cbmclean

I don't think that strong of a claim was ever made, at least I did not see it. I think the claim boils down to: "there is not statistical evidence that the snowfall at DCA is in a long-term decline", which is a much smaller scope. Now from what I have seen in discussion here, I am still very skeptical of that claim, but I am interested to here what that fellow has to say in detail.

Fell free to nerd out. I enjoy a good statistical analysis. And no, no one asked me to move the discussion here but I noticed some impatience with it in the main thread, so this gets it out of the way for those who are not interested.

So here is the probabilistic forecast for the NPJ state from https://www.atmos.albany.edu/facstaff/awinters/realtime/Probabilistic_NPJPD.php I'm trying to understand how to interpret thia graph So looks like we are going from a "poleward phase" to an "extended phase". But the magnitude in the extended phase is not really all that high (I am assuming that magnitude equates to distance from the origin).

Perhaps this is a good place to discuss DCA snow statistics? @WesternFringe I'd like to give your thesis a fair hearing. What specifically is your claim? From your latest post I see: "the data don’t show a huge downturn". Some specific questions: 1. "Data": Which dataset are you using? 2. "Don't show": What do quantitatively are you claiming the data shows or does not show? Which metrics have you calculated to evaluate that claim? From the recent debates in the thread it seems as if you were focusing on decadal averages of the 1980's vs the 2010s. Is that accurate? 3. "huge": What would constitute a huge downturn?

Thanks for the link, interesting stuff.

Thanks for the information, as always!

What factors impact the strength and position of the NPJ? From weather 101 I would expect the strength to positively correlate with the latitudinal temperature gradient. That would make me expect the NPJ to be getting weaker. So I guess that's not the whole story. I remember earlier seeing something about EAMT playing a role. I also remember one of @psuhoffman's "sweet dreams for @Maestrobjwa" posts from last year saying that the WPAC warm pool might be making it stronger? Since there's nothing to track, lets do a NPJ tutorial, if anyone has knowledge they'd like to share.

Eastern ridge definitely starting to be beat down by Jan 8th, but 2m anomalies still mostly warm through Jan 12. Not sure of that is residual from Pac Puke or just the new pattern is meh.

What hour are you looking at?

The CLT only applies if the variables are independent and identically distributed. I suspect that this does not apply to at least some aspects of weather/climate.

Celebration?

For one who is trying to learn, would you mind pointing out the features which indicate confluence?

Looking at the GEPS and the GEFS together with the end of the GFS I am noting a significant trend of positive anomalies centered around Hudson Bay, and weaker but still widespread negative anomalies around the Aleutians. Not horrible. Generally kind of ridge-ish in the west. Better than pac puke. GEFS example below.

Speaking of MIA, Chuck has been quiet lately. Hope he is ok.

I see Ji would be happy at around Hr 300 on the 00z GFS. That aside that GFS run does not amuse me. Way too much blue at H5 around Alaska all the way to 384. At 384 perhaps the merest hint of a nascent -EPO building in the Yukon. I know op at range worse than useless. But if people can be happy about the blue I can be sad about the other blue.

Thank you for taking the time to explain this. Can you help me understand how blocking works? I am particularly trying to understand why a 50/50 low makes a -NAO more effective as a blocking agent.

Gonna be pretty quite for a while as we wait for the vortex to retrograde. Anyone care to spend a paragraph to explain the way in which patterns of geopotential height controls the flow of airmasses and storm systems? I'm having trouble finding that level of detail on easily available internet resources. The closest I can find is a mention on the Wikipedia articel about geopotential height: "Geophysical sciences such as meteorology often prefer to express the horizontal pressure gradient force as the gradient of geopotential along a constant-pressure surface, because then it has the properties of a conservative force. For example, the primitive equations which weather forecast models solve use hydrostatic pressure as a vertical coordinate, and express the slopes of those pressure surfaces in terms of geopotential height." So if this is accurate patters of gph are actually equivalent to patterns in plain air pressure gradient force. This intrigues me but I do not understand how it is so. Anyone feeling didactic tonight?

I'd say we're on the way up on the sine graph.

Actually it did verify to some extent as seen in the composite posted by DarkSharkWX. But as he noted the ridge axis was considerably further west than ideal. Edit: And yes I know the MA used to not always need perfect ridge axis placement for snow.

Interesting that in that composite no WAR really shows up, but we know it was there when it counted. You can also see that the mean trough is much further west compared to say Dec 2010 or March 2018 which itself hints of higher heights in the SE.

I cannot personally remember a SSW event that worked for the eastern CONUS. But I believe that the Great Plains blast of Feb 2021 was related to a SSW event from that January. So in theory that could happen to us next time (although I could do without the power grid disruptions). Or alternatively our new super-WAR overlord might mean that SSW-related cold blasts will forever shunted away from us. I say that in jest, but I think it is something that needs to be considered.

I know this was a typo but I think it should be made an official pattern descriptor. If it's worse than shut the blinds its SHITS THE BLINDS

Depressing statistics aside I would say that this month has actually been a good one for long-range guidance as far as verification performance. They missed the "squirting" vortex which looked to be previously trapped under the ridging ~12/10 but since then they've all been spot on as far as I can tell. They saw the transition period from 12/15 or so followed by chilly temps followed by a full-fledge arctic blast. They saw the rapid transition to Pac Puke following the collapse of the -EPO. And they saw it all at long lead times. Yeah they did initially fail to see the giant cutter that crushed our dreams of a white Christmas, but they did unanimously catch on ~120 hours with some catching on long before that (the GFS suite was the hold out for a long time). My understanding is that the GEFS and GEPS are both showing some signs of hope after the puke period. Hopefully the EPS is also on board (can't see past 144 on TT).

But we (MA and the SE) are both at ~200% of the average epic pattern quota.

I'm hearing reports of strains on the grid with Duke power. Anybody have issues?