Winter 2014-2015 Pattern Discussion Thread I

[franklin NCwx]

Unfortunately, been there, done that.

Very nice analysis.

Just been dog bit before .....

what about gator bit?

[pcbjr]

what about gator bit?

 You mean gator bait ....

[GaWx]

The NAO looks more neutral to me, but it's a great look. Xmas eve things flip cold and are really cold for the east the last 12 days of the run. This should start coming into range of the EPS this weekend.

Edit: I just the WSI week 4 and see the -NAO. Interesting the WB maps aren't more neutral but doesn't matter.

 

Pack,

 My week 3 shows a modest -AO and pretty neutral NAO. However, my week 4 clearly shows a +NAO with below normal 500 mb hts over and all around Greenland. However, who cares? Besides, the +NAO could easily be temporary. That map wouldn't necessarily mean we'd have a +NAO for the month of January as a whole. IF this map verifies, we're going to transition from a warm week 2 to a cold week 4 via week 3's transition. This should make for lots of happiness here, -NAO or +NAO. The most important thing is that it is showing the return of solid cold, finally!! The +PNA is a beauty. People should be rejoicing. Rumor has it that even Tony's moles had a special drink when they saw the weeklies. Then again, those critters will drink to anything including drinking, itself, per Tony.

[superjames1992]

I really think the NAO is much more important for us later in the season than it is now. Also I think the reason for the Aleutian low to retrograde during this type (Modoki El Nino/+PDO) regime may be due to the way they cause the pressures to change from their normal locations. Kind of like an external forcing if you will, but that is just conjecture on my part

 

Obviously, given a choice I'd rather have a -NAO, but as last winter shows, it was certainly possible to produce a snowy winter (especially for more inland areas) even with a neutral/positive NAO.

 

ftp://ftp.cpc.ncep.noaa.gov/wd52dg/data/indices/nao_index.tim

Monthly Teleconnection Index: North Atlantic Oscillation (NAO)                                                
Indices are normalized using the 1981-2010 base period monthly means and standard deviations.

Values are set to -99.90 for calendar months when the pattern
is not normally a leading mode of variability.

The data is written in format(i4,3x,i2,1x,f6.2).

YEAR MONTH INDEX
2013   11   0.81
2013   12   0.79
2014    1  -0.17
2014    2   1.07
2014    3   0.44

[Webberweather53]

Unfortunately, been there, done that.

 

Very nice analysis.

 

Just been dog bit before .....

 

 

I certainly have as well, but this year has been fairly remarkable from this vantage point & the only condition I've come across that may be a negative factor is the solar flux being a bit high that would in different circumstances act to prelude any SSW, but our rather extreme snowpack, pre-existing anomalous wave activity flux & SST distribution should be suffice, but even without a stratospheric warming event to boot, it's going be exceedingly difficult to shake off our current rather & robust +PDO state w/ some enhancement from +ENSO & that should at the very least keep the southeastern US in check, in fact, it is the one region of the US where I have the highest confidence that temps will end up below normal... I made this map a month or two ago & posted some conditions I was looking into at the time & if anything, I probably should increase the confidence (not actual anomalies) for cold east of the Rockies, especially further to the south & east .

[packbacker]

Pack,

 My week 3 shows a modest -AO and pretty neutral NAO. However, my week 4 clearly shows a +NAO with below normal 500 mb hts over and all around Greenland. However, who cares? Besides, the +NAO could easily be temporary. That map wouldn't necessarily mean we'd have a +NAO for the month of January as a whole. IF this map verifies, we're going to transition from a warm week 2 to a cold week 4 via week 3's transition. This should make for lots of happiness here, -NAO or +NAO. The most important thing is that it is showing the return of solid cold, finally!! The +PNA is a beauty. People should be rejoicing. Rumor has it that even Tony's moles had a special drink when they saw the weeklies. Then again, those critters will drink to anything per Tony.

