Winter 2023/24 - Discussions & Forecasts

[Cheshire Freeze]

Can we even be sure the IOD ‘ruined’ 19/20? I think it was certainly scapegoated but I recall at the time that some people were claiming it was a minuscule factor in the resultant UK weather?

Seems to me it was a case of ‘oh look the IOD is off the scale and we’re having a crap winter, must be because of that’.

Either way, ENSO in theory would usurp it and even at its forecast peak it looks a fair bit less strong than in 19/20.

Edited September 12, 2023 by Cheshire Freeze

[Methuselah]

34 minutes ago, Cheshire Freeze said:

Can we even be sure the IOD ‘ruined’ 19/20? I think it was certainly scapegoated but I recall at the time that some people were claiming it was a minuscule factor in the resultant UK weather?

Seems to me it was a case of ‘oh look the IOD is off the scale and we’re having a crap winter, must be because of that’.

Either way, ENSO in theory would usurp it and even at its forecast peak it looks a fair bit less strong than in 19/20.

It makes you wonder what ruined all our other winters since 2013, doesn't it? 

[Cheshire Freeze]

16 minutes ago, Methuselah said:

It makes you wonder what ruined all our other winters since 2013, doesn't it? 

Well yeah.

Then there’s the fact we have no clue how various IOD states interact with other factors. It could be that El Niño plus +ve IOD equals enhanced cold potential for the NW Europe winter, for example. We don’t know because weather isn’t formulaic to that extent.

It’s a chaotic system.

Edited September 12, 2023 by Cheshire Freeze

[cheeky_monkey]

29 minutes ago, Cheshire Freeze said:

Well yeah.

Then there’s the fact we have no clue how various IOD states interact with other factors. It could be that El Niño plus +ve IOD equals enhanced cold potential for the NW Europe winter, for example. We don’t know because weather isn’t formulaic to that extent.

It’s a chaotic system.

which is why it always baffles me when people just look at analogs of atmospheric conditions across just a portion of the globe (ie NH) and don't look at the whole global atmosphere..even if you start with the exact starting point you can end up with millions of different outcomes 3 months down the line and we have what a maximum of 50 verified data sets to start with? 

[Methuselah]

23 minutes ago, cheeky_monkey said:

which is why it always baffles me when people just look at analogs of atmospheric conditions across just a portion of the globe (ie NH) and don't look at the whole global atmosphere..even if you start with the exact starting point you can end up with millions of different outcomes 3 months down the line and we have what a maximum of 50 verified data sets to start with? 

And that's not accounting for all those conveniently timed coronal mass ejections, either. 

[blizzard81]

48 minutes ago, Methuselah said:

And that's not accounting for all those conveniently timed coronal mass ejections, either. 

Indeed. Well said. 

[Mike Poole]

2 hours ago, Cheshire Freeze said:

Can we even be sure the IOD ‘ruined’ 19/20? I think it was certainly scapegoated but I recall at the time that some people were claiming it was a minuscule factor in the resultant UK weather?

Seems to me it was a case of ‘oh look the IOD is off the scale and we’re having a crap winter, must be because of that’.

Either way, ENSO in theory would usurp it and even at its forecast peak it looks a fair bit less strong than in 19/20.

It was the Met Office who made the link with the extreme +IOD in 19/20 (prior to winter in their contingency planners forecast) - so that carries some weight for me.

I agree with the bold bit and that’s my take on it as well.  It has been and still is worth watching in case it gets modelled to be stronger (a very small number of ensemble members do push 19/20 values), but I think it will be overtaken by other factors.  A strong eQBO is also something that we have this year and we didn’t have in our favour in 19/20.

 

[Uncertainty]

4 hours ago, Cheshire Freeze said:

Can we even be sure the IOD ‘ruined’ 19/20? I think it was certainly scapegoated but I recall at the time that some people were claiming it was a minuscule factor in the resultant UK weather?

Seems to me it was a case of ‘oh look the IOD is off the scale and we’re having a crap winter, must be because of that’.

Either way, ENSO in theory would usurp it and even at its forecast peak it looks a fair bit less strong than in 19/20.

That hideous season also had a (very well forecast) Antarctic ssw. I’ve read that a weak vortex in one makes a strong vortex in the other more likely, though I know little about it. The +nao signal at this stage in the modelling was about as strong as the (JFM) -nao signal is now. Crucially it had a wqbo too and we know it’s going to be a strong EQBO.
 

the one caveat to my excitement is that I do think we will, once again, need an ssw to spark this off. I think the models are seeing one. We need that Aleutian low + Greenland low / Scandi high dipole combo to come good for us in November. And then some mjo support to boot. I think both look likely though especially in early 2024.

