ORH_wxman

When we discuss attribution, we’re really discussing “net impact”…CC changes the weather so if we’re being extremely literal as in “butterfly theory”, then of course CC causes everything….it might have caused today to be a partly sunny day in Florida instead of a category 5 hurricane. That’s why we discuss net impacts. We know deep PNA troughs have dug into Baja California before so we can see how the patterns looked when that happened in the past and the compare it to a deep Baja CA trough in Dec 2022. Frankly, any dismissal of skepticism on attribution studies as someone denying CC at all is just as bad as someone actually claiming there is no effect. It’s usually a tactic to try and shut down discussion rather than engage using empirical evidence. Both are not scientific inquiry…and more like dogma.

I agree with the loaded dice comment....I think where you and I probably fundamentally disagree the most is how much weight we are putting on these shorter term patterns. I view most of them as natural variation that exist on top of an underlying warming trend which CC enhances or mutes....which means that when we get a canonical warm pattern, its REALLY warm and when we get a canonical cold pattern, it's not as cold as the previous ones. It's why I refer back to earlier proclamations of regime shifts that didn't stand up over time. The "new hot thing" back in the 2009-2014 years was the "warm arctic, cold continents" pattern in winter that CC had driven because of low sea ice. Several peer-reviewed papers were published on this topic. There was legit discussion about how these patterns might be paradoxically more common because of CC.....then it all shifted away from that theory quite quickly in the following 8-9 years. Prior to that, we had peer reviewed literature talking about a semi-permanent +NAO/AO based on the big increase in those patterns in the 1980s/1990s....and then the 2000s of course shifted the other way. Now maybe CC has caused a near-permanent SE ridge which means 2016-2023 is the new normal....again, I would bet against that, but maybe this time it will stand the test of time unlike the previous shifts. I do think it's good to look at the effects of SST warming in regional spots....but at the same time, warming is not evenly distributed on a temporal/spacial scale and relative changes will cause certain areas to cool or warm differently than perhaps they did in the previous decade or two. Prior to the mid-2000s, the fastest warming region in the CONUS was the upper plains/Rockies....now they are the slowest warming region in the CONUS while New England and SE Canada are the fastest.

I think it's good to try and discuss the impacts....so I don't mind these discussions. I've seen a lot of over-attribution in the last 15 years to specific patterns that then change and we stop hearing about them for a while and we move onto the next attribution study. CC is related to all this in some form, but untangling it from natural variation is hard when it comes to specific pattern regimes....and this is doubly true when we are discussing 8 year chunks. That's a terribly small sample to make a lot of longer term conclusions from. We know what the longer term trend is, but trying to "Adjust" our projections of temperature changes or pattern changes based on very short timescales has it's major drawbacks. I know the longterm trend for ORH temperatures in DJFM is 0.4F per decade....but if we use only the trend since 2008, then it's at 2F (!!) per decade. So that's the end of the debate, right? We can assume it's going to be 2F per decade over the next 20 years or so? Nope, if we did the exact same exercise from 1985-2000, the trend was also 2F per decade....but then the next 15 years was actually a negative trend of -1.1F per decade. In the mean, the positive trends will outweigh the negative trends, but from an empirical standpoint, there is no evidence that they just continue unabated. I'm certainly open to some "tipping point" that has permanently given us a Philadelphia winter climate, but I would obviously treat such claims with extreme skepticism and they should be until evidence is way stronger.

Actually not a terrible match over North America, though the PNA trough is deeper in 2022-23 and the NAO block is in a much better spot in '55-56 for northeast snow (west based near Hudson Bay and Baffin).

When I look at the most recent 8 winters and compared them directly to the previous 8, I see a larger scale regime shift in the polar domain and the PNA region....that's by far the primary cause of warmth to me in the northeast and not underlying CC change. The underlying CC trend makes our patterns warmer than they used to be all else equal, but it is not the primary driver of this type of shift we see where heights are lower in the NAO region and PNA region and higher over the east coast. Now, maybe you are arguing that CC caused the PNA trough to dip so far south that Pasadena and many other areas that hardly ever get cold enough were getting snow? Maybe....that's a bold claim.... but I haven't seen compelling evidence on that front. I buy that the downstream ridging is warmer in a warmer world, but that still doesn't explain the larger regime shift which we have seen historically. Are you arguing that this new paradigm in the last 8 years is a permanent feature? I'd bet against that for sure. It doesn't mean we will go back to averaging 2008-2015 temps, but that same pattern would still be significantly colder than the 2016-2023 pattern even with underlying CC warming.

Agreed...but Ray's point is that this was pretty extreme. It wasn't solely because of some underlying trend...otherwise it would have been very visible prior to just the last few years. The underlying height trend helps exacerbate strong ridge response when you get a deeply negative PNA trough out west, but it's not the primary cause of the event in the first place. When Pasadena CA is getting snow, it was probably a tough lift even in 1955 to get good snows in New York City in that pattern.

Data retrieval has gotten significantly worse in the past 2 years. Pretty frustrating since it should be easier considering the raw concentration daily data is available on NSIDC. It's just nobody is putting into numeric form anymore.

I like warm falls these days, but still want a couple cold shots to kill the bugs and remind us winter is getting close. I usually like to see first flakes in late October or early November. Those frigid Septembers back in the late 1980s/early 1990s were useless. (except seeing snow on the last day of Sept 1992....that actually was pretty awesome)

Unless there was a revision to past area, I have 2023 as 4th lowest. Either way, this is one of the stronger late melts on record post-August 1st. 2012: 2.228429 2016: 2.463209 2020: 2.5859 2023 low so far is 2.63, but it's only at 2.67 right now, so it could fall further into 3rd still. The area file I used to reference is no longer active, so I don't have a good way to look up revisions. But I do have the old data saved. Is there a good archive of the data somewhere now? I only have cryosphere computing, but that only gives us a single day shot and doesn't seem to archive the daily numbers.

