Jump to content

Teleconnections - Interactions and Impact


Recommended Posts

  • Replies 117
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

Arctic Oscillation (AO) – The influence of Snow Cover Extent (SCE) and the Snow Advance Index (SAI) We are now in the last 10 days of October and it’s a good time to look at the scientific resear

Thanks Interitus. An interesting and informative paper. If I may do a quick summary of my take: SAI/AO mechanism: This works through positive snow anomalies enhancing the stationary wave activi

The one teleconnection not included thus far is the -EPO pattern which is heavily influenced by the SSTA in the North pacific- This year the SSTs are set back west than the last fee years where t

Posted Images

The Madden-Julian Oscillation (MJO)

A look at what the MJO is currently doing and forecasts going forward. But first a quick overview of the MJO and how it can impact the UK for those wishing to learn.

The MJO is an intra-seasonal (possible multiple events each season) tropical phenomenon in which a disturbance of clouds, rainfall, winds, and pressure travels east around the planet following the line of the equator, returning to its initial starting point in 30 to 60 days on average.

The tropical disturbances that represent an active MJO create equatorial Kelvin and Rossby waves as the surface pressure, heavy precipitation and subsequent condensation releases (latent) heat into the atmosphere. The key generation area for Kelvin-Rossby waves is roughly from 120E to 120W. The following charts represent a NWP model of the atmosphere and show the equatorial Kelvin-Rossby wave response as it propagates eastwards:

Response Day 1: 808347414_Kelvin-RossbywavereponsetoMJODay1.thumb.jpg.9266fb880a767601e6d953303fce0460.jpg Response by Day 25: 1971785640_Kelvin-RossbywavereponsetoMJODay25.thumb.jpg.deb041b7e470f3a2c0cda65c59ea66b9.jpg

Source: Professor Adrian Matthews School of Environmental Sciences and School of Mathematics, University of East Anglia, Norwich, UK.

The MJO makes a large contribution to various weather events in the mid-latitudes when in different phases. And certain Phases can also impact what happens in the stratosphere.

“It is clear that phases 7 and 8 are preferred during the 12 days preceding Sudden Stratopheric Warmings (SSW). During days 13 to 24 before SSWs, MJO phases 4, 6, and 7 are preferred, while during days 25 to 36 before SSWs, MJO phases 2 and 3 are preferred.”

Source: Observed connection between stratospheric sudden warmings and the Madden-Julian Oscillation

The progress of the MJO around the globe can be followed through the Phase diagram updated regularly by NOAA and other organisations. Here’s the GEFS forecast showing the location of the MJO from Oct through Nov and into early Dec. Each point on the chart is the date. The green is the forecast period and the MJO is shown to be imminently heading into the COD (circle of death) resulting in little continued influence on the mid-latitudes. The further away from the COD, the stronger the MJO.

1306374912_MJOGEFSForecast20Nov-4Dec.thumb.gif.991e9db15dbbaf0f0814445dd6a55bc3.gif

Source: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/clivar_wh.shtml

Phases 8 and 1 are when the MJO can exert its most impact on UK weather, as illustrated by the following annotated Sea Level Pressure charts for Phase 8 and Phase 3 - 4.

Phase 8 suggesting support for a negative NAO: 865649734_MJOPhase8SLPAtlanticimpact.thumb.jpg.f97c86b4652b19238530d58474c26c55.jpg

Phase 3 – 4 suggesting support for a positive NAO: 1851501605_MJOPhase3-4SLPAtlanticimpact.thumb.jpg.ac66b91c81dde91ce6d0fcbce14e8e6b.jpg

Source: Professor Adrian Matthews School of Environmental Sciences and School of Mathematics, University of East Anglia, Norwich, UK.

There are also composite 500hPa geopotential height anomaly charts available that have been built up from past MJO activity and show the typical tropospheric synoptic pattern for each Phase. (A note of caution here – Arctic Warming may now be impacting on previously expected patterns so composites should be viewed accordingly). Variants are available for different phases of ENSO, so with ENSO currently neutral here’s the composite chart for Phase 1 in November, and for comparison and out of interest, the GEFS Mean 500hPa Anomaly for 27th Nov from 21st and 22nd Nov:

1458259146_MJOCompositeNovPh1ENSOneutral.thumb.png.8dd02134b2ba7ca93eeafe60fb4fd47b.png1475915724_GEFSMeanAnomalyon21Novfor27Nov.thumb.png.09ac15a02508c03e63e6e26f0d66ae1b.png1619212804_GEFSMeanAnomalyon22Novfor27Nov.thumb.png.43a38f925bf150a25fb2441cdad7da25.png