[Cheshire Freeze]

CFS still sticking to its prognosis...it's the usual story

3 months of early spring-

Daffodils out in January

Trees budding in February

Winter commences in March

With the complete flip in height profiles come March, it looks like the CFS is sniffing a mid Feb SSW. Could once again 'ruin' the first couple of months of spring if anywhere near reality.

Edited September 13, 2023 by Cheshire Freeze

[SqueakheartLW]

"September, the warmest CET month of the year? Only occasion that happened was in 1890

Both June and September warmer than the July and August in between them?  That would be even more remarkable"

 

Just read the above in the September CET thread. Rather interesting fact this one that it happened in 1890

We all know from CET records what happened in December 1890. Hope we can see a repeat of that month to open up winter 2023/24

[Chesil View]

5 hours ago, SqueakheartLW said:

"September, the warmest CET month of the year? Only occasion that happened was in 1890

Both June and September warmer than the July and August in between them?  That would be even more remarkable"

 

Just read the above in the September CET thread. Rather interesting fact this one that it happened in 1890

We all know from CET records what happened in December 1890. Hope we can see a repeat of that month to open up winter 2023/24

I 'd certainly take what happened in December 1890 and also for the southwest what happened in March 1891.

Edited September 13, 2023 by Chesil View

[blizzard81]

6 hours ago, SqueakheartLW said:

"September, the warmest CET month of the year? Only occasion that happened was in 1890

Both June and September warmer than the July and August in between them?  That would be even more remarkable"

 

Just read the above in the September CET thread. Rather interesting fact this one that it happened in 1890

We all know from CET records what happened in December 1890. Hope we can see a repeat of that month to open up winter 2023/24

Would be nice to see this during this November. Negative tilted low. Always a great sign. Looks like happening next week as well. 

[sebastiaan1973]

On 12/09/2023 at 19:41, Cheshire Freeze said:

Can we even be sure the IOD ‘ruined’ 19/20? I think it was certainly scapegoated but I recall at the time that some people were claiming it was a minuscule factor in the resultant UK weather?

Seems to me it was a case of ‘oh look the IOD is off the scale and we’re having a crap winter, must be because of that’.

Either way, ENSO in theory would usurp it and even at its forecast peak it looks a fair bit less strong than in 19/20.

Yes we can. https://rmets.onlinelibrary.wiley.com/doi/10.1002/asl.1005

Northern Europe and the UK experienced an exceptionally warm and wet winter in 2019/20, driven by an anomalously positive North Atlantic Oscillation (NAO). This positive NAO was well forecast by several seasonal forecast systems, suggesting that this winter the NAO was highly predictable at seasonal lead times. A very strong positive Indian Ocean dipole (IOD) event was also observed at the start of winter. Here we use composite analysis and model experiments, to show that the IOD was a key driver of the observed positive NAO. Using model experiments that perturb the Indian Ocean initial conditions, two teleconnection pathways of the IOD to the north Atlantic emerge: a tropospheric teleconnection pathway via a Rossby wave train travelling from the Indian Ocean over the Pacific and Atlantic, and a stratospheric teleconnection pathway via the Aleutian region and the stratospheric polar vortex. These pathways are similar to those for the El Niño Southern Oscillation link to the north Atlantic which are already well documented. The anomalies in the north Atlantic jet stream location and strength, and the associated precipitation anomalies over the UK and northern Europe, as simulated by the model IOD experiments, show remarkable agreement with those forecast and observed.

[virtualsphere]

The IOD forecast by UKMO at least appears to have been over-estimated.  Looking at their ensembles from April, many were going for a peak between July and Sept in the 1.5C region with some exceeding 2C: 

The Sept update shows the actual value to have been below 0.5C for much of that period and with a peak now expected at the end of the year but fewer members now touching the 2C ceiling on the chart.  

(Source)

This latest chart seems similar to the latest BOM update posted by @Mike Poole on the previous page, though I'm not sure if you can view previous BOM runs in the same way to compare.  

This wouldn't be on the scale of the two previous extreme IOD events from 2019/20 and 1997/98 which topped out with anomalies +3C, though the positive IOD periods closer to +2C in 1994/95 and 2006/07 were also rather uninspiring from a UK winter perspective.  As others have posted there's not much data to go on though, and it's just one variable to throw into the mix.  

