Winter 2013-14 medium range discussion

[donsutherland1]

Hi Don,

 

I'm not sure I follow your +AO and MJO thoughts on risks for a warm december.  Despite a record positive AO, we are seeing especially cold bursts continue to hit the east coast once a week.  To me, the record positive AO is only going to increase the chances of a severe cold spell, if we do in fact see a -NAO develop given how cold it is in the Arctic.

 

With regards to the MJO, it's mostly been in the circle of death and not really flexing its influence.  I'm not sure why barely breaching into phase 1-3 would do anything significant for a warm december anyways.

Typically following a November when the AO is strongly positive, December winds up warmer than normal in the East. Since 1950, November has had 14 cases during which the AO averaged +0.500 or above for the month. 10/14 (71%) saw warmth focused in the East in December. There were four exceptions: 1975, 1977, 1993, and 2003. A warmer than average December does not preclude some shots of cold. The historical probabilities would argue that odds favor a warmer December.

 

As the wave lengths are still shorter than they typically are during the winter and the EPO has been favorable, November has witnessed regular shots of cold. I posted the temperature anomalies associated with the state of the teleconnections that prevailed during neutral ENSO months (Message #38). So, while it might seem somewhat implausible that a strongly positive AO has led to the kind of anomalies that have occurred to date, once all the teleconnections are considered for neutral ENSO periods, the outcome is not unusual.

 

Such cold shots are forecast to continue and while the 12z GFS might be overdone in the extended range, that forecast is probably closer to what might happen than the much warmer 0z run. Certainly, the pattern from the forecast teleconnections has been arguing that the 11/22-30 period would be colder than normal on average for some time. Indeed, the latest teleconnection cases show cold November anomalies where some of those anomalies have been developing in recent days and would continue to develop if the ECMWF and GFS are reasonably accurate. The center of the warmth that has been occurring in Europe is also reasonably respresented on the composite maps based on those cases. Unfortunately, those same cases applied to December support a warmer composite anomaly with a few exceptions e.g., 2000.

 

The MJO forecast has changed somewhat, with the MJO now forecast to swing back through Phase 8 and then into 1 or 2 in early December. Some guidance takes it out of the low-amplitude circle. If the MJO continues to progress through phases 3 and beyond during December, that would also favor the development of warmth. The shifting MJO forecasts have added a little more uncertainty to the mix, so we'll see how things turn out with the MJO down the road.

[uncle W]

if this is going to be a plus AO winter then a cold December could happen but the rest of the winter will be milder...1988-89 had a very positive AO...Only two days that winter had an AO in the minus column...December was cold with record breaking cold around the 12th...there was very little snow that month...1989 was another + ao winter and it had the very cold December and mild January and February...Both years had their coldest temperature in December with very little snow...The AO and NAO are forecast to dip to more normal levels or go negative...If enso continues to warm we could be seeing a plus neutral winter...I'm hoping the AO hits its lowest point sometime during January and February...This way we could see at least some significant snowfall then...

[wildweatherman179]

Just wanted to say hello and I really have enjoyed reading your discussion here. So much so that I had to join the site. Hopefully there are some intelligent thoughts I may be able to contribute at times.

[Absolute Humidity]

Just wanted to say hello and I really have enjoyed reading your discussion here. So much so that I had to join the site. Hopefully there are some intelligent thoughts I may be able to contribute at times.

Welcome to Americanwx

[wildweatherman179]

Thank you. I was wondering, I see all of the discussion about the AO/NAO and the potential for them to be positive this year. If positive or negative, what are the possible effects if any on the temperature/storm track here in the south central US. Is it possible that the PNA is a larger prognosticator for the weather in this part of the nation this year than the NAO? It may be a completely stupid question altogether because I do understand what the AO tends to do for temperatures here but the other 2 oscillations I'm a little more unsure of. Thanks.

[griteater]

Is the stratosphere frigid in Siberia like what some people are claiming?

