2024-2025 La Nina

[George001]

20 minutes ago, snowman19 said:

Because I knew what was coming next to prove a point…he always does. Doom and gloom then bliss. Dr. Jeckyll and Mr. Hyde. As predictable as the rising sun. I started thinking the SAI was BS back during the 15-16 super El Niño. He was going for an arctic cold winter for the east because Siberian snowcover build up was very high. The hype was off the charts even as region 3.4 hit +3.1C at the end of November. Then winter happened and that wasn’t the only example over the last 15 years….

I don’t see 15-16 as a good example of the SAI being complete BS, but I do see it as a good example of it being overrated in that it did what it was supposed to do, but other factors (mainly ENSO) were stronger drivers. It did what it was supposed to do, in Jan and Feb of that winter the PV was displaced south with periods of blocking. But again, the super Nino was the primary driver that winter.
 

I do agree with you that the hype should not have been off the charts. I have no idea why Cohen forecasted an arctic cold winter during the 2015-2016 winter regardless of what the SAI did. 2015-2016 was the strongest El Niño winter on record, when ENSO gets that strong that trumps SAI every time. Even if last winter had a record high SAI, I still would have gone mild with below normal snowfall for my area due to the high end strong Nino, -PDO, and the parade of storms crashing into the Pacific Northwest during the fall. 

 

[bluewave]

1 hour ago, George001 said:

Siberian snow cover is advancing rapidly, the quickest pace since October 2014. According to Cohens research, rapid advance of the Siberian snow cover is linked to -AO pattern during winter and a weaker polar vortex. It is especially interesting that this is happening in a year with a fairly strong +NAO and +AO signal (high solar, high geomag, etc).

It seems to have had the opposite effect in 14-15 with one of the strongest +NAO +AO winters into March on record. October 2014 featured the 2nd fastest snow advance index on record to that point. Was reading some studies that the rapid Arctic warming could have altered the correlation from when the Arctic was more stable in the old days. Tough to know for sure since it hasn’t been used as much since the 14-15.

[snowman19]

42 minutes ago, Cobalt said:

he's not wrong though? You certainly wouldn't have shared a Judah Cohen tweet touting a high snow cover ranking, 

In that post I stated clearly “for those who follow it, I don’t”. I know some on here don’t have twitter so I gave a FWIW update in case they were wondering what Cohen’s thoughts were at the time, in case they were interested. When his theory first came out, I thought it had validity, then I saw the SAI’s record over the last 15+ years and changed my opinion 

Edit: @George001 How do you explain the SAI’s miserable failure for the 14-15 winter? Record high SAI yet one of the strongest ++AO/++NAO winters on record? By Judah’s theory, that should have been a -AO/-NAO orgy

[40/70 Benchmark]

25 minutes ago, Eduardo said:

Can you explain this (when you have time)?  I’ve always been a skeptic myself—more so in recent years, obviously.

Its just another piece of guidance, all of which have their stengths and limitations. It makes sense to me that it would fall flat during a super el Nino...for instance, the polar domain was actually pretty decent in 1997-1998, but due to the situation at hand it didn't matter. I think its fine to use the SAI to either increase or decrease confidence in a forecast and/or in the absence of no other prevalent indicators.

[brooklynwx99]

55 minutes ago, snowman19 said:

I live rent free in your head lol Must have my posts saved on a file on your home computer lol

relax. i just remembered from last year

we all have biases, not a huge deal. i just thought it was kinda funny

[George001]

45 minutes ago, snowman19 said:

In that post I stated clearly “for those who follow it, I don’t”. I know some on here don’t have twitter so I gave a FWIW update in case they were wondering what Cohen’s thoughts were at the time, in case they were interested. When his theory first came out, I thought it had validity, then I saw the SAI’s record over the last 15+ years and changed my opinion 

