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Snowy Hibbo

Teleconnections: A More Technical Discussion

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"Look South, ENSO Forecasters"

 

Prof. Jason Furtado has just written a very interesting 'guest article' for the NOAA/Climate.gov website giving details of his research into the role that the South Pacific Oscillation (SPO) plays in helping determine the type and strength of developing EL Ninos. The article includes many informative charts.

 

Key extracts:

 

......let’s consider the evolution and development of an El Niño event. In June when an El Niño event is developing, warm water anomalies are already present in the central tropical Pacific. For development to continue, those warm central tropical Pacific SSTs have to build eastward and amplify during Northern Hemisphere summer and early fall. This eastward propagation of anomalies is driven by westerly winds and the formation of Kelvin Waves in the ocean in the eastern tropical Pacific, thus allowing waters to get warmer there. Since the SPO modulates the strength of the South Pacific trade winds in the eastern tropical Pacific, and it is most active during JJA, the phase and magnitude of the SPO can either help or hurt those Kelvin waves and the winds during the critical growth phase for ENSO.

 

If the SPO is in the positive phase (i.e., a weaker South Pacific subtropical high), then the southeasterly trade winds weaken, which reduces the cold-water upwelling in the eastern tropical Pacific and allows for easier eastward propagation of the warm waters from the central tropical Pacific to the eastern tropical Pacific.

 

However, if the SPO is in the negative phase (i.e., a stronger South Pacific subtropical high), then the southeasterly trade winds intensify, and the cold-water upwelling in the eastern tropical Pacific also increases. These two factors create an environment hostile for eastward expansion of the warm waters. Thus, the warm SST anomalies tend to remain in the central tropical Pacific.

 

.......we identified all El Niño events (regardless of flavor) from 1950-present and then examined what the magnitude and sign of the JJA SPO was for that year. Using only that information, we predicted what the flavor of that El Niño event would be the following winter. The results indicate that our simple prediction scheme correctly predicted the flavor of the event nearly 3 out of 4 times.

 

What does the SPO have to say about the expected flavor of this year’s El Niño event? The figure above illustrates that the SST warming thus far over the eastern tropical Pacific is spotty with evidence of subsurface warming present. Note that south of the Equator, however, there is an expanse of quite cold waters. More importantly, the SLP pattern in the South Pacific resembles a negative SPO signature. Indeed, for June 2018, the SPO index was about -1.3, and the SLP anomaly pattern in the South Pacific thus far for July also suggests a negative SPO value for the month. Without a substantial turnaround for the SPO in August, the JJA SPO for 2018 could turn out negative. Thus, based on what I argued above, if an El Niño event forms this upcoming winter, it will most likely be a weak/CP El Niño event. Luckily, I am not totally alone in this prediction. The latest forecast from the NMME models (below) hints at a weaker/CP El Niño event evolving this winter.

 

SST Forecast for OND 2018 NMME in Jul2018.jpg

 

Full article: https://www.climate.gov/news-features/blogs/enso/look-south-enso-forecasters

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After its annual summer break the Polar Vortex is set to return thanks to increasingly weak insolation (warming from the sun) at higher latitudes allowing the upper stratosphere to cool. The GEFS forecast suggests this will happen around August 24th with the return of weak westerly Zonal Mean Zonal Winds at 10hPa 60N. During the Fall I'll do a comprehensive post on the various teleconnections that are likely to impact the PV and thus influence our weather over the winter months - including MJO, QBO, ENSO, SST and more - and I'll include reference to the many excellent papers held in the 33andrain Research Portal.

 

In the meantime, welcome back PV - we look forward to you having a very disturbed winter! :)

 

GEFS ZMZW forecast 16Aug2018.jpg

http://weatheriscool.com/index.php/stratospheric-forecast-zonal-mean-u-wind-60n-10hpa-gefs/

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I have been away dealing with some personal issues, but now I am back. Now it's time for me to get my head back in the game, and have a little look at how we are tracking heading into autumn (well for the NH at least). 

 

For a bit of fun to start, here is the CFS Monthly charts (moving GIF) of the stratosphere over the Arctic.

IMG_5113.GIF

The takeaway here is a pretty average entry into winter stratosphere wise, but perhaps a tad early and slightly more dramatic exit (SSWs in February?). Definitely something to watch, but not to dwell upon.

 

My pet chart, the CFS Weekly model at 10hPa 60 degrees North (note the inclusion of GEFS ensembles as well).

IMG_5112.PNG

There is a lead with the GEFS ensembles mean that show a weaker than normal progression in the next two weeks, countering the recent slightly above average progress of the strengthening SPV. The CFS Control seems to follow on from these GEFS ensembles, but the general CFS trend shows typical growth of the SPV until mid October. Then all of the CFS ensembles in a major consensus weaken (-AO drop possible around here), and stay weak throughout November into December. This is a very unusual event, but this could prompt a -AO stratospheric setup, which would promote a similar tropospheric regime. And of course the desired effects for the Eastern United States. But I am probably reading too much into this rather unlikely and complex forecast, with various unforeseen implications.

 

But I am going to move on from the stratosphere. There's so much that still needs to be calculated in that area that we can't foresee at this very moment, such as Siberian snow cover, ENSO, etc.

 

Let's begin the next discussion with another CFS chart (really well used today clearly...). This is a follow-up or a companion, or really just some thoughts on @Tamara's post in the winter thread as mentioned above.

 

IMG_5114.PNG

The CFS GWO chart from Victor Gensini displays a clear trend of +AAM progression from our current neutral position. This is because CFS's current strong Nino forecast, so it will show a tendency for that way.

 

Though even with this Nino bias it now has, could it be on the money?

 

A bit of keen spotting gets you this image (GFS TT MSLP)

 

IMG_5119.PNG

You could say this looks like any old weather chart, but to any keen GWO enthusiast, it looks like a production chamber for a +EAMT. Notice the high over Kazakhstan and the low over Tibet, and then the bars in between. This carries over the mountains and into the uppers, creating a jetstream moving into China (movable GIF)

IMG_5120.GIF

 

This ultimately equals a North Pacific Jet extension, although one that isn't potentially influential to the West Coast of the US.

IMG_5118.PNG

 

These are the little quirks we need to look for to see where these events occur, so we can spot the downstream effects. This will ultimately help create some sort of positive GLAAM state with the support of other torques. I don't suggest it to the proportion of CFS' proposal, with no other major modelled +MT events, but maybe I am looking at the wrong areas. The FT has been slowly increased over the past few days, but it is currently stagnant with a -FT event in the Southern Ocean. Nonetheless, doesn't change my conclusion.

IMG_5122.GIF

 

Feel free to rebut or discuss, as usual. 

 

Just as a quick post script note to @Blessed Weather 's post about the QBO, my thoughts before my (sort of) hiatus were that we would get across the line with a -QBO winter. But increasingly including with guidance from EPS and GFS, it seems clear that we may cross the line just before or during winter. This would probably provide a fairly neutral effect from the QBO in isolation. But as he said, a key issue this autumn to watch as it progresses.

 

 

 

 

 

 

 

 

 

 

 

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Great post @Snowy Hibbo. I particularly like the chart with the strong jetstream which seems to be a direct hit on the Mongolian Mountains. We'll be looking for similar set-ups in winter as research shows that mountain torque in that area can have a big impact on the stratosphere. In 'ideal' conditions this can reduce the stratospheric jet strength by 1/3 and increase the chance of a SSW from 0.08/year to 0.60/year. Link to Paper.  