Based on posts I've read from skierinvermont, his findings are that a colder than normal stratosphere at 70mb in central and east Asia in November strongly favors a +AO for Dec and Jan, with that correlation breaking down in Feb. I can't post the images now, but I looked yesterday and so far this Nov, the stratosphere temps are running below normal in east Asia at 30, 50, and 70mb. We'll have to see how the temps look at month end. Other Oct indicators favor a +AO as well. The SAI was likely something around +1.25 based on cfbagget's graphs and a comparison with the SAI from Oct 2007. Related to the SAI, the Siberian High across northern Eurasia was weaker than normal in Oct which correlates to a +AO. Finally, the new OPI was +1.60, also showing a + AO signal. We will obviously have to see how it plays out, but many of the Oct/Nov indicators point to a +AO, potentially moderate to strongly positive.

[donsutherland1]

Thank you. I was wondering, I see all of the discussion about the AO/NAO and the potential for them to be positive this year. If positive or negative, what are the possible effects if any on the temperature/storm track here in the south central US. Is it possible that the PNA is a larger prognosticator for the weather in this part of the nation this year than the NAO? It may be a completely stupid question altogether because I do understand what the AO tends to do for temperatures here but the other 2 oscillations I'm a little more unsure of. Thanks.

AO and EPO have about an equal correlation in eastern Oklahoma. In western Oklahoma, the EPO has a slightly stronger correlation. Precpitation is positively correlated with both the EPO and AO. Hence both an EPO+ and AO+ would favor a little more precipitation.

[wildweatherman179]

Thank you Don. That helps me fill in a couple of variables I was looking for. It looks like a pretty decent winter for snow here as long as the southern storm track verifies. Correct?

[CVA]

The Pacific certainly trumps any of the Atlantic indices. This seems to be heading into one of those winters where the Atlantic side really doesn't matter that much nor the AO. There's been some great posts in SNE forum from mets on why that might be the case this year..and why we may be looking at a cold winter. Perhaps that's what the Euro seasonal and CFS are keying on .

 

But the Euro seasonal has a warm signal for almost the entire continental US for DJF. 

[SnowGoose69]

One of the things gnawing at me is Nov 78 and 93 vs Nov 94 and 11?? Anyone wanna guess why? The outcomes were totally different BUT WHY? Thus why was 78-79/93-94 so cold were as 94-95/11-12 the total opposite? BOTH sets had the Nov +AO? So what made the difference? Enso? QBO? Solar? Something else or perhaps a combo of all?

 

Adding to what Will posted, it also seemed to me in 93-94 the polar vortex was just absolutely monstrous, you probably could have had that same pattern again another winter with the EPO/NAO/AO state the same and had a very mild winter with little snow because the vortex simply would not have been big enough to drop the cold air down below 45N, overall that winter had alot of good timing for snow events more than anything else.  There were quite a few locations in the Southern Plains and TN Valley I think that had their least snowiest winters on record that year, I believe both Memphis and Wichita did and alot of the SE was mild. I remember how warm it was down in Florida when I was there twice that winter.

[tacoman25]

I know a lot of the discussion has been regarding the signs pointing towards +AO, especially the first half of the winter, but what are people seeing in regards to the EPO. The AO and EPO certainly don't always go hand in hand, and it seems like some of the prominent analogs to this year had significant -EPO periods....especially from late December to early February.

[uncle W]

the AO was close to +4.300 today...Highest since 12/2/2011...The last time there were two consecutive days with the AO +4 or higher was in Feb. 2008...the last time we have seen +4 in November was in 1994..1994 was +4.444 on 11/20 and four 4+ AO days that month...November 2, 1978 had a +4.544 AO...78 had two days with a +4 AO...

[donsutherland1]

Today, the Arctic Oscillation stood at +4.287. That was the second highest figure on record for November 15. The daily record is 4.363, set in 1994. It is also the 4th highest figure on record for November and only the 7th November reading at or above +4.000. In contrast, the EPO was strongly negative.

 

The ENSO + teleconnection combination still suggests warmth in the CONUS for December and cold anomalies across a large section of Europe. Those themes are consistent with repeated daily analyses of the partial teleconnection cases (excluding ENSO).

