Mike Poole
-
Posts
11,391 -
Joined
-
Last visited
-
Days Won
84
Content Type
Forums
Blogs
Gallery
Events
Learn About Weather and Meteorology
Community guides
Posts posted by Mike Poole
-
-
-
-
ECM clusters this morning, with some earlier interest (surprisingly) in the T192-T240 timeframe:
Clusters 1, 2 and 6 all show a ridge sufficiently to the west of the UK to bring in cold from the north by day 10. Clusters 3 and 5 edging that way too, just cluster 4 has the ridge initially through the UK and a mild flow.
T264+:
Cluster 1 really set apart with the big high lat block over Greenland and northerly winds, trough in Europe. The others are a bit nondescript by comparison, 5 and 6 showing some interest in a northerly too.
-
6
-
-
2 minutes ago, damianslaw said:
Just musing but doesn't a SSW result in a flushing out of the westerlies so to speak before its affects imprint fully.
It does usually, when it’s on the back of a strong strat vortex, but there aren’t any significant westerlies there to flush down in this case, because of the weak strat vortex all winter, and of course the previous SSW in January.
For example, GFS 12z zonal winds:
If there were strong westerlies to flush you’d see a strong pink anomaly (right chart) in the lower strat moving down with time with the blue anomaly from the reversal above it. It isn’t there.
Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5036863-
1
-
-
-
7
-
-
summer blizzard Big change on today’s plot compared to that:
Much increased cluster going for the second dip a week after the first, and a big reduction in the mean extending over several weeks.
-
- Popular Post
- Popular Post
daz_4 Nah! It’s still autumn!
-
14
-
- Popular Post
- Popular Post
The zonal winds chart is interesting, in as much as there seems to be an increasing cluster going for a second, deeper, dip (increase in easterly winds) about a week after the initial SSW.
Will make for an interesting March, I think, and a delayed start to spring.
-
11
-
1
-
2 minutes ago, damianslaw said:
Just musing but doesn't a SSW result in a flushing out of the westerlies so to speak before its affects imprint fully.
It does usually, when it’s on the back of a strong strat vortex, but there aren’t any significant westerlies there to flush down in this case, because of the weak strat vortex all winter, and of course the previous SSW in January.
For example, GFS 12z zonal winds:
If there were strong westerlies to flush you’d see a strong pink anomaly (right chart) in the lower strat moving down with time with the blue anomaly from the reversal above it. It isn’t there.
-
2
-
3
-
-
- Popular Post
- Popular Post
ECM clusters T192-T240:
Cluster 2 (contains the op) looks interesting more as to what comes after, with low Euro heights and a ridge building west.
T264+:
Once again, promise in the extended. Cluster 2 the puck with south Greenland high, cluster 1 with Atlantic ridge also cold. Clusters 3 and 4 northwesterly wind for the UK, cluster 5 high retrogressing a bit. All very jam tomorrow, but there’s wasps in the jar by now.
-
10
-
2
-
6 minutes ago, North-Easterly Blast said:
the records certainly show that it has always been very rare to get colder winter weather after an anomalously high September CET.
We had this discussion in the run up to winter. The problem is, these days, it is very rare to get colder winter weather after any September (cold, average, warm, the lot). And with climate change, warmer Septembers than historic averages are more common so it is possible to perceive a link that is not there. Correlation is possible, therefore, but it doesn’t imply causation. There is no logical reason I can see why a warm September in the UK of all places should affect weather patterns three months later. (There are other places in the world where Autumn weather may affect the coming winter because it affects the developing polar vortex - the UK is not one of them!)
It may just be one of those statistical anomalies (like the 13th June used to be), but it is a theory that is rolled out every year. Problem is, after this year, its nose will grow a few inches!
-
6
-
1
-
-
ECM clusters T192-T240:
Cluster 2 and 5 have the ridge in the Atlantic west of the UK, cluster 5 a bit pathetic really as it only has 2 members. Block’s not up to much on clusters 3 or 4 and cluster 1 it remains mid-latitudes during this timeframe.
