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Carvers Gap

Winter Pattern Discussion 2014-2015 (December/January)

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December is about to begin.  Let's see how all of this verifies....

 

CFS2 for next six months...December has progressively been warmer on the CFS2 while the trend for January is cooler.  In other words, as the model updates it seems December is getting warmer on the CFS2 and January is cooling off.

post-769-0-11920400-1417100077_thumb.jpg

 

 

Here is the NAO outlook.  Not great.

post-769-0-40557500-1417100076_thumb.jpg

 

 

Here is the PNA outlook.  Would seem to hint at a developing western ridge, eastern trough towards mid-December.  That rarely works out for us in the TN Valley, but certainly did last January.

post-769-0-66517500-1417100075_thumb.jpg

 

 

Here is the AO outlook.  Would appear some cold will be in North America for troughs to draw from when plunging southward.

post-769-0-94187100-1417100074_thumb.jpg

 

 

Here is the Nov 24 ENSO summary from CPC. 

post-769-0-25652900-1417100074_thumb.jpg

 

 

Here is the probability of an El Nino from the aformentioned report.  Looks like CPC is leaning towards a Nino.  Could it be that our winter is weighted towards mid-late winter?  That would correspond with the developing Nino.  Is it possible the atmosphere will lag in response and respond during the mid-late winter time frame?

post-769-0-75415300-1417100073_thumb.jpg

 

 

Here is the multi-model(correct term?) prediction for the ENSO this winter. This index certainly points to a cold snowy, winter in the East.  A weak Nino is perfect.  Will this index be the "golden ticket" or the source of grumbling?  Time will tell. 

post-769-0-38268400-1417100072_thumb.jpg

 

 

Here is the CFS2 prediction for the ENSO this winter.  This is where my concern is rooted, but it is an outlier.  However, even as an outlier, the mid-range models do lend some support to it or I would throw it out.  CPC felt the need to include it in their update.  That said, it can be a very squirrelly model. In this image, the CFS2 seems to hint at why it is warmer.   It has a stronger Nino in place.

post-769-0-10706600-1417100073_thumb.jpg

 

 

Summary:  Well, this will give us a baseline to work from as the winter progress.  It might also help to determine over time what drives sensible weather.  I should also add that November has been incredibly cold.  October and September were not.  October was slightly above normal and September much above at KTRI.  In general, Fall climo will be cooler than normal due to an anomalous November.  A weak El Nino in the right place in the Pacific basin could mean the TN Valley is in business.  We will see what that impact is.  Is the CFS2 on to something or is it off on its own?  Will the warmish Euro weeklies be correct as they almost always are?  Many Nino winters have been spectacular here in the valley, some have not.  As stated earlier, I think that the temps for Dec-Feb will be slightly above.  Snow near normal for the season - which I count as first snow to the last snow regardless of the month.

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Here is some MJO information. Here is a link on what it is. I failed to mention that above. It can sometimes trump any pattern. Here are some images in relation including the current MJO and how it corresponds to WX in North America.

Current MJO and forecast.

post-769-0-89109800-1417102582_thumb.jpg

MJO precip and how it correlates in late fall and early winter.

post-769-0-98045500-1417102568_thumb.jpg

MJO temp and how it correlates in late fall and early winter. Check out phases 5, 6, and 7 where it is predicted to go.

post-769-0-93180800-1417102569_thumb.jpg

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Joseph D'Aleo at WB has a good post about the difficulties in the modeling as we go through the transition of the seasons. He discusses a few hints as to why he thinks the models will soon change toward a colder east coast solution

I enjoy his blog, probably as much as anyone.

I wish I still had a pro.accuweather subscription. I really enjoyed Lundberg's blog as well. Similar in that they are usually well reasoned thoughts that don't carry much bias.

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Joseph D'Aleo at WB has a good post about the difficulties in the modeling as we go through the transition of the seasons. He discusses a few hints as to why he thinks the models will soon change toward a colder east coast solution

I enjoy his blog, probably as much as anyone.

I wish I still had a pro.accuweather subscription. I really enjoyed Lundberg's blog as well. Similar in that they are usually well reasoned thoughts that don't carry much bias.