 

 

The 11/15 0z run of the GFS ensembles (312 hours through 360 hours) hinted that the cold anomalies would be retreating toward the area outlined for the most notable cold anomalies on the above maps. The animation is below:

 

 

Often pattern changes are rushed on the guidance, so it remains quite plausible that November ends cold and December starts cold with a transition toward the milder pattern perhaps unfolding in the 12/5-10 timeframe. That idea continues to be supported in rolling forward the partial teleconnection cases. Nevertheless, at this time, uncertainty remains quite high. Should the more extreme blocking shown by some ensemble members develop and wind up being sustained, that development could increase odds of a colder outcome in North America to go along with the trend toward a colder outcome in a large part of Europe.

[okie333]

This morning, the Arctic Oscillation (AO) Index stood at +3.716. That's the highest reading since December 25, 2011 when the AO was +3.824. A number of ensemble members forecast the AO to peak at or above +4.000. The November montly record is +4.544, which was set on November 2, 1978. In the extended range, the MJO is forecast to be meandering through Phase 1, which may suggest a continuation of mild periods alternating with some cool shots. If so, the ridge in the West/trough in the East showing up on the ensembles for the extended range could be transient.

 

In the meantime, on a more wintry note, it does appear increasingly likely that Baltimore, Philadelphia and New York City and adjacent suburbs could see some snowflakes overnight into tomorrow morning with some coatings on grassy surfaces. Cities such as Cleveland and Pittsburgh might pick up a light accumulation of snow tonight.

 

I wouldn't mind a 1978 repeat...

[donsutherland1]

Brief morning thoughts...

 

1. AO: +4.317 (beats old daily record of +3.754 set in 1994) and is the 4th highest on record for November. The AO is forecast to go negative in the long range. Big question: Will that mark a temporary departure from the predominant winter pattern or a more persistent blocking regime? Odds still favor the former.

2. EPO looks to remain primarily neutral or negative through the rest of the month.

3. Partial daily teleconnection cases from today's data rolled forward to December maintain anomaly ideas similar to those shown in Messages #57 and #73, both for Europe and North America.

4. The latest CFSv2 monthly took a step toward the above-referenced ideas for North America, but remain warm for Europe.

[uncle W]

Brief morning thoughts...

 

1. AO: +4.317 (beats old daily record of +3.754 set in 1994) and is the 4th highest on record for November. The AO is forecast to go negative in the long range. Big question: Will that mark a temporary departure from the predominant winter pattern or a more persistent blocking regime? Odds still favor the former.

2. EPO looks to remain primarily neutral or negative through the rest of the month.

3. Partial daily teleconnection cases from today's data rolled forward to December maintain anomaly ideas similar to those shown in Messages #57 and #73, both for Europe and North America.

4. The latest CFSv2 monthly took a step toward the above-referenced ideas for North America, but remain warm for Europe.

thanks Don...can you link where you get the daily ao numbers...I lost that link a while ago...one can only hope this year turns out like 1978-79 but my gut feeling now is a winter similar to 1988-89...Atlantic city did get a blizzard in February 1989 so there is some hope...

[donsutherland1]

thanks Don...can you link where you get the daily ao numbers...I lost that link a while ago...one can only hope this year turns out like 1978-79 but my gut feeling now is a winter similar to 1988-89...Atlantic city did get a blizzard in February 1989 so there is some hope...

The daily numbers can be found here: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/history/history.shtml

[uncle W]

The daily numbers can be found here: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/history/history.shtml

bookmarked...thanks again...

[Wow]

thanks Don...can you link where you get the daily ao numbers...I lost that link a while ago...one can only hope this year turns out like 1978-79 but my gut feeling now is a winter similar to 1988-89...Atlantic city did get a blizzard in February 1989 so there is some hope...

 

All it can take is one big storm to write the history of an entire winter season.

[yhbrooklyn]

All it can take is one big storm to write the history of an entire winter season.

