Thursday, November 3, 2016
Thursday Morning Video Discussion: Big Pattern Change 2nd Half of November
Video below discusses what I believe will be a major pattern change for the 2nd half of November (14th on). The ideas supporting colder than normal temperatures with storminess are gaining traction. Still early for any news making snow in Mid Atlantic, but up in New England maybe we can get those ski areas off to a good start! Enjoy the video.
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Hi Willy, good analysis, but can I make one comment . . . You pretty much rely on the ensemble models to establish an eastern troughing pattern after mid-month, but as to temperature anomaly, you pick out a few runs showing cold waves. However, my look at the GEFS and GEPS averages this morning indicate that the temp departures from the 15th thru the 20th are mostly neutral or slightly positive (warmer). Don't know what the Euro ensemble is saying, maybe it is chillier. My point is that I thought we use ensemble averages on the idea that the average of many runs with slightly different starting assumptions is usually more reliable than any one run, including the operational run (which shows a pretty strong cold wave in the east by Nov 20th!). I.e., we don't pick out particular ensemble scenarios w/o good reason (and hey, I've sure violated that rule!), although we still take the operational runs seriously. I agree that significant cold shots COULD happen, but more "Indian Summer" also occur on some of the ensemble runs (however, given what the Cubs just did to the Indians, perhaps that is less likely!). OK, just putting it into the context of what I've heard regarding ensemble model averages.
ReplyDeleteFrom what I can see from the GFS, no strong AO or NAO patterns are anticipated over that period; both move from negative zones next week to slightly positive. The EPO also seems mostly non-committal into the later part of the month. The warm blob in the GOA is still there, but there's also a big cold pool right below it, from Japan to Seattle. So we might not yet be getting a strong kinked northern jet pattern settling in. I'm just saying, maybe the winter pattern is not yet locking into place, perhaps this is still the inter-season back-and-forth. As to the stratosphere layer temps, looks like a small heat bump has been progressing upward, but the lower layers may now be leveling off or declining. So this one might not be a big SSW event, but perhaps it is a sign of more to come.
Joe Cioffi had a good note about the Eurasian snow cover, and he thinks that the October 2016 build-up predicts a below-average temp / above-average snowfall winter for the NY Metro area. He cites the fact that the southern build-up below the 60 line was strong, finds analogies with previous snowy winters here. He has a very nice chart comparing the October buildup over the past 40 years. Looks like 1970 is a pretty good comparison point for 2016; just about the same level of October snow cover, and a weak La Nina. Result was an average cold / average snowfall winter in NY / NJ. My two cents -- this year is different from 70 because of the current historically low Arctic sea ice. The Arctic waters are probably warmer and the sea level Arctic air is definitely warmer now versus late 1970. I think that we both agree that this games the Arctic region for more stratospheric warmings, and thus more cold shots down here as the polar vortex weakens and occasionally splits thru the winter.
So the Arctic might already be setting up for colder temps down here thru March, but the Pacific and Atlantic dynamics (which will help determine precipitation patterns) might still be evolving right now. And then again, maybe I'm all wrong about all of this . . . but it's still fun to ponder, one way or another! Jim G
Hey Jim, I see your point and you are 100% correct when you look at the models. They are showing what seems to be a ridge and trough relationship but have no impressive anomaly outputs for the surface. When I look at the long range I look at a variety of things and then try to use the models as support for my ideas. For example, the stratospheric impacts should keep this AO negative as we get into the latter part of Nov. Also, based on where the PV is expected to move does support more of a riding/toughing relationship as we head into late November. Also, this is supported by my major analogs that I have been looking at for the winter. Pile into that the MJO moving into a favorable spot and we MIGHT have a recipe here. I think you would agree, its not as if the models are not showing hints that this can happen. They just are really volatile right now in the day 8-16 period. I attribute this to the computers struggling to handle all the complex variables that are occurring right now due to the seasonal transition of the jet. With that being said, the issue right now is the strong pacific jet stream. This could absolutely kill my forecast if it does not weaken as it will just undercut the Aleutian low and spray mild air into the US.
DeleteSo here is my bottom line. If I was just looking at the ensemble averages then yes I wouldn't have a big case for a flip to colder than normal for 2nd half of November. When I tie in other methods like my analogs, MJO, PV etc. it changes the equation. At the end of the day you are right, the purpose of an ensemble is to show more consistency compared to an operation run. The reason I like to also look at the individual ensemble members is to see if there are any ODD looking members that might be skewing off the average. For example, if we know it is likely we will have at least a ridge/trough relationship (magnitude still in question) I might remove a few members that do not show anything close to this pattern just to play around. Eventually only one of the members ends up being close to correct many fail as the long range approaches the short range, so it is helpful to see the trends of individual members where instead of using an average maybe you remove outliers and look at the median.
So we will see what happens. As I said in video I do not expect snow for the mid atlantic in November but up in New England I do think if this pattern evolves as I expect, the ski areas do see some before the turn of the month. I do not expect a major turn to cold but I think it will be cold enough to end November to be notable. At that point I think we will then be able to evaluate the seasonal transition and if it is lining up with my winter ideas.
Joe Cioffi is great. Im interested to read that analysis. Remember I expect the worst of the winter to be in New England. We should do well here but I do not think its a banner snow year, just slightly above average where south jersey and lower mid atalntic average.
I agree that below average temperatures will occur later in the winter, but I'm just not sure about November and December. Also, I'm not sure if there is any indication as to when the drought in the Northeast (which has pretty much been around for a year) will end. If it stays, it may limit snowfall, even with a lot of cold.
ReplyDeleteWe will find out soon. I think by 2nd week of December we will see if this seasonal transition goes the way I expect. I am fairly confident however that New England does well with snow this year. Especially if we see a lot of clipper like systems. Mid atlantic is a battle zone.
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