Winter 2015-2016 Medium-Term Discussion

[nycwinter]

how can anyone write off winter already when it officially begins dec 22.. only a numbskull would do such a thing....

[Great Snow 1717]

The journey through Winter 2015-16 has now passed the mid-point of December. Much of North America has wandered horribly off course. Did North America lose its seasonal maps or GPS?

 

Rather than encountering the rising Arctic blasts and periodic blankets of snow typical of deepening winter, much of North America has instead found itself locked into a seemingly endless inferno relative to seasonal norms. As of December 16, cities such as Chicago, Detroit, Minneapolis, New York, and St. Louis have accumulated monthly temperature anomalies of 10° or more above normal. New York City has already shattered its December record for the most days on which the minimum temperature has remained at 50° or above. Buffalo has yet to experience a measurable snowfall.

 

Put simply, a nightmare is unfolding. A hypothetical scenario for a record-breaking El Niño (http://www.americanwx.com/bb/index.php/topic/46340-possible-strongsuper-el-ni%C3%B1o-forming/page-31#entry3660754) suggested that such a nightmare was plausible. Both the latest CFSv2 forecast for January and the January outcome from that hypothetical scenario provide little relief for those in search of winter.

 

 

The latest trimmed objective analog pool from the GFS ensembles suggest that cities such as Boston, Chicago, Detroit, New York, Philadelphia, and St. Louis have a high to very high probability of experiencing a warmer than normal January 1.

 

Some may well be tempted to write off winter even before it has had a chance to exert its influence. Yet, even as such a nightmare scenario cannot fully be dismissed (especially with the ensembles pointing to a continuation of the EPO+/AO+/PNA- teleconnection combination through the remainder of December), there remain suggestions that this nightmare can pass.

 

First, a number of El Niños (1957-58, 1965-66, and 2006-07) featured a dramatic turnaround from seemingly endless fall to winter.

 

Second, among the GFS ensembles’ objective analogs are cases from those three “turnaround” winters.

 

Third, even as it has been dented, the PDO remains positive. That scenario favors a PNA+ pattern, so it remains more likely than not that the PNA- regime will eventually yield to the return of the PNA+.

 

In short, even as Canadian and American snow geese alike have been worn down by day-after-day of unrelenting waves of warmth, there remains a reasonable prospect that Winter 2015-16 will awaken. Before then, the days ahead could bring more misery of warmth and hunger for snowfall.

 

Finally, winter is not absent from the entire continent. Alaska has been experiencing noted cold. The western third of North America is likely to experience often cooler than normal weather with prospects of above normal snowfall through much of the second half of December. In fact, the same objective analog pool suggested that Seattle had an implied 57% probability that January 1 would wind up colder than normal. In short, winter has a toehold in parts of North America. So long as all the cold is not driven to the other side of the hemisphere, there remains hope for a change, especially when the “turnaround” El Niño cases are considered. Therefore, I am not ready to "cancel" winter even as the mercury rises yet again into the balmy 50s as I post these thoughts.

Don,

  As always thank you for your fantastic contributions to the board. I'm not the least bit surprised that we are looking at a potential nightmare scenario for  this winter considering the overall warming trend of winters during the last 30-35 years. Sooner or later we are/were due for a nightmare scenario winter. 

[scottmartin49]

My biggest surprise so far? It would be truly shocking to accept the CFSv2 was actually 'right'.

[Bubbler86]

how can anyone write off winter already when it officially begins dec 22.. only a numbskull would do such a thing....

 

 

Considering there is little chance of meaningful winter through early January and the fact that "real winter" for most on this board is late Nov through Late Feb, winter is at least 1/3 to 1/2 over by the time any cold can get here.  Cannot cancel winter but one can worry about it at this point.

[donsutherland1]

The Return of the PNA+?

 

Across much of North America, when one steps outside, one finds December 2015 lies in charred ruins. Where there should be a blanket of freshly fallen snow, one finds, barren ground, green grass, and even occasional buds and blossoms. In cities where the thermometer should routinely drop to freezing or below, getting there is a seemingly hopeless ordeal. In place of a typically biting North wind, balmy breezes have largely vanquished the concept of wind chill.

 

Just beyond the first half of December, much of North America has been covered by an ocean of warmth. If one looks at the latest CFSv2 idea for January, that model expects more of the same.

 

If one looks at the latest objective analogs from the GFS ensembles, one finds 1988-89 and 2001-02 in the mix (20% of the 8-day and 11-day analogs).

 

Nevertheless, that does not mean that December’s warmth will roll on through the winter until the arrival of spring.