(Source)

Of note this page suggests the IOD was positive in 1963 so make of that what you will... (though not necessarily the start of the year!) http://www.bom.gov.au/climate/enso/#tabs=Indian-Ocean&indian=History 

 

[blizzard81]

1 hour ago, virtualsphere said:

The IOD forecast by UKMO at least appears to have been over-estimated.  Looking at their ensembles from April, many were going for a peak between July and Sept in the 1.5C region with some exceeding 2C: 

The Sept update shows the actual value to have been below 0.5C for much of that period and with a peak now expected at the end of the year but fewer members now touching the 2C ceiling on the chart.  

(Source)

This latest chart seems similar to the latest BOM update posted by @Mike Poole on the previous page, though I'm not sure if you can view previous BOM runs in the same way to compare.  

This wouldn't be on the scale of the two previous extreme IOD events from 2019/20 and 1997/98 which topped out with anomalies +3C, though the positive IOD periods closer to +2C in 1994/95 and 2006/07 were also rather uninspiring from a UK winter perspective.  As others have posted there's not much data to go on though, and it's just one variable to throw into the mix.  

(Source)

Of note this page suggests the IOD was positive in 1963 so make of that what you will... (though not necessarily the start of the year!) http://www.bom.gov.au/climate/enso/#tabs=Indian-Ocean&indian=History 

 

My heart sinks in terms of the winter ahead with that post. You can clearly see that the peak has been delayed until winter proper with the September update. It was meant to peak during Summer on the April update then decline after September. The latest update delays it so that it peaks later. During winter to be exact. Not good. A negative mark for me personally in terms of a cold winter. 

[damianslaw]

IOD one factor amongst many others. I only recall it being mentioned as a factor in 2019-20, and surprised not to have heard of if before, if it is considered a significant factor. 

 

[Don]

2 hours ago, blizzard81 said:

My heart sinks in terms of the winter ahead with that post. You can clearly see that the peak has been delayed until winter proper with the September update. It was meant to peak during Summer on the April update then decline after September. The latest update delays it so that it peaks later. During winter to be exact. Not good. A negative mark for me personally in terms of a cold winter. 

Yep, not good is it?!  Perhaps it will get delayed further, or is overestimating the strength?!

Edited September 14, 2023 by Don

[SqueakheartLW]

14 hours ago, Don said:

Yep, not good is it?!  Perhaps it will get delayed further, or is overestimating the strength?!

Significant +IOD events seem to occur most often with EP El Nino's or sometimes non modoki CP El Nino's on occasions.

2019/20 seems to be a big outlier considering ENSO was neutral in that season.

There is a difference between EP, CP and modoki El Nino's and a lot of us assume all CP events are modoki as well.

Modoki events are measured on the difference of the anomalies between Nino 4 and 1+2 whilst EP and CP is the difference between Nino 4 and Nino 3.

Therefore we have several El Nino types:

• Standard EP El Nino (Nino 3 and 1+2 warmest anomalies)
• Modoki EP El Nino (Nino 3 warmer than Nino 4 but Nino 1+2 cooler than Nino 4)
• Standard CP El Nino (Nino 4 and 3.4 warmest anomalies but 1+2 not much cooler)
• Modoki CP El Nino (Nino 4 and 3.4 warmest anomalies. Warmer than Nino 3 and much warmer than Nino 1+2)
• Basin wide El Nino (All 4 Nino regions close to the same anomaly)

Standard EP El Nino's have greatest chance of significant +IOD events with modoki CP  El Nino's the least. 1997 is a great example of a Super EP El Nino combined with significant +IOD. 2009 is also El Nino but a modoki CP event and barely registers anywhere on the IOD, just above neutral but not enough to be defined as a +IOD event.

[Dorsetbred]

7 minutes ago, SqueakheartLW said:

Significant +IOD events seem to occur most often with EP El Nino's or sometimes non modoki CP El Nino's on occasions.

2019/20 seems to be a big outlier considering ENSO was neutral in that season.

There is a difference between EP, CP and modoki El Nino's and a lot of us assume all CP events are modoki as well.

Modoki events are measured on the difference of the anomalies between Nino 4 and 1+2 whilst EP and CP is the difference between Nino 4 and Nino 3.