Source Composite chart: https://www.meteonetwork.it/models/mjo/
Source GEFS anomalies: http://www.meteociel.fr/modeles/gefs_cartes.php?code=21&ech=132&mode=5&carte=1

The MJO forecast going forward into December

The following chart shows Outgoing Longwave Radiation (OLR) which represents the differing reflection levels given off by a cloudy or clear sky. Here the brown shading indicates clear skies and dry weather (MJO inactive), with green indicating cloudy skies and wetness (MJO active). The active MJO is shown within the solid black line area, with the inactive MJO area within the dotted black line area. We can see the current MJO activity over the Kelvin-Rossby wave generation area drawing to a close during late November. However, in the forecast area of the chart the next event (strong greens) is getting going in the Indian Ocean and, as indicated by the solid black line area, is set to move into the KW generation area later into December.

696576162_MJOolr_cfs.eqtrNCIS21Nov.thumb.png.611fc527fae616c6c6b2750f4e064e2d.png

Source: Climate Forecast System (CFS) https://ncics.org/portfolio/monitor/mjo/

The CFS 200hPa Velocity Potential Empirical Wave Propagation forecast uses upper atmosphere dynamics to forecast the potential for precipitation for the next 40 days. Here’s the latest output for 20th Nov to 30th Dec with the red anomalies indicating drier/inactive phase (no support for precipitation) and green supportive of moisture and convection thus precipitation/active phase. Each box represents a 5-day forecast period. Again we can see as November draws to a close a new Phase of MJO activity is building in the Indian Ocean. This crosses the mid-Pacific around the middle of December but not moving towards the west-Pacific and favourable Phases 8 and 1 for UK impact until towards the end of December.

841893216_MJO200hPaVelocityPotential20Novto30Dec.thumb.gif.f5d0a3ec7491fad4f1fd98509bd8a3bc.gif
Source: http://www.daculaweather.com/4_mjo_phase_forecast.php

 

  • Like 5
Link to post
Share on other sites
logo-2559612375.png
EVENTS.ECMWF.INT

#StratosphericWS This workshop brought together experts to discuss and propose ways forward in representing the stratosphere in current and future...

A lot of presentations to get through but worth a watch, lots of learnings. Amy Butler's presentation is superb in session 1.

Interesting take from the presentation is the El Nino / La Nina relationship to SSW.  Pre 1981 data shows a relationship between strong EL Nino years and SSW but post 1981 this relationship is no longer there and there have been more SSW's during La Nina years showing the lack of linear relationship between ENSO and SSW's.

The representation of stratosphere-troposphere coupling in S2S models

Speaker: Amy Butler

 

  • Like 4
Link to post
Share on other sites

 

Quote

A lot of presentations to get through but worth a watch, lots of learnings. Amy Butler's presentation is superb in session 1.

Well I'm going to be stuck indoors for the next couple of days anyway ?

  • Like 1
Link to post
Share on other sites

ENSO Modulation of the MJO

That’s a great paper you’ve spotted @Kirkcaldy Weather and worthy of a more detailed look. It articulates with great clarity the way in which multiple teleconnections interact to impact weather around the world and specifically the way in which the combined impact of ENSO and MJO interworking impacts the NAO and thus UK weather. At the end of this post I draw my conclusions about the implications for the current outlook for the UK.

So first of all the title (with embedded link to full paper) and ‘plain English’ abstract:

ENSO Modulation of MJO Teleconnections to the North Atlantic and Europe

"The Madden‐Julian Oscillation (MJO) is the dominant source of differing weather conditions in the tropics on timescales within a season. The remote linkage (teleconnection) from the MJO to the North Atlantic‐European (NAE) region provides a source to modify or persist weather conditions and add predictive power to weather forecasts on 10‐ to 30‐day timescales. The El Niño‐Southern Oscillation (ENSO) has an influence on the seasonal climate state, through which the waves and linkages from the MJO to the NAE region travel. Here we find a robust dependence of these teleconnections from the MJO to NAE weather regime patterns on the ENSO state, such that under certain states of the MJO, certain regimes occur more than twice as often. The different sources and pathways also become clearer, with the teleconnections travelling via the troposphere and the stratosphere. This dependence on ENSO state has significant implications for predictions on 10‐ to 30‐day timescales."

