rwtwm

Norfolk_N_chance On meteociel you're looking for Rafales. If I've got the link to work, this should be the high-res WRF for the UK. https://www.meteociel.fr/modeles/wrfnmm.php?ech=3&mode=52&map=330

With the SPV over Scandi, and a favourable MJO, I'm fairly confident of a cold spell in the middle third of the month. But I think the front and back ends will be notably warm. 6.9C and 51mm please

I know I wasn't the target, but thought I'd have a go anyway. Firstly, a fairly even split (28/23) across the two regimes. There's a little promise on both, as they show a relaxation in the heights over Europe. There also seems to be a mean flow North of West on both too. Cluster 1 has a more impressive looking Mid Atlantic Ridge, but I think cluster 2 holds more promise. There's a strong negative anomaly over the Alps, and a hint of the high migrating to the North East. All in all not quite as depressing as the current OP runs suggest. I'd also highlight that cluster 2 shows what many would call a 'locked in' pattern eroding in 4 days. (As ever, none of this is a forecast, just trying to interpret the output)

I've disagreed with a lot of your upthread commentary but I think this is spot on. I don't think a matrix helps with people's understanding of the warnings. This wording at least would help clarify what was expected of people when each level was breached. (Then we could argue if a warning was justified for a certain area rather than arguing about an amber warning!) But to comment on the validity of the Amber in your or any area. You are using the event itself to determine whether an advance warning was justified. That doesn't make any sense when you think about it. In a way, the weather behaves like a quantum system. We can only talk about the future probabilistically, but we only actually observe one outcome. To determine if a weather warning is valid, you have to look at the probabilistic information available before event. And then you have to empathise enough to say that even if you didn't think that probability was sufficient to justify a warning. Is it truly outrageous that someone with the same information thinks it might be?

I can only assume the escalation to red is useful for on duty responders, and perhaps government/council funding rather than the wider public in this instance? I agree it does seem mad to upgrade in the dead of night, but if it was only for Joanne Public checking the app, it seems unlikely they'd have bothered?

In the pages I've read, and the forecasts I've watched this morning, I've seen 'violent', 'potentially damaging', 'severe' and a debate about wether this is a one in 2 or one in 5 year event. Yours is the first mention of 'historic' I've seen.

I find the 'accessible alternative' much easier to deal with. You do have to scan the list for your region, but when there's a bunch of overlapping warnings, it's a lot easier to parse.

Do share any blogs or papers please. I know we look to the raising of the ridge as a spoiler, but I tend to think of the Euro ridge as a consequence rather than a cause, our weather comes from the west after all. But I'm just an amateur overly reliant on heuristics. Happy to see anything that contradicts me!

Unfortunately I've seen moves larger than that on the day a low moves in. Snow and rain. I wouldn't be surprised if we're looking at a 50-100 mile window for northward extent come Tuesdays 12zs

To those looking at the output concerned about how dry it looks... To find an example where the moisture/shower activity was underestimated 3 days from the event you have to go all the way back to... Last weekend. This isn't me claiming that there'll be at least as much snowfall or anything like it. Just pointing out the frailty of precipitation forecasts ahead of the range of the local hires models.

What a wonderful winter's day! Clear blue skies, a hint of warmth from the sun, and a crisp feel to the air. Perfect for a lunchtime walk.

You've been a great contributor in the run up to this spell, but I think this is a bit of a mischaracterization. ECM means for 1am 15th: 240h 216h 192h 168h (This morning) Until this morning the trend was for the ridge to become less pronounced, and for the core of the cold to move further East. And this is just illustrative. Even though other models had better means more scatter was appearing across all the ensembles. I've stayed fairly calm, because I've seen trends like this revert, and I've seen them continue to degrade. I think those that are better at teleconnections can be feeling pretty good, because as I said before, the lower end of the envelope looks like 'underwhelming' rather then 'bust', and the outcomes we're seeing today (though I'm typing this as the 12zs roll out) are back towards the best that we've seen this chase. But that doesn't mean that it was a rogue op run or two that was causing the twitches, and I think the suggestion is unfair on some who have been providing good analysis this weekend based on the genuine breadth of output that existed.

This is the ECM 6z mean for Sunday! Nearly as good as some of the fantasy charts from late last week. We're now rapidly approaching the reliable with this. I'd say we're now in a position where the worst case scenario for early next week is underwhelming, rather than an absolute bust.