Lundberg does a great job. I agree. D'Aleo is savvy. Feel "free" to let us know anything in the future. Sometimes I wonder how much that Pacific hurricane(Ana?) had to do with the cold November. Really shook the pattern up. One would think that the El Nino will begin influencing NA at some point this winter, if it is not already. Going to have to get that strongly +NAO out of the way. Let's see if another strong storm doesn't shake-up the pattern and repeat the process. That might be the signal, as it usually is. Looks like the current cold spell is over.

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SurfT_HighmLow_SnowCover_Detrend_Blog_sm

 

 I strongly recommend that people look at this absolutely fascinating animation of the high Oct. Eurasian snowcover sfc temp.'s minus the low Oct. Eurasian snowcover sfc temp.'s. I just noticed this for the first time. Not only is it absolutely fascinating, but more importantly it should ease the worries (due to the expected relative mild first week of Dec.) of those expecting an overall cold E half of US DJF based on Cohen's work. According to that link's animation, the high Oct. Eurasian snowcover years are actually clearly biased solidly warmer in the E half of the US than low October Eurasian snowcover years during the first week of Dec!! Note the reds then. Then afterward, it gets close to a wash for the 2nd week of Dec. The relative mild returns one last time over most of the US for 12/13-19. After that, the blues (cold) dominate the E 2/3 of the US from 12/21 through 2/18 almost nonstop! Then 2/19-28 is back and forth. So, this animation suggests a solidly cold dominated 60 day period over the E 2/3 of the US during the climo coldest part of winter after a mild dominated 12/1-19. After looking at the E US, I then recommend folks focus on Greenland. Note that Greenland doesn't have reds dominating until ~12/18. Then, 12/18-2/13 is heavily dominated by relative warmth, which suggests a solid west based -NAO would be favored for the 12/18-2/13 period.

 

 By the way, one of my top analogs is 1939-40. After a mild dominated 12/1-19, it was very cold dominated at least through the end of Jan.

Did anyone else notice what I did for both the E 2/3 of the US and for Greenland? If so, any comments?

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I strongly recommend that people look at this absolutely fascinating animation of the high Oct. Eurasian snowcover sfc temp.'s minus the low Oct. Eurasian snowcover sfc temp.'s. I just noticed this for the first time. Not only is it absolutely fascinating, but more importantly it should ease the worries (due to the expected relative mild first week of Dec.) of those expecting an overall cold E half of US DJF based on Cohen's work. According to that link's animation, the high Oct. Eurasian snowcover years are actually clearly biased solidly warmer in the E half of the US than low October Eurasian snowcover years during the first week of Dec!! Note the reds then. Then afterward, it gets close to a wash for the 2nd week of Dec. The relative mild returns one last time over most of the US for 12/13-19. After that, the blues (cold) dominate the E 2/3 of the US from 12/21 through 2/18 almost nonstop! Then 2/19-28 is back and forth. So, this animation suggests a solidly cold dominated 60 day period over the E 2/3 of the US during the climo coldest part of winter after a mild dominated 12/1-19. After looking at the E US, I then recommend folks focus on Greenland. Note that Greenland doesn't have reds dominating until ~12/18. Then, 12/18-2/13 is heavily dominated by relative warmth, which suggests a solid west based -NAO would be favored for the 12/18-2/13 period.

By the way, one of my top analogs is 1939-40. After a mild dominated 12/1-19, it was very cold dominated at least through the end of Jan.

Did anyone else notice what I did for both the E 2/3 of the US and for Greenland? If so, any comments?

Great animation. FWIW, I think many indicators give pause to the cold forecasts such as the CFS2, Euro Weeklies, to some extent the MJO, and a warm start to December. The global indicators of a weak El Nino and snowcover in Asia are still much in favor of a stormy winter. I am genreally in the crowd that questions things that look too good to be true. I like that you bring excellent scientific evidence to support your view. Good stuff.

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Here is an excerpt from Judah Cohen's article mentioned on the main board. A very good example of the variability in wx that cannot be predicted. Also, it is a good example of why good science involves good questions that elicit possible new answers.