In my previous post above I’ve described how the MJO, via Rossby-Kelvin Waves, impacts weather around the world, so I’ll not cover that aspect again. Rather, I’ll focus on the new aspects revealed in this paper. Significant aspects shown in bold.

First up, this paper states that the MJO impact on the North Atlantic-European (NAE) region is typically around 10 Days, but this can vary depending on the strength of the MJO and also Phase (where it is in its circumnavigation of the globe) as each Phase lengthens or shortens the teleconnection pathway.

  • MJO Phase 3 – approximately 10 days after this Phase (active convection over the eastern Indian Ocean), the occurrence of +NAO regime is increased by ~60% relative to climatology.
  • MJO Phase 4 - This +NAO impact can extend for up to 12 days after phase 4.
  • Following the above Phases 3 and 4 there is a small (~30%) increase in the chance of a Scandi Block (SB) and Atlantic Ridge (AR) developing at lags of around 0–6 and 10 days, respectively, likely as a result of in situ development and dynamics in the NAE.
  • MJO Phase 6 – at lags of 10+ days after (active convection over the western Pacific Ocean) there is an increased occurrence of a -NAO by up to ~70%.
  • Phase 7 and 8 – the increased occurrences of a -NAO lasts through MJO Phase 8.

The above impacts are nicely summarised in the next diagram, also posted by @sebastiaan1973 above:

1661565445_MJONAEimpactbyPhase.thumb.jpg.06d13225037606e5b53f16f01f7e8ecd.jpg

 

ENSO Impact – this teleconnection with its El Nino (EN - warm Pacific) and La Nina (LN - cold Pacific) provides the key backdrop within which the MJO propagates. The paper finds that during the extended winter months of Nov – March there is a robust dependence of the MJO > NAE teleconnection on the differing status of ENSO (EN, LN and Neutral).

El Nino Impact

  • During EN years the +NAO teleconnection is of a much larger amplitude, significant following MJO Phase 1, with increased occurrence up to ~100% (twice climatology), restoring to climatology around 6 days (one MJO Phase) later.
  • When there is no active MJO teleconnection (Phase 0; around one third of winter days), there is an increased frequency of -NAO and AR, and decreased frequency of +NAO.
  • The -NAO regime has significant increases in occurrence only after MJO Phase 7 (also up to ~100%).
  • The paper concludes that the MJO‐NAE teleconnection during El Niño years results in a much more frequent +NAO regime state, occurring after MJO phases 1–5 and dominating the seasonal mean teleconnection.

Neutral ENSO Impact

  • The paper concludes that the MJO‐NAE teleconnection results in a slightly more frequent +NAO state after MJO Phases 1 - 4 and a much more frequent -NAO regime state after MJO Phases 6 - 7.

La Nina Impact

  • The paper concludes that the only complete MJO‐NAE teleconnection during LN years is a strong -NAO teleconnection but this only occurs late in the MJO Phase 8 and rapidly fades. 

This illustration is a good visualisation of the processes involved:

702813425_MJOENSOimpactillustration.thumb.jpg.d6180818a8b3a12107b7a3fbab5ca56f.jpg

 

Implications for current UK Outlook

The MJO is currently flirting with Phase 0 (Circle of Death - COD) but expected to move into Phase 1 and progress through Phases 2 and 3. Here’s the latest ECM forecast for 27th to 11th December:

946641829_MJOECMforecast27Novto11Dec.thumb.gif.fba284ef28c52aae129cbeacd34716c9.gif

Based on the MJO Phase and current ENSO Neutral status, what 500hPa pattern should we expect in our neck of the woods? A look at the following diagrams from the paper shows the expected 500hPa heights anomalies for the various combinations of MJO Phase and ENSO status. I’ve marked the relevant patterns which are in line with the findings of the paper for a "slightly more frequent" +NAO state in Phases 1 - 4. The +NAO signal lasts until the MJO once again cycles through to Phase 6 where this switches to supporting a "much more frequent -NAO regime". Current MJO forecasts suggests the progression to Ph 6 will not be until late December:

With MJO Phases 0 and 1: 669617098_MJOENSO500hPaAnomalies.thumb.jpg.62623730a42e35150ddf3e48b35c3299.jpg

With MJO Phases 2 and 3: 1179887544_MJOPh2and3ENSO500hPaAnomalies.thumb.jpg.5866b081ed05df1ef664db60e699f3a1.jpg

Edit: There are other teleconnections that also impact the NAO (and indeed the MJO) such as low solar activity, Strat Polar Vortex strength and whether there is an easterly or westerly QBO. In this post I have focussed on the findings of this new paper and have made no attempt to introduce any potential impact from other teleconnections. There are many complex interactions and feedback loops between various teleconnections and these will be subject to further posts.