 

Back to the El Nino (EN) discussions. I've just found another paper on the impact of an eastern versus central Pacific based EN.

 

The changing impact of El Niño on US winter temperatures

"....the impact on US winter temperatures is different for the different types of El Niño. While the conventional Eastern-Pacific El Niño affects winter temperatures primarily

over the Great Lakes, Northeast, and Southwest US, the largest impact from Central-Pacific El Niño is on temperatures in the northwestern and southeastern US."

 

El Nino EP & CP impact USA temps.jpg

 

Link to paper Research Portal.

 

So of interest is the latest blog from PerspectaWeather which is clearly coming down on the side of a central Pacific based El Nino:

 

El Nino conditions are starting to appear in the Equatorial Pacific Ocean and its specific location raises the prospect of a cold and snowy winter in the Eastern US.

 

"The first sign of an "central-based" El Nino may be occurring right now with a noticeable area of warmer-than-normal water situated in the central Pacific.  In addition, some computer forecast models (e.g., NOAA CFSv2, JAMSTEC) suggest the upcoming winter will indeed feature a "central-based" El Nino.  In recent history, strong El Nino’s that were “eastern-based” generally have been associated with warmer-than-normal winters in the eastern US whereas “central-based” weak-to-moderate El Nino’s have been correlated with cold and snowy winters. For instance, two strong and "eastern-based" El Nino’s that resulted in warm winters in much of the eastern US took place during the winters of 1972-1973 and 1997-1998.  On the other hand, two weak-to-moderate El Nino's that were "central-based" and  resulted in cold and snowy winters occurred in 2002-2003 and 2009-2010."

 

El Nino SST chart Perspecta blog.jpg

 

El Nino JAMSTEC DJF forecast.jpg

 

Full blog: https://www.perspectaweather.com/blog/2018/8/29/1100-am-el-nino-conditions-are-starting-to-appear-in-the-equatorial-pacific-ocean-and-its-specific-location-raises-the-prospects-for-a-cold-and-snowy-winter-in-the-eastern-us

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A REVIEW OF A BRILLIANT YOUTUBE PRESENTATION ON THE NAO AND CLIMATE VARIABILITY IN THE NORTH ATLANTIC

 

I've been busy adding yet more papers and presentations to the Research Portal and I'm currently focusing on the North Atlantic Oscillation (NAO).  I found a paper entitled: "Skilful Predictions of the Winter North Atlantic Oscillation One Year Ahead" published in 2016 by a leading team at the UK Met Office.  Unfortunately, the full paper is still behind a paywall but on researching the citing literature I found this superb YouTube presentation made by the same authors last year (a few months later) with a slightly modified title.  In this post, I shall review this presentation which belongs equally on the Teleconnections thread as well as on the Climate Change thread, so it's going on to both!

 

Firstly, the link to the Research Portal entry (just click on the title):    Near-term Climate Predictions of the North Atlantic Region - YouTube Presentation

From there you will find a direct link to the full presentation. It's nearly an hour long but is well worth the time - so pour yourself a glass of your favourite tipple and sit back and enjoy. You'll see that I also provide the link there to the "Nature GeoScience" website entry and anyone who is a subscriber can view the full paper.  Here's a copy of the abstract:

 

"The winter North Atlantic Oscillation is the primary mode of atmospheric variability in the North Atlantic region and has a profound influence on European and North American winter climate. Until recently, seasonal variability of the North Atlantic Oscillation was thought to be largely driven by chaotic and inherently unpredictable processes. However, latest generation seasonal forecasting systems have demonstrated significant skill in predicting the North Atlantic Oscillation when initialized a month before the onset of winter. Here we extend skilful dynamical model predictions to more than a year ahead. The skill increases greatly with ensemble size due to a spuriously small signal-to-noise ratio in the model, and consequently larger ensembles are projected to further increase the skill in predicting the North Atlantic Oscillation. We identify two sources of skill for second-winter forecasts of the North Atlantic Oscillation: climate variability in the tropical Pacific region and predictable effects of solar forcing on the stratospheric polar vortex strength. We also identify model biases in Arctic sea ice that, if reduced, may further increase skill. Our results open possibilities for a range of new climate services, including for the transport, energy, water management and insurance sectors."

 

Now to the presentation itself. I should emphasis that all of us can take something out of this presentation as it provides some simple explanations with clear charts for early learners as well as some much more technical aspects. The main presenter, Dr Nick Dunstone, heads up the "Climate Dynamics Group" which is part of a team of over 200 research scientists based at the Hadley Center, a section of the UK Meteorological Office. Nick has been studying climate variability for many years and completed a PhD in Astrophysics in 2008. The first half of the presentation focuses on climate variability and although slightly orientated towards the UK and Europe, there is plenty on the North American climate impacts too. There is a great explanation of the "AMO" (Atlantic Multidecadal Oscillation) also known as the "AMV" (Atlantic Multidecadal Variability) and a long section on "decadal climate variability". The second half is on the "NAO" with the focus on predicting winter patterns and related climate impacts for not only one year ahead but also 2 years ahead with seasonal and interannuual timescales.

 

There is a look into climate prediction models.  The UK Met Office "used" to use separate computer systems and models for assessing shorter term forecasts and longer term climate patterns and that is still how most international research (including that in the US) is carried out.  Their new supercomputer came into use two years ago. This enables both short term and long term assessments and predictions to be conducted by extending the paramiters of the same computer models.  This has produced some much more accurate results. The term "hindcasting" has been used increasingly in recent years. This is where a predictive model or individual programme's reliability (strengths and weaknesses) can be tested by inputting past data to see how accurate the results are - measured against what is known to actually happen. This includes all the short term (as well as the longer term) variables and where the new "single" system approach has enormous advantages over totally independent systems. it's also advantageous to have all this under one roof - some countries use completely separate, offices, research teams and even organisations and yet this is all so inter-related.  When assessing and comparing human influenced climate change and natural climate variability this more integrated type of measurement and assessment should prove to be invaluable to get at the real facts.  The UK Met Office take a balanced and open minded approach to climate change and this presentation is a great demonstration of that neutral position which is so important to avoid all the politics and hype at both extremes of the global warming and climate change debate.. Here is a small selection of slides to whet your appetite but you'll need to watch and listen to the full presentation to get the real benefit :

 

met4.PNG

 

met5.PNG

 

met6.PNG

 

met7.PNG

 

met9.PNG

 

met10.PNG

 

met11.PNG

 

met12.PNG

 

met14.PNG

 

met15.PNG

 

I hope that you can now see why this post belongs on both the Teleconnections and the Climate Change threads.  David :) 

 

 

 

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Man this thread is loaded with top notch info! I need to take week off just to digest it all

 

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An update to my post above (Aug 31st). The 30mb Equatorial Zonal Mean Zonal Wind index has continued it's sharp upward trend and the World Climate Service is now saying a Westerly QBO by winter is in "little doubt".

 

QBO Index 30mb Equat ZMZW 14Sept.jpg

 

https://twitter.com/WorldClimateSvc/status/1040616985317572610

 

Edit: My apologies to early readers - my original posting said "Easterly QBO in little doubt" and this should have said "Westerly QBO in little doubt" as the QBO index looks like crossing the line between negative (easterly) and positive (westerly during the late fall/early winter.