 

Thanks Larry!  Looks good, now that I am on my computer I can see it better.  The control run of the weeklies is sick, consistently cold day 20+ and periodic shots of -20+ 850's.

[Met1985]

This is a good read from WSI.

http://www.wsi.com/blog/energy/el-nino-update-it-is-here-now-and-is-impacting-circulation-but-dont-cancel-off-winter-just-yet/

[GaWx]

1) Now that I just looked at the Euro week 4 from a different perspective (polar view), it does appear the week 4 AO is then modestly negative. However, the NAO still looks clearly positive to me.

 I'm still expecting a strong -AO by January as per the Cohen analogs. A -NAO should follow per analogs.

 

2) Interesting thoughts from both webberwx and Mike Ventrice regarding El Nino analogs with their cold Jan-Feb. outlooks!

[packbacker]

 

Obviously, given a choice I'd rather have a -NAO, but as last winter shows, it was certainly possible to produce a snowy winter (especially for more inland areas) even with a neutral/positive NAO.

 

ftp://ftp.cpc.ncep.noaa.gov/wd52dg/data/indices/nao_index.tim

Monthly Teleconnection Index: North Atlantic Oscillation (NAO)                                                
Indices are normalized using the 1981-2010 base period monthly means and standard deviations.

Values are set to -99.90 for calendar months when the pattern
is not normally a leading mode of variability.

The data is written in format(i4,3x,i2,1x,f6.2).

YEAR MONTH INDEX
2013   11   0.81
2013   12   0.79
2014    1  -0.17
2014    2   1.07
2014    3   0.44

 

 

NAO certainly helps us big time...posted this in the banter thread...not a deal killer but definitely we need it more than most.

[griteater]

NAO certainly helps us big time...posted this in the banter thread...not a deal killer but definitely we need it more than most.

 

For Asheville, 11 of top 15 snowfall winters since 1950 had a -NAO

[Bob Chill]

Pack & Larry,

I think one of the most promising signs on the weeklies is the fairly strong long lead ridge signal across a large portion of Siberia that connects to the -epo ridge. Pretty much a roadblock. Could be early signs of a real -ao developing. It's unusual for the weeklies to show height anomalies like that at such long leads.

I also see ridging pushing into greenland with a nice kink in the isobars on the east side. The whole look makes me think the pv gets the squeeze and gets stuck spinning se of hudson. Probably weenieing out because of the dreadful ensemble runs lately but it's not unrealistic.

[Webberweather53]

Anyone know the reasoning for this tendency for the Aleutian Low to migrate west in +ENSO/+PDO winters?

 

Pardon me for not responding earlier to this question. I think the retraction of the Aleutian Low you observed in the analogs is somewhat random & is likely a reflection of small sample size, however you do bring up an interesting point. I've noticed in my analysis that the Aleutian Low w/ stratification for ENSO intensity, placement (Modoki/Central Pacific, Hybrid, & Traditional/East-Based) & the PDO state as well as regression of the PDO/ENSO 500mb there is a tendency towards a southward shift of the Aleutian low from December to January (possibly related to the influence of ENSO, PDO, WAF, etc. on the NAM/AO, forcing a negative state in January & February, hence forcing the Aleutian Low to the south) there's very little-no noteworthy westward shift in the Aleutian Low, apart from some of the weaker, more central Pacific based warm events where the low height signal for Aleutian Low is already rather weak & transient in nature & an eastward shift isn't all that hard to come by.

