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Winter 2014-2015 Medium-Term Discussion


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Back in #119 (December 2), I advised that temptations to write winter's obituary should be held off. If one finds the siren songs of winter's premature demise too tempting to resist, one should probably focus more on the coming joy of Hanukkah and Christmas (sentiments that should always be close at hand regardless of the variability in the weather). Almost certainly, winter will return.

 

On Tuesday evening, as the first candle of Hanukkah is lit, there will be the usual joy associated with the start of that festive time. But if one is looking at the latest guidance, there will also be the added joy that the approaching return of winter brings.

 

At present, there is now a growing body of evidence that the pattern change will get underway just after mid-month. The transition will feature efforts to build troughs, across parts of the CONUS, but those troughs will prove transient. Nevertheless, one cannot rule out the possibility of some snow across parts of the Midwest, southern Canada, and into the Northeast during this transitional time. The transitional period will likely last approximately a week, roughly running from 12/16 through about 12/23. Afterward, the trough will become established and begin to deepen.

 

The 12/11/2014 0z run of the GFS ensembles illustrates this pattern evolution. Both the GFS ensembles and ECMWF ensembles are in strong agreement where things are forecast to be at 240 hours (just after the mid-point of the transitional period).

 

GFSEnsembles121120140z.jpg

 

ECMWFEns121120140z.jpg

 

If one looks at the Day 11 analogs on the GFS ensembles and rolls them forward 6 days, one gets a scenario very similar to the 12/11 0z CFSv2 forecast for Days 21-25.

 

GFSAnalogs12112014.jpg

 

Among the objective analogs are December 29, 1995 and December 23, 2009.

 

In short, the return of winter is now on the proverbial radar.

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weenies listening  to JB will do that. There was  NEVER  EVER   NEVER EVER any hint of  ANY   cold in  DEC   2014 

 

NONE  ..   ZERO.

 

 

  " just like 1976-77"...  opps  time for a time for a drink

FWIW, JB wasn't cold for Dec. Had a strip of -1 to -3 down the middle of the CONUS and normal (+/-1) elsewhere. Dec. analog is 77/78 & 02/03 where cold pulled back. Jan/Feb are cold.
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FWIW, JB wasn't cold for Dec. Had a strip of -1 to -3 down the middle of the CONUS and normal (+/-1) elsewhere. Dec. analog is 77/78 & 02/03 where cold pulled back. Jan/Feb are cold.

Very true. He always said there would be a pull back. He never called for wall-to-wall cold from November through March.

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The forecast he posted November 29 for December showed the entire center of the country below normal 1-3 degrees all the way to the coast covering the mid Atlantic, norther North Carolina to south of New England. With most of the Midwest 3-5 below normal. I would consider 3-5 pretty impressive cold that, unless it turns cold pretty damned fast and with impressive departures hard to achieve.

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Comparison of the CFSv2 Forecast for December vs. December 1-10 Outcomes:

 

CFSv212122014.jpg

 

If the ensemble guidance is representative, parts of the eastern U.S. and eastern Canada (eastern Ontario, Quebec, New Brunswick) could finish December with cold anomalies, especially with the increasingly likely pattern change in the medium-term.

 

Even as it is near the end of its fantasy range, the 12z run of the operational GFS brings a shot of Arctic air into the CONUS. This outcome is supported by some of the earlier ensemble guidance and Day 21-25 CFSv2 forecasts.

 

In short, even as next week looks mild across much of North America, a pattern change toward colder weather with increasing opportunities for an expansion of North American snow cover looks increasingly likely afterward.

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Quick evening thoughts...

 

1. Ensemble support for the forthcoming pattern change is increasing.

2. Several recent runs of the operational GFS are showing Arctic cold in the extended range. Details are not that important, but the support for the colder pattern is important.

3. The subtropical jet looks to remain active for at least another 2 weeks, so some opportunities for snowfall appear likely. Even some snow during the transition to a persistent cold pattern can't be ruled out for some parts of the Midwest, southern Canada, and Northeast.

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Don are you concerned about the MJO I know the European model has it going to phase 3 and then to into four also I would like to say I concur with everybody else on this board that your analysis are second to none keep up the great work. Chris

I'm somewhat cautious about that, but it seems that the MJO forecasts have varied quite a bit from model to model. This uncertainty may, itself, be a hint of an imminent transition in the current pattern. I suspect by later next week, we'll have a much better idea about the MJO's likely progression.

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I'm somewhat cautious about that, but it seems that the MJO forecasts have varied quite a bit from model to model. This uncertainty may, itself, be a hint of an imminent transition in the current pattern. I suspect by later next week, we'll have a much better idea about the MJO's likely progression.