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An ostensible shift occurred w/ respect to the forcing paradigm from mid July-Aug to early-mid September; specifically, a more Nino-esque regime dominated through mid/late summer (which was reflected in other proxies as well such as the GWO, AAM), while, thus far in September, we've taken a step backward w/ respect to Nino progression. This is expected in generally very weak events (that is, occasionally countervailing tendencies / irregular patterns); however, certainly, if a more Nina-esque atmospheric regime attempts to persist into October, it could augur a different sensible weather outcome for the ensuing winter. My personal NAO indicator - though it's in the early stages of the monitoring period - is suggestive of a +NAO modality for the ensuing winter. However, I'll need through early November to incorporate all the data.

 

4t61ef.gif

 

xdggpl.gif

 

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On 9/12/2018 at 3:30 PM, Blessed Weather said:

ENSO Developments - Update Sept 12th 2018

 

ENSO NOAA update 10Sept2018.jpg

 

SNIPPED

 

A BIG SET BACK THIS WEEK - EL NINO LIKELY TO BE FURTHER DELAYED!

 

Hi Malcolm, thank you for a great post and I really liked the way that you used several different sources to pull together a good consensus overview of the "still" generally predicted movement towards a weak El Nino this fall. In a minute I will show some figures that indicate that there has been yet another set back in the progress towards that elusive El Nino.

 

In recent months we have both been posting a number of updates on the ENSO changes.  Initially, we were posting these on this Teleconnections thread where they belong. Then we sometimes migrated to the Hurricane thread as there is such a strong Teleconnection between ENSO changes and the impacts on the Atlantic and east Pacific hurricane seasons.  Last month there was an ENSO discussion on the Countdown to Winter 2018/19 thread and I decided to place one of my comprehensive updates on there. I see that an "El Nino 2018/19?" thread was started off briefly but has now been archived - very confusing. From now on, I shall take your lead and keep all my ENSO posts on here and perhaps give them a plug on the hurricane when it's relevant to a post on there.  It'll be great if we can get an ENSO debate going on here and I see that while I'm preparing this post, Tom @Isotherm has just posted on this topic.

 

It's amazing how quickly regional SSTs can change so quickly and there has been a real battle going on in the Pacific Nino regions. The changes have been erratic to say the least. I haven't got much time now, so I'll post these charts and then come back to my main point. 

 

el3.PNG

Nino 4 rose strongly during the first half of August but fell sharply later in the month before rising again until yesterday.. 

 

el1.PNG

Meanwhile, the key Nino 3.4 region has fallen back to its lowest level in 3 months. More below.

 

el2.PNG

Nino 3 (central/east Pacific) which has been behaving quite differently to Nino 4 (central/west Pacific) has struggled to remain +ve.

 

el4.PNG

Just to complete the abrupt turnaround Nino 1+2 (east Pacific) has recovered strongly! 

 

I won't go into any reasons now but will just make a mathematical point. As you point out, we need three consecutive months where the Nino 3.4 region has an average SST anomaly of +0.5c or higher to meet the accepted definition of an El Nino episode.  NOAA "were" going for a 60% chance of getting there in the fall and they clarify that as S/O/N.  Well it has been averaging more like +0.15c for the first half of September.  To average more than +0.5c for the whole of September it will need to have values quickly rising to +0.85c or higher to get there. With the ssts moving down not up, I'm almost certain that we can discount September from the equations.I mentioned this in an ENSO/SST post on the Hurricane thread last week. So at the very least a one month delay and pushing back the chances of an El Nino developing closer to the winter. 

 

IMPORTANT EDIT: Malcolm @Blessed Weather has kindly reminded me that the NOAA definition is somewhat ambiguous (and I completely concur) and is a little longer and goes beyond the 3 month (or season) rolling periods (it must be averaged over 5 consecutive seasons for their table to go blue for La Nina or red for El Nino episodes) and this changes the maths to some extent!  I am preparing another post right now, dealing exactly with this and also all the different definitions used by different countries  

 

You quoted the NOAA weekly ENSO report which I also often focus on. Their weekly updates with their headline (60% chance of Nino in the fall - S/O/N and 70% during winter - D/J/F) is actually only updated once a month. Their monthly "ENSO Discussions" report, ironically, came out the day after your post - it's always published on the 2nd Thursday of each month. Her'e the link to it:  http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.pdf  We can expand on NOAA's views  and reasons as part of our debate but I'll show this now:

 

Extract: 

Synopsis: There is a 50-55% chance of El Niño onset during the Northern Hemisphere fall 2018 (September-November), increasing to 65-70% during winter 2018-19. ENSO-neutral continued during August, as indicated by a blend of slightly above- and belowaverage sea surface temperatures (SSTs) across the equatorial Pacific Ocean (Fig. 1). Over the last month, the westernmost Niño-4 region was the warmest (latest weekly value was +0.5C), while the Niño-3 and Niño-3.4 regions were weakly positive, with Niño1+2 remaining negative (Fig. 2). Subsurface temperature anomalies (averaged across 180°-100°W) were positive (Fig. 3), with an increase in aboveaverage subsurface temperatures in the central Pacific and slight expansion of negative anomalies in the eastern Pacific (Fig. 4). Convection returned to near average over the Date Line, and was slightly enhanced over Indonesia (Fig. 5). Low-level westerly wind anomalies re-developed across the east-central and western Pacific, although they were only slightly evident in the monthly average. Upper-level wind anomalies were westerly over the eastern Pacific. Overall, the oceanic and atmospheric conditions reflected ENSO-neutral. The majority of models in the IRI/CPC plume continue to predict the onset of El Niño sometime during the Northern Hemisphere fall and continuing through the winter (Fig. 6). The forecasters also favor El Niño formation during the fall, and are leaning toward the more conservative model guidance that indicates a weak El Niño event. The persistence of above-average subsurface temperatures and continuing flare-ups of westerly wind anomalies also support the eventual development of El Niño. In summary, there is a 50-55% chance of El Niño onset during the Northern Hemisphere fall 2018 (September-November), increasing to 65-70% during winter 2018-19

 

So they have only just reduced their forecast slightly to 50%-55% chance but still S/O/N which is remarkable - they surely should have changed it to at least O/N/D. Your other sources include the IRC/CPC, who partially updated their output but their next full monthly update for all the main models comes out on Sept 19th.  It will be interesting to see how much (or little) the model consensus has changed since mid August. it looks like your other sources were just updated to a few days ago, just prior to the recent set back. All my comments directed to at least a one month delay are only a very small part of this. I look forward to debating the underlying reasons, some of which have been mentioned and I've posted on them before. More this weekend.  David :)

 

 

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Ah yes, the tropical Pacific, lets go there. It's time to get comprehensive about ENSO..... 

 

First up are we going to actually have an El Niño? The question on everyone's lips. The answer to this is still not clear at all, primarily because the models have converged and made their consensus. For example, the NMME forecast, featuring the main North American ENSO ensembles, go from a full on Niño with CFS, to the CMC models that show a borderline Niño at best, to the NASA model, that is pretty stagnant and stays warm neutral.

IMG_5240.PNG

 

In contrast, the JAMSTEC model shows a fully strong Niño event. Which I think has been consistently forecasting for a while.