 

These papers should further shed some light on your question & the one significant point that is made in the 2nd paper is that the Aleutian Low is stronger & displaced further north & west in -AO El Nino winters & vis versa with +AO El Ninos, which given the information presented in my last post regarding the low heights in the North Pacific & stratospheric warming events, makes some sense...

http://onlinelibrary.wiley.com/store/10.1029/JC090iC01p00857/asset/jgrc3394.pdf?v=1&t=i3axvuql&s=0a0b029df80a2b9e829120234cbc9cb57d086e0b

 

http://www.pmel.noaa.gov/foci/publications/2006/bondG700.pdf

[Webberweather53]

Allan Huffman made an interesting tweet/observation earlier today & I think it's worth sharing. He noticed the striking similarities between this year through December 19th and 2006. However, before anyone starts to worry about this year being a torch until February like 2006, I want to point out though that the largest difference in the height anomalies is over Northern Eurasia & Siberia. Notice in 2006 the Siberian high during this period is virtually nonexistent, but this year it's quite strong. (thanks SAI/SCE).. This certainly implies a more rapid decay of the stratospheric polar vortex, thus given the SSWE in 2006 didn't begin in earnest until late January, I anticipate that if we are to experience a sudden stratospheric warming event, it should occur at least a few weeks earlier, perhaps beginning in either late December or early January. This is also supported by my previous post highlighting stratospheric warming precursors in the height field by mid December, especially over the North Pacific, and if this happens to verify it would equate to a warming event commencing no earlier than the last week of December (i.e. around Christmas)...

[griteater]

Pardon me for not responding earlier to this question. I think the retraction of the Aleutian Low you observed in the analogs is somewhat random & is likely a reflection of small sample size, however you do bring up an interesting point. I've noticed in my analysis that the Aleutian Low w/ stratification for ENSO intensity, placement (Modoki/Central Pacific, Hybrid, & Traditional/East-Based) & the PDO state as well as regression of the PDO/ENSO 500mb there is a tendency towards a southward shift of the Aleutian low from December to January (possibly related to the influence of ENSO, PDO, WAF, etc. on the NAM/AO, forcing a negative state in January & February, hence forcing the Aleutian Low to the south) there's very little-no noteworthy westward shift in the Aleutian Low, apart from some of the weaker, more central Pacific based warm events where the low height signal for Aleutian Low is already rather weak & transient in nature & an eastward shift isn't all that hard to come by.

 

These papers should further shed some light on your question & the one significant point that is made in the 2nd paper is that the Aleutian Low is stronger & displaced further north & west in -AO El Nino winters & vis versa with +AO El Ninos, which given the information presented in my last post regarding the low heights in the North Pacific & stratospheric warming events, makes some sense...

http://onlinelibrary.wiley.com/store/10.1029/JC090iC01p00857/asset/jgrc3394.pdf?v=1&t=i3axvuql&s=0a0b029df80a2b9e829120234cbc9cb57d086e0b

 

http://www.pmel.noaa.gov/foci/publications/2006/bondG700.pdf

 

Webber - thanks for the reply.  That first paper may be behind a paywall, so I didn't see it.  I did look through the 2nd one.  One thing I didn't like in there was how they put together the +AO vs. -AO composites across all ENSO strengths and PDO phases.  From what I've seen, there is a stronger correlation with the Aleutian Low positioning based on the ENSO strength (Nino strength) and PDO phase...I think it would make sense to first establish those tendencies, then apply the +AO vs. -AO comparison to further capture the differences.

 

At any rate, regarding the original question on the west movement of the Aleutian Low through the winter, it may be as simple as this...for winters that feature an Aleutian Low in the means, and that begin with the Aleutian Low in the Gulf of Alaska in Dec, the natural tendency will be for it to retrograde to the west through the winter in the absence of strong east-based forcing (typically associated with strong El Ninos).

[GaWx]

 1) Grit, interesting.

 

2) Meanwhile, the wishy washy good doc is back to being colder for the SE US still again! It has gone back and forth soooo many times indicative of a low confidence period. It now has highs no higher than the 40's for most on 12/10-11 with clearcut freezes for many for both mornings as well as for a decent % on 12/12. NC still has highs in the 40's on 12/12 with light freezes for many there on 12/13. So, a mini cold snap island within a sea of mild perhaps? We'll see.