All very plausible, but for the couple of days near 27.5 C around the 13th, for which you've allowed an exception.

Not so much Fantasy Island, as an outcrop in the furthest reaches of the Fantasy Archipelago but... That's one hell of a tasty slider at the end of the GFS run.

For day 11+ the clusters are a little disappointing in the context of the outputs of the last 2 or 3 days. Not a disaster, and probably eyebrow raising if the last few days hadn't been quite as picture perfect. Cluster 1 ends with the flow north of west, and there may be hints of a re-rebuild of heights, potential snowmaker at day 12 too depending on how much warm air gets drawn up. Clusters 4&5 are closer to the locked in cold that the last few days have promised. Cluster 4 in particular had hints of the oscillating high latitude high. Could do without cluster 2. Even if it reamplified afterwards, we'd have to rebuild the cold from scratch.

Whoops! Sorry forgot so will have to take a penalty. 4.2c and 74mm please.

It's taken me a long time to get round to looking at this I know. Lots of new terminology to internalise with the regime classifications! I'm gonna need a few more passes to really understand it, so what follows might be based on a misinterpretation. I think the state models at the end are really useful. I have one hesitation around the correlation matrices though. Whenever a composite is posted, it's normally for a specific month. Phase 1 in January can look quite different to the same composite in March for example (and I haven't checked so that example might be rubbish!) The paper seems to correlate the MJO with a lagged regime regardless of when the phase occurs. Nor is it mentioned as a follow up activity, suggesting that in the eyes of the authors at least, it's maybe not that important? Is it possible then that the sample size of the composites is too small to be useful? Or are the authors overlooking an important aspect? Or have I missed something? FWIW - The best Phase 1 (Our current place in the cycle I think) correlation I can see in the paper is for the SA, and SWZ regimes. That's the top right and bottom left on the below. Not quite nirvana?

I'm not sure that finding one example of each scenario is sufficient to declare a rule? Given that the definition of a (major) SSW is a mean reversal of the zonal stratospheric wind, I'd find it unlikely that such an event can lead to increased zonality overall. This is just on a purely academic level. I'd have some sympathy with the suggestion that we were in a blocking regime conducive to cold, an SSW might encourage the block to migrate elsewhere. That said, I don't have the data to back that up, and this is one of the busiest weekends of the year for me, so I haven't the inclination to check.

While I remember 2003 clearly, the absolute maxes overshadowed in my memory just how prolonged that spell of weather was! An absolute monster of a heatwave that's going to take some beating!

The MJO is an equatorial phenomenon. The maps at the bottom of this page suggest that the range is 20°N to 20°S. I can't see anything that suggests the projection is limited in someway. http://www.bom.gov.au/climate/enso/#tabs=Tropics

No, it doesn't. But it's worth noting that ECM doesn't foresee a high amplitude MJO through phase 7/8, so I wouldn't expect the consequences to be reflected either. This is yesterday's ECM. There has been discussion up the thread of amplitude decay being a known bias of MJO forecasts. Well luckily it seems that the ECM page from which I've drawn the above has a recent history. ECMWF | Charts CHARTS.ECMWF.INT Below is the same chart from Nov 28th and Dec 2nd: Note the change of the amplitude in phase 5 (in particular) as we move from 1 week ago to today. Bear in mind of course that previous performance is no guarantee of future success. In the same way that if the first 3 lows miss us to the south, doesn't mean the next will. The BOM has been posted a few times, but for quick reference, here it is again... I've been sympathetic to the thought that highlighting the BOM feels a bit like 'cherry picking'. But I have to concede it's been consistent with this. I can't find a BOM 240 chart for our part of the world to compare (do they exist?) but that's where if be looking to test the impact of phase 7/8 on our weather, that's where I'd look.

Deja vu from 15 years ago in the Mad Thread. Tempted to play out both sides of the faux cold discussion in full to save us the trauma.

I agree with pretty much every word. When I'm discussing it in circles where I'm trying to influence people, I use the same pitch. In my post I was referring to my optimism, not whether it's worth trying anyway. We've got no choice but to fight for every fraction of a degree, but I mention the time because the idea of halving emissions by 2030 to have a chance of staying within 1.5c is fairly widely accepted.

I'll go for the first non summer entry. Sept 2023. I wasn't even in the country for this so I've no idea what it was like. Looking forward to finding out.