Met4Cast

Let the upgrades flow.

HUGE upgrade on the EPS. The mean now stays below -5C until the 19th/20th, the 00z run didn't even get the mean below -5C. Very nice colder cluster with fewer milder members. Game on!

Early EPS ensembles show a rather large upgrade in clustering, far fewer milder members..

We can click the images ourselves you know.. Definitely an upgrade, lovely to see things going back in the right direction again!

The MJO may actually mill around in phase 3 for a while longer looking at latest modelling which wouldn't be a bad thing at all! Worth noting the MJO is just 1 variable within the broader windflow (GSDM) budget so shouldn't be taken in complete isolation. I flagged the 20-25th on Twitter as a period where the jet may begin to edge northwards as blocking wanes, this suggests to me the potential for high impact snow events as weather systems hit the colder air across the UK (Indeed, Tamara echoed this in her earlier post here). With Atlantic weather systems comes the potential for milder air depending on exactly how/where they track and something that wont be resolved for at least another 7-10 days. A waxing and waning of blocking seems likely but plenty to suggest renewed blocking into February as per @Catacol's (I believe?) post earlier today. Original post: https://community.netweather.tv/topic/99706-model-output-discussion-into-2024/?do=findComment&comment=5000068

See my above post answering exactly that!

The MJO may actually mill around in phase 3 for a while longer looking at latest modelling which wouldn't be a bad thing at all! Worth noting the MJO is just 1 variable within the broader windflow (GSDM) budget so shouldn't be taken in complete isolation. I flagged the 20-25th on Twitter as a period where the jet may begin to edge northwards as blocking wanes, this suggests to me the potential for high impact snow events as weather systems hit the colder air across the UK (Indeed, Tamara echoed this in her earlier post here). With Atlantic weather systems comes the potential for milder air depending on exactly how/where they track and something that wont be resolved for at least another 7-10 days. A waxing and waning of blocking seems likely but plenty to suggest renewed blocking into February as per @Catacol's (I believe?) post earlier today.

haha bloody hell. yeah exactly this, they were poor in terms of the lack of deeper cold runs compared with previous outputs, the mean however was still broadly good which was a little odd. I don't think this is resolved yet despite this evenings outputs and we do need to begin discussing the uptick towards the 20th across all modelling, even though it could potentially be pushed back (GFS 12z Det a good example of how that's possible).

The pages in this thread are going by at a rate of knots so I guess the ECM has done a thing.. Fantastic det outputs across the board this evening, would like to see something of a tightening amongst the ensembles before my confidence begins to increase again but much better than yesterday evening!

The ECM is generally the best performing model & certainly the best performing ensemble suite. Having ANY model disagreeing causes concern because on occasion, the model disagreeing is right!

The GFS is certainly sticking two fingers up at the ECM this morning with better amplification into Greenland. It's a good start!

It's not the Atlantic causing the issues here though, it's the Pacific high draining the heights away from Greenland which then allows the jet to nudge further north. The jet stream is very south shifted and not all that strong or interested in pushing back northwards. One positive is that modelling is absolutely all over the place in terms of the Pacific and there's still time for things to trend back the other way, background forcing remains favourable for HLB on our side of the Atlantic, we have a weak Atlantic and a weak polar vortex. Westerly momentum overall remains fairly high following recent strong +MT events albeit it has fallen off a little and the MJO remains stalled in a slow moving phase 3. All in all, from a background forcing point of view blocking is favoured & to be fair, blocking is what we're going to be seeing/are seeing currently, today. The only issue is whether the UK, a tiny island can tap into some much colder air or not. The teleconnections have done their job re: the broadscale pattern and have produced blocked patterns, that just doesn't = UK cold unfortunately, we need a little luck on the regional/smaller scale for that. It's possible poleward momentum stalled slightly and that could be the reason for the less weaker Iberian heights but that's beyond my current paygrade. Original post: https://community.netweather.tv/topic/99706-model-output-discussion-into-2024/?do=findComment&comment=4999028

I've seen a couple of reports but I think any wintriness mostly confined to above 200-300m, the WBFL is around 600-800m in that area. Deep cold was always a low likelihood outcome on the ensemble suites despite some very enthusiastic det outputs.

It's not the Atlantic causing the issues here though, it's the Pacific high draining the heights away from Greenland which then allows the jet to nudge further north. The jet stream is very south shifted and not all that strong or interested in pushing back northwards. One positive is that modelling is absolutely all over the place in terms of the Pacific and there's still time for things to trend back the other way, background forcing remains favourable for HLB on our side of the Atlantic, we have a weak Atlantic and a weak polar vortex. Westerly momentum overall remains fairly high following recent strong +MT events albeit it has fallen off a little and the MJO remains stalled in a slow moving phase 3. All in all, from a background forcing point of view blocking is favoured & to be fair, blocking is what we're going to be seeing/are seeing currently, today. The only issue is whether the UK, a tiny island can tap into some much colder air or not. The teleconnections have done their job re: the broadscale pattern and have produced blocked patterns, that just doesn't = UK cold unfortunately, we need a little luck on the regional/smaller scale for that. It's possible poleward momentum stalled slightly and that could be the reason for the less weaker Iberian heights but that's beyond my current paygrade.

There’s no two ways about it really, this is a poor set from the EPS.

More spread than a tub of utterly butterly. Background forcing remains okay I think the main issue is modelling with the Pacific high & any smaller shortwave features as things move closer.

Interested to see what the spread is here, definitely looking for wedges now and ensemble means will be very smoothed out. I think the individual EPS members will be a better guide over the means beyond day 5/7.

Modelling appears to have vastly underestimated this mornings convective shower streamer across the SE (all rain currently) which might bode well for tomorrow, wouldn't surprise me if one or two spots saw a bit of a surprise tomorrow morning! Longer range modelling is good this morning, MOGREPS/NAEFS remain cold, GFS is okay and ECM is an improvement. I think we've lost a real solid Greenland high overall now so we're going to have to hope we see a decent wedge of heights instead & that still seems likely for the time being.

Fantastic 00z MOGREPS! mean falling off rapidly towards day 7.

The NAEFS (GEFS & GEPS) mean is great at 192.

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Unfortunately there's no archive so I'm not sure but I doubt it would have looked too different, the ensembles weren't suggestive of deep (sub -10C) cold even 3 days ago really.

For what it's worth the multi-ENS which comprises of multiple model ensembles seems rather solid for a proper cold spell from this northerly. I often find this to offer the best guidance at times of uncertainty.

We've certainly come along way from this run just 2 days ago.. But.. we're still not quite done yet. It's a shame so much uncertainty has been injected into the modelling because things were counting down so well but I guess it wouldn't be a cold UK weather chase without some sort of spanner being thrown in somewhere along the lines. We need to watch the block across Greenland and hope modelling has just gone too far in the opposite direction with underplaying it, often is the case.

Not *too* worried about that yet given the scatter & uncertainty that has suddenly been thrown into the mix, we do often see modelling too eager to remove blocking & that could be what's at play here too, especially given the spread on how the blocking evolves in the first place. I wonder if the uncertainty with the MJO is playing a part here along with the current minor warming in the strat.