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Winter 2020-21 Discussion


CAPE
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28 minutes ago, NorthArlington101 said:

Guess we might need a LR thread soon, but the GFS has consistently  been throwing out some pretty serious cold for this time of year around Halloween.  

Maybe you all will get paid back for the snowstorm that misses you back in December of 2018. And we get even more rain down here.

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Looking at the latest LR global means, some significant changes up top. Lots of blue, and CFS weeklies continue that through November. The -NAO period was possibly just a transitional thing. The CFS run of indicating HL help for the winter months seems to have finally ended. Its h5 depiction for DJF aligns with most other climate/seasonals now.  Has a +AO/NAO throughout. The mean EPAC ridge location/orientation could be worse though. Actually has hints of an EPO ridge, esp for late winter. fwiw.

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16 hours ago, frd said:

Nina results vary,  but cool to see the various temp profiles going back to 1925. 

 

Back in July, never in a million years did I think this Niña event would ever approach strong, but it appears to be doing just that. The models continue to get stronger with it. It’s now fully coupled, ENSO region 4 has dropped like a rock. There are also shades of the 88-89 strong La Niña showing up, which HM and Ben Noll have pointed out: 

 

 

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1 hour ago, psuhoffman said:

Simply the fact the Nina is strong doesn’t necessarily mean a torch winter. There have been some cold or somewhat snowy strong Nina’s. However, there are plenty of other factors that in conjunction with a strong Nina aren’t good. 

As Uncle W just pointed out, 73-74 was the strongest La Niña in history and had a severely negative PDO yet it was a decent winter

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59 minutes ago, snowman19 said:

As Uncle W just pointed out, 73-74 was the strongest La Niña in history and had a severely negative PDO yet it was a decent winter

Significant HL blocking can mitigate a lot of bad elsewhere. Unfortunately we are on a bad run in that dept.

I suppose we are due. :rolleyes:

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57 minutes ago, CAPE said:

Significant HL blocking can mitigate a lot of bad elsewhere. Unfortunately we are on a bad run in that dept.

I suppose we are due. :rolleyes:

Very true. I guess you also have to consider that the 73-74 super La Niña occurred during a totally different, cooler climate era. I kind of doubt that even with a complete carbon copy of 73-74 this winter, you’d have the same results in the temperature and snowfall departments....

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20 hours ago, CAPE said:

Significant HL blocking can mitigate a lot of bad elsewhere. Unfortunately we are on a bad run in that dept.

I suppose we are due. :rolleyes:

This part of the equation is where my pessimism lies. We can and have had decent snowfall in a strong Nina. But every instance took high latitude blocking. Not some. Not most EVERY SINGLE one. I can’t stress that enough. Since 1948 Baltimore hasn’t had a single warning level snowfall during either a strong Nina or a central pacific ridge (predominant effect if said Nina) without blocking. Even when we include non Nina years that featured a Central pac ridge I found not one single significant snowfall with that pac pattern that didn’t include blocking. 
 

I get the sense some people think we might luck our way into a snowstorm even with a strong pac ridge and +NAO. But history suggests we won’t. That if we do get the currently expected pacific and Atlantic patterns we are just as much toast as we were last year. 
 

I’m not saying we won’t get snow. But I’m saying we need one of those two patterns to break our way. Not the whole winter. Look at 2000. We only got the high latitudes to cooperate for a few weeks but that was enough to save us.  But if we do get a wall to wall +NAO like we’ve seen for years now...I am not optimistic “luck” saves us. 

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Just to illustrate my point. Even if we do get some NAO help were still not likely to get a great winter. But history suggest something close to median and maybe avg if we’re lucky. Not too bad. But let’s say we get another wall to wall +NAO. The best analog matches are then 1949/50, 1975/76, 1988/89 and 2007/08. I am not going to run the numbers for every location but 2 of those 4 years were WORSE here than last year!  And the other 2 were only marginally slightly better. And only better due to flukes. 1976 all the snow came from a big mid March save. And 2007/8 almost all the snow came from an early December clipper that somehow dropped 7” on only .25 qpf.  Otherwise those 2 years were just as awful with virtually no snow here the rest of winter. So history says if we don’t get NAO help it’s likely to be just as bad as last year. Last year wasn’t bad luck. It wasn’t a fluke. It was exactly what a strong Nina pac pattern looks like with a +AO/NAO. (Yes I know it wasn’t a strong Nina but the atmosphere behaved like one so my point is valid). 

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3 hours ago, psuhoffman said:

To be more optimistic if we do get some blocking help the better analogs become 1955/56, 1973/74, 1999/00, 2010/11. They all features some respectable cold periods and some decent snowstorms. We’re still not looking at a blockbuster but those years felt like we had a winter at least. 

Agree here. The 73-74 winter is real interesting, you had a raging strong La Niña (strongest in history) and a very deeply negative PDO, yet it turned out to be a pretty decent winter for cold and snow. That really illustrates your point of how important both AO and NAO blocking are for the east coast during moderate and strong La Niña events....

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It will snow this winter. Projected mean patterns are just that. We normally get a few shots each winter. Last winter was an o-fer for most, and while it could happen again this winter, it probably won't.

Nina winters don't often produce above avg snow, and can be super frustrating with the typical NS dominant flow/late developing coastals. I will say this again- the last 2 Ninas produced slightly below median, and slightly above avg snowfall here, respectively. Both produced big snowstorms(one was a blizzard) for the immediate coastal plain, with no blocking. Clearly better outcomes than the so called Nino and warm neutral of the past 2 winters for my yard.

And yes, while DC-BWI and west missed both of those Nina events, it wouldn't have taken much for better outcomes in those areas.

Ofc this is a imby business, so I don't care. B)

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Has anyone ever done correlation analysis between conditions in October/November and the resultant NAO state during DJF? I'm sure it's been done, and I'd be interested in reading if anyone has a link. It's hard to just cancel winter when there is some off-chance that we do have -NAO. While it has only occurred few times in the past 20 years, it's not theoretically impossible, right? It even happened during a Nina in 2010-2011. 

 

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5 minutes ago, IUsedToHateCold said:

Has anyone ever done correlation analysis between conditions in October/November and the resultant NAO state during DJF? I'm sure it's been done, and I'd be interested in reading if anyone has a link. It's hard to just cancel winter when there is some off-chance that we do have -NAO. While it has only occurred few times in the past 20 years, it's not theoretically impossible, right? It even happened during a Nina in 2010-2011. 

 

Go back and read the previous few pages ITT. This has been discussed at length.

Also I am not sure anyone is 'canceling' winter. Well maybe Ji has, but he doesn't count.

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