I'm sorry but I do remember this forum from 20 years ago and back then it was all about the era of the modern winter, oh how the climates not like it used to be blah blah blah. But then we had a run of very cold winter spells 08/09- 09/10 10/11.
But once again we find ourselves saying the same old same old like you have above, and nsrobins post about using data that is "15" out of date as it doesn't represent our climate now. Do we not learn?
Originally Posted by: picturesareme
I repeat what I say - the "AI" models are trained on old data and are pattern matching our old climate.
https://www.ecmwf.int/en/about/media-centre/aifs-blog/2025/introducing-anemoi-training-ready-version-era5
("Using a time period spanning 1979 to 2023")https://www.ecmwf.int/en/newsletter/178/news/aifs-new-ecmwf-forecasting-system
It remains a fact that snowy midwinter easterlies were common in the 80s. They were still frequent in the 90s, then we had the 2-week long easterly in 2005, which Philip Eden speculated might be the last proper easterly spell. I commented a couple of weeks ago, when the "AI" models were producing epic cold and snowy runs day after day, that they were pattern-matching 2005. They showed the classic pattern of the Siberian High ridging westwards over Scandinavia, then the "ping pong" of highs between Scandinavia and Greenland which kept the deep cold air topped up. This was a very familiar pattern and it's why the east and even the SE saw lots of snow back in the day - here, as I've said many a time, a fall of an inch or two would be nothing to write home about, whereas in the 80s and 90s falls of 6 inches were commonplace... or more. And even back in the 80s, comparisons were made with the classic spells of the 40s, 50s, 60s and 70s, which saw even more snow! I can't comment on those, though, as I wasn't alive to experience them.
Things were already changing 20 years ago, as Philip Eden noted, and of course since then we've not had any of those classic midwinter easterlies - we've had some northerly outbreaks, we've had "blink and you'll miss it" ridges zipping across Scandinavia and swiftly collapsing, but one thing we've not had is that prolonged, repeating "ping pong" easterlies of old. There are all sorts of other changes too, for example you could (rarely) get sleet or snow, briefly, as cold fronts cleared eastwards from Atlantic lows back in the 80s - as there was that much more cold air around.
It's clear as day that the pattern matchers, trained as they are on old data, have been using the examples of easterlies in their database in this current spell. After all, in 2005 we had a similar setup: a prolonged jet far to the south, a persistent block to the NE, and we did indeed get weeks of cold and snow (here at least) out of it. This time? Not even close, and as per the rainbow analogy the pattern matchers eventually twigged and removed the cold air and stellar synoptics.
FWIW the ECM "AI" model uses the specially-prepared ERA5T dataset - which is a subset of their ERA5 reanalysis data specially formatted for training purposes. It covers plenty of fields but crucially doesn't include any historical model runs, just starting conditions. I would argue that having the model input from previous runs is essential - as it could then learn *why* things went wrong, rather than just how a similar - but not the same - situation evolved in the past.
EDIT: Two other points worth mentioning. One, the climate has warmed by 1.5C down here between 61-90 and 91-20 and yes, that has a marked effect on our weather patterns. And two, as those who've been around on here for 25 years will remember, pattern matching was once very much in vogue - the NOAA composite charts were much posted back in the day during winter. And you know what? More often than not they didn't reflect what eventually happened. The best that can be said about this spell so far is that we know in the 80s and 90s we'd have been much more likely to have seen cold and snow from it.
Edited by user
31 January 2026 04:51:40
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