 

First, the CFSv2 is still outside its skillful range for its month ahead forecast.

 

Second, since 1870, there were three prior El Niño cases that saw overwhelming coverage of December warmth similar to what has been the case so far this month: 1877-78, 1941-42, and 1957-58. 1877-78 saw some relaxation of the warmth in January. 1941-42 and 1957-58 featured a much larger turnaround.

 

 

Third, the same pool of objective analogs includes the turnaround winters of 1957-58 and 2006-07. In fact, those winters account for 30% of the analogs.

 

Fourth, the latest GFS ensemble guidance suggests the possibility of a return to PNA+ values around December 27-28. In 1957-58 and 1965-66, the return of PNA+ values coincided closely to the return of Arctic Oscillation blocking.

 

 

For now, relentless waves of warmth continue to roll across North America, one after another. Nevertheless there are some hints of possible future change. Within 6-8 days, a more sustained period of colder weather is likely to overspread western Canada and the western United States. Whether one witnesses the birth of a trough in the East will depend on how the pattern evolves from there. A return of the PNA+, if it occurs, could facilitate that process.

 

Should such a scenario play out, the next question would be whether winter would make a temporary stay over a small part of the Continent (as happened in 1877-78) or a much more sustained and widespread stay as happened in 1941-42 and 1957-58.

[Isotherm]

Don - not sure if you meant to utilize 1940-41 rather than 41-42 in your analog pool? 1940-41 was the stronger of the two El Nino's, and also featured a reversal from CONUS torch December to colder Jan/Feb. Nevertheless, it appears both of those years were Nino's which featured the second half reversal.

[leo2000]

Don - not sure if you meant to utilize 1940-41 rather than 41-42 in your analog pool? 1940-41 was the stronger of the two El Nino's, and also featured a reversal from CONUS torch December to colder Jan/Feb. Nevertheless, it appears both of those years were Nino's which featured the second half reversal.

 

Hi Isotherm, I hear a lot about the vortex breaking down too and a split. Many meterologist's are now declaring that they are thinking a pattern change from January 10th onward. 

 

Joe Bastardi ‏@BigJoeBastardi  Dec 16Pennsylvania, USA

HT http://www.tropicaltidbits.com/  major stratospheric warming develops wk 3/4. Precursor to flip to colder east Jan 10 on

 

EPAWx Authority ‏@epawawx  21h21 hours ago

Indisputable fact: ALL guidance now shows a weakening of the PV through several SSWE events. 2nd week of January pattern flip with lag time.

[donsutherland1]

Don - not sure if you meant to utilize 1940-41 rather than 41-42 in your analog pool? 1940-41 was the stronger of the two El Nino's, and also featured a reversal from CONUS torch December to colder Jan/Feb. Nevertheless, it appears both of those years were Nino's which featured the second half reversal.

When working on my list, I also filtered the data using a Nov-Dec MEI value of +1 or above. That's why I didn't use 1940-41, but that El Niño also featured widespread December warmth followed by widespread cold, especially in February and March. The November Armistice Day storm in the Plains and March 1941 blizzard were additional highlights of that winter.

[coh]

Have there been any other cases that featured the kinds of magnitudes of December warmth (not just area covered) seen this year and in 1877? That's what really jumps out from the set of plots shown a few posts ago.

[donsutherland1]

Have there been any other cases that featured the kinds of magnitudes of December warmth (not just area covered) seen this year and in 1877? That's what really jumps out from the set of plots shown a few posts ago.

December 1939 came close. January 1940 featured widespread cold with the Pacific Coast being an exception.

 

December 1889 had extreme warmth centered over the CONUS while a lot of Canada was close to normal. The winter remained generally warm across much of the CONUS except for the West, which was very cold in January.

[leo2000]

Looks like the AO is going strongly negative as well. As well as a negative drop in the NA0. Possible slightly negative EPO as well. 

[NittanyWx]

 

 

Second, since 1870, there were three prior El Niño cases that saw overwhelming coverage of December warmth similar to what has been the case so far this month: 1877-78, 1941-42, and 1957-58. 1877-78 saw some relaxation of the warmth in January. 1941-42 and 1957-58 featured a much larger turnaround.

 

 

 

 

1982 isn't a bad fit either here Don.

[Rainman]

Looks like the AO is going strongly negative as well. As well as a negative drop in the NA0. Possible slightly negative EPO as well. 

 

It goes barely negative for like a day.

[donsutherland1]

1982 isn't a bad fit either here Don.

I agree, NittanyWx.

[The_Global_Warmer]

Looks like the AO is going strongly negative as well. As well as a negative drop in the NA0. Possible slightly negative EPO as well.