Yeah they are definitely “seeing” something. But it’s hard to weight it too much this far out. If it stays that way when November updates are coming out, then I’ll be more intrigued.

I wouldn’t much stock in any of the seasonal models yet. If they are still all agreeing with eachother in November then I think there’s probably some predictive skill….but there’s been so many times they just shat the bed.

I dunno. You just told me the Baffin differences Re: 2009 vs 2023 were due to high Atlantic SSTs….that seems like a claim very similar to my other examples which haven’t held up over time. Also, doesn’t the literature show a lot more cloudiness in recent years over the arctic high latitudes? That wouldn’t square with more sunshine being the primary culprit in heating the sfc. But I also realize these debates are better suited for another thread rather than detracting from the ENSO discussion.

Yeah I disagree with his attribution claims RE: 2009 vs 2023. I’ve found over and over again that SSTs being blamed for extreme patterns seems to not hold up against time. We saw this with the low sea ice (which makes the sfc much warmer in the arctic) claims as being the reason for big -AO patterns in the 2009-2013 period or the Pacific warm blob being blamed for the exceptional PNA ridging in 2014 and 2015. Local SST anomalies can enhance a mid-latitude pattern, that is pretty well known…but they are almost never the primary cause. The only region where the literature is extremely robust is in the tropical pacific…though that doesn’t affect a pattern directly by raising heights, but rather it does it mostly through convection.

I don’t think those patterns are THAT similar for summer. Look how much further southwest the ridge axis is over the west in 2009. This year essentially had a block over the Beaufort/CAA instead of just a ridge over the GOA. That’s a pretty big difference IMHO for cold delivery. In addition, this year has a relative min over Baffin on the Atlantic side while 2009 had a relative max there which is more favorable for driving cooler air into SE Canada.

CC should be a non-factor on an 11-15 day forecast for typical NWP guidance.

It's a pretty weak R squared value at 0.12....probably falls below 0.1 if you remove the crazy 2014-15 outlier.

Oh I thought I remember seeing reference to it earlier as a super Nino. I know the data from back then is pretty spotty anyway.

I think there's plenty of reasons to not assume the usual monster GOA low or even if there is a GOA low, there's reason to assume it won't be as overpowering as other super ninos: 1. Our sample of super Ninos is really small. If you include 1925-26, then we get another and that Super Nino did have a further west Aleutian low. Also, you left out 1965-66 which didn't match any of those examples....1965-66 almost acted like a La Nina at times despite being borderline super at 2.0 ONI peak. I supposed you could put '65-66 into very strong territory, but I'm not sure the usefulness of parsing 0.1C to eliminate it from the already tiny sample. 2. Relative to the waters near and just west of the dateline. this Super Nino isn't as "super" as the others on your list. So does that make this act more like a strong Nino ala 1957-58 where there was a GOA low but not so strong to overpower everything? Hard to say. 3. This isn't guaranteed to even be a Super Nino yet. It's probably still favored, but it might end up closer to 1.8-2.0 range too. But again, is the ONI peak all that matters here? RONI and MEI are severely lagging the other super ninos. They will need to make an incredible surge to reach those years. 4. Our sample of Super Ninos is really small. 5. Our sample of Super Ninos is really small. Sorry I repeated the sample size issue, but I believe it's very important to acknowledge.

There won't be a La Nina pattern this year....agreed. None of the seasonal models show a La Nina pattern either....they all show big +PNA with STJ riding underneath it. The polar domain and the Aleutian low position will determine whether it's a good pattern for the northeast or not.

The late Jan/early Feb 2021 period was really driven by an exceptionally favorable Atlantic....the PAC pattern was a -PNA, but the trough wasn't digging into Baja CA/S CA like we saw last winter and for a time in Dec 2021 too....so because it wasn't digging that far southwest, it allowed the NAO block to successfully produce a classic height response over the Northeast and Atlantic region. Late Dec 2010 through first half of Jan 2011 also saw this pattern though the PAC was even a little more favorable (though still a -PNA) to produce an even colder height response than the 2021 pattern. These are aren;t super uncommon for "good" La Nina patterns. I'd expect a lot more +PNA though this winter.

Here's 2008-2015 when we had a lot of colder winters mixed in. Total from 2008 to present: You can see southeast Canada is the warmest on both outside of the arctic sea ice regions further north.

Last year we couldn't buy even a stale polar high to our north. Doubt we keep up that weird anomaly. Even a marginal polar high in some of those storms last year would've made the entire complexion of winter different as some of those storms wouldve been large snow events much closer to the coast or even right to it. This is as good a season as any for some positive regression in our source region in SE Canada/NNE for colder temps and right down into much of the northeast....they've been the most anomalous for warmth in the past 8 seasons. No surprise who has been the coldest (that -PNA region from W Canada to N plains/N Rockies)

Boston has had some weird quirks of very large seasonal snowfall during strongly +NAO seasons....1992-93 and 1993-94 also are in the group....or even strongly positive NAO months like Jan 2005.

EPS mean doesn’t even get it to 70W…there is still a lot of work needed on this one to make it compelling outside the Cape/Islands.

The only thing that gives me a bit of pause is really haven’t seen a N PAC like that in a super Nino. Even the great Jan-early Feb 1966 period was mostly driven by an ideal Atlantic pattern and the PAC was just kind of meh…but not hostile enough to ruin the great NAO block. But the sample size for super ninos is admittedly pathetically small….and I don’t think enough people take that into account when expressing high confidence in pattern tendencies. Also, if this is effectively just a “strong Nino” (RONI, MEI, etc), then that changes things too I’m sure.