IMG_5241.GIF

 

 

To add to the above models, the ECMWF shows a fairly weak EP El Niño, and the Met Office (UKMET) forecasts a slightly stronger, perhaps moderate El Niño event. And as @Blessed Weather shows, the brand new ACCESS (developed from the same core as the UKMET's) model shows an El Niño developing.

 

But with the graphics posted by @Bring Back 1962-63, that show a warm neutral Niño not really moving anywhere, are we going to move towards an El Niño. Many of the above models do take into account this neutral period, and still come out with a fairly strong El Niño event. One of the more interesting trends to examine with these graphics, is that Niño 3 (more Eastern Pacific) is much more neutral than Niño 4 (more Central Pacific). So with this in mind, it would seem that it would be easier to reach Central Pacific Niño or Modoki Niño. One thing all the models (that I have examined) are clear on is that we aren't going to see cold Niño 1+2 SSTs. Most show warm neutral and often Niño level warmness in the region. This shows that we may be in for warming across both the Eastern Pacific and Central Pacific regions in general. This is a sentiment echoed in my last blog update here

 

Quote

During a true Niño Modoki, you see cooling around the South American coast at the equator, this doesn't happen here. Yes it is weaker than the warm anoms further out into the Pacific, but they aren't cooling. This is why none of the Modoki index forecasts I have seen show this as a proper Modoki, because of the warm Niño 1+2 anomalies off South America. This is why I think this event carries both hallmarks of ENSO in various ways, as we all know, no two ENSO events are alike.

On this topic, let's analyse the latest CFS run, and it's product subsurface temps. 

IMG_5245.GIF

The warm subsurface temps are around the Dateline in the observations over NH summer. But CFS shows them moving up (as expected), but also eastwards. And we have started to see this a little bit this month. This creates a warm NIÑO 3 (Eastern Pacific) and NIÑO 4 (Central Pacific).

So maybe a bit of both? If we manage to get one for the most part....

We are starting to see some movement in the last month or so, from the atmosphere, in this example from the SOI and Dateline cloudiness.

IMG_5242.PNG

SOI is moving more negative since June, an indication of a move towards Niño.

IMG_5243.PNG

And Dateline cloudiness starting to shift towards negative OLR values which are associated with an Niño event. But from both of these indicators, we really need a follow through towards Full Niño. 

 

Another indicator, the AAM or Atmospheric Angular Momentum has also been noticeably Nina-esque, as noted by this Victor Gensini chart. -AAM correlates with a generally Nina like atmosphere. And remember that there is a difference between the Atmospheric Niño indicators and the Oceanic Niño factors, because they are sometimes not correlated to each other.

 

IMG_5244.PNG

 

It has been slightly heading positive over a monthly timescale, but still fairly negative moving towards neutral (much to the denial of CFS and Bias Corrected GEFS at the moment). Trade winds are also neutral, with several WWBs in the Pacific over the last few months, but now we are heading into a period of big easterly trades in the Central Pacific region in particular. You want weak/westerlies for an El Niño.

 

This all shows us that we are a long way from any form of a Niño, not until November at least. And my tip is for a warm Weak El Niño in both the Eastern Pacific and Central Pacific regions. This could aid a -AO and Eastern troughing, while also giving California it's big snow dosage. But on the other hand, my other tip is for the atmospheric enso factors to stay warm neutral, and the GWO/AAM to stay neutral with entrances to both +AAM (Niño) and -AAM (Nina) territory. This could make for a very interesting up and down winter for all regions IMO.

 

 

 

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7 hours ago, Snowy Hibbo said:

Another indicator, the AAM or Atmospheric Angular Momentum has also been noticeably Nina-esque, as noted by this Victor Gensini chart. -AAM correlates with a generally Nina like atmosphere. And remember that there is a difference between the Atmospheric Niño indicators and the Oceanic Niño factors, because they are sometimes not correlated to each other.

My own angle on analysis and benchmark for monitoring is highly symmetrical with this particular aspect of thinking and the importance attached to the differences. as stated.

 

As I see it, when we are looking at the atmosphere/ocean relationship and trying to incorporate that (plus a variety of other drivers) into a geopotential height anomaly NWP framework pattern, whether that is shorter or longer term - the bread and butter starting consideration is the precise relationship that the atmosphere adopts to the ocean base state. In that sense, looking at the ENSO base state per se is not going to give any accurate foresight into NWP evolution beyond the usual broad-brush teleconnectic assumptions. Its not that these are not helpful - its just that it leads to some x+y assumptions which are nowhere near as linear as they may appear at face value.

 

These principle key beliefs, plus a whole load more, are why I place so much faith in the Global Synoptic Dynamical Model (GSDM) as a starting point to my own study and curiosity into matching up weather patterns according to the balance, or budget of wind-flows in the global atmospheric circulation at a given time - which in turn can give such good clues and insight as to how weather patterns may evolve both in the shorter and longer terms.

 

When I speak of wind-flows, largely this refers in simple English to the movements and velocity of the Jetstream.  Tropospherically, within the tropics and extra tropical boundaries where momentum energy flux constantly interchanges to alter wind-flow according to angular momentum budgets,  the Pacific is a large engine room of upstream and downstream control on circum-global weather patterns and why the relationship of the atmosphere to the complex changes that occur within the ENSO zones are such an important consideration.

 

So enough background and good vibration appreciation of the concepts, how about some analysis consideration of some background to the here and now vs the possible way ahead:

 

There is clearly no need for me, as part of my own assessment, to reproduce the data that the good folk so far have provided as part of the jigsaw on this subject. :)  But to further investigate the GSDM atmospheric key responses provides what I believe is a very reliable barometer to the processes involved

 

I was well aboard the Nino-esque low tropical frequency signal and +ve relative AAM anomaly gravy train during the latter part of the summer following the brief , but still significant, coupling of the atmosphere vs ocean that took place in late July. The periodicity (timeline recurrence) of low frequency tropical signalling had been consistently very buoyant right back to prior to the SSW that took place in February. This pattern had continued right into the summer - culminating in the eastward progression of that standing wave signal during July into the Pacific

 

2018-09-15 (10).png

 

This drove both angular momentum tendency and total global atmospheric angular momentum into +ve territory, briefly - but still not replicating the spike attained during  the very temporary reversal of the La Nina standing wave that was the culmination of the tropical>extra tropical momentum transport that 100% destabilised the stratospheric vortex in late winter.  A retrospective plot of the The Global Wind Oscillation, which is a plot depiction of total global wind-flow  in the atmospheric circulation and therefore a reflection of where AAM sits against parity,isn't currently avaialble by way of further illustration - but it laddered up into the El Nino attractor phases 5,6 and 7 in reflection of the strength of the momentum transport anomaly

 

Below is a retrospective AAM anomaly chart courtesy of Victor Gensini maproom creation.

 

MR-latest-365days.png

This one year retrospective AAM anomaly plot advertises number 1:

 

The long domination of the La Nina standing wave that had prevailed up to the SSW in February - as depicted by how much time has been spent with greater -ve or easterly trade wind domination at the expense of westerly wind additions added to the atmospheric circulation,

 

and number 2:

 

Just how much the atmosphere has still struggled to shake off the shackles of this Nina legacy since the SSW, despite the progression of the ENSO ocean base state to take on a more Nino-like spatial status, at least within the central Pacific

 

Its this context, which I think illustrates that' its the atmospheric response in terms of how the tropics and extra tropics process easterly  (or -ve momentum flux) and westerly  (or +ve momentum flux), that determines the arrangements of the longwave hemispheric patterns - as also dictated  (augmented or detracted) through natural seasonal wavelength changes.