Edit: @George001 How do you explain the SAI’s miserable failure for the 14-15 winter? Record high SAI yet one of the strongest ++AO/++NAO winters on record? By Judah’s theory, that should have been a -AO/-NAO orgy

Good question, my explanation is while there is something to the SAI theory, the correlation with the AO/NAO is much weaker than Cohen implies. From what I’ve seen though, during high SAI advance years we do see more PV disruptions (we saw the PV stretched south of a typical strong PV in 14-15 and 13-14), regardless of the overall strength of the PV and NAO phase. When it comes to the NAO/AO, the high solar/high geomag combo favors a strong PV/+NAO/+AO pattern. High geomag in particular has a strong correlation (>.7 r^2 value) to the NAO. I don’t know the exact r^2 value for the correlation between SAI and NAO, but I suspect it is much lower. So make no mistake, I’m still on board with a strong PV/+NAO/+AO winter, but I do think the vortex will be more susceptible to being displaced south than is typical for a strong PV/+NAO/+AO winter. This does not invalidate the 07-08 analog AT ALL. If anything, it strengthens it as this south based +NAO was seen during the 07-08 winter (my #1 analog). 

[Typhoon Tip]

not sure how this compares to norms but here's the 30 day anime from usicecenter.gov

[Typhoon Tip]

also... just cursory eye-ballin'    2024/ 10/17 is about 20% more so on this date than 2023/ 10/17  fwiw

[Terpeast]

23 minutes ago, Typhoon Tip said:

not sure how this compares to norms but here's the 30 day anime from usicecenter.gov

That’s quite an explosion in snow cover!

[GaWx]

2 hours ago, bluewave said:

It seems to have had the opposite effect in 14-15 with one of the strongest +NAO +AO winters into March on record. October 2014 featured the 2nd fastest snow advance index on record to that point. Was reading some studies that the rapid Arctic warming could have altered the correlation from when the Arctic was more stable in the old days. Tough to know for sure since it hasn’t been used as much since the 14-15.

 I was among those closely following the 2014 SAI and was deeply disappointed. This 11/1/14 post from cfbaggett sums up well the excitement many of us had in the annual fall snowcover thread:

 

And so October ends…

 

Amazing month. The slope, as I calculate it, was 295,000 km^2/day. Thus, it appears we can predict with reasonable confidence a strongly negative AO winter.

 

After this major fail, the SAI never regained its former luster. 2014-5’s AO was the most + since 07-08!

[MJO812]

6 hours ago, snowman19 said:

Not surprising given the very strong Niña background state 

We just came off an El Nino.

[bluewave]

53 minutes ago, GaWx said:

 I was among those closely following the 2014 SAI and was deeply disappointed. This 11/1/14 post from cfbaggett sums up well the excitement many of us had in the annual fall snowcover thread:

 

And so October ends…

 

Amazing month. The slope, as I calculate it, was 295,000 km^2/day. Thus, it appears we can predict with reasonable confidence a strongly negative AO winter.

 

After this major fail, the SAI never regained its former luster. 2014-5’s AO was the most + since 07-08!

Yeah, there were hopes that the relationship prior to 14-15 would work out for the 16-17 winter. But the extensive fall Siberian snow cover strengthened the Pacific Jet instead. So after 14-15 and 16-17 it hasn’t really been used as much.

