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A Winter's Tale

The Seasonal Forecast Thread

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1 hour ago, bluearmy said:

Btw, that forecast went well for wsi  .......

Indeed, and the thing is that the Feb stratospheric warming event was well within the range of the models at the point at which they made that forecast. 

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A great forecast layout by RJS with some tentative bullish comments in there.  I’ve got a hunch that verification stats could be very positive come the end of the winter.

 

BFTP 

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On 11/01/2018 at 21:53, Summer Sun said:

Met office maps have updated for Jan the next 3 monthly period of Feb to April looks mild and unsettled

2cat_20180101_mslp_months24_global_deter_public.thumb.png.a5a62c287196e8cd340a7e23334ada67.png2cat_20180101_prec_months24_global_deter_public.thumb.png.cc9f7535ceeb5be493892774b7aacae6.png

2cat_20180101_temp2m_months24_global_deter_public.thumb.png.c5c7f5a0f341b32d566d545cc8388ce7.png2cat_20180101_t850_months24_global_deter_public.thumb.png.ace5cb1d3ff4fa2ae07462a42b4408fd.png

Not sure it turned out that way.... (if it did it hid the Cold outbreak at the end of winter very well)

 

Lesson to be learnt here 

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5 hours ago, DR(S)NO said:

Interesting read Roger...my feeling is  the stormy spells may stem from the Northwest.... keeping it colder than average through these spells particularly for Northern Britain.

Or do you envisage them coming from a milder direction?

I would agree on your interpretation for northern Britain, as the overall scenario implies a tight gradient from about 250-270 deg perhaps and in later stages of stormy periods more like 290-310 so spikes in temperature may be confined to southern Britain and parts of Ireland. 

Just reading on the other thread (winter 2018-19) and apparently while I went out on a limb, various other weather scoundrels of note (re Express article) have found the biggest tree in the forest, climbed to the top, and I'm in danger of getting hit on their way down, or maybe they will just taunt me with a barrage of chestnuts (as long as they don't throw Bartletts should be okay). I am reassured to be back in the middle of the road (where we normally find roadkill). 

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Things seem to be unfolding along the lines of the LRF that I posted, in terms of early winter being zonal with frequent storms especially at new and full moons -- the new moon occurs tomorrow at 0721z just about when strongest winds are being  recorded in northern parts of Ireland and western Scotland. The next lunar energy peak around the 21st-22nd should be pivotal to how the winter develops, if cold air can get established shortly after the expected stormy period then, it might settle in for a good spell.

I note that there was a major windstorm on 8 Dec 1886 and the interval from 17 Dec to about 17 Jan 1887 was quite cold, with a mean temperature close to zero degrees C. 

This is relevant mainly as a guide to how long it sometimes takes for a raging zonal period to transition to blocking and colder weather (although it was not especially mild during that particular storm with CET values near 4 degrees). The storm in question produced a record low barometer reading in Northern Ireland in the 920s, and 90-100 kt wind gusts over the Irish Sea with ships run aground on the Lancs coast. 

Edited by Roger J Smith
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16 hours ago, Roger J Smith said:

Things seem to be unfolding along the lines of the LRF that I posted, in terms of early winter being zonal with frequent storms especially at new and full moons -- the new moon occurs tomorrow at 0721z just about when strongest winds are being  recorded in northern parts of Ireland and western Scotland. The next lunar energy peak around the 21st-22nd should be pivotal to how the winter develops, if cold air can get established shortly after the expected stormy period then, it might settle in for a good spell.

I note that there was a major windstorm on 8 Dec 1886 and the interval from 17 Dec to about 17 Jan 1887 was quite cold, with a mean temperature close to zero degrees C. 

This is relevant mainly as a guide to how long it sometimes takes for a raging zonal period to transition to blocking and colder weather (although it was not especially mild during that particular storm with CET values near 4 degrees). The storm in question produced a record low barometer reading in Northern Ireland in the 920s, and 90-100 kt wind gusts over the Irish Sea with ships run aground on the Lancs coast. 

delete

 

Edited by BLAST FROM THE PAST
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Someone posted in November a video link of the Meteo France winter forecast-which predicted a cold snowy December for the UK-safe to say that was very wrong at such a short timescale! Let's just hope many of the other models that went for a mild December followed by colder January/ February are correct!

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On 08/12/2018 at 06:51, Roger J Smith said:

The latest (00z) GFS run starts to look like this scenario of cold engaging around Christmas, and there are some juicy charts on offer by 23rd-24th...

Roger, I wondered if you are intending to post an update on your winter LRF? From my novice perspective it seems your timings have been quite accurate (switch from mobile to blocking aroind Xmas) but perhaps the block hasn't set up as far north as you anticipated?  If so, does this impact your original forecast for a second cold spell towards the end of January?  Any thoughts welcome, always enjoy reading your LRFs.

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Sorry, I did not see the post above in real time, just came in here to offer a post-mortem on the winter forecast which failed to anticipate the mild trend but had some accurate comments about storminess and North American outcomes.

