Oglem

Hello, I had a question about the above statement about the AAM. Is it saying that when there are -ve momentum anomalies at the equator, there also have to be positive anomalies at the higher latitudes? I get the feeling that I misunderstood this statement, because then how could a global AAM anomaly even exist if -AAM at the equator is balanced out by +AAM at the poles. Or I might just be missing something in the physics of angular momentum. From what I see on the relative AAM chart, there's a lot of -ve anomalies but no positive balancing anomalies at the higher latitudes. Another question of mine is how ENSO is linked to AAM. I see how La Nina generates easterly anomalies over the Pacific, but doesn't it also generate westerly anomalies over the Indian ocean that would balance this out? Why does a La Nina = -AAM for the most part? Thank you so much to anyone who answers my questions

To add to the earlier discussion on early color/leaf drop, quite a few trees in my area have already lost their leaves. I didn't think it had been that dry, though. I have a theory that this is all somewhat related to the March 2018 snowstorms, at least for my area. One of them dumped 7 inches of heavy wet snow in 2 hours. Many trees lost large/key branches that day, and if I remember right, there is a certain cutoff diameter when losing a branch of that size affects the tree long-term. I believe it's 3 or 4 inches, but I could be wrong on that. The reason is that the tree is not able to fully seal the wound, so bugs and bacteria are able to get in. If the tree is small or weak, or already inherently susceptible to modern diseases (like ash or certain pines) that could be a devastating blow. I know of several trees that have never been quite the same since that storm.

Light rain here right now and 55 degrees.

Hey everyone, I just wanted to share this really interesting twitter post I just found. It says that at lower latitudes and warmer SSTs, slight changes in SST have a greater impact on the weather than they would in higher latitudes. I wonder why that is.

Thanks! Here's a map of the correlation index for the PMM: So if I'm reading that right, the r-value for our area should be -0.484, which is pretty good considering there's so many other factors that influence our weather too. Although this map is for dec-feb PMM vs dec-feb temps, so we need the positive anomalies to stick around. It might be interesting to see how often a +4 PMM summer leads to positive values in the winter. The map for Jun-Aug PMM shows a weaker correlation to our area, something like -0.2, but it's still there. The chart you posted is really cool, I like the normal distribution stats. It's interesting just how positive the PMM has been this September, I think the fact that it's +2 standard deviations from all months is especially impressive. The good thing is it's been going upwards lately, so fingers crossed that's a sign of what's to come. I think it would be good to do more research into what causes a +PMM to continue or subside. I read somewhere that the North Pacific Oscillation initiates a +PMM event, and I would think that the current +IOD event can only help by keeping those cool anomalies by the maritime continent.

Made it down to 43, currently 46 degrees here. It's impressive that there were some freezes in North Jersey, I think that's pretty early for them.

This is the only link I know of right now: https://www.esrl.noaa.gov/psd/data/usclimdivs/ You can check out correlation between different indexes here: https://www.esrl.noaa.gov/psd/data/usclimdivs/correlation/ And compare SST/Temps historically to now: https://climatereanalyzer.org/reanalysis/daily_maps/

Hey everybody, I just wanted to say thank you for sharing information on analogs, it really helped me out. I took a look for years with similar PMM and ENSO. I found 6 years with Jun-Jul-Aug PMM > 4, and they were 1958, 1967, 1986, 1992, 1994, and 2016. 1986 and 1994 were moderate nino winters, so I removed them since this winter is likely going to be a neutral/borderline weak nino winter, although 1994 wasn't too far into moderate territory. Here's the result: Looks like the core of the cold will be in the Upper Midwest, with some cold in the NE and a SE ridge flexing a little bit too. This is only looking at PMM/ENSO, though. Assuming the PMM stays positive, it has the strongest correlation coefficient for the Northeast and Southwest, so it does seem like it would contribute to cold in the NE. Additionally, the PMM is related to Central Pacific warming, so it should be a factor in our favor going into the winter .

Thanks, that makes sense!

I had a question about finding analog years. I was trying to get into seeing which years are similar to this year, but I'm not sure where to start. I can find similar years based on ENSO, but then if I look for really good matches in some other teleconnection, I end up finding a different set of years. How do you go about narrowing your choices, and how do you weigh the different factors? We don't have enough records to get exact matches in terms of ENSO/AMO/PDO/QBO/Solar and all the other teleconnections, so how do you decide whether a year is "similar enough"? Do you put extra weight on the teleconnections that are currently most anomalous (say the extremely +Pacific Meridional Mode over this past summer?) If someone could direct me to a beginner's guide to this sort of thing, that would be great. Thanks

I agree, flakes/dusting of snow in November seem to be followed by good winters. 2014-15 and I believe 2013-14 both had flakes before Thanksgiving, too, and those winters were awesome.

Great questions, I'd love to see them answered too. I agree with your observation that the +IOD is messing up the RMM plots, yet the strongest SST in the IOD are in Phase 2 region. It would be interesting if SST anomalies actually produce max convective activity slightly behind the strongest anomalies, but idk why that would be the case. If I had to guess, maybe the overall warmth in that area of the Indian Ocean matters more than the exact location of the warmth, and convection / SST could be somewhat decoupled from each other, although generally connected. That could mean that for this specific case, the convection develops in the Phase 1 area in response to the overall IO warmth vs. developing in the Phase 2 region of max oceanic warmth. Also, maybe there's something else influencing besides the IOD?

Do you think the +IOD would decrease the strength of the MJO in the warm phases/Maritime Continent, too? If so, that could be a good influence on our winter, although if the IOD weakens later in the autumn it might not matter.

Really good work here, that's an interesting statistic. I wonder how the winters looked for those 13 cases?

Interesting. I had a question: I know the QBO is the direction of the tropical stratospheric winds, but how does the anomalously cold tropical strat temperatures affect the QBO? Does it make the W or E phase more likely, and by what mechanism? Thanks so much!