https://www.aer.com/science-research/climate-weather/winter2017/

Summary

• Winter 2016/17 was characterized by warmth in Central and Eastern North America, Northern Europe, Central and East Asia but cold in much of Europe, the Middle East and Siberia.
• The dominant story in the fall was extensive October Siberian snow cover that resulted in very cold temperatures across Northern Asia in November.
• The strong temperature gradient across Asia provided fuel for a strong North Pacific Jet Stream that cooled sea surface temperatures in the mid-latitudes of the North Pacific.
• The strong sea surface temperature (SST) gradient in the mid-latitudes of the North Pacific maintained an active Jet Stream into the West Coast of the United States (US) resulting in cool temperatures and record rainfall along the US West Coast but flooded the rest of North America east of the Rockies with mild, maritime air.
• Low sea ice in the Barents Kara seas helped anchor high pressure in the region, especially Northern Europe, for much of the winter. Northeasterly flow around the high pressure, especially in January, resulted in an overall cold winter for Europe except near the center of the high across Northern Europe.
• Analysis of the relationship between warming in the Barents-Kara Seas and surface temperatures across the Northern Hemisphere (NH) suggest the record low sea ice in the Barents-Kara seas may have contributed to warm temperatures both across Northern Europe and the Eastern US.
• Extensive Eurasian snow cover and low Arctic sea ice in October contributed to an early and strong Siberian high that favors a weak polar vortex. However the most impressive polar vortex weakening and subsequent coupling with the troposphere took place in the fall followed by a relatively strong polar vortex and a positive Arctic Oscillation (AO) in mid-winter. This contributed to front ending cold temperatures with the back end relatively mild across the NH.
• There was a brief major mid winter warming (wind reversal at 60°N and 10 hPa) in early February but its impact was relatively minor and short lived in the troposphere. It is possible that the westerly phase of the quasi-biennial oscillation played a role in reducing the strength and duration of the major warming and its impact on the weather.

[Eduardo]

6 hours ago, 40/70 Benchmark said:

Its just another piece of guidance, all of which have their stengths and limitations. It makes sense to me that it would fall flat during a super el Nino...for instance, the polar domain was actually pretty decent in 1997-1998, but due to the situation at hand it didn't matter. I think its fine to use the SAI to either increase or decrease confidence in a forecast and/or in the absence of no other prevalent indicators.

Me too, but isn’t it just a (perhaps weak) proxy for assessing other indices then?  Even if it’s used solely for confirmatory purposes, why not just keep to the major indices, teleconnections, etc.?

[George001]

4 hours ago, bluewave said:

Yeah, there were hopes that the relationship prior to 14-15 would work out for the 16-17 winter. But the extensive fall Siberian snow cover strengthened the Pacific Jet instead. So after 14-15 and 16-17 it hasn’t really been used as much.

https://www.aer.com/science-research/climate-weather/winter2017/

Summary

• Winter 2016/17 was characterized by warmth in Central and Eastern North America, Northern Europe, Central and East Asia but cold in much of Europe, the Middle East and Siberia.
• The dominant story in the fall was extensive October Siberian snow cover that resulted in very cold temperatures across Northern Asia in November.
• The strong temperature gradient across Asia provided fuel for a strong North Pacific Jet Stream that cooled sea surface temperatures in the mid-latitudes of the North Pacific.
• The strong sea surface temperature (SST) gradient in the mid-latitudes of the North Pacific maintained an active Jet Stream into the West Coast of the United States (US) resulting in cool temperatures and record rainfall along the US West Coast but flooded the rest of North America east of the Rockies with mild, maritime air.
• Low sea ice in the Barents Kara seas helped anchor high pressure in the region, especially Northern Europe, for much of the winter. Northeasterly flow around the high pressure, especially in January, resulted in an overall cold winter for Europe except near the center of the high across Northern Europe.
• Analysis of the relationship between warming in the Barents-Kara Seas and surface temperatures across the Northern Hemisphere (NH) suggest the record low sea ice in the Barents-Kara seas may have contributed to warm temperatures both across Northern Europe and the Eastern US.
• Extensive Eurasian snow cover and low Arctic sea ice in October contributed to an early and strong Siberian high that favors a weak polar vortex. However the most impressive polar vortex weakening and subsequent coupling with the troposphere took place in the fall followed by a relatively strong polar vortex and a positive Arctic Oscillation (AO) in mid-winter. This contributed to front ending cold temperatures with the back end relatively mild across the NH.
• There was a brief major mid winter warming (wind reversal at 60°N and 10 hPa) in early February but its impact was relatively minor and short lived in the troposphere. It is possible that the westerly phase of the quasi-biennial oscillation played a role in reducing the strength and duration of the major warming and its impact on the weather.