1982-83, 2005-06.

[donsutherland1]

AO begins its decline...

 

This morning, the AO stood at +3.138. It is forecast to go negative down the road. At the same time, both the ensembles suggest a strong shot of cold for the closing 10 days of November with readings of perhaps 1.5 standard deviations below normal in areas. The timing of the arrival of the cold air could make a difference as to whether there is a small to perhaps even moderate snowfall in parts of the East late next week.

 

Prior to that, an impressive severe weather outbreak centered over the Ohio Valley is likely to unfold today and then spread eastward overnight.

 

The key to December's outcome is whether the blocking that is currently forecast to develop becomes sustained. Odds still are against that outcome, but fairly low run-to-run consistency of the long-range guidance suggests higher than usual uncertainty. The partial teleconnection cases still argue for a warm December in much of the CONUS and cold in parts of Europe.

[WidreMann]

1982-93, 2005-06.

Indeed, the entire decade of the 80s was a pretty awesome winter.

[donsutherland1]

As has been noted throughout this thread, I use partial teleconnection cases (excluding ENSO) to look at trends. There continues to be little change in the overall consistency of taking those cases and rolling them forward to December. Looking upstream to Canada, they paint a picture that is quite similar to the 10-day ensemble mean anomalies posted by Environment Canada. Subsequently, the area of cold anomalies would retreat westward once those cases are rolled forward for December.

 

 

In the meantime, the CFSv2 had flipped back to cold in the eastern CONUS for December. The recent poor run-to-run continuity on that guidance suggests a lot of uncertainty. In a few more days, that ensemble system will be reaching a timeframe where it has demonstrated some skill. It will be interesting to see where things stand at that time.

[easternsnowman]

I was wondering what professional weathermen's take will be on this winter. I know over at accuweather they say mild although stormier and cold second half and DT who is very good seems to be going cold and stormy

[BxEngine]

Cold and snow NYC north.

[easternsnowman]

Cold and snow NYC north.

I like that

[donsutherland1]

Morning thoughts...

 

The ensemble guidance continues to point to an impressive cold shot during the 11/24-29 timeframe, with 1-2 standard deviation anomalies in parts of the East in the 11/26-28 period. Such anomalies would mean that Washington, DC would see at least its first freeze of the season and possibly low in the 20s. The following chart shows highs and lows that are 0.5σ to 2.5σ below normal (11/20-30 period under the 1981-2010 baseline):

 

 

In the medium-term, the Arctic Oscillation (AO), which has been strongly positive through much of this month is forecast to go negative. The big question concerns whether the blocking will prove temporary or perhaps more sustained. The outcome would have a large influence on December. Right now, the ensemble guidance is split into two camps so to speak:

 

 

That leaves December somewhat up for question. The partial teleconnection cases have argued consistently for a mild December across much of the CONUS and cold in parts of Canada. For the first time, the rolled-forward cases suggest a smaller area of warm anomalies. That is the result of factoring in the cluster of ensembles pointing to a possible sustained period of blocking. Excluding those ensemble members, the consistent idea from earlier guidance remains intact. Odds may still favor that former situation.

 

In the meantime, the CFSv2 has again flip-flopped. It is again showing a milder outcome from much of the CONUS and is quite consistent with most of the earlier partial teleconnection cases:

 

 

 

Finally, some mention of last night's GFS "craziness" is in order. The 11/18 6z GFS was very cold in the long range, but the 0z run featured an extreme early-season cold shot following an early-season snowstorm. At 372 hours, the 2 meter temperatures were forecast as follows on that run:

 

Boston: -7.6°C (18°F)

New York City: -11.0°C (12°F)

Philadelphia: -14.7°C (6°F) -- This would be a record low temperature and the coldest so early in the season

Washington, DC: -10.7°C (13°F)

 

Such Arctic outbreaks have often occurred in Decembers that proved colder than normal in the affected region and during winters that also proved colder than normal. There were some exceptions with either warmer Decembers (1965, 1967) or warmer winters (1989-90). There were a number of winters that were notable for cold and/or snow (1958-59, 1966-67, 1976-77, 2002-03). In short, while the GFS likely was overdone with the cold shot, that development, if it unfolds, could provide some insight into the upcoming winter.

