifying a thought

Dear God, just look at the state of it. I'm hopeful I may see some snow next week from some shots of PM air due to my altitude, but this isn't what I signed up for damn it! I don't think there's been a winter where I've been so consistently duped by model output in the medium-long term. Pretty sure I've been championing a pattern change ever since mid-January The strat forecasts have traditionally been fairly reliable even out to +384h, but this winter it just kept teasing us only for any predicted warmings to be incredibly watered down, and the sPV shaking off any minor hits it does take. Right now, it doesn't even look at all likely that we'll get a consolation of an early-Spring "winter".

Phwoar. Nothing showing up to offer any real excitement just yet at the trop level, but with charts like these then surely it won't be too long before we see the tPV get absolutely shredded. Really is the last chance saloon now, but I'm optimistic for a decent cold spell cropping up by the end of Feb now.

March 2013 was exceptional also. (Though I think the SSW that year was in January)

A bank rate that would make even Wonga blush I'm ready to be hurt again.

I've been keeping a close eye on the GEFS' zonal wind speed projection, and the mean forecast has been steadily dropping over the last week or so - it now sits at ~20ms which is significantly better than it has been for the vast majority of winter, with some getting tantalisingly close to a late Jan/early Feb technical SSW. Can we get a back-loaded winter to give us some long-awaited winter joy before Spring sets in? In the short-term, though the GFS turns into much of a muchness into FI, I really like the look of 192h, as it's not too far off some of the ECM FI charts we were seeing a week or so ago. If we could eek out a bit more retrogression of the mid-atlantic ridge, we could well conjure up a pretty decent northerly before, in my opinion, some proper fun could begin as we head into Feb.

At least the GEFS have the zonal wind speeds dropping closer towards average...Our glass isn't entirely empty ?

In the same way that when LRFs show cold/blocked winters and we end up with mild/zonal winters, they can also be wrong in the other direction. Or, the fact that an overall milder forecast does not prohibit colder spells, and that these colder spells may well become locked in due to the apparently stochastic nature of weather at times. Back to the models themselves, my view has not changed since last night - although there is cross model agreement on the developing UK/Iceland/Scandi high collapsing under the pressure coming from the west, there is enough variation in this to allow the possibility of an undercut. Still a case of wait and see how it develops over the next couple of days in my opinion.

In the pub run we trust! The secondary low manages the undercut, and then the fun and games begin! Can see this becoming a bit of a nightmare to model correctly and we'll be seeing elation and despair in equal measure here over the next few days...Here's to hoping elation wins out.

Good evening all! The output is, basically, a complete mess with major uncertainty on how things will play out even at +144h. Not necessarily the longwave pattern, but definitely in terms of how things set up in our small section of the NH. See the GFS/ECM/UKMO below: The GFS is the most amplified in terms of getting that negative tilt on the incoming LP, but even here the block is transient at best and it isn't strong enough to avoid being toppled in due course. The UKMO offers a somewhat more robust high, but the angle of attack from the west is worse, so, another toppler. The less said about the ECM, the better. 192h While both models produce a secondary LP, the GFS combines it with the main trough to the west, which delays the flattening of the ridge. This is only to be a delay though, because the jet is then positioned SW-NE...less than ideal. The ECM does not model this as such; due to the ridge being weaker and further east, it is allowed to simply run east and barrel over the ridge, heralding a return of zonality. 240h The GFS, despite the escape at 192h, then powers up the jet, aided by the migration of the main portion of the PV over to Greenland, creating something of a doomsday scenario for us coldies with an Atlantic profile as flat as a pancake. The ECM offers up limited amplification, which may present the opportunity of a PM flow at times. Overall thoughts: What we know for certain is that there is an opportunity for a ridge forming roughly around the UK/Iceland/Scandi sector around the 27th Dec. The models cannot agree on the exact setup, but none of the big 3 are showing a scenario where the Atlantic is held at bay, or undercuts. Given the uncertainty however, there does remain a small chance that the LP positioning may be more favourable and we can prevent what follows should this buckle (more rain, and more despair for those of us who wish to see some more seasonal weather). Again, this is very unlikely, and the strat profile at the minute doesn't suggest that the TPV will be lacking the strength to simply flatten out what is a rather weak ridge. Ever the optimist, I will be looking for any signs that this period is to be modelled more favourably for us. However, my sights are definitely set more towards what fun and games may be had in the SPV potentially by mid-Jan - there's certainly plenty of members going for a dive in zonal wind speeds, so I shall leave this here to end on a more positive note!