 

This being much more relevant and important in this respect in my opinion than the ENSO base state per se despite its changes away from a La Nina state in this time. ENSO base state relationships with the atmosphere  can manifest themselves in a variety of ways from one matched up face value scenario to the next. Especially if we take other pernicious drivers like unstable sea ice patterns and associated superimposed warming forcing into account which further amplify and distort the synoptic patterns that occur as manifestations of those variable relationships. The days of the analogue and "one size fits all pattern match" is on stony ground. At least for those who attempt seasonal forecasts out there.

 

This summer in 2018, despite the barometer reflection of the atmosphere lagging the ocean Nino progression with a stubborn  Nina-like circulation  the gradual warming profiles of the Pacific through repeated oceanic convectively coupled kelvin wave activity ....

 

2018-09-15 (5).png

 

 

 

...…...serving to move bodies of sub surface water eastwards and to the surface to increase the spatial extent of warming within the ENSO profile.

 

I think this tweet from MV in late August summed up that situation

 

 

 

Importantly though, the movement of the low frequency tropical signal though late July had already started coupling up and imprinted the atmosphere onto the newly developing El Nino standing wave.

 

This might have appeared to represent a real coupled shift regime at last. Tentative and provisional  as this move was, it was the first signal since the huge momentum processes leading up to the SSW that tha atmosphere finally wanted to go along with the shifting base state.  Its been this (and admitted desire to see change out of a rut!) that had driven my own enthusiasm for a slow, but steady process towards a weak El Nino state during  September and October and establishing more generally into the late part of this season and early winter.

 

This summer seasonal momentum has not carried though however, much as previous analysis on this page has noted and by the AAM anomaly chart which, as illustrated above, has slipped back to previous generally -ve status.

 

If we take a look at frictional torque tendency...…

 

2018-09-15 (7).png

 

……..then resumption of the Nina type signal of repeated easterly trade wind propagation has occurred since mid August around 20 to 30N which has created a -ve tendency to wind-flows and negated/supressed the Asian jet extensions in the extra tropics that are triggered by both low frequency tropical convection attempting to head into the Pacific, and the micro scale cyclonic activity as represented by the fledgling Nino standing wave trying to get implemented

 

 The persisting -ve South Pacific Oscillation largely responsible for this - meaning anomalous heights in the South Pacific with trade winds emanating north from the region and counter-acting the ENSO warming induced by westerly wind bursts c/o of CCKW, MJO and ACE related tropical activity.

 

These countervailing trade bursts showing up on the Hovmollers wind anomaly plots as shaded blue close to the dateline

 

u.anom.30.5S-5N.gif

 

Where the extra tropical westerly wind bursts are met by these tropical trade wind easterlies, then an eddy and amplification in the jet stream occurs. This is effectively the inflexion point of the -ve frictional torque response around 30N - with height anomalies propagating polewards from the tropics into the North Pacific and displacing atmospheric disturbances downstream over the US.  

 

Frictional torque responses lead mountain torque tendency responses, so the inverted pattern with greater easterly tendency present overall than westerly tendency results in a -ve Asian MT ……

 

2018-09-15 (6).png

 

 

 

.......and the effect of falling frictional and mountain torque tendency impacts on relative and global atmospheric angular momentum and is reflected by the GWO back towards a low amplitude La Nina type Phase 1 signal

gwo_fnl.pngFurther downstream from the Pacific, the response of the deceleration of the jet in the Pacific is to also

bolster sub tropical high pressure in the Atlantic c/o of both Bermuda and Azores ridges. The easterly trade winds emanating from the tropics  help steer the developing tropical activity coming off the AEW with minimal wind shear to aid their development. Much as Florence and her family are more than amply demonstrating at present as everyone is aware.

 

The tropics are very much engine of pattern change, and the periodicity of the MJO cycle points to the look out for a next amplitude cycle. AAM modelling, as mentioned, has been and still is persistently bullish about an upturn in AAM tendency relative to increased low frequency signal.

 

2018-09-15 (8).png

 

 

Its this, that is required to redress the AAM budget within both the tropics and extra tropics to induce a more sustained and greater +ve frictional torque and extra tropical +ve momentum response as westerly winds change the budget of wind-flows (essentially re-configure the jet stream patterns from upstream).

 

Converse to the processes within a -ve frictional lowering angular momentum signal, increased +ve westerly wind momentum gaining the upper hand results in an increased Asian jet extension, which serves to de-amplify the sub tropical high pressure in both the Pacific and then downstream in the Atlantic - and in the process change the greater balance of convectively coupled ocean>atmosphere cyclonic/hurricane activity back to the Equatorial Pacific

 

The EPS VP200 convection anomaly depict a changing signal in the 15 day period, with some credence to greater westerly wind activity and in turn a cessation of the "destructive" Nina-like action on the ENSO zone - and with warming from the sub-surfaces replacing cooling.

 

2018-09-15 (9).png

 

The AAM budgets and the GWO will ultimately provide for me the litmus test of how the atmosphere responds in reality away from model forecast suggestions

 

The GWO response would be one of tracking away from the La Nina type Phase 1,2 and 3 orbit signature and a representation of +ve frictional torque increasing +EAMT into tendency above parity. Such an increase within the AAM wind-flow budget implies the GWO heading back to "transitional" precursor El Nino phase 4.

 

However, this is only half the story for the extended period for those looking towards late season and on into winter. If the Nino standing wave is to recover assertion, let alone sustain, then the frequency of westerly wind bursts needs to sustain and the low frequency MJO signal provide the sort of eastward amplitude progression of late July to make this happen.

 

Should this be insufficient, and there is no way of answering this at this time, then question marks will be raised at the particular

ocean vs atmosphere status that will be in place at the same time  as the stratospheric vortex is under-going its usual seasonal traditional rituals. This of course relating also to QBO +ve westerly phase descent as well as solar cycling all attendant with Brewer Dobson circulation of ozone transport from the tropical stratosphere in Southern Hemisphere Spring-Summer to the Northern Hemisphere opposite seasons.

 

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THE DIVERSITY OF ENSO DEFINITIONS AND THE UNCERTAINTIES THIS PRODUCES

 

There are some great posts already in this fascinating ENSO debate that we've just started on this Teleconnection thread. I strongly recommend the contributions from Malcolm @Blessed Weather, Tom @Isotherm, Tams @Tamara and,  of course,  Zac @Snowy Hibbo (who should take a lot of credit for creating this specialist thread a few months ago). While a number of us (hopefully a larger number very soon) intend to fully contribute to this fascinating topic as I do, there are some basics that I feel need to be addressed to assist some of the readers (and posters too!).  In this post, I had wanted to look at some of the uncertainties over the ENSO state going forward but decided to leave that until my next post in a few days time. I started looking into the difficulties on defining exactly what an El Nino is in terms of when we have one. There is no international consensus over this. It can also be far from straightforward in understanding a single country's definition!  Some countries use a different set of measures too. So when various commentators produce their reports, papers, presentations, blogs, tweets and forum posts they may not always be referring to the same definition. There is "some" common ground but not nearly enough.