Whole article: http://www.vwkweb.nl/index.php?page=537&sl=1

Excerpt:

"Question 19. In your blog 14 November you wrote that the current atmospheric configuration is somewhat orthogonal to the mean atmospheric response to snow cover with the strengthening and expansion of the Siberian (high) different from composite analysis based on high minus low snow cover. We wonder in what way the current (14 November) configuration differ from the expected one and what might be the cause of that? Was the Siberian high in November in the right place for changing the Jetstream and for WAFz?

The deep polar low in Northwestern Asia that developed in November has interfered with the expansion of the Siberian high. The WAFz was active in November but I believe that it would have been even more active had the polar low not formed in that unusual location. That is what I was referring to when we wrote that the atmospheric response is orthogonal to high snow cover extent in the in blog dated November 14. In Cohen and Jones 2011 (on tropospheric precursors) and Cohen et al. 2014 (J. Climate) we provided plots of the atmospheric anomalies that are optimal for breaking down the stratospheric polar vortex and that are associated with high Eurasian snow cover. The models have been predicting that low to slide off to the south and east closer to its climatological position and more favorable for further expansion of the Siberian high as shown in the above mentioned papers. However today the models are predicting that the polar low will redevelop further west. I am watching this development very closely. If the low deepens in the location as the models predict and remains persistent that would destructively interfere with triggering further WAFz and weakening of the polar vortex, something more common with low snow cover extent. "

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18z GFS shows no Arctic outbreaks over the southeast for the entire modeled time frame.  Enjoy the warm-up.  It would seem that cold wx will not return to the upper south until at the earliest mid-December.  Could be later, but that seems to fit the MJO on the GFS.  However, at this time, I do not see any delivery mechanisms for cold air this far south.  Is it possible the models could miss this much like they did in November?  Sure.  But the typhoon had much to do w/ reshaping what the models had portrayed for that time frame.  That could certainly happen again.  But at the moment, looks like a tranquil pattern for the Tennessee Valley in terms of winter weather for at least the next 16 days...my guess 3 weeks roughly.  Then, I think (assuming the feature in northwest Asia doesn't set-up shop) we settle into a typical and normal winter wx pattern for January.  Jury is out on February w/ the CFS2 pointing to a torch, but global indicators like a weak El Nino saying otherwise.  Kind of a bummer to begin December, but it is what it is.  I think it is time to set reasonable expectations on this winter.  Most of December looks void of winter wx, minus the last week or so.  I have been trying to temper expectations for the past week or so.  On the positive side, it just takes 2-3 good winter wx events for most of us to reach normal and be happy.  I certainly still think that is in the cards.  I think the weak El Nino should serve up at least a few GOM events.  While it won't be epic, it certainly should be satisfactory for most from Memphis to Bristol. And hey...keeping it real...December isn't a great month for snow anyway for most.  With January-March still on the table, I think many will cash in during that time frame.  I will also add, the cold later in December is not a guarantee either.  I am just saying mid-December is the earliest it shows w/ late December more of a reality.  Feel free to counter.

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 As long as indicators suggest a return to cold domination ~12/20, I'll remain not the least bit worried about DJF averaging cold. As a matter of fact, that animation that I saw today of high Eurasian snow years minus low snow years showing mainly warmth (reds) for 12/1-20 tells me that any early to mid Dec. warmth would actually be a good sign that the Cohen analogs are working nicely. If, say, it looks warm dominated two weeks from now when looking out 15 days, then I'd probably start worrying some.

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As long as indicators suggest a return to cold domination ~12/20, I'll remain not the least bit worried about DJF averaging cold. As a matter of fact, that animation that I saw today of high Eurasian snow years minus low snow years showing mainly warmth (reds) for 12/1-20 tells me that any early to mid Dec. warmth would actually be a good sign that the Cohen analogs are working nicely. If, say, it looks warm dominated two weeks from now when looking out 15 days, then I'd probably start worrying some.

Seems like a good observation. I would generally agree with the initial start time for cold. I still think the winter averages warmer than normal.

Seems to be a pretty natural progression of a warm neutral/weak El Niño with a +PDO and high SAI to me Carvers.

That is true. I will start watching that feature Cohen mentioned in his article - the feature over northwestern Asia. Edit...Not a given this is a weak El Nino.

