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Winter 2018/2019 - General Discussion
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Probably time for a post-mortem on this non-winter (almost).
Forecasts almost universally called for some serious cold and snow and tended to suggest January as the time for it, some were more into a late January first half of February winter core. So it wasn't just me.
Looking at my own particular take on it, the entire winter turned out about 3 degrees milder start to finish, the variations were about what was expected but when I said cold, it was just around average (in mid to late January), running a bit colder than normal in parts of Britain then, and when the forecast suggested average or mild it was very mild (for example about now, also early to mid December).
Meanwhile, some seriously cold and snowy intervals did materialize a bit further east into Germany, Poland and parts of central Europe into the Alps. This would tell you that the predicted patterns were further east than expected. There wasn't much blocking to be found, just rather stationary ridge-trough setups that never quite delivered the goods even when there was a bit of an opening in late January (some 10-15 day prog charts were wonderful so that tells you the atmosphere was within one turn of the dial from delivering, but it didn't and there's no denying that fact).
Across North America, the patterns expected were somewhat closer to the mark. Severe cold continued to sit over north central Canada almost all winter and sometimes made forays south, Chicago had one of its coldest four day periods on record at the end of January. What was probably largely unexpected was that the arctic air made a retrograde move into western Canada and then south into the western USA, a pattern which shows no signs of abating. This has not been your typical El Nino winter although the first half of it was largely similar to expectations here. The pattern change took place on Groundhog Day, and we have been below normal here ever since.
Did the SSW event screw things up? I don't accept that sort of reasoning because any working LRF system must be able to anticipate such events and therefore must incorporate them into the outlook. To treat them as external to the challenge is defeating the whole purpose of making a long-range forecast. If anything, the SSW event should have pushed the cold winter forecasts over the finish line around mid-January, and hundreds of pages of model discussion later, this turned into an epic fail. Whatever the SSW event actually did, it failed to produce high latitude blocking highs or retrogression over Europe and Asia at least. So it may as well not have happened at all from the point of view of most forecasters.
Can anything be learned from all this? I've been reading no end of commentary on other long range forecast threads (both sides of the Atlantic) where people say "next time I will blah blah" but in my case, the challenge never really changes, I just have to keep plugging away at a method that has had some degree of success longer term and see if it's possible to improve the performance by discovering new elements to add to the index value set that I use. This gets so complicated that I don't expect there to be sudden flashes of inspiration followed by marked improvements. The next seasonal forecast I derive from the techniques may be back to a reasonably good outcome without doing anything, but I am always thinking about new lines of investigation that would justify adding new material to the method.
Without even running the model I would say that winter may not be over in the meteorological sense. There's probably a final twist to the tale lurking when the circulation flattens out this western North American ridge-trough combination. I have the feeling that there will be a snowstorm at some point in March or maybe even April this year, nature will not be happy with moving April to February but could retaliate by moving February to April.0 -
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