Edited by Blessed Weather
  • Like 4
Link to post
Share on other sites

An interesting Tweet from Simon Lee referring to new research into the impact of warming in the Indo-Pacific tropical oceans causing a slowing of the progression of the MJO in Phases 5 - 7. I've also copied the abstract from the paper he refers to but unfortunately the full paper is behind a paywall. It would be good to see the full paper as Phases 6 and 7 are supportive of -NAO and SSW developments.

1121154904_SimonLeetweet28Nov2019.thumb.jpg.89047d120a9cb8916ba3c4ec25587766.jpg

Twofold expansion of the Indo-Pacific warm pool warps the MJO life cycle

The Madden–Julian Oscillation (MJO) is the most dominant mode of subseasonal variability in the tropics, characterized by an eastward-moving band of rain clouds. The MJO modulates the El Niño Southern Oscillation1, tropical cyclones2,3 and the monsoons4,5,6,7,8,9,10, and contributes to severe weather events over Asia, Australia, Africa, Europe and the Americas. MJO events travel a distance of 12,000–20,000 km across the tropical oceans, covering a region that has been warming during the twentieth and early twenty-first centuries in response to increased anthropogenic emissions of greenhouse gases11, and is projected to warm further. However, the impact of this warming on the MJO life cycle is largely unknown. Here we show that rapid warming over the tropical oceans during 1981–2018 has warped the MJO life cycle, with its residence time decreasing over the Indian Ocean by 3–4 days, and increasing over the Indo-Pacific Maritime Continent by 5–6 days. We find that these changes in the MJO life cycle are associated with a twofold expansion of the Indo-Pacific warm pool, the largest expanse of the warmest ocean temperatures on Earth. The warm pool has been expanding on average by 2.3 × 105 km2 (the size of Washington State) per year during 1900–2018 and at an accelerated average rate of 4 × 105 km2 (the size of California) per year during 1981–2018. The changes in the Indo-Pacific warm pool and the MJO are related to increased rainfall over southeast Asia, northern Australia, Southwest Africa and the Amazon, and drying over the west coast of the United States and Ecuador.

Link: https://www.nature.com/articles/s41586-019-1764-4

 

  • Like 2
Link to post
Share on other sites

With some intresting research

The North Atlantic Oscillation (NAO) and eddy-driven jet contain a forced component arising from sea surface temperature (SST) variations. Due to large amounts of internal variability, it is not trivial to determine where and to what extent SSTs force the NAO and jet. A linear statistical–dynamic method is employed with a large climate ensemble to compute the sensitivities of the winter and summer NAO and jet speed and latitude to the SSTs. Key regions of sensitivity are identified in the Indian and Pacific basins, and the North Atlantic tripole. Using the sensitivity maps and a long observational SST dataset, skillful reconstructions of the NAO and jet time series are made. The ability to skillfully forecast both the winter and summer NAO using only SST anomalies is also demonstrated. The linear approach used here allows precise attribution of model forecast signals to SSTs in particular regions. Skill comes from the Atlantic and Pacific basins on short lead times, while the Indian Ocean SSTs may contribute to the longer-term NAO trend. However, despite the region of high sensitivity in the Indian Ocean, SSTs here do not provide significant skill on interannual time scales, which highlights the limitations of the imposed SST approach. Given the impact of the NAO and jet on Northern Hemisphere weather and climate, these results provide useful information that could be used for improved attribution and forecasting.

-> 

JOURNALS.AMETSOC.ORG

 

  • Like 2
Link to post
Share on other sites
  • 2 weeks later...

MJO Update 9th December

Forecasts from a couple of weeks ago that the MJO might progress into Phases 8 and 1 - supportive of a negative NAO – seem to have been wide of the mark. Current signals from the tropics over the next couple of weeks suggest little MJO influence on the UK weather pattern. The Indian Ocean Dipole – which set a new November record - continues to interfere with the development of the MJO in the IO, in particular causing uncertainty about its eastward progression going forward.

