Winter 2023/24 - Discussions & Forecasts

[damianslaw]

3 hours ago, bluearmy said:

December on the latest cfsv2 run 
This is not a consistent output btw 

A cold trough, southerly tracking jet, potential for snow on northern flank often. Interesting. 

 

[John88B]

As the outside temperature cools the temperature in the mod thread rises. The bickering is starting and will only increase as we head into winter.

The bickering, the toy throwing and great input from the knowledgeable contributors make it compulsive viewing.

It's going to be a long, hard winter in the mod thread and hopefully outside too

[Weatherman_93]

37 minutes ago, John88B said:

 

The bickering, the toy throwing and great input from the knowledgeable contributors make it compulsive viewing.

 

Sad at times as the weather will do what it wants to do and no amount of fancy graphs and charts will ever change that. But whatever gets you through the winter 

[MattH]

Afternoon.

Just some thoughts and a point of reference (let's see how this ages) with regards to December. To summarise the short-term, after weeks of being stagnant through phases 8-1 the MJO is on the move back to the Western Hem and this does continue to support a more dominant Westerly pattern to return into December, in some shape or form.

However, jumping ahead of that and it is the next eastward movement of the MJO that is of significance and importance as we look through December. The latest data is now showing some weakening of the IOD as well, which is what was expected to occur by the end of the year anyway. For the last several weeks there has been a very slow-moving tropical pattern in terms of forcing, with key areas of subsidence over the Maritimes, while forcing and uplift (convection) have dominated near the dateline (MJO phases 8-1).

Finally, however, things are on the move. There is evidence for the -ve 850mb ZWA's over the I/O to weaken, while the latest EPS plot, in particular, shows a far more active west-to-east movement of the key VP200 anoms looking ahead, with strong surface convergence and upper-level divergence over the W Hem and the I/O over the remainder of November.

With evidence for the long-standing easterly to be waning over the I/O then all eyes will be on how the MJO and the -ve VP200 signature evolves through December. Primarily how far east does it progress and with what potency, in terms of the amplitude, etc.

A few extra plots which are based on the CFSv2 looking ahead highlight what may happen in terms of this next MJO event. Indeed, the signal on the Real Time CFS plot is thickening up with another significant WWB set to propagate into the west and then central Pacific through Dec. The result is, therefore, a resultant signal for AAM to rise, along with the GWO as well. It should be noted not to take the AAM and the GWO plots literally, but to use them as a guide as to the overall evolution looking ahead, especially if it's a consistent signal.

Lastly, the ever-useful EWP Zonal Harmonics plot also highlights this evolution too...

As we found out last December, any significant eastward progression of the MJO in Dec, especially through phases 6-7-8 with amplitude could be significant, not just from a trop perspective but also the strat as well. Therefore, this signal needs to be monitored closely in the next 2 to 4 weeks, as another WWB with a GWO rise and if there is a reasonably high amplitude MJO event too, again through phases 6-7-8, then all eyes would be on some potentially very interesting synoptics (amplification/blocking/colder weather potential) from approx mid-December onwards.

With regards, Matt.

[Met4Cast]

Fantastic post @MattH thank you. Very much along my current thinking and something I mentioned back in September in a tweet re: Late Dec/early Jan on the back of the previous (although ultimately failed) MJO cycle. Good to see the easterly winds beginning to fade over the Indian Ocean, hopefully this will help drive AAM tendency up more concisely as December progresses. 

Those EPS 200hPa charts from weathermodels are fantastic, out of interest which tier of subscription gains you access to those? Are they available on the "personal tier" do you know?

Thanks

[sebastiaan1973]

Tweet by Judah Cohen. 

[Liam Burge]

1 hour ago, sebastiaan1973 said:

Tweet by Judah Cohen. 

Definitely exciting times ahead of us.

[damianslaw]

Will be good reading winter forecasts in the remainder of what is left of Autumn. Only 10 days until 1 December.

Amplified flows and aleutian lows could be key features..

[January Snowstorm]

6 minutes ago, damianslaw said:

Will be good reading winter forecasts in the remainder of what is left of Autumn. Only 10 days until 1 December.

Amplified flows and aleutian lows could be key features..

I'd say a lot of them are being rewritten as we speak!! A stormy start to December will have to be deleted  

[CryoraptorA303]

Remember when I said that going on the natural cycle of things (last dry period in September), things would probably dry up later on in November and no one believed me? To be fair I almost didn't believe myself after the first two weeks.