 

To emphasise this point, I'll quote this paragraph from Wikipedia - slightly edited to remove footnote insets:    

 

"Currently, each country has a different threshold for what constitutes an El Niño event, which is tailored to their specific interests. For example, the Australian Bureau of Meteorology looks at the trade winds, SOI, weather models and sea surface temperatures in the Nino 3 and 3.4 regions, before declaring an El Niño. The United States Climate Prediction Center (CPC) and the International Research Institute for Climate and Society (IRI) looks at the sea surface temperatures in the Niño 3.4 region, the tropical Pacific atmosphere and forecasts that NOAA's Oceanic Niño Index will equal or exceed +0.5 °C for several seasons in a row.  However, the Japan Meteorological Agency declares that an El Niño event has started when the average 5 month sea surface temperature deviation for the NINO.3 region, is over 0.5 °C (0.90 °F) warmer for 6 consecutive months or longer. The Peruvian government declares that a coastal El Niño is under way if the sea surface temperatures in the Niño 1 and 2 regions equal or exceed +0.4 °C for at least 3 months."

                           

Providing that we take account of these differences, we can start to compare like with like but this does add an extra tier of complexity that can only serve to confuse any reader, including some of the specialists! I vote for a new international standard which may be something of a compromise but at least would pave the way forward for everyone to at least have the same starting criteria (....but read on!). I thought where better to go than to the World Meteorological Organisation (WMO) website.  There I found nearly 60 different country definitions and that is just those that are members of the WMO!  They did produce this guide in 2006: "Catalogue of Indices and Definitions of El Niño and La Niña in Operational Use by WMO Members"  Here's the link:       http://www.wmo.int/pages/prog/wcp/wcasp/documents/ENSO-Indices-Catalogue_12062006.pdf  

 

Although some individual countries may have modified their own definitions since 2006, many have not. I'll just show a small sample here and as this is essentially a US weather forum, I had better start with this one:

 

USA:

Definition of El Niño in use operationally A phenomenon in the equatorial Pacific Ocean characterized by a positive sea surface temperature departure from normal (for the 1971-2000 base period) in the Niño3.4 region greater than or equal in magnitude to 0.5°C, averaged over three consecutive months. . Definition of La Niña in use operationally A phenomenon in the equatorial Pacific Ocean characterized by a negative sea surface temperature departure from normal (for the 1971-2000 base period) in the Niño3.4 region greater than or equal in magnitude to 0.5°C, averaged over three consecutive months

 

This is the definition used by NOAA (except that it goes further than this (more later below).  Many other countries do now use this or a very similar definition. Some countries do not use any definition at all. 

 

UK:

Definition of El Niño in use operationally The Met Office does not currently use an objective definition of El Niño or La Niña. Because links between El Niño/La Niña and European climate are weak it would be very difficult to define an index threshold that would be suitable or meaningful for the UK region. At present the Met Office prefers to provide information in the form of indices that can be interpreted for local application by forecast users.  

 

When I read this, I was very surprised!  As that was over 12 years ago, I checked on the UK Meteorological Office website. While they still do provide their own definition, they have adopted the US NOAA definition or at least refer to it.

 

Australia:

Definition of El Niño in use operationally At present the Bureau of Meteorology does not employ formal definitions to trigger declarations of events at either end of the El Niño – La Niña cycle, but rather uses various indices as assessment tools. The assessment of El Niño/La Niña status is conducted within a scientific yet largely subjective framework and encompasses at least one formal meeting (The Monthly Climate Meeting) per month of operational and scientific staff to discuss the full range of analysis of the atmospheric and ocean state. This includes examination of the indices listed above, as well as proxy indicators such as trade winds, high cloud amount/outgoing longwave radiation, ocean subsurface temperatures, sea surface temperature distribution and model outputs. This assessment is used to develop the text for the Bureau's “ENSO wrap up” discussion, updated weekly in times of El Niño development, and publicly available on the web (http://www.bom.gov.au/climate/enso).

 

Now, I was already aware that Australia is one of a number of countries that use a very different approach and Zac would have been brought up on this one and will often refer to it. They also use a wider series of measures: 

 

Index (indices) in use operationally  Troup Southern Oscillation Index (SOI) - The standardized anomaly of the Mean Sea Level Pressure difference between Tahiti and Darwin.  Niño1, 2, 3, 3.4, and 4 Sea Surface Temperature (SST) indices.  Multivariate ENSO index (MEI) - A weighted average of the main ENSO features contained in six variables: sea-level pressure, the east-west and north-south components of the surface wind, SST, surface air temperature, and total amount of cloudiness.

 

Since Australia developed this way of measuring ENSO, many other countries (mostly in the southern hemisphere) have adopted it or a form of it.

 

India:

Definition of El Niño in use operationally An oceanographic phenomenon in the equatorial Pacific Ocean, characterized by a positive sea surface temperature departure from normal in the Niño3.4 region greater than or equal in magnitude to 0.5°C. The base period for the normal is 1971-2000. To classify as a full-fledged El Niño episode, this threshold must exceed for a period of at least 5 consecutive months.  

 

Like some others, India partly adopts the US definition of the Nino 3.4 region and the +0.5c threshold but note that they extend the 3 month period to 5 consecutive months (more in a minute).  

 

Bangladesh:

Index (indices) in use operationally Highly positive SOI ( 5) and highly negative SOI ( - 5) contribute excess and deficit rainfall respectively in monsoon. 5. Definition of El Niño in use operationally SOI  5 for consecutive three months. 6. Definition of La Niña in use operationally SOI  -5 for consecutive three months.

 

I put this one in to make a point. Some Asian countries focus, quite understandably, on the strong  ENSO impacts on their monsoon season.  There is a strong correlation with the +ve phase of the SOI (Southern Oscillation Index). On the other hand, India do not use this method!

 

Peru::

Index (indices) in use operationally  Sea surface temperature anomalies in the equatorial Pacific (Niño4, Niño3.4, Niño3, and Niño1+2) and at coastal stations;  Mean and anomalous subsurface temperatures in the equatorial Pacific and along the Peruvian coast;  Variations in the depth of the 15°C isotherm;  Longitudinal position of the 27°C and 28°C isotherms in sea surface temperatures;  Mean and anomalous low-level (below 850 hPa) zonal winds in the equatorial Pacific;  Pressure systems at 200 hPa near the Peruvian coast and tropical convection;  Others: OLR (outgoing longwave radiation); SOI (Tahiti-Darwin Southern Oscillation Index); MEI (Multivariate ENSO - El Niño-Southern Oscillation - Index); intensity and configuration of the South Pacific anticyclone and minimum air temperature along the coast; biological indicators of warm and cold waters between 50 and 100 nautical miles from the coast. 5. Definition of El Niño in use operationally  Positive sea surface temperature anomalies greater than 1°C in the Niño4, Niño3.4 and Niño3 regions and anomalies greater than 2°C in the Niño1+2 region and coastal areas;

 

Arguably, Peru is the closest country and in the most direct firing line of an El Nino episode. They go way beyond the basic definition and consider many more variables and measures.  They seem to incorporate almost all the other countries' criteria and even more besides! I'm aware of some papers produced by Peruvian (or other South American) meteorologists and I shall seek them out to see why they adopt this approach. It may well be worth considering why they go into this level of detail and what predictability benefits they derive from them. You can see that they are taking account of surface, sub surface and deeper ocean temperatures and air pressure patterns. The "South Pacific anticylone intensity"  is fascinating.  The term SPO (south Pacific oscillation) only came into use during the last few years (2013 I believe) but this would seem to be a general reference to it and this was the basis they used in 2006 and it's likely that they used it much earlier than that. We may well find that there is some very useful medium term research available - I'll conduct an investigation.  if I find any useful papers, I'll place them in the Research Portal and we can review them on here as part of our debate. The wider ramifications may be that it will help with assessing erratic developments and stalls in the progress towards an El Nino, like we've seen recently - the cold current upwellings in the east and their spread along the equator (driven by a -ve SPO) battling with the warmer surface currents. If we could throw in AAM (atmospheric angular momentum) , the torques, the GWO (Global Wind Oscillation) phases and Kelvin wave activity into the equation, we might have some more answers? Apart from stalling information, this Peruvian data might assist in determining the flavour of an El Nino - an east or central Pacific based one (Modoki) or a sub mix.