[SnowGoose69]

 1) Grit, interesting.

 

2) Meanwhile, the wishy washy good doc is back to being colder for the SE US still again! It has gone back and forth soooo many times indicative of a low confidence period. It now has highs no higher than the 40's for most on 12/10-11 with clearcut freezes for many for both mornings as well as for a decent % on 12/12. So, a mini cold snap island within a sea of mild perhaps? We'll see.

 

If its correct on how big the NE U.S. system is it will be right because that sucker will dig at 500mb so much it will bring cool air all the way down, if the GFS is right it will be way warmer.

[GaWx]

If its correct on how big the NE U.S. system is it will be right because that sucker will dig at 500mb so much it will bring cool air all the way down, if the GFS is right it will be way warmer.

 

Snowgoose,

 Yeah, I see the GFS and Euro continue to be miles apart in addition to the Euro, itself, wavering on whether or not the SE gets in on some decent intensity and duration of cold next week. The period of ~12/11-12 has been wavering for several days now due largely to that NE storm.

[Webberweather53]

Webber - thanks for the reply.  That first paper may be behind a paywall, so I didn't see it.  I did look through the 2nd one.  One thing I didn't like in there was how they put together the +AO vs. -AO composites across all ENSO strengths and PDO phases.  From what I've seen, there is a stronger correlation with the Aleutian Low positioning based on the ENSO strength and PDO phase...I think it would make sense to first establish those tendencies, then apply the +AO vs. -AO comparison to further capture the differences.

 

At any rate, regarding the original question on the west movement of the Aleutian Low through the winter, it may be as simple as this...for winters that feature an Aleutian Low in the means, and that begin with the Aleutian Low in the Gulf of Alaska in Dec, the natural tendency will be for it to retrograde to the west through the winter in the absence of strong east-based forcing (typically associated with strong El Ninos).

 

 

Sure, no problem, hopefully this link works & you should at least be able to see the abstract if you aren't able to see it by looking at the PDF version...

http://onlinelibrary.wiley.com/doi/10.1029/JC090iC01p00857/abstract

 

I threw in the 2nd article to present another factor that has a measurable influence on the Aleutian Low & I think you may have misinterpreted its purpose, as they were well aware of the PDO's influence and it does indeed have a larger effect (especially w/ stronger signals) on the strength/intensity Aleutian Low, however for the purpose of that paper, they were concerned with examining the influence of the AO & ENSO only. One key point mentioned that makes sense knowing the behavior of the NAM to the Aleutian Low which along w/ the Siberian High is a primary determinate in imparting WAF on the polar vortex... "During El Nino, both phases of the AO are associated with anomalously low 500 hPa heights extending from the Bering Sea southeastward into the North Pacific, but the center of the composite anomaly for AO− (Figure 1(a)) is deeper and located to the northwest of its counterpart for AO+ "

 

 

Stratifying the El Ninos by placement & intensity as I mentioned in previous response reveals the most significant behavior noted in the Aleutian Low across the board is its southward displacement from December to January in response to the decreasing NAM state. Westward progression of the Aleutian Low as it pertains to the intensity & placement of El Ninos is negligible at best, and it's behavior becomes generally more erratic with decreasing El Nino intensity . Any further categorization of the events is superfluous at this juncture (such as Modoki-Weak, Hybrid-Strong, etc) because the sample size is far too insignificant for any confident analysis (a reflection of the relative lack of data we're up against on a daily basis in this field) except for perhaps the Moderate-Hybrid composite (which exhibits an appreciable amount of internal variance on its own) and has 6 events (1951-52, 1986-87, 1991-92, 1994-95, 2002-03, 2009-10)...