[CryoraptorA303]

7 minutes ago, January Snowstorm said:

I'd say a lot of them are being rewritten as we speak!! A stormy start to December will have to be deleted  

Let's hope it doesn't change to a stormy end to December, or a stormy start to January in any case. Maybe now we could actually see a drier than average winter dominated by blocked patterns, and not the usual extended autumn that seems to be so persistent in the last few years. Right now I'd say December+January will be average veering on dry to notably dry, and February at average or veering on dry. As said several times I feel a dry 2010-style Nino spring coming...

Or going in line with this year's extremes, perhaps this December will be the driest on record Would be quite ironic in what will likely be a top 10 wettest year.

Edited November 21, 2023 by CryoraptorA303

[andy989]

Does anyone happen to have links to model output threads of previous cold events? I’m trying to put together an overview of model behaviour in the run up to cold events. Which one tends to sniff them out first, which ones drop the idea then picks it up again, which ones tend to swing to others late and so forth. Thought I’d ask if anyone had links saved before i go on a deep dive searching for them 

[Matty88]

The Met-Office has and will be flip-flopping on the upcoming cold set-up more than a fish does out of water - you wait till they change their tone in the next update. Nearly all models (including theirs) have been struggling with the up-coming pattern change. Looks almost certain like they will have to row back on the start of December being a mild westerly theme. 

There's still much we and they do not yet know about our atmosphere and the triggers for pattern changes. Common sense does seem to play part of it - ie after 2 months of Westerlies and LP's was this honestly going to carry on and on? HP was overdue to make an appearance.  The atmosphere has a freakish knack of balancing itself. 

[CryoraptorA303]

1 hour ago, Matty88 said:

The Met-Office has and will be flip-flopping on the upcoming cold set-up more than a fish does out of water - you wait till they change their tone in the next update. Nearly all models (including theirs) have been struggling with the up-coming pattern change. Looks almost certain like they will have to row back on the start of December being a mild westerly theme. 

There's still much we and they do not yet know about our atmosphere and the triggers for pattern changes. Common sense does seem to play part of it - ie after 2 months of Westerlies and LP's was this honestly going to carry on and on? HP was overdue to make an appearance.  The atmosphere has a freakish knack of balancing itself. 

That was precisely my thinking. Eventually due to simple momentum and chaos the pattern will shift. Continued westerlies was imo a very weak bet that had a high chance of not materialising. The question now is whether we revert to stormy westerlies after this interlude. Right now I'm betting on quite a dry winter from this point. Hopefully that translates to cold but dry could also include some sort of February 2019 heatwave, so nothing is guarenteed yet. I doubt we'll be seeing anything like this October or November from this point forward now in any case - if any month this winter is wetter than average it will be by a low percentage, and I don't see the whole winter being wetter than average at all. We'll have at least one considerably dry month, either December or January. Wet, stormy autumns have quite a decent track record of throwing out drier winters after them, such as last year, so this in itself was also not too much to predict.

As I mentioned earlier, it would be funny now if an upcoming winter month or the winter as a whole was the driest on record after what we've seen this year. It'd be quite the shift although you'd generally want notable cold for an exceptionally dry winter month, and I'm not sure if we could get the notable cold needed to keep precip lower than the current 100+ year old record holders that occured in a cooler climate than today. Even if not the outright driest, notably dry winter months are clearly still possible, as last February proved. Last February was the driest since 1990, and I'm pretty sure Feb 1990 is one of the driest on record.

[damianslaw]

19 hours ago, CryoraptorA303 said:

Let's hope it doesn't change to a stormy end to December, or a stormy start to January in any case. Maybe now we could actually see a drier than average winter dominated by blocked patterns, and not the usual extended autumn that seems to be so persistent in the last few years. Right now I'd say December+January will be average veering on dry to notably dry, and February at average or veering on dry. As said several times I feel a dry 2010-style Nino spring coming...

Or going in line with this year's extremes, perhaps this December will be the driest on record Would be quite ironic in what will likely be a top 10 wettest year.

Winter 09-10 was notably dry, Cold and much precipitation fell as snow. I keep getting 09-10 vibes, I think July did it, almost a carbon copy of July 09. 

[CryoraptorA303]

5 minutes ago, damianslaw said:

Winter 09-10 was notably dry, Cold and much precipitation fell as snow. I keep getting 09-10 vibes, I think July did it, almost a carbon copy of July 09. 

I've been feeling the same. Wet July, warmish August and warm September, warm start to October and now a wet November (in the first half anyway, we got over 100mm in the first two week vs 75mm monthly average) that is beginning to dry up. Not to mention the atlantic tripole. Very 09/10.

