Met4Cast

There remains a marked divergence around the 17th within ensembles in regards to the track of the first low pressure system. Milder members favour a more northerly track and hence temporarily bring in milder air whilst many members favour a more southerly track and hence keep the cold air in place across southern England. The GEFS in particular is awful at resolving undercutting & disrupted low pressure systems so it's not really a surprise to see the deterministic output wobbling about across the envelope of possibilities, this is why ensembles exist, to provide some much needed context. MOGREPS 06z is more in favour of a southerly tracking low and for the most part keeps the colder air in place. At this range I'd favour MOGREPS over the GEFS, but the more northerly tracks can't be discounted yet.

GWO - Global Wind Oscillation GLAAM - Global Atmospheric Angular Momentum AAM - Atmospheric Angular Momentum Annular mode - Essentially the Arctic Oscillation

There was a discussion a few weeks ago on this actually. The 00z runs appear to flatten the patterns more quickly only for the 06z and 12z runs to slowly re-amplify the pattern again. Not sure if this is a genuine observation or just a bit of confirmational bias creeping in but it is something i've noticed over the years of model watching.

How about this from GLOSEA then..

Well.. Bloody hell. This is probably the strongest wording I've seen you use in terms of cold & significant winter weather impact potential for NW Europe. In essence, teleconnections remain solid for -NAO and -AO throughout the rest of winter with likely repeated periods of high latitude blocking. The next MJO cycle progresses eastwards will see a return to strong +FT & +MT driving total AAM tendency upwards once again from an already high established Nino (+AAM) base state. Myself and @Catacolhad noted that AAM tendency had bottomed out & returned to more neutral/positive values faster than anticipated, reading your post it seems you had expected a greater fall than observed too (GWO remaining above phase 4). Thanks Tamara. As someone who is a lover of cold/snowy weather but also tries to remain balanced & unbiased in the context of the GSDM, for me, this is a very exciting update!! Though of course, more regional (UK) based milage may vary, macro vs micro.

Unfortunately the GFS 06z det really goes off on one in the extended!

EXETER KEEP THE FAITH! Extended update via app, they see the block & hold holding on into February!

Can’t say I’m seeing anything worthy of a red being modelled for next week..

The GEFS mean are a substantial shift towards colder outcomes with far fewer milder members in the mix, I suspect many have followed the det in sending the lows south of the UK rather than into the UK. I mentioned we'd probably see something like this happen a few days ago. Away from deterministic runs the day 5 means from the ECM & GFS are very similar. Cold northerly across the UK with snow showers/likely longer spells of snow from any disturbances. Any widespread significant snow risk will depend on the track of the lows coming in from the west but honestly, don't be surprised to see these miss the UK entirely.

Yes, drawn up by the on duty chief forecaster I believe.

Yup very, very good GEFS 06z suite.. If we can see the same from the EPS later today this place will be putting out the balloons.

Very, very good 06z. very very good day 4 FAX..

I can’t say I’m liking the overnight runs either. We seem to be losing the more robust Greenland high signal & relying more and more on the low dropping into Scandinavia. There is no consistency between models. It’s not ECM/UKM vs other models it’s every model vs every model. Pretty much impossible to see where we’re actually heading this morning.

The 18z GEFS are actually more strongly clustered towards the colder options vs the 12z GEFS run. The det might be all over the place but overall I'd say it's an improvement.

Either MOGREPS, UKMO and the ECM/EPS all have this wrong and somehow the GFS det is correct despite the GEFS being a complete and utter mess with no discernible signal, or the GFS is just rather useless. I know which camp I'm in. We'll see on the overnight runs, can't discount the GFS but the evidence is certainly against it.

GFS isn't having it. Onto the overnight runs.

The bold green line is the GFS deterministic run that some people are looking at and calling winter over. The rest of the lines are ensembles. Looking at the chart above the cold air hangs on across the UK until the very end of the run, the det whilst not an outlier has very little support. The UKMO was very good. GEM was good, the EPS are good, MOGREPS are good. There is more evidence to support a decent cold spell vs against. Could that begin to change? Yes, of course, but currently, today, it hasn't. Original post: https://community.netweather.tv/topic/99706-model-output-discussion-into-2024/?do=findComment&comment=5003643

Well it is cold out..

It's not gone fully GFS but neither has it gone fully UKMO, seems to be a bit in the middle.

The bold green line is the GFS deterministic run that some people are looking at and calling winter over. The rest of the lines are ensembles. Looking at the chart above the cold air hangs on across the UK until the very end of the run, the det whilst not an outlier has very little support. The UKMO was very good. GEM was good, the EPS are good, MOGREPS are good. There is more evidence to support a decent cold spell vs against. Could that begin to change? Yes, of course, but currently, today, it hasn't.

GFS det is way above the ensemble pack and verging on outlier territory, majority of the GEFS remain below the mean line. No worries from me. Onto the ECM!

This thread can be incredibly confusing at times, especially for those new/less knowledgable. I do wonder if much like the "Pro/Meteorologist" tag whether it might be worth a new tag for those who consistently & frequently post informative, non-biased balanced views to the forum, just as a reference point that what that person is saying can be "trusted"? It may help ease the confusion a little @Paul Whilst the GFS deterministic run flops about like a fish out of water, the UKMO & to an extent GEM remain rather consistent. As @Tamarapointed out a few days ago the ensemble means will be next to useless in the extended due to a large amount of spread and an overall "smoothing out" of small-scale features. I don't think the GFS deterministic is correct. I also don't think the UKMO is correct. BUT. Broadly, ensembles point towards cold conditions next week with a growing risk of high impact snowfall events as lows attempt to move in across the UK, this remains firmly routed within NWP modelling and is also consistent with the teleconnections. “All models are wrong, but some are useful” – George Box

Perhaps worth noting that the UKMO and GFS are verifying equally poor at the moment at day 5 with the ECM & GEM leading the way. If the GFS is wrong then equally the UKMO could be too.. (albeit UKMO has far more support at the moment, it does often produce output that is too clean).

Would personally take MOGREPS, EPS & UKMO at this range over the GFS and thus far those all remain solid. We'll see where the GFS det sits within the ensembles, it's far too messy in it's evolution. GFS doing a classic GFS most likely.

They literally said he was the chief forecaster & that he is in charge of weather warnings, i.e the role of chief forecaster. He also does other stuff too though. P.S. There is more than 1 'chief forecaster'.