T264+:
Clusters 3 and 4 develop a strong block over Greenland, although on cluster 4 it looks to be weakening at day 15. Both are well orientated. Cluster 1 and 2 have more of a ridge in the Atlantic, but both pull in air from the north by day 15. So, again, in this timeframe, there is potential, not sure if it is related to the SSW, but it will need to get its skates on if it is to turn into anything meaningful.
-
6
-
1
-
-
ECM clusters tonight show some movement, T192-T240:
The op is in cluster 2, which has the ridge go up west of the UK - it has 14 members. Cluster 1 similar but doesn’t get as far north. Cluster 3 pushes the ridge over the UK and it ends up to the east. Clusters 4 and 5 don’t really push the ridge up much at all.
T264+:
Roughly even split between the two clusters. Cluster 1 has a strong block which is also well positioned. Cluster 2 with a weaker ridge that eventually moves west of the UK, but maintains heights to our south.
-
4
-
1
-
-
Run of the day is the KMA 12z, here at T216:
The key to this, as I’ve said before, is getting the initial push of heights north to take place west of the UK and not over the UK. Will be interesting to see what the EPS show in terms of the likelihood of this.
-
6
-
-
ECM showing a much more positive evolution out to T192:
-
8
-
-
- Popular Post
- Popular Post
This thread is very necessary! And, quite fitting, in a weird way, to have the post-mortem while this excuse for a winter is still alive!
Before giving my thoughts on winter, I just wanted to make a comment on the GSDM - I don’t usually, because I don’t want to get caught in the crossfire between those who are passionate believers and very defensive when challenged, and those who use it as an easy target for criticism when it doesn’t snow. I don’t have access to the GSDM charts myself, but I do factor into my thoughts the excellent posts on here from those that do. I have read some papers on it, and @Tamara kindly provided me some useful help on aspects of it a few years ago - it seems sound and very useful, and given it is founded on the principle of conservation of angular momentum, it makes sense to me as a physicist. I don’t think it is infallible though, forecasts seem to be predicated on the assumption that AAM will rise/fall in a predictable way, and I also have a question mark (in winter) about how intuitions derived from the GSDM fit with things occurring in the vertical dimension i.e. the stratosphere, which I think has been relevant this winter. It also doesn’t inform on local UK-scale issues which can be so important.
The backdrop to this winter was world weather patterns out of past precedence with extraordinary sea surface temperatures. My view in the run up to winter, was that any attempt to make predictions based on analogues was therefore pointless, and I put more weight in the seasonal models - because they simply simulate the laws of physics, without knowledge of past patterns, I figured they would be the best guide. They weren’t! At best, they could be said to have predicted a weak vortex, which there definitely was, but on pressure patterns relevant to the UK, they have not performed well.
We have had a very weak strat vortex ever since the Canadian warming (first one for 30 odd years). The trop has been leading the dance most of winter, and the strat vortex has been behaving really quite oddly. I thought that surely with that in our favour we must be in with a shout of a decent winter. Wrong! But why? It seems to me that there are two primary possible reasons:
- Climate change has done something to global weather patterns that have made it next to impossible to get the kind of synoptic patterns which in the past would have delivered cold to the UK - the dreaded ‘Iberian high’ being a symptom (but not cause) of this.
- We were just very unlucky this year. Even unfettered by the strat vortex, the trop vortex just never got itself into a favourable position. I still think with a different roll of the dice we could have ended up with something memorable.
One of the reasons I don’t (yet) believe reason 1, that decent UK winter patterns have become next to impossible, is because they have showed up in the models this year, not just the odd run, but substantial clusters of ensemble runs - we have just not managed to count them down into the reliable. They would not show up if they were no longer physically possible, for whatever reason, due to climate change. So, I put most of it down to bad luck.
Which brings me to my final learning point which is disregarding the model output. It is OK to bin an individual run if the output gets so contorted you know (from looking at charts that have actually verified) that a run is garbage. But, I think we have been a little quick to dismiss larger swathes of model output on the assumption that ‘the models are misreading the progression of the MJO’, ‘the models always underestimate Iberian heights’, ‘the ECM is prone to over-amplification’, or ‘the GFS is off on one and will come into line’ etc. I hold my hand up - I’ve done this - and found later that the disgraced model was on to something after all.