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December 2002 did feature the significant ice storm in the Carolinas in the early part of the month. The daily temperature variances would be helpful to compare but the evolution was probably different....Next week is certainly not a torch relative to normal here with the trough moving through the eastern US but the Euro ens looks to provide no cold air past that at this point...there are signs of a split flow and some west coast ridging at the end of the period, but we are still not yet there for the classic winter pattern everyone wants. Nevertheless, it does not look the least bit hopeless unless you feel robbed by having a slightly above normal December!

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Moral of the story. .... The GFS sucks in the western Pacific too?

On topic, does a non-recurving typhoon delay the processes to take the eastern US back below normal temp wise?

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Moral of the story. .... The GFS sucks in the western Pacific too?

On topic, does a non-recurving typhoon delay the processes to take the eastern US back below normal temp wise?

There's no telling if a blanket assumption can be made. Fwiw, are you aware of the complete JB typhoon rules?

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I would think higher resolution, like the Euro, would win the day more often than not, regardless of the location it's trying to model...

I am aware of the implications of what JB thinks a re-curving typhoon means to the downstream pattern over North America, but not his complete rule book......

I am more curious about the implications of a non-recurving typhoon though, as shown on the Euro....

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I would think higher resolution, like the Euro, would win the day more often than not, regardless of the location it's trying to model...

I am aware of the implications of what JB thinks a re-curving typhoon means to the downstream pattern over North America, but not his complete rule book......

I am more curious about the implications of a non-recurving typhoon though, as shown on the Euro....

Just my opinion but I do not think we need a recurving Typhoon to change the pattern. IF it were to recurve then we may see changes sooner than later but I do think we will get a change either way sooner or later.

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I would think higher resolution, like the Euro, would win the day more often than not, regardless of the location it's trying to model...

I am aware of the implications of what JB thinks a re-curving typhoon means to the downstream pattern over North America, but not his complete rule book......

I am more curious about the implications of a non-recurving typhoon though, as shown on the Euro....

http://weather.kopn.org/wp/

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C. AFTER TAU 72, THERE IS A SIGNIFICANT BIFURCATION IN THE
MODELS. THE GFS AND COAMPS MODELS HAVE BEEN CONSISTENTLY SHOWING THE
SYSTEM MOVING POLEWARD THROUGH THE WEAKNESS IN THE STR THOUGH TAU
120 BEFORE SLIGHTLY TURNING BACK TO THE SOUTHWEST UNDER THE
NORTHEASTERLY SURGE THROUGH THE EAST CHINA SEA. OPPOSING THAT, THE
ECMF TRACKER HAS THE SYSTEM CONTINUING TO TRACK WEST INTO CENTRAL
PHILIPPINES INDICATING THAT THE WEAKNESS IN THE RIDGE IS NOT
PRONOUNCED ENOUGH TO SIGNIFICANTLY CHANGE THE TRACK OF HAGUPIT. THE
NAVGEM SOLUTION HAS BEEN SHIFTING BETWEEN THE TWO PREVIOUS
SOLUTIONS. THE JTWC FORECAST TRACK ENCOMPASSES ELEMENTS OF BOTH OF
THESE SCENARIOS. WITH THE SYSTEM INTENSIFYING WELL ABOVE MODEL
GUIDANCE, AS WELL AS INCREASING IN SIZE. THERE IS A HIGH PROBABILITY
THAT THE SYSTEM WILL START TO TURN POLEWARD INTO THE WEAKNESS IN THE
STR THOUGH TAU 96. HOWEVER, BEYOND THAT, THE ELONGATED STR IN
COMBINATION WITH THE LOWER-LEVEL NORTHEASTERLY SURGE WILL CONTRIBUTE
IN PUSHING THE SYSTEM ON A MORE WESTWARD TRACK INTO SOUTHERN LUZON.
OVERALL, THERE IS LOW CONFIDENCE IN THE EXTENDED FORECAST TRACK DUE
TO THE SIGNIFICANT BIFURCATION IN THE MODELS AND THE POSSIBILITY OF
AN ALTERNATE FORECAST SCENARIO, WITH THE SYSTEM EITHER SIGNIFICANTLY
RECURVING EAST OF THE PHILIPPINES OR TRACKING WESTWARD INTO THE
SOUTHERN PHILIPPINES.//
NNNN

http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/warnings/wp2214prog.txt

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