Therefore we have several El Nino types:

• Standard EP El Nino (Nino 3 and 1+2 warmest anomalies)
• Modoki EP El Nino (Nino 3 warmer than Nino 4 but Nino 1+2 cooler than Nino 4)
• Standard CP El Nino (Nino 4 and 3.4 warmest anomalies but 1+2 not much cooler)
• Modoki CP El Nino (Nino 4 and 3.4 warmest anomalies. Warmer than Nino 3 and much warmer than Nino 1+2)
• Basin wide El Nino (All 4 Nino regions close to the same anomaly)

Standard EP El Nino's have greatest chance of significant +IOD events with modoki CP  El Nino's the least. 1997 is a great example of a Super EP El Nino combined with significant +IOD. 2009 is also El Nino but a modoki CP event and barely registers anywhere on the IOD, just above neutral but not enough to be defined as a +IOD event.

So, are you saying there is a no direct correlation OR there is a correlation that can be used for forecasting?

[Don]

17 hours ago, blizzard81 said:During winter to be exact. Not good. A negative mark for me personally in terms of a cold winter. 

Well, you must have known something would hinder winter this year?!  If it’s not a positive IOD, it will be El Niño, solar activity, a bear farting in the USA or goodness knows what?!

[Met4Cast]

46 minutes ago, Dorsetbred said:

So, are you saying there is a no direct correlation OR there is a correlation that can be used for forecasting?

There's definitely a correlation between +IDO events and +AO, however other variables often complicate things. With El Nino you'd expect to see stronger westerly winds being injected into the overall budget which tends to support higher latitude blocking, two competing signals. 

Figuring out which signal over rides the other will be the challenge for anyone producing a winter forecast this year I think. The MJO perhaps will be the difference between strong westerly winds or a slow, blocked pattern so i'm interested in seeing how that evolves in the coming weeks/couple of months. 

The AAM continues to be disconnected from the oceanic base state, so forecasting beyond the medium term at the moment is proving quite tricky on a more local scale.

[summer blizzard]

51 minutes ago, Dorsetbred said:

So, are you saying there is a no direct correlation OR there is a correlation that can be used for forecasting?

There is.

Basically it’s atmospheric wavelengths. When forcing is in the ordinary Nino zones and coupled it produces areas of subsidence or enhanced convection, normally producing a stronger convective response in the West Indian Ocean. What S is alluding to is that when forcing is biased to the west like 09 then it can in turn push those areas of convection and subsidence further west. In that case the Indian Ocean received minimal forcing because it got pushed to Africa.

2019 was different in that the IOD was the driver and not the follower. 

[Cheshire Freeze]

The CFS over the past 24 hours has had a volte face. The daily runs are now much improved all of a sudden after weeks and weeks of constant dross. The second chart looks like some of the anomalies we've seen on other long range products with heights to our N but also heights over S Europe.

Massive if the CFS shifts its stance IMO as it's been the constant thorn in the side.

Let's hope it continues to churn out better runs...if it does we'll see the plotted average anomalies improve too.

Perhaps it has something to do with what someone mentioned the other day- it toning down the El Nino strength. I actually think there's a tight path to tread this coming winter. If we can get El Nino as much towards moderate as possible and tone down the IOD forecasts to weaker side of moderate then we could be in near perfect territory. Weak enough drivers for it not to be a slam dunk zonal winter but strong enough to allow enough fuel for a fairly significant mid winter warming of the stratosphere.

At this point I'm reasonably confident we'll see some winter this year but in terms of longevity and frequency of cold I'm less confident at this point. We'll probably need another 6 weeks until we can firm up.

Edited September 16, 2023 by Cheshire Freeze

[Weather-history]

1 hour ago, Cheshire Freeze said:

The CFS over the past 24 hours has had a volte face. The daily runs are now much improved all of a sudden after weeks and weeks of constant dross. The second chart looks like some of the anomalies we've seen on other long range products with heights to our N but also heights over S Europe.

Massive if the CFS shifts its stance IMO as it's been the constant thorn in the side.

 

Mental health warning

 

"Should not to be taken seriously"

Never understood why you are such a champion of CFS, Crewe. 

[Cheshire Freeze]

3 minutes ago, Weather-history said:

Mental health warning

 

"Should not to be taken seriously"

Never understood why you are such a champion of CFS, Crewe. 

It’s one of many long range forecasting tools, that’s all Kev. It’s simply that I post about it slightly more often as we have free access to more data from it. We can see how it updates in ‘real time’ through the month as opposed to monthly like the GLOSEA and EC.

It’s one I do like to have on side though as very occasionally it can pick a pattern 2-3 months out.