Don ,

Also, I suspect that despite certain tendencies for US wx for each respective MJO phase that there is a pretty good amount of variance based on some initial research I did a while back. I may revisit this to freshen up about it. If so, I may post about it. More specifically, I may check out past winter cases of phases 3 and 4 as well as within the circle.

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The subsidence portion of an eastward moving Kelvin wave is messing with the MJO forecasts and thus the dynamic MJO forecasts. That may give a false reading into the COD and also mess around with the reemergence of it. It looks like it will gather some steam again over the maritime continent and push east. Thus, it may eventually help reinforce some -EPO ridging heading into early January. 

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the only reason JB used 1976-77 was 1917-18 wasn't available...I think even he thought it wouldn't get that cold...December 2014 is almost one degree below average so far in NYC...Unless we torch again the average could be -2 or lower in NYC when it's over...

I've been following the progression since early fall into the season and I know I will probably get laughed at but 1917-18 has legs when compared to what has happened so far this year. It featured harsh early cold followed by a pull back and then it was absolutely ridiculous when the cold and snow showed up. It will be very interesting to see how January-February plays out but my bets are on harsh cold and some places with lots of snow.

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I've been following the progression since early fall into the season and I know I will probably get laughed at but 1917-18 has legs when compared to what has happened so far this year. It featured harsh early cold followed by a pull back and then it was absolutely ridiculous when the cold and snow showed up. It will be very interesting to see how January-February plays out but my bets are on harsh cold and some places with lots of snow.

How early was the initial cold? Before the New Year's cold wave?

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the only reason JB used 1976-77 was 1917-18 wasn't available...I think even he thought it wouldn't get that cold...December 2014 is almost one degree below average so far in NYC...Unless we torch again the average could be -2 or lower in NYC when it's over...

Correct me if I am wrong, didnt 77-78 have a close match pattern, where Winter came on with a vengance around Christmas?

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I've been following the progression since early fall into the season and I know I will probably get laughed at but 1917-18 has legs when compared to what has happened so far this year. It featured harsh early cold followed by a pull back and then it was absolutely ridiculous when the cold and snow showed up. It will be very interesting to see how January-February plays out but my bets are on harsh cold and some places with lots of snow.

we may see a pattern like 1917-18 or 1976-77 but the sensible weather isn't the same so far...NYC had a 10" snowfall with arctic cold on this date in 1917...I doubt it gets as cold as 1917-18...-13 in late December and -6 in February...NYC hasn't seen a below zero day since 1994...

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Some quick thoughts...

 

1. The anticipated pattern change continues to appear increasingly likely. Support remains sustained on the GFS and ECWMF ensembles.

 

2. The transition will very likely be underway by the 17th with a duration around a week +/- a few days.

 

3. Some snowfall is possible across parts of the Midwest, southern Canada, and Northeast during the transition.

 

4. The 12/14 12z run of the GFS appears to be out of line with the ensemble forecasts, which have had good run-to-run consistency lately. A snowfall event appears possible for parts of the Mid-Atlantic and New England regions during the 12/24-25 period as a trough in the East is continuing to build.

 

GFSensembles12142014.jpg

 

5. The mild weather of the next few days should not fool one to believe that the anticipated pattern change is not happening. The ensemble guidance suggests otherwise. The cold front that will move across the Midwest and then off the East Coast during the 12/17-18 period will mark the opening of the transitional stage.

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This pretty much covers the fall and winter of 1917-18.

https://www.google.com/url?sa=t&source=web&rct=j&ei=zAeOVKalKZKfyATa0IDQDw&url=http://archive.org/stream/jstor-207470/207470_djvu.txt&ved=0CCMQFjAB&usg=AFQjCNGnChxHBg94YjRhix1jTB5DBMhk4A&sig2=ICXPqPb-tLBSZuhmRnzbxg

I don't know if the link will work or not but I'll try it when it posts. It's a bit of a lengthy read but it's a good one in my opinion.

If you're looking for 'exact' timing and patterning with stuff, you're not going to find it anywhere. I've tried. The incredible similarities to this year so far are pretty good though.

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I've been following the progression since early fall into the season and I know I will probably get laughed at but 1917-18 has legs when compared to what has happened so far this year. It featured harsh early cold followed by a pull back and then it was absolutely ridiculous when the cold and snow showed up. It will be very interesting to see how January-February plays out but my bets are on harsh cold and some places with lots of snow.

 

Meh, I don't find that fall 1917 matches too well. 

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1917-1918 isn't a very good match up here in southern Ontario. December 1917 was one of the coldest Decembers on record, in fact the coldest until 1989. This December, thus far, has been nothing of the sort.

I know. That's why I said to move all the months forward 1 month. It is a similar pattern it is just occurring later in the year.

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