Not really.

[PB GFI]

The AO does not go NEG.

But the EPO does around the 1st on the euro weeklies.

Weeks 3 and 4 take 850 anomalies from plus 2 to N in N/E and the Northeast.

Good to see the weeklies with hints of N .

[leo2000]

The AO does not go NEG.

But the EPO does around the 1st on the euro weeklies.

Weeks 3 and 4 take 850 anomalies from plus 2 to N in N/E and the N .

Good to see the weeklies with hints of N .

Sorry your right I am still learning. 

[leo2000]

The AO does not go NEG.

But the EPO does around the 1st on the euro weeklies.

Weeks 3 and 4 take 850 anomalies from plus 2 to N in N/E and the N .

Good to see the weeklies with hints of N .

That is good the EPO goes negative though really helps out in my area as well. 

[40/70 Benchmark]

1982 isn't a bad fit either here Don.

1941 is my other main analog, along with 2006.

[donsutherland1]

After spending five days below 0 and having fallen as far as -1.084, the Arctic Oscillation (AO) returned to positive values today (+0.644). So far, the AO is averaging +0.828 this month and has been positive on 72% of the days.

 

The latest ensemble guidance shows the AO returning to strongly positive values in coming days and likely to remain predominantly positive to strongly positive the remainder of December and into the first days of January.

 

 

Given the AO forecast, a monthly average of +1.000 or above appears likely. However, even if the AO forecast proves accurate, that does not automatically mean that a scenario similar to 1988-89 that saw the AO remain predominantly positive to strongly positive throughout January and February is assured.

 

At least two big AO regime changes occurred followed the AO’s rebounding to strongly positive values at the end of December. On December 31, 2004, the AO rose to +3.133 and averaged +3.532 during the January 1-10, 2005 period. On December 30, 2006, the AO reached +3.640 and averaged +3.604 for the January 1-10 period and +3.342 for the January 1-5 timeframe.

 

Both winters saw blocking develop during the second half of January and blocking throughout much of February. On January 21, 2005, the AO went negative and was predominantly negative to strongly negative through March. On January 21, 2007, a short period of blocking developed. Sustained blocking took hold on February 1 and lasted through February 26.

 

Of course, during the nightmare of 1988-89, the AO fell below 0 on just 1 day (-0.318 on March 4, 1989) out of the 104-day period running from January 1, 1989 through April 14, 1989. Even then, much of the CONUS saw colder-to-much colder than normal temperatures during February 1989.

 

In short, two points are important:

1. The return of strongly positive AO values does not mean that blocking must largely be written off this winter.
2. Even if the AO+ predominates, other aspects of the pattern can still allow for wintry weather during parts of January and/or February.

[bheberto]

A look at the latest JAMSTEC model http://www.weather5280.com/blog/2015/12/18/updated-jamstec-model-and-beyond-el-nino/ 

[donsutherland1]

At 2:54 pm, Buffalo reported light snow and 33°.

 

 

If Buffalo receives 0.1" or more snow, that will be Buffalo's first measurable snowfall since April 4, 2015 when 0.3" fell. The 257-day stretch without measurable snow is Buffalo's longest such period.

[donsutherland1]

Buffalo has now had its first measurable snowfall of the season. From the NWS in Buffalo:

 

NWS BUFFALO ‏@NWSBUFFALO 27m27 minutes ago

Buffalo airport records its first measurable snow of the season. http://ow.ly/i/flCjs

[CoastalWx]

So can this warm December be firmly attributed to El Nino?  I take it for granted that AGW makes any warm spell more severe than it would otherwise be, but the magnitude of the warmth stands out liek a sore thumb compared to the last few years.

 

This hasn't been your text Nino December with a warm east/southeast and cooler NW. Nino definitely had a say in this, but there probably was some other intraseasonal things going on to create that look. Not much of a STJ over the south.

[donsutherland1]

Hints of Change?

 

If one examines the 8-day and 11-day GFS ensembles, one finds that 50% of the ensemble years from the 8-day pool are replaced in the 11-day pool. This lack of consistency can occur ahead of evolving pattern changes. 

 

If one proceeds to look at the trimmed pool of common objective analog cases, on finds four winters: 1954-55, 1974-75, 2006-07, and 2007-08. The area of December warmth from that pool is reasonably similar to the warmth that has covered North America to date, though it is of lesser magnitude. January also shows a fair degree of warmth, but less than that shown on the CFSv2.

 

However, if one looks more closely at the second half of January, 3 out of the 4 cases feature widespread cold anomalies.