 

Right, I've shown enough examples to demonstrate the diversity. Whilst I appreciate that many countries see very different impacts from an El Nino event I would still say that they could easily adopt the NOAA definition and then superimpose their own parameters to adapt to their own Nino or NIna impact assessments and predictions. From now on, I will focus on the NOAA definition. This appears to have evolved since 2006. I tried to find a confirmation of that earlier definition and when (or if) any changes took place. To show what I mean, I repeat their 206 definition as printed by the WMO:   

 

2006 El Nino definition:   A phenomenon in the equatorial Pacific Ocean characterized by a positive sea surface temperature departure from normal (for the 1971-2000 base period) in the Niño3.4 region greater than or equal in magnitude to 0.5°C, averaged over three consecutive months.

 

Now the current NOAA Climate Prediction Center (part of the National Weather Service) definition: The onset of an El Nino episode when the 3-month average sea-surface temperature departure exceeds 0.5c in the east-central equatorial Pacific between 5N-5S and 170W-120W (the Nino 3.4 region) - note: this is as previously but then they add this:  For historical purposes, periods of below and above normal SSTs are colored in blue and red when the threshold is met for a minimum of 5 consecutive overlapping seasons. Their full definition is shown in their ENSO table below:

image.png.67d8c4b6801a01cbf10756057c006a

 

16a.PNG

 

Now, Malcolm @Blessed Weather kindly brought something to my attention this morning and I seem to have made an error in my last post (and a couple of previous ones) when I criticised NOAA for retaining their September (was 60%) 50% chance of an El Nino developing this fall (defined as S/O/N) and said that this was almost mathematically impossible.  I wrongly considered that we take an average for each month and then roll them up until we get 3 consecutive months with with an average of +0.5c or more. As Malcolm correctly says, if one reads the wording carefully, it is the average over any consecutive 3 month period.  So September could be well below the 0.5c threshold (as indeed it is) but October and November could end up well above and sufficiently so to pull the 3 month average over the threshold. So, I apologise for misleading anyone (if you noticed my error!). 

Furthermore, the addition to their official definition is that the threshold must be exceeded for a minimum of 5 consecutive rolling/overlapping 3 months periods.  That is why in the table above reds (El Nino) and blues (La Nina) do not run for less than 5 periods. For example the long La Nina episode that ran from M/J/J 2010 until F/M/A 2012 was broken by the M/J/J 2011 when the average  fell just below the threshold.  Malcolm has prepared an excellent chart to demonstrate this much more easily and I told him that he must take the credit for it and post it himself :)  

What Malcolm's comments did was cause me to research all this today and pull this post together. Some of the detail may not be that relevant but it has thrown up some fascinating variations. Overall, as I commented in several earlier posts, the NOAA definition (or any other for that matter) is actually a very crude measure. We have seen Nino-like and Nina-like conditions while the Nino 3.4 region  has been weakly +ve ( mostly in the +0.05c  to +0.5c  SST anomalies range) since June.  The Atlantic hurricane season has shown an amazingly rapid response to "seemingly" relatively minor ENSO changes and has been an excellent barometer of ENSO impacts. It started early (May into early June) with several hurricanes when the recovery from La Nina conditions was just underway. Then that rise peaking at 0.5c for only one day but remaining above +0.2c from late June to mid July killed all the activity. Then that fall back to +0.1c was sufficent to bring about some Nina-like conditions again and the Atlantic burst into activity. Despite all the named storms showing in the Atlantic, only Isaac is still actually in the "tropics" and tropical activity has slowed down for the last few days and this is just after that rise from early September to just 3 days ago.  Now we have seen the sharpest set back since mid June and this may well be enough to regenerate the tropical Atlantic activity.  

15a.PNG

As I've been demonstrating there is far more to it than just the Nino 3.4 region. I posted the charts for all 4 regions yesterday on here.

ens1.PNG

Meanwhile the east Pacific has just warmed to it highest level of the year or since before the last La Nina begun.  This is effectively a reversal of the warmer CP and cooler EP and, even if we see a recovery towards an El Nino later in the year, may mean that it is not a CP based one (or so-called Modoki) as others have alluded to.

I'll do a comprehensive assessment of NOAA's weekly report on Tuesday and look into sub surface currents and other influences to (hopefully) complement what the others are posting.

Everyone is very welcome to contribute to this debate and ask questions.  David :) 

 

 

 

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1 hour ago, Bring Back 1962-63 said:

THE DIVERSITY OF ENSO DEFINITIONS AND THE UNCERTAINTIES THIS PRODUCES

 

There are some great posts already in this fascinating ENSO debate that we've just started on this Teleconnection thread. I strongly recommend the contributions from Malcolm @Blessed Weather, Tom @Isotherm, Tams @Tamara and,  of course,  Zac @Snowy Hibbo (who should take a lot of credit for creating this specialist thread a few months ago). While a number of us (hopefully a larger number very soon) intend to fully contribute to this fascinating topic as I do, there are some basics that I feel need to be addressed to assist some of the readers (and posters too!).  In this post, I had wanted to look at some of the uncertainties over the ENSO state going forward but decided to leave that until my next post in a few days time. I started looking into the difficulties on defining exactly what an El Nino is in terms of when we have one. There is no international consensus over this. It can also be far from straightforward in understanding a single country's definition!  Some countries use a different set of measures too. So when various commentators produce their reports, papers, presentations, blogs, tweets and forum posts they may not always be referring to the same definition. There is "some" common ground but not nearly enough.

 

SNIPPED

 

image.png.67d8c4b6801a01cbf10756057c006a

 

Now, Malcolm @Blessed Weather kindly brought something to my attention this morning and I seem to have made an error in my last post (and a couple of previous ones) when I criticised NOAA for retaining their September (was 60%) 50% chance of an El Nino developing this fall (defined as S/O/N) and said that this was almost mathematically impossible.  I wrongly considered that we take an average for each month and then roll them up until we get 3 consecutive months with with an average of +0.5c or more. As Malcolm correctly says, if one reads the wording carefully, it is the average over any consecutive 3 month period.  So September could be well below the 0.5c threshold (as indeed it is) but October and November could end up well above and sufficiently so to pull the 3 month average over the threshold. So, I apologise for misleading anyone (if you noticed my error!). 