All in all, a very disappointing winter, but while we have had no meaningful snow (locally, again, 4 years on the trot now), it has been a (morbidly) fascinating learning experience.
-
12
-
1
-
ECM clusters T192-T240:
Clusters 3 and 5 look good for a cold plunge by day 10, clusters 2 and 4 have things too far west, cluster 6 settles on a UK high, cluster 1 can’t lose heights to the south.
T264+:
Cluster 3 looks good with a nicely placed ridge into Greenland by day 15, cluster 2 has a weak Greenland block that goes a bit too far west, cluster 1 rather has the blocking collapse.
There’s still potential here, and with the SSW to factor into the mix, cluster 1 looks to me unlikely. But getting anything at all into the reliable just seems problematic…
-
5
-
1
-
1
-
-
ECM clusters T192-T240:
All four clusters look blocked, cluster 4 the strongest with a persistent block in Greenland. Cluster 3 has things a little too far east, cluster 2 the Atlantic low is too progressive, cluster 1 the build of heights too much through the UK.
T264+:
There does seem a genuine theme in these, that wasn’t there this morning or in yesterday evening’s output, for a continuation of a blocked theme, a block somewhere around Greenland in all 5 clusters at day 15. Pointless looking in any detail at that, and if it is fallout from the SSW, then the models will make a meal of it before deciding on anything useful in terms of a forecast, but the interest remains, even if the clock is ticking into the red zone…
-
5
-
-
feb1991blizzard Yes, would agree we need a good EPS suite to give even an entry pass to the last chance saloon. The SSW might still deliver, but the trouble is, SSW, MJO, GWO, all are backed by good science but I wouldn’t trust any of them to deliver cold to the UK.
The opposite, though, if any signal is predicting mild, it’ll be bang on!
-
7
-
-
ECM extended clusters, T264+:
These are not as good as the 0z by a margin. Cluster 4 looks decent, cluster 6 looks OK ish, cluster 3 the block is too far north and west, and the others the blocking is disintegrating - I think that is the change from this morning, this is no longer trending towards a blocked outlook.
-
4
-
1
-
-
Met4Cast Clusters 3 (with a westwards tweak) and 5 look decent also. Better than I was expecting at T240 to be honest. Clearly there is some signal still to build the ridge west of the UK.
-
4
-
-
- Popular Post
- Popular Post
2 minutes ago, nick sussex said:Time to put this winter out of its misery . Even worse that we didn’t really have a strong PV for most of the winter which makes the fact it was generally woeful even more disappointing.
Yes, another poor ECM - will wait to see what the ensembles say, but I would not be surprised to see a down turn after promising clusters this morning.
You’re right about the PV - there has been an extremely weak strat vortex all winter (since the Canadian warming, in fact), which another time could have produced an epic winter, but as far as the trop patterns were concerned this year what can go wrong has gone wrong. For snow in my location, and barring a major turnaround in the next 20 days, it has been the 4th consecutive 0/10 winter.
Never mind, next winter model watching will be much easier. My predictions are:
- Westerly QBO winter.
- After brief northerly tease, rampant PV sets up shop over Greenland in the first week of December.
- Safe to declare winter over on 7th December and we can go and do something more productive instead.
-
14
-
1
-
UKMO T168:
Much better, more room between the low and the UK.
-
6
-
-
Model Output Discussion - Spring Has Sprung
in Forecast Model Discussion
Posted · Edited by Mike Poole
ECM clusters T192-T240:
Cluster 1 which contains the op, and follows the line of thought that the GFS has had recently, has 29 members, so the northerly by day 10 is definitely on the table. Cluster 2 remains flat.
T264+:
Cluster 1 with 19 members continues the blocked theme, although it diffuses by day 15. Cluster 3 also has some interest, but looks like the ridge is a toppler. Cluster 2 is westerly, and so is cluster 4 with heights to the south.