In essence, I think the trend line was the main problem, January (in particular second half) was colder than either December or February which was probably implied in the forecast, but all three months were probably about three degrees warmer than implied, December around 7 C, January around 4 C and February will once again finish near 7 C on the CET scale which will be a top ten winter average. Had January stayed as mild as it started, this would be a contender for the 1868-69 crown of mildest winter. It was only that interval (which was advertised to become exceptionally cold even on 10-day prog charts at times) that pushed the outcome away from the extreme category.

So I'm not sure whether a busted trend line with reasonably accurate variations over top of that represents a model error or the beginning of some sort of serious breakdown of the model's ability to cope with climate change signals. This will be one to monitor for several more seasons before getting close to an answer. I've always feared that if the AGW signal ever accelerated or if the magnetic field weakened substantially, all this research might become outdated by new realities. 

However, I think what probably caused the faulty trend line was that the ridge-trough couplet over Europe was further east than anticipated, allowing several prolonged cold spells to drop into central Europe. There was a tendency for the jet stream to drop far south in late January as implied in the forecast and that did lead to some exceptionally severe snowfalls in the Alps and heavy rains in Italy and parts of southeast Europe, with heavy snow added in other regions including northern Greece. 

As to snow in Britain, that amounted to almost nothing at lower elevations but I don't see that as an added model failure, it's just a consequence of the temperature trend failure. The late January colder spell did bring some significant snow to parts of Scotland and northern England, and one or two quite low overnight readings. Probably the forecast reads better in Scotland than in any other part of the British Isles. 

Events in North America have been much closer to what I was expecting and I can see that my forecasts are holding up because I'm either leading or second place in various snowfall contests and in the American weather forum temperature forecast contest. And the fields in those include professional forecasters (more so than here) which probably means less than you might suppose (pros have trouble with this too). 

There have been exceptionally cold intervals in central regions extending "at times out to both coasts" as stated, and I feel like I was ahead of the herd on the weakness of El Nino against the Canadian cold complex that had showed up early in the season. In fact, El Nino is out for the count with February becoming the coldest in many decades in the west, and snow instead of rain out to the coasts as far south as Oregon, and onto hills all over the southwestern US. The east coast has been relatively mild with a few brief cold spells, and not much snow. The heavy snow has fallen in the Great Lakes, Midwest, and northern New England regions, as well as pockets across the northwest U.S. (not so much into British Columbia which has been on the dry side mostly). 

So I am giving the forecast a D rating for Europe and a B+ to A- rating for North America. It's frustrating that the gains that I have made in my research in North America have not solidly transferred across the Atlantic, my research thread shows a lot of indications that it should enjoy a similar success rate with index values almost as strongly defined, but maybe it's my lack of feel for the climate of a continent where I don't actually reside, or a more challenging set of paradigms, that has caused this lack of equal progress. There has been progress if I look at all forecasts made since about 2005 when I expanded my efforts to the European theatre. But it's not a satisfying feeling of equal progress as the North American forecasts tend to stay in a fairly comfortable zone. These European ones have proven to be rather hit or miss, and the hits sometimes occur in situations that cry out with an obvious outcome like last summer which I never really felt was any sort of accomplishment to forecast heat and drought. 

Part of my own post-mortem will be to run the actual numbers against index values to see what sort of error trends can be spotted, because sometimes you can isolate a new research inquiry from that. I never thought that this research had reached its final stages, and have always expected to find new variables worth incorporating. 

As to the widely discussed SSW event that more or less failed to dislodge the mild pattern (obviously it was trying to do so around 21-31 January) I don't have much to say on that subject because I have assumed that my method would "back door" SSW events into the mix, although I have not succeeded in finding a cause and effect hypothesis that fits into the theory (was trying to link them from known occurrences but the data sets don't go back very far and it turns into a guessing game for 90% of the data I have analyzed). Then there's the MJO business, there again, I have tried to isolate research variables that might give a cause and effect predictive relationship with MJO, but if MJO also fails to do what it's supposed to do, then I sometimes ask myself, why bother with it? It could be like that Siberian early snow business, an interesting correlation but low-value for seasonal forecasting long-term. 

We're going to get to the bottom of this mystery eventually. It may be a couple of generations after you and I have moved on, but I can't see this remaining a permanent puzzle. It is interesting that ours is probably the only remaining science with so much mystery involved in it. I do know that whoever does eventually succeed will somehow have to "stand on the shoulders" of some of us who worked on whatever lines of research before them, but I can't really say with much assurance whether this will be part of it, or an accidental partial duplication of something totally different in structure, or irrelevant to the final result. My North American work convinces me that this is the way to go, and I can't really imagine a global paradigm in which it only works in one region, although I suppose you could have a situation where there's enough force in the connections to work where the magnetic field is strongest and not enough elsewhere reducing them to random energy dissipation zones. That would suck but the NMP is coming your way. :)

 

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