 

In case you're curious as to my determination of "hybrid" events, they are simply denoted as El Ninos w/ +SST anoms. in the NINO 1-2 region (thus not a modoki) while having core of the strongest +SSTs outside NINO 1-2... I first encountered issues with El Nino categorization in interactions w/ HM several months ago & it was made fairly clear to me that profound confusion exists over what precisely is a central Pacific or east based El Nino. I've also come across a loose conglomerate of methodologies with their own different flavor & when you attempt to explain the internal variance of a multifaceted, elusive phenomena such as El Ninos with two dimensional indices, you're going to run into problems and I concur with others such as Mike Ventrice for example that we are in need of major revisions to our current El Nino categorization, because it is atrocious... Additionally, I found the modoki term to be rather meaningless because it only describes a brief snapshot of the total evolution of an El Nino event, and the majority of El Ninos were at some point in their evolution east based, but the timing & strength of the oceanic Kelvin Wave as it relates to the typical boreal winter phase locking often observed w/ ENSO can determine the degree an east-based event fades into a modoki, with weaker events being naturally more vulnerable to variations in upwelling & hence revealing (especially later in the winter) -SST anomalies in the NINO 1-2 region, where as stronger El Ninos often don't observe such a SST distribution (if @ all) until much later in their lifespan. Although I admit what I'm doing is certainly not perfect, it's better than what we currently have, w/ a El Nino category describing events that don't completely fulfill the Traditional or Modoki definitions.. I really like how the SST, 500mb, & US temps anomalies look, nice flow & progression through each category...

 

 

 

Combining the Monthly US temps based on the intensity & placement of the El Nino, our current temperature distribution makes a lot of sense. January looks to be a huge 180 from this upcoming pattern & February continues to look confidently cold, especially here in the southeastern US, better times likely lay ahead...

 

 

Looking at the verification for November, the Hybrid-Moderate events take the cake. The Modoki composite is laughable...

 

 

[DaculaWeather]

I wish I could show you the Euro Ensemble Control but damn. 31st has 534's into Georgia. Massive trough. 

[packbacker]

I wish I could show you the Euro Ensemble Control but damn. 31st has 534's into Georgia. Massive trough. 

 

Yeah I saw that, it has -20+ 850's all the way down to ATL, -10 down to ORL and -5 down to MIA.  

[Cold Rain]

I wish I could show you the Euro Ensemble Control but damn. 31st has 534's into Georgia. Massive trough. 

 

Draw a Wilkes picture in paint and post it!

[packbacker]

Draw a Wilkes picture in paint and post it!

 

LOL, 850 temps looks like this...but a little colder and focused a litter further south.  

[Cold Rain]

Nice, that's a good look, Pack!

[packbacker]

Lots of SSW chatter starting to gain steam for the next few weeks, Eric talked about it yesterday.   All I know is the GFS has been increasing the warming at 10mb day 10+ for several runs now.  Hopefully the 12z run keeps it up.  I only have the Euro out to 10 days so hopefully in a couple of day it starts showing the same.

[Jon]

I was going to post this yesterday but it didn't post. Sorry for the MS Paint. I'm liking the way the GEM ensemble mean looks in the LR. Looking at the Euro weeklies only confirm this type of setup if you're hugging the Euro weeklies (Which I would). When I was looking at the GEM, I drew in my own trough cause there simply wasn't any negative anomaly near the east but I knew there had to be one, and  if you look at the newer runs it's obviously there now. Also I'm not saying we want the trough there, but we just want a trough and we're going to get our +PNA question is for how long and will an -NAO develop.

 

 

Check out the canadian ensemble mean late, notice the bottom image is Dec 18th and Top is Dec 20th. What do we see? We see Scandinavia with a deep anomaly for an ensemble this far out. Any run you look at you see deep anomalies here including the new Euro weeklies that came out, and GEM OP runs. I haven't been looking at individual GFS runs because of the image I'm about to post below but the models are finally going to start sniffing out a pattern change for the last half of the month. I think there's going to be a trough over scandinavia most likely going to be in the -300's or so (green in the bottom color bar) when it comes to fruition. The top image (Dec 20th) shows my thoughts of what this model is trying to sniff out. When Scandinavia is having fun, so are we. The ridge in the bottom image is misplaced, and the trough in the top image (which was deep over Scandinavia) is now spread out into greenland which is a fault of the ensemble mean. If you look at control runs you can see the evolution and this pattern being sniffed out. The trough anomaly near the east coast in the bottom image is larger and deeper in the new runs.