Pretty remarkable that we don't achieve an undercut on this run at 180h from this position. Feeling cold nonetheless around Christmas, despite a complete lack of agreement of how exactly this comes about! (ECM at 192h for comparison) Furthermore, deep FI again presenting a highly amplified NH pattern which I've been banging the drum for for a few days now:

There's no need to get too hung up on run-run variances when the interesting stuff isn't anywhere near the reliable - I understand it and definitely partake when for instance the trigger for an approaching cold spell is within 144h, but it's unnecessary in our current position! The "less cold" 6z GFS in my eyes continued the promising theme of an FI assault on the PV: That there, though in extreme FI, shows an astonishing three-pronged shredding of the PV. In isolation, meaningless, but given the trend I would suggest that the models are certainly picking up on some sort of signal. Don't look at the exact positioning of such highs or associated uppers hitting the UK; the trend is what is important and, if we get this PV shredding into a more reliable timeframe, then we can start looking into the specifics. All eyes on the 12z coming out now, we shall see if this trend continues... And I'm left with egg on my face it seems We'll see in due course whether or not this is an outlier however.

Clearly a theme for a highly amplified NH pattern by 240h which is definitely a good thing - uncertainty as is to be expected at this range over exactly where the amplification will occur and thus whether or not the UK will benefit as we head into the deeper realms of FI. In broad terms, it almost looks like a pattern which may represent a wave 3 attack on the stratosphere, with substantial blocking centred around the Atlantic, Siberia, and the Bering Strait[?] (excuse my somewhat limited Geographical knowledge for that part of the world). Exciting period of model-watching approaching!

Quick one before I go off to work, this is one of the most bizarre charts I've seen the GFS throw out in FI Monster block, but a monster PV! Chances of seeing this exact scenario virtually 0% at this stage, but my god would something like this be fun to see play out...

The zonal train rolls on it seems. ECM/UKMO/GFS below at +144h. Despite some fairly large discrepancies at D7, the overall picture remains very much the same between the big 3; cold and wet NWs gradually changing to somewhat milder SWs as the Atlantic troughs stall over the UK. Meanwhile, there is an attempt at Arctic heights and, by D7, a building of heights over Scandinavia. In order to really pull up those heights we need to see a link up between the fledgling heights to our NE and the arctic high, or see amplification upstream. GFS and ECM are both saying no currently, by D10. Now, deep into FI by this point (particularly so, seeing how there are rather substantial differences in the shortwave pattern even by D7), should the Scandy/Arctic high option fail as seems currently likely, our next point of interest should be the development of the Aleutian HP - the GFS says no and flattens it out beyond 240h, but I would suggest that this is the next opportunity to make inroads into the PV and promote, perhaps, renewed ridging in the Atlantic. With the SPV strength predicted to at least drop back to somewhat average levels, then we may have a chance here as we move into the New Year.

The problem however is that, despite undercutting, the Canadian PV lobe throws out another LP right behind it which doesn't allow any WAA up the US east coast. Interesting NH profile though with the gradual strengthening of the Arctic high. We do need this to trigger upstream amplification however if we are to realistically benefit, otherwise we risk being stuck on the mild-muck side of the Euro block. Edit: I was hoping to have a "BOOM" chart to discuss for my 500th post on here but, alas!

Interesting 216 ECM, very elongated atlantic trough, potentially sending the Jet down south east in subsequent frames while HP rises northwards from the US perhaps?

Well well well, what a difference 24 hours makes...I (obviously) admit that I was wrong to be so upbeat yesterday. I really thought that +120h was reasonably close enough to make the initial strong northerly a thing at the very least, regardless of the later promising setup, what with the UKMO being the only dissenting model of the big 3. Not typically a good idea to be so brash when 1 model disagrees, but typically the UKMO has a poor verification score after 120h or so. Alas, an early-winter lesson learned. What we have now is essentially a nice brief opener to winter, with a couple of toppling northerlies which could deliver transient snow events for the north, before FI indicates a period of "cold" zonality which may be a boon to the Scottish skiing industry but not much else. Not to be too downbeat though, even in the face of somewhat concerning LRFs, it's early days and the jet remains rather southerly tracking; it wouldn't take too much upstream amplification to deliver something akin to the eye candy produced the previous 2 days.