CAPE

That oddity in the regular cycle in 2016-17 really stands out. Makes one wonder if that sort of thing will become more prevalent. I suppose it could have simply been related to the strong Nino during that period, or maybe a sign of things to come.

That tends to be the case with the "legit" blocking winters. Doesn't mean we can't get some HL help though. SPV is not likely going to be disturbed in the near term based on current forecasts. WAFz looks minimal over the next 10 days. Unless the SPV becomes becomes a persistent, giant blue ball of death over the coming weeks and couples to the troposphere, there is still the possibility of HL + h5 heights developing towards the end of November as the long range GEFS and EPS are suggesting. Time will tell, as always.

There is a generally accepted connection between the easterly(negative) phase of the QBO and disruption/weakening of the SPV, but any direct correlation between QBO phase and HL blocking episodes seems a bit more nebulous. It may be that winters with sustained blocking are more associated with easterly QBO due to increased likelihood of a weaker SPV, and this leads to development of a sustained -AO. By the same token, if the SPV remains more intact, but not an absolute beast (say in a somewhat weak westerly QBO), with no coupling to the troposphere/towards the surface, periodic HL blocking episodes may still occur.

I would take it because its pretty rare, and getting cold and and snow when the days are the shortest is cool.

I'm good with QBO 101. But thanks.

The transfer of heat from the equatorial regions to the high latitudes is necessary to build anomalous heights there/warm the upper atmosphere and potentially weaken/disrupt the SPV, so it makes sense there is a connection between the MJO and the AO. The QBO also has an impact as a modulator, and even though it is currently positive, it is only weakly so at this point. I don't know enough about the intricacies of the processes involved and the tendencies (eg location and magnitude of tropical forcing, ENSO state, QBO phase, etc). Above my pay grade. It's interesting, so keep us updated with the techno geek discussions on SW potential.

Continuing to monitor trends in the LR guidance for HL +height anomalies, because it may be the only thing that can save us, along with some semblance of a decent Pacific for a time. Below is the extended GEFS for a month out- towards the end of November, and below that is the Euro(weekies) for approximately the same time period off of the free site. Crappy graphics but I think you can see the look is very similar, and would be an acceptable one heading towards Dec.

Not unrealistic in a Nina.

Yeah I am just looking for hints as we head towards December. There are some thoughts that the first part of winter may favor higher h5 heights up top, while the PAC hasn't gone full puke mode yet. CFS doesn't have a particularly favorable AO/NAO, but hints at a ridge over/north of AK for Dec and Jan.

The GEFS extended range continues to advertise some improvement in the high latitudes for mid to late November. We shall see how this works out, but if there is to be some semblance of a -AO/NAO as we head into December, we should continue to see indications on guidance over the next few weeks.

Yeah it was EPO/WPO driven. The AO/NAO was predominantly positive to neutral at times.

It did seem so easy. It was like the inverse of what we typically see. Temps would start off marginal than get colder as the snow fell. (-AO/NAO) The exception was the late Jan cold powder moderate event with temps in the mid teens. I loved that one, as it ended the "snow drought" and we could see the potential in the LR for what was to come in Feb. That was one winter where "we"(relatively speaking) actually worked. lol.

Underscores the importance of a sustained -AO/NAO in setting us up for the perfect storm track, with easy access to fresh cold air. The rest was due to the pronounced STJ, courtesy of the moderate Nino. Memories...

Yup. It was rare and perfect. Sure it was a slushy, foggy mess by Xmas day and it rained, but that's how we roll here.

Hard to beat the December 2009 storm for me. December is mostly a Fall month around here, and we rarely see a KU event before Xmas.

We always talk about the importance of HL blocking, but many times it is not sustained. In 2009-10 it was pretty much wall to wall, legit -AO/NAO for the entire winter (see my display pic). That sets us up so we don't have to thread the needle. Ofc it was also a Modoki Nino. We get that combo and its hard not to see a few big winter storms.

Getting it to snow here is fluky most winters. It's probably become more so recently.

Capital Weather Gang article with a potpourri of winter outlooks. DT is thinking back-loaded and above normal snowfall for DC. https://www.washingtonpost.com/weather/2020/10/21/washington-dc-winter-forecasts-2020/?fbclid=IwAR0KbqBko3L1eyFPIZbWE5vr9l-LDSN2NUloXhSlZxFWXhsDGyG7lWz-j4w

We generally need some HL 'help' to get average or above average snow. In the absence of a -AO/NAO, a -EPO can get it done.

There is a correlation between the AO phase and the ENSO state, and the AO is the index most highly correlated to snowfall for DC-BWI. The NAO is almost always in the negative phase when there is a negative AO, so the NAO is a factor. I don't have the numbers, but I would bet a predominately -AO for DJF is more likely during a Nino than a Nina. Not sure if there is a large enough sample size, but a Moderate, CP-based Nino might have the highest correlation to a -AO. @psuhoffman can probably give the numbers off the top of his head.

It will be interesting to see if the extended range GEFS is on to something, as it continues to advertise increasing h5 heights up top, and especially in the NAO domain towards mid November. Also keeps the Pacific (puke) in check. Some of the MJO forecasts have the tropical convection moving into the W Pac, and then possibly into Phase 8, so that may give some credibility to the idea of increasing high latitude h5 heights down the line.

Good ol' CFS at range.. December would be acceptable too, with a +PNA, and the -EPO taking shape. Not the likeliest of outcomes in a moderate Nina.

Just my opinion, but I think it will take some -EPO episodes to save us from another generally crap winter. I don't see any significant indicators suggestive of a predominant negative AO/NAO, other than possibly solar min, and that correlation is nebulous at best.

lol It's probably neutral, not that it matters at hour 816 on a GEFS run.

^That little blue spot off the MA coast is probably a blizzard.