That’s really interesting, I didn’t know rapid SAI could do that. That’s a great example of how simplifying things to rapid SAI = cold and snowy for the east, paltry SAI= warm and less snowy isn’t accurate. Things are a lot more complicated than that. We know right now the SAI is high, but whether or not that will be a good thing for the east remains to be seen. 

[michsnowfreak]

On 10/17/2024 at 8:18 PM, Stormchaserchuck1 said:

Yeah. Possibly well above average, as the normal jet stream is south in the Winter, but a SE ridge would have storms riding up to the Great Lakes. 

You could be pretty excited by the CPC's Winter forecast, with cold dropping in not too far away, but I'm not really agreeing with them. I think they are really underestimating the potential warmth in the east, only giving 40-50% chance for above normal here.  I think this Winter will have a lot of variation/volatility.. I think we may see -WPO/-EPO periods, but they may not last more than 5-8 days. The overall trend will be warm. It's a little bit different when a Winter is wall-to-wall warm, vs very warm periods and below average periods.. You can get snow in Winter's of variance.. I had a 20" storm in 99-00. If we have a +NAO jet stream like I think, the timing with a -EPO period could give you a nice snowstorm(s).  It's not all ridgy everywhere like the last few years, so northern areas should do ok I think. 

Ninas often are up and down anyway. Really not worried at all about getting so.e gold periods. The question is how many?

[michsnowfreak]

13 hours ago, jm1220 said:

In any Nina I’d be excited if I lived in the Great Lakes. Doesn’t score there 100% of the time but odds are certainly better given the Lake cutter storm tracks. 

This is true. Plus the lake belts usually enjoy a huge bonanza of fun.

[Stormchaserchuck1]

1 hour ago, CCM said:

Looking increasingly likely that we have the warmest November of all time this year. Something tells me this can't be a good sign for the coming winter, but I guess we'll see.

Yeah, really some strong +EPO signals coming forth for the 1st week of November. This is a typical cold season pattern of late, 2018-2024. 

[Stormchaserchuck1]

1 hour ago, michsnowfreak said:

Ninas often are up and down anyway. Really not worried at all about getting so.e gold periods. The question is how many?

We haven't had a +NAO Winter since 19-20. And only 1 time since 15-16. 

Actually, here is a temperature and precip map of our last 4 +NAO Winter's, as defined by negative anomalies around Greenland, if that holds true.. 

 

Since we have already seen 9 +NAO periods this year, something tells me we have exhausted that option.. But Maybe more solar flares will keep the correlation going. 

[PhiEaglesfan712]

The NOAA ONI has finally been updated for JAS (-0.1). The JJA number has also been revised from 0.1 to 0.0

[jm1220]

2 hours ago, michsnowfreak said:

This is true. Plus the lake belts usually enjoy a huge bonanza of fun.

I-90 is a pretty good marker of where El Niño becomes better south of there vs La Niña north of there. Maybe in the Lakes area a little south of I-90 into northern/central IL, IN, OH, and around here maybe the NY/PA border. Where I live we’ve had our share of good Nina winters but we need help from some other factor like a big west based -NAO to force storms underneath us. Otherwise they will all try to cut way too far west. And the snow belts get a second dose of fun in the NW flow behind the cutters. 

[40/70 Benchmark]

5 hours ago, Eduardo said:

Me too, but isn’t it just a (perhaps weak) proxy for assessing other indices then?  Even if it’s used solely for confirmatory purposes, why not just keep to the major indices, teleconnections, etc.?

You can....feel free. But given how difficult the polar domain is to forecast on a seasonal level, I consider every tool that I can.