[damianslaw]

5 minutes ago, CryoraptorA303 said:

I've been feeling the same. Wet July, warmish August and warm September, warm start to October and now a wet November (in the first half anyway, we got over 100mm in the first two week vs 75mm monthly average) that is beginning to dry up. Not to mention the atlantic tripole. Very 09/10.

El Nino and Eqbo also the same as 09-10, whilst analogue comparisons should come with margins for error, I believe teleconnection wise 09-10 is closest to 23-24. There was an election in 2010 as well...

Edited November 22, 2023 by damianslaw

[cheeky_monkey]

21 minutes ago, damianslaw said:

El Nino and Eqbo also the same as 09-10, whilst analogue comparisons should come with margins for error, I believe teleconnection wise 09-10 is closest to 23-24. There was an election in 2010 as well...

Nov 2023 is shaping up to be being very similar if not identical to Nov 2009 here thus far...both very mild dry and no snow

[LetItSnow!]

17 hours ago, CryoraptorA303 said:

Last February was the driest since 1990, and I'm pretty sure Feb 1990 is one of the driest on record.

I think you mean February 1993. February 1990 is one of the wettest on record. 

[Mike Poole]

20 hours ago, andy989 said:

Does anyone happen to have links to model output threads of previous cold events? I’m trying to put together an overview of model behaviour in the run up to cold events. Which one tends to sniff them out first, which ones drop the idea then picks it up again, which ones tend to swing to others late and so forth. Thought I’d ask if anyone had links saved before i go on a deep dive searching for them 

Funny you should ask that.  A few weeks ago I read through the MOD threads for 2009/10 - that was before I joined Netweather and I wanted to see what people were saying in advance of that cold spell.  

You can find those threads about page 233 (and counting down) of the parent thread to this, here:

https://community.netweather.tv/forum/1-autumn-weather-discussion/page/223/

It was actually very interesting to read these, remember that winter was also on the back of a long run of mild winters that some thought at the time was irreversible.  

[Liam Burge]

Could definitely be an interesting (and cold) start to Winter!

[andy989]

2 hours ago, Mike Poole said:

Funny you should ask that.  A few weeks ago I read through the MOD threads for 2009/10 - that was before I joined Netweather and I wanted to see what people were saying in advance of that cold spell.  

You can find those threads about page 233 (and counting down) of the parent thread to this, here:

https://community.netweather.tv/forum/1-autumn-weather-discussion/page/223/

It was actually very interesting to read these, remember that winter was also on the back of a long run of mild winters that some thought at the time was irreversible.  

Amazing Thankyou! 

[CryoraptorA303]

9 hours ago, LetItSnow! said:

I think you mean February 1993. February 1990 is one of the wettest on record. 

That's the one. February has a long history of being the black sheep and going against the yearly trend.

This is also why I say a wet autumn or winter doesn't really do much for determining the severity of the next year's hypothetical dry periods and heatwaves. A wet autumn or winter doesn't make much difference if the next spring and/or summer is bone dry. The moment the rain stops and the sun comes out is the moment groundwater starts evaporating. Heat just makes it worse. Hell, even a wet spring or wet June sometimes doesn't make too much difference: June 2019 was overall very wet, but July broke the all-time record in a brief heatwave regardless. Having a dry autumn/winter period before a dry spring or summer just adds insult to injury really. Let's not forget spring/summer 2022 didn't really care about the wet year before it or the wet February. Once a few drywarm periods took their course it didn't mean much.

Edited November 23, 2023 by CryoraptorA303

[CryoraptorA303]

8 hours ago, Liam Burge said:

Could definitely be an interesting (and cold) start to Winter!

Especially if you're further north, but at least it's not going to be particularly mild in the south. My tty weather app is going for around 5-6C from tomorrow on out, which is far from the worst late autumn-early winter weather I've experienced. Also looking dry and sunny from here so hopefully that sun works on some of the surface water and gets rid of it for any potential snow in December.

Edited November 23, 2023 by CryoraptorA303

[summer blizzard]

Regarding the SSW hunt, for those who want an early event like 2013 or 2021 its worth saying that the CFS is showing the next strong wave event in the Pacific passing between the 10th-20th December which should increase poleward heat flux. While the strength is not something i'd focus on with CFS, the timing should not be off. Given that we are early in the season though, we probably have to wait another ~month for the passage after but it's worth an eye on given that the vortex is already in some distress (or forecast to be) rather than continuing to cool and strengthen.