Furthermore, the addition to their official definition is that the threshold must be exceeded for a minimum of 5 consecutive rolling/overlapping 3 months periods.  That is why in the table above reds (El Nino) and blues (La Nina) do not run for less than 5 periods. For example the long La Nina episode that ran from M/J/J 2010 until F/M/A 2012 was broken by the M/J/J 2011 when the average  fell just below the threshold.  Malcolm has prepared an excellent chart to demonstrate this much more easily and I told him that he must take the credit for it and post it himself :) 

 

That's a great summary of the various ENSO definitions in use David. As you say, this being a US forum we should mainly focus on the NOAA definition and prognosis in this thread, although with great analysis also undertaken by the Australian and Japanese meteorological bodies, it's always worth looking at their views on ENSO developments.

 

Thank you for your kind comment about my NOAA 'ENSO calculation' illustration. I've included it below.

 

And while I'm here, may I say what superb analysis @Tamara and @Snowy Hibbo have posted above. This is a great ENSO discussion going on!

 

ENSO threshold illustration.jpg

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ENSO DEBATE - A PAPER REVIEW:  THE NORTH AND SOUTH PACIFIC MERIDIONAL MODES

 

During the early stages of our ENSO debate, I thought that it might be helpful to briefly review a few papers and presentations that we have in the Research Portal which I think may be relevant to the current ENSO phase and the "potentially" emerging El Nino episode.  I'll start off with this one:

 

Impact of the South and North Pacific Meridional Modes on ENSO: Observational Analysis and Comparison (click on the title to go to the portal entry with a link to the full paper)

 

Abstract:

An interannual variability mode in the southeast Pacific with a physical interpretation similar to that of the Pacific meridional mode (PMM) in the North Pacific was recently identified. Both modes have been shown to influence the subsequent development of El Niño–Southern Oscillation (ENSO) events. This study investigates the relationship between ENSO and the two PMMs using observational and reanalysis data. The results show that the South Pacific meridional mode (SPMM) mainly favors the development of sea surface temperature anomalies (SSTAs) in the eastern equatorial Pacific, whereas the North Pacific meridional mode (NPMM) mainly favors the development of SSTAs in the central equatorial Pacific. Both of the meridional modes are considered to be analogous in terms of their physical interpretation and can be important predictors of ENSO when considering different flavors of ENSO. Neither the NPMM nor the SPMM can be precluded as accurate indicators when forecasting particular flavors of ENSO.

 

This 2016 paper assesses the influences of these two modes on the ENSO state and on the types or flavour of upcoming El Nino episodes. It also considers the north and south Pacific oscillations (NPO and SPO) and the pattern of SST developments (note that they do not use the specific term SPO which had only just been coined shortly before this paper was published).  It covers several  examples from recent ENSO past events where the influence from one or the other mode dominated as well as how they interact. It starts off with a great summary of the earlier research in this area and how it evolved. I copy some short extracts from the paper below:

 

Over the past two decades, numerous studies have established a robust relationship between the development of ENSO and the extratropical variability of the atmosphere

 

Recent studies have shown that most El Niño events in recent decades have been preceded by apparent NPMM (positive phase) activity.

 

the Pacific meridional mode in the Southern Hemisphere, defined as the South Pacific meridional mode (SPMM), has a larger equatorial signature than the NPMM for the same amount of extratropical variability, particularly in the eastern equatorial Pacific.

 

the predictability of ENSO events, particularly the specific flavors of ENSO, are closely related to atmospheric and/or oceanic precursors responsible for the excitation of events at certain lead times

 

The SST-driven meridional circulation in the subtropical southeastern Pacific was relatively significant from the boreal spring to the autumn.

 

the subtropical precursor in the Southern Hemisphere, which presents different behaviors and influences than the NPMM in our interpretation, was as important as the subtropical precursor in the Northern Hemisphere when considering its contribution to a different flavor of ENSO.

 

the variability of ENSO related to the NPMM is more confined to the central Pacific and has relatively less influence on the eastern equatorial Pacific, whereas the variability of ENSO related to the SPMM has less of an impact on the central equatorial Pacific.

 

From the closing discussion:    

 

This study has several potential implications. First, the different influences of the NPMM and SPMM on ENSO, which are associated with the North and South Pacific extratropical variability, were compared in both hemispheres. The differences may account for different ENSO flavors, which are particularly important for the prediction of ENSO. Second, the NPMM and SPMM may also inhibit the development of ENSO events under special backgrounds, which is similar to the 2012 and 2014 ENSO events

 

when considering the origins of the SPMM, other questions remain. Although the SPMM originates from the South Pacific extratropics independent of ENSO in the previous boreal winter (Fig. 4b), the question of whether the SPMM originates solely or partly from the remote tropical forcing in other seasons according to fully coupled models and observation data requires further study

 

This study emphasizes the importance of climatic variability of both the Northern and Southern Hemispheres in the tropical Pacific climate, and it suggests that both the NPMM and SPMM in the subtropical Pacific can be important ENSO predictors in the future. Therefore, forecasts of a particular ENSO flavor may be improved, although such forecasts will certainly require further research.

 

I realise that it can be misleading to quote parts of a paper which may be taken out of context and I strongly recommend that you read the full paper which is quite short and an easy read with some excellent charts and  diagrams.. 

 

Well this whetted my appetite, so I'll close with a several charts:

pmm1.PNG

PMM in strongly +ve mode but falling this year. As we know, the SST anomalies have changed to some extent since August - so here's the current chart for comparison.

en5.PNG

Much of the sub tropical south Pacific tropical has cooled again as has the tropical and eastern tropical Atlantic and the Indian ocean. We need to keep an eye on those rising tropical EPAC ssts and I'll check today's ENSO region ssts.  If there's a noticeable change, I'll post these shortly.  

 

NOAA do not yet produce any charts showing the SPO and I've been trying to find some meaningful charts.  Perhaps Zac @Snowy Hibbo our resident southern hemisphere specialist can help?  I found this:

en6.PNG

I imagine that this would be more useful if we read it in conjunction with the MLSP  charts. 

 

spac_slp_00hr.png

EDIT:  This is an auto updating chart (run by run), so that we can keep monitoring the changes in the the circulation pattern in the south Pacific

The "Stormsurf" chart runs from T+0 to T+180 (just the current updating T+0 shown above). Since Malcolm @Blessed Weather posted that "For ENSO Look South" paper in the portal and reviewed it on here a few weeks ago (near the top of this page) I've been researching the SPO and realise just how important it is - particularly this year in -ve phase and its influence on the El Nino development probably being a significant contributor to the erratic progress  As the paper that I reviewed above says, more research is needed.  I have some more papers on all this "southern" influence and if this sparks some interest, I'll happily review several more of them on here. The lack of s hem info compared to the n hem is stark and yet we are starting to appreciate the great significance of these SPAC wind and circulation patterns on driving the surface and sub surface currents from further south and the rate and amount of mixing into the equatorial waters.

 

When I posted yesterday on the different country ENSO definitions, I found those detailed measurement criteria that Peru applies.  I've only just started looking at their Met and climate offerings but it looks like I will find some very useful research which is highly relevant to our discussions. Meanwhile, Zac, it really would be useful if you could post some links on the southern ocean models, charts and marine climate. Apart from posting on here, I also want to do further posts on the Arctic thread which includes "Antartica" and it has a strong influence on the southern oceans and (I think) may, at certain times, have a quite direct influence on the SPO.  So all this will have a knock on effect on the ENSO state - when, to what extent and how dominant a factor this might be needs to be investigated.  If there are papers out there, I'll try to track them down.  David :)  

 

 

 

 

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