 

 

Whether or not the pattern will, in fact, change toward one that favors a lot more cold at some point during the second half of January remains to be seen. But at least some of the guidance provides a measure of possible support for that outcome. 

[donsutherland1]

During the past four weeks, there has been only a slight decay of the ongoing super El Niño. Below are the changes in anomalies for the ENSO regions for the week centered around December 16 vs. the week centered around November 18:

 

Region 1+2: +0.3°C

Region 3: -0.1°C

Region 3.4: -0.2°C

Region 4: -0.1°C

 

The average sea surface temperature in Region 4 has now been at or above 30.0°C for the last eight weekly periods. In coming weeks, some of the ENSO region cooling should pick up a little bit, but strong El Niño conditions appear likely to persist through much of January and perhaps February, as well.

 

However, as began to show up in the ensembles (Message #65), what had been a tentative signal for the return of a PNA+ pattern is now a more certain signal. As a result, one could begin to witness the development of some ridging in the West as 2016 approaches and arrives.

 

At the same time, some of the guidance suggests a potentially large drop in the SOI. Such an outcome during strong El Niño events has offen seen the development of a weak trough in the southeastern United States.

 

So all in all, it appears the that pattern responsible for what will likely be an historically warm December in parts of North America could yield to some relaxation. While the northern tier might well remain warmer than normal, the anomalies should be less excessive than they were in January. Cool shots could become somewhat more frequent and a little sharper.

 

In the West, where cool anomalies are likely for the closing 10 days of December, moderation will likely take place as January gets underway. It still remains to be seen whether this relaxation in the pattern will mark a longer-duration pattern change or a pause prior to the return of the predominant pattern that has provided for much above normal temperatures in large parts of North America during both November and December.

[WXeastern]

Out of the 5 Ninos thats considered strong on record (this one not counted yet). On average 4 had positive AO/EPO values during the month of December. The winter temp anomalies from those 4 show a warmer than normal northern US and a colder than normal southern US continental wide! I assume its because these nino winters turned back to negative AO/EPO/NAO during Jan and Feb.

 

[wxdudemike]

During the past four weeks, there has been only a slight decay of the ongoing super El Niño. Below are the changes in anomalies for the ENSO regions for the week centered around December 16 vs. the week centered around November 18:

Region 1+2: +0.3°C

Region 3: -0.1°C

Region 3.4: -0.2°C

Region 4: -0.1°C

The average sea surface temperature in Region 4 has now been at or above 30.0°C for the last eight weekly periods. In coming weeks, some of the ENSO region cooling should pick up a little bit, but strong El Niño conditions appear likely to persist through much of January and perhaps February, as well.

However, as began to show up in the ensembles (Message #65), what had been a tentative signal for the return of a PNA+ pattern is now a more certain signal. As a result, one could begin to witness the development of some ridging in the West as 2016 approaches and arrives.

At the same time, some of the guidance suggests a potentially large drop in the SOI. Such an outcome during strong El Niño events has offen seen the development of a weak trough in the southeastern United States.

So all in all, it appears the that pattern responsible for what will likely be an historically warm December in parts of North America could yield to some relaxation. While the northern tier might well remain warmer than normal, the anomalies should be less excessive than they were in January. Cool shots could become somewhat more frequent and a little sharper.

In the West, where cool anomalies are likely for the closing 10 days of December, moderation will likely take place as January gets underway. It still remains to be seen whether this relaxation in the pattern will mark a longer-duration pattern change or a pause prior to the return of the predominant pattern that has provided for much above normal temperatures in large parts of North America during both November and December.

Don,

I see you brought up the SOI drop which I've seen others allude to as well. Do you know if there has been any research done on SOI fluctuations (very short term) and the affect on the eastern US pattern or is more just tribal knowledge so to speak?

Sent from my Nexus 5X using Tapatalk

[WinterWxLuvr]

Out of the 5 Ninos thats considered strong on record (this one not counted yet). On average 4 had positive AO/EPO values during the month of December. The winter temp anomalies from those 4 show a warmer than normal northern US and a colder than normal southern US continental wide! I assume its because these nino winters turned back to negative AO/EPO/NAO during Jan and Feb.

Is there a reason that 97-98 is not in that list?

[donsutherland1]

Don,

I see you brought up the SOI drop which I've seen others allude to as well. Do you know if there has been any research done on SOI fluctuations (very short term) and the affect on the eastern US pattern or is more just tribal knowledge so to speak?

Sent from my Nexus 5X

I used the word "often" because the sample size is small. One can't be too certain. Below are some composite 500 mb and surface temperature anomalies (January):