 

 

 

GFS individual ensemble members and why the GFS ensemble is struggling (below). Notice some of the members show a favorable, at least for it being this far out, pattern for the US. WC ridge EC trough. It's just going to take some time (roughly mid month) until these models and means start spitting out stuff that's actually realistic. You can look at the MJO and warming all you want but the fact is the modeling is crap right now and just know anything is possible come Dec 20 to the end of the month, especially heading into January. I think we'll get the pattern set up just in time for ample opportunities. Maybe it's wishcasting, but anything is on the table right now.

[FallsLake]

Man that's a big change on the 12z GFS. Much colder in the LR. You would think it's setting us up for something good just before X-mas.  

http://mag.ncep.noaa.gov/Image.php?fhr=384ℑ=data%2Fgfs%2F12%2Fgfs_namer_384_850_temp_mslp_precip.gif&model=gfs&area=namer&param=850_temp_mslp_precip&group=Model+Guidance&preselected_formatted_cycle_date=20141205+12+UTC&imageSize=M&ps=model

[Jon]

Man that's a big change on the 12z GFS. Much colder in the LR. You would think it's setting us up for something good just before X-mas.  

http://mag.ncep.noaa.gov/Image.php?fhr=384ℑ=data%2Fgfs%2F12%2Fgfs_namer_384_850_temp_mslp_precip.gif&model=gfs&area=namer&param=850_temp_mslp_precip&group=Model+Guidance&preselected_formatted_cycle_date=20141205+12+UTC&imageSize=M&ps=model

Yeah, I'm hoping the new weeklies show an earlier change instead of around the end of the month. It wouldn't surprise me to get this earlier, after the 20th, maybe the 22nd-25thish area. Just waiting twiddling my thumbs on new output and means to look at. Can't wait for the weeklies, haha. The block over the top on Jan 1st on the weeklies is just nasty.

[GaWx]

Yeah, I'm hoping the new weeklies show an earlier change instead of around the end of the month. It wouldn't surprise me to get this earlier, after the 20th, maybe the 22nd-25thish area. Just waiting twiddling my thumbs on new output and means to look at. Can't wait for the weeklies, haha. The block over the top on Jan 1st on the weeklies is just nasty.

 

Jon,

 Actually, the weeklies' week 3 (12/22-8) shows the change taking place then (warm early and cold late, which is consistent with the prior run) to bring us to the full cold week 4 (12/29-1/04).

[packbacker]

Man that's a big change on the 12z GFS. Much colder in the LR. You would think it's setting us up for something good just before X-mas.  

http://mag.ncep.noaa.gov/Image.php?fhr=384ℑ=data%2Fgfs%2F12%2Fgfs_namer_384_850_temp_mslp_precip.gif&model=gfs&area=namer&param=850_temp_mslp_precip&group=Model+Guidance&preselected_formatted_cycle_date=20141205+12+UTC&imageSize=M&ps=model

 

The GEFS so far keep us (SE-E) cooler than average the next 10 days, granted it's not a snow pattern though.  The 6z GEFS run was a torch days 11-15 for everyone, curious if any changes occur today.  

[LithiaWx]

JMO, since I've been on the warm bandwagon for a while.  I'm still seeing a few signs that a real change could be developing after the 20th.  I can assure everyone I wouldn't be saying that I see signs if I wasn't.  Time will tell but the trends are good, albeit slow.  I don't think the people saying a change is coming are grasping at straws like a few other posters said.