weatherwiz

Agreed, I think there's a pretty good chance we see multiple blocking periods emerge this winter. My top analogs in my winter outlook all featured winter's which featured more blocking than not. I think the only one of my years I heavily looked at was 1986-1987 (or maybe it was 1987-1988 I don't remember off hand) which didn't have much, if any, blocking. But like you said, moderate-to-strong EL Nino's tend to favor blocking and given how the QBO is already quite easterly my thinking is that will prevent the PV from becoming too strong as we ramp towards into winter.

I've posted this in the SNE ENSO thread, but I think this EL Nino is going to be more reflective of earlier EL Nino events (pre-1980) and alot of those seasonal models have been yielding that look. Not sure if the increase in the Modoki EL Nino is the leading contributor in how EL Nino's have behaved, but there has been a clear cut shift in the behavior of EL Nino since around 1980. This is going to be one of the more interesting EL Nino's (when you factor in PDO, tropical forcing, etc.) we have seen in a while.

IIRC correctly, they do quite well precipitation wise during EL Nino episodes. Ultimately though, I don't think there is a strong signal overall between ENSO phase and snowfall for the Sierra's. I think if you look at their top 10 snowiest seasons there is a heavy mix of EL Nino/La Nina. However, it is interesting to note that when they got whacked last winter it was during a pattern which resembled more of an EL Nino than the La Nina state we were in.

Also nice to see a severe threat emerge in the Lower Mississippi Valley region but its near 300 hours.

Second half of next week could be quite warm...meanwhile the Sierra's could see their first significant winter storm of the season.

That almost kind of looks like December/January of 1929.

Yeah it is borderline...I was thinking too that precip rates could influence p-type there and whether that little dry slot would influence as well. Another factor to consider too is the NAM may be a bit tool cold at the sfc there

If we are going to get any good chances in December it will come with a period where the PAC is rather favorable. I don't think we'll be getting Arctic support but that will change as winter progresses. That's a pretty decent look there...we may have to watch the N PAC for some potent storms which may help drive a brief, but favorable period.

Yeah this does kind of resemble a SWFE. I was just looking at some soundings on the 12z NAM and this is some textbook sleet stuff EDIT: best guess precip type says freezing rain but ehhh

There may be a heavier burst too of wintry precip...probably up near the MA/VT/NH border. I could see some spots, especially higher terrain getting a couple inches.

I wouldn't be surprised if the PNA is rather transitory through the winter...so when looking back at the DJF or DJFM average the overall index won't be overly strong or overly positive. I really wish these indices were also broken up into bi-weekly data as opposed to just a raw monthly value. I believe the CPC provides daily readings for NAO, AO, and PNA (maybe not PNA?). I don't have the mathematical mind to do such a thing...I suppose you can just take two weeks worth of data and get an average, but I don't think that would be an accurate method of going about it.

Going through this and comparing to the link I was using. I really wish I had come across this data source sooner. At the end of the day, I probably was incorrectly using the data source I used but the information on the link you provided is much more in-depth.

Very interesting, thanks for that link! This is what I was using for SOI data. https://crudata.uea.ac.uk/cru/data/soi/soi_3dp.dat

In terms of the first bolded there is nothing that is screaming an above-average winter temperature wise across the CONUS. In terms of the second bolded, SSW episodes don't just correlate to what happens on our side of the hemisphere. There have been plenty of SSW events that have had zero impact on our side of the hemisphere.

I've posted this one the New England side (probably should have been more active in here since this is where the discussion is at) but I am quite intrigued to see if we see a shift in the tropical forcing moving through winter, however, there are no signs of that happening. At least according to my breakdowns (and this is just my breakdown meaning it doesn't mean it is correct and it's open to interpretation) there was only one true moderate EL Nino event in which the tropical forcing was west of the dateline for the winter and that was 1925-1926. There has never been a strong EL Nino with tropical forcing west of the dateline. This doesn't mean it can't happen it just hasn't happened yet. For a moderate or I guess you could say borderline strong EL Nino, the SOI isn't really reflective yet (though haven't seen the Oct value yet) and the MEI, at least to me, indicates the ocean-atmosphere is not coupled yet and I guess we see that as well with the AAM (which I'm trying to find the plot I saw posted in this thread earlier. When I was working on my winter outlook and going through previous EL Nino events and looking at strength, structure, and incorporating PDO, PNA, QBO, etc...there were alot of mixed signals but what I found to be the most significant on the overall look of winter was 1. Aleutian Low - strength, structure, and where it was located 2. Arctic domain I think this is a winter where the Arctic will be a significant driver in the pattern over North America. Below is a 500mb composite for all EL Nino winters in which the tropical forcing was west of the dateline. I understand there are great uncertainties with OLR data prior to the 1980's or so.