[bluewave]

5 hours ago, 40/70 Benchmark said:

You can....feel free. But given how difficult the polar domain is to forecast on a seasonal level, I consider every tool that I can.

My guess is that the extreme AO shift this month is related to that nearly off the charts burst of forcing in the IO. It’s short term changes like this which can be tough to access much ahead of time due to the competing marine heatwaves across the tropics right now. It  goes to the how extreme polar domain volatility has become over the last decade.

 

 

[Terpeast]

3 hours ago, bluewave said:

My guess is that the extreme AO shift this month is related to that nearly off the charts burst of forcing in the IO. It’s short term changes like this which can be tough to access much ahead of time due to the competing marine heatwaves across the tropics right now. It  goes to the how extreme polar domain volatility has become over the last decade.

 

 

Interesting on the relationship between IO forcing and the AO. And maybe more volatility will keep things at least somewhat interesting for the winter. 

[40/70 Benchmark]

11 hours ago, Stormchaserchuck1 said:

We haven't had a +NAO Winter since 19-20. And only 1 time since 15-16. 

Actually, here is a temperature and precip map of our last 4 +NAO Winter's, as defined by negative anomalies around Greenland, if that holds true.. 

 

Since we have already seen 9 +NAO periods this year, something tells me we have exhausted that option.. But Maybe more solar flares will keep the correlation going. 

You must be going by some other metric because we haven't had a negative NAO winter since 2009-2010 going by CPC.

[40/70 Benchmark]

3 hours ago, bluewave said:

My guess is that the extreme AO shift this month is related to that nearly off the charts burst of forcing in the IO. It’s short term changes like this which can be tough to access much ahead of time due to the competing marine heatwaves across the tropics right now. It  goes to the how extreme polar domain volatility has become over the last decade.

 

 

And even if you get the DM seasonal concept generally correct in terms of the mean index calculation, good luck with the timing of the seasonal progression.

[40/70 Benchmark]

La Niña should be peaking pretty quickly...

[40/70 Benchmark]

Should be a really strong push towards -1.0C in 3.4 over the next week or so before that happens.

[George001]

Interesting, in the latest IRI update on ENSO the spread has decreased significantly and the mean has converged around a -0.5 ONI peak

[SnoSki14]

4 hours ago, 40/70 Benchmark said:

You must be going by some other metric because we haven't had a negative NAO winter since 2009-2010 going by CPC.

I'm not seeing these big California troughs thus far. In fact we've seen record warmth in the SW which has fed into the large positive SST anomalies off the West Coast and much more SW ridging. 

PDO will be negative but that's another competing influence it'll be up against. I think the Pacific could be a lot more favorable this season, which matters much more than a very negative NAO/AO. 

In fact it might be better for us to see a +NAO given its diminished effects. 

[George001]

17 minutes ago, SnoSki14 said:

I'm not seeing these big California troughs thus far. In fact we've seen record warmth in the SW which has fed into the large positive SST anomalies off the West Coast and much more SW ridging. 

PDO will be negative but that's another competing influence it'll be up against. I think the Pacific could be a lot more favorable this season, which matters much more than a very negative NAO/AO. 

In fact it might be better for us to see a +NAO given its diminished effects. 

This is correct. It has been warm CONUS wide, but the core of the warmth has been centered over the plains. We aren’t seeing a trough out west with storms barreling into the Pacific Northwest like the last 2 falls (that pattern then continued into winter, leading to back to back ratters).

For the NAO…. Im not sure it will be a good or bad thing yet. The signals are fairly strong for a +NAO winter, but that doesn’t tell us anything in itself. The -NAO patterns we had in recent years have been bad for the east because they have been south based events that linked up with the SE ridge. A raging north based raging +NAO where the cold is bottled up over the pole is obviously bad (this is what happened in 19-20, 01-02, etc), while a south based +NAO can actually be a good thing depending on where you live (14-15, 13-14, 07-08, 92-93 and 93-94 all had south based +NAOs).