 

[Jonger]

CFS looks average to me....

 

For my winter playground (northern Michigan), perfectly fine and much better than the previous 2 winters.

 

I'm liking the long range GFS, big cold shot... Major LES and then seasonal to below to maintain it on the ground. The last 2 winters haven't started out even close to this nice.

[donsutherland1]

Evening thoughts...

 

1. The Arctic is undergoing another bout of widespread warmth with its warmest anomalies so far this season. November has been warm across a growing part of the Arctic, but some areas have been cold for the month to date.

 

2. Very cold air has been displaced, and is currently located in the vicinity of Alaska and western Canada. Pieces from that cold air mass will likely be dislodged and sent into the CONUS over the next few weeks, but barring a classic dual PNA-AO block, it is unlikely that this frigid cold air would be driven into the CONUS in the kind of dramatic shot depicted on the 11/18/2013 0z run of the GFS.

 

 

3. The latest EPO forecast data has been incorporated into the partial teleconnection cases and the look for North America and Europe for December remains remarkably stable (maps are below). When rolling forward the dates, one still sees a pattern change to milder across much of the CONUS unfolding during the December 5-10 period.

 

4. Both the 11/18/2013 12z and 18z runs of the GFS have backed off the extreme to record-breaking cold that had been shown on the 11/18 0z run for early December and the still severe outbreak shown on the 6z run.

[donsutherland1]

Hints of a Possible Pattern Change in the Long-Range...

 

At present, with the ensembles and operational guidance in good agreement, the idea that pieces of a very cold air mass located in an area running from western Canada into Alaska, will periodically enter the CONUS is on track. As a result, the next two weeks will see cold outduel the warmth in the Plains States and eastward. An impressive cold shot should produce readings 1-2 standard deviations below normal during the November 22-30 timeframe. With a little luck, the timing of systems could coincide with the cold air producing at least the opportunity for snowfall in some areas. Lake effect snows are highly likely.

 

However, this increasingly appears to be a transitional period. This morning's ensemble forecasts show exceptionally large spreads among the ensemble members. Such spreads often widen in advance of large-scale pattern changes. The spread is especially large as it relates to the all-important Arctic Oscillation (AO). The AO has been strongly positive for November and tools such as the Snow Advance Index (SAI) and October Pattern Index (OPI) all suggest a predominant positive phase for the winter. A period of blocking has been forecast to develop, but the overriding question had been whether this would be a temporary period of blocking or the start of a more sustained blocking regime. The resolution of that question holds the key to December and also a large part of the winter. The aforementioned tools argued for the former. Now, the ensembles are showing huge spreads with a significant number of members hinting that the upcoming blocking is likely to be temporary before the AO returns to a positive to strongly positive regime.

 

The PNA also has a large spread, but the forecast is tame relative to the AO. Given the continuing PDO- odds generally favor a neutral to negative PNA with some positive outcomes.

 

Even as the uncertainty is elevated at present, if one takes the latest teleconnection information and rolls it forward for December, one still winds up with a consistent theme: warmth over a large part of the CONUS, cold across parts of Canada. The big battleground is Europe. If the AO reverts to a strongly positive phase, warmth could predominate there, too, during December. If it is weakly positive, December could be cold across parts of Europe.

 

 

The progression of the MJO could also provide insight. Recent ensemble forecasts for the MJO going into December have been, even to put it diplomatically, quite terrible. Forecasts have ranged from Phase 8 to Phase 3 entering the month. Currently, the MJO is in phase 4 at a very low amplitude. Since September 1, the MJO was in Phases 8 or 1 26% of the time, Phases 2 or 3 24% of the time, and Phases 5 or 6 46% of the time. Until the guidance clears things up, odds probably favor Phase 8 or 1 being temporary with a risk that Phases 5 and 6 might be more likely to be predominant.