It was actually disappointing we didn't get any fall severe weather threats this year. Actually I can't even remember the last time we have a severe setup...probably like August (gross).

What we have to watch for moving towards the end of the month into December are sneaky threats. I doubt we'll see any significant storm signals several-plus days out, however, there may be hints within the indices which could provide some clarity into these periods.

I love this look. This evolution is really textbook EL Nino and especially textbook for Nino's pre 1980. I know there has been a lot of work done with Modoki EL Nino's and I have read some papers, but I still want to explore this all further because it is quite intriguing how much EL Nino evolution has changed since the early 1980's. Is it solely due to the emergence of Modoki EL Nino's which have become more common? It's possible, but I don't think it's a sole driver.

Was nice out earlier had sun off and on but was nice when it was out

I did weigh tropical forcing, but it wasn't a significant influence in my forecast. My goal coming into this was to not be heavily invested into the analog approach but take more of a hybrid approach. I was looking at the following (the order listed below is not order of importance or significance just a general listing) 1. ENSO strength 2. ENSO evolution (are we headed towards modoki? has EL Nino peaked? will it strengthen) 3. SOI/MEI 4. PDO evolution 5. QBO evolution 6. Tropical Forcing What I did was these 6 was work to eliminate certain EL Nino solutions. I was looking for historical EL Nino events which sort of fit the mold with how everything listed above was evolving. What I found difficult with the tropical forcing aspect was, the dataset for tropical forcing west of the dateline with moderate or stronger EL Nino's is virtually non-existent - that doesn't mean this can't happen, just means it hasn't happened yet. The good news is, for the EL Nino events in which the tropical forcing was west of the dateline, there seemed to be a pretty high correlation to more troughing across the Northeast region. However, that signal weakens with some of the more recent EL Nino events and this could be tied into the emergences of modoki events. Also, at least in terms of ONI and SST's within the ENSO region, the structure of the tropical forcing isn't what you would see for a stronger EL Nino event. Many of the stronger events the degree of convection seems to be much more widespread across the equatorial Pacific while now its much more focused over a smaller area. Ultimately, I think it's going to be how the Aleutian Low materializes and how the Arctic materializes which are going to be the biggest drivers overall. Now I'm sure tropical forcing probably plays a role in this but the question is, how significant of a role?

sweet, going to mark this on the calendar now

It's something like this that could really open the window for a winter threat in that time frame. I suspect (at least through December) we will see chaos within the PNA domain which will result in bursts of +PNA and then into -PNA. This would keep things active and hopefully we can load some cold in with maybe some EPO support.

I don't think it's just using models alone...maybe some are but much of it has to do with an understanding of the climatology behind EL Nino's along with how things are currently progressing. As Will highlighted in a few separate posts, it is typical for EL Nino December's to be on the warmer side but like he said that is not always the case. So what you want to do is understand why some EL Nino Decembers were warm and why some were cold. Will also highlighted last night the GOA vortex perhaps becoming established. This is something that could favor warmer as well, but this is dependent on where it is positioned, the structure, and even what's happening within the Arctic. I don't think anyone is guaranteeing a warm December, but climo should be respected until we are proven otherwise.

I think a lot too plays on where the core anomalies with the GOA are located. If we can keep those west, either over the Aleutians or just west and can get some Arctic support we may be able to avoid a torch here and at least see something that could favor interior. The one thing I at least like is I don’t think we are going to get porked at any point by the Arctic. There will be occasions where the PAC pork’s us but I think the evolution of the PAC through the winter will eventually be in our favor. I am tooting 57-58 hard

Can't hate the 50/50 low there. Shift that ridge axis in the west slightly farther east and I'll throw some bets on the table