IOD record Nov peak: 1980958732_IODIndexNov2019.thumb.jpg.818b1af7852b840b28c15c732321a971.jpg

The Phase diagram from the GFS Ensemble (bias corrected) shows the MJO in Phase 2 over the next week, then briefly Phase 3 in week two, before slipping into the COD (denoting insignificant impact on the mid-latitudes).

1188306280_MJO_GEFSBC_member09Decto23Dec.thumb.gif.42ffb8f255cd6afb60604446f7a9153c.gif

Source: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml#discussion

Beyond that the CFS forecast 850hPa wind anomalies out to 6th Jan (also showing MJO, Kelvin and Rossby Wave activity) has good and bad news. The good news is the strong easterly anomalies over the IO fade as the IOD also enters its natural period of winter decay. This allows westerly wind anomalies and an active MJO to start building again, this time – with fading IOD interference - hopefully looking good to move east into the Kelvin Wave generation area (approx. 135E to 170W) around the end of the year/early January.

310560392_MJOuwnd850_orig.eqtr09Decto06Jan.thumb.png.01b2bfc923fcd8be03f4590c6b60929d.png

Source: https://ncics.org/portfolio/monitor/mjo/

  • Like 7
Link to post
Share on other sites

QBO Update 17th Dec

A quick look at where we are with the QBO. First of all the NASA monthly data and this shows that the ZMZW at 30mb was still westerly with a value of +5.07 (ms -1) for Nov 2019. A simple extrapolation shows the rate of decrease has been running at an average of 1.58 (ms -1) per month for the last 6 months, suggesting the QBO is very unlikely to officially turn negative (easterly) in December; more likely late Jan or Feb 2020.

2061628151_QBO30mbZMZWNov2019.thumb.jpg.b9fa54f362a2307bfa4df93d9dff4700.jpg

Source: https://www.esrl.noaa.gov/psd/data/correlation/qbo.data

A descending easterly QBO is known for erratic progress, often stalling, as described in this paper. A look at what the ECMWF Zonal Mean Zonal Wind charts have been showing so far this month certainly illustrates progress of descent has not been following forecasts. First the position on 7th Dec with the ECM showing QBO still westerly but forecasting that by day 10 (17th Dec) to have turned easterly all the way down to nearly 40mb:

ECM T0 7th Dec: 218942671_ECMZMZW07Decfor07Dec.thumb.gif.9c37d9d4a3a29c37159e1c109813eb66.gif Forecast T240 17th Dec: 1900718840_ECMZMZW07Decfor17Decmarked.thumb.jpg.37f6195d7dcc3c6754d289278ba5cd8d.jpg

So did the ECM forecast verify? No, the latest chart for the 16th Dec shows the descending easterly apparently still not quite over the line at 30mb:

ECM T0 16th Dec: 392442220_ECMZMZW16Decfor16Decmarked.thumb.jpg.607d3e01a45c32bded388e74b165ea73.jpg

Source: https://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/index.html

But whilst the official measure based on the monthly mean of the zonal wind is unlikely to show negative (easterly) until early 2020, clearly the QBO based on current daily Singapore sonde u-wind readings is fluctuating close to easterly at 30mb. And worth noting previously quoted research Surface impacts of the Quasi Biennial Oscillation that suggests in early winter the winds at 20mb may have a bigger impact than the winds at 30mb (which are more influential further into winter).

So going forward into early 2020 - as the above paper suggests - the descending eQBO should be more supportive of vertically propagating wave attack into the stratosphere and weakening of the SPV. Another positive is that an eQBO also supports enhanced amplitude of the MJO.

  • Like 4
Link to post
Share on other sites

This week's update from NOAA/NWS rather more encouraging that the MJO, currently in the Indian Ocean and about to briefly move into Phase 3 before slipping into the COD (neutral zone), will nevertheless continue to propagate eastward before re-emerging in the Western Pacific in a couple of weeks time. Both dynamical models are in reasonable agreement on this, although GEFS going for re-emergence in Phase 7 whilst ECM briefly 6 before then moving into Phase 7:

GEFS: 1922460938_MJOGEFS16Decto30Dec.thumb.jpg.f16cef5cb212b3ca5789ca8bd8d64b45.jpg ECM: 1980611189_MJOECM16Decto30Dec.thumb.jpg.810b3790d3cc91192fdc3cc8e1ef1d9c.jpg

To be treated with appropriate caution, but both Phases 6 and 7 composite charts for ENSO neutral conditions show high level blocking and a negative NAO:

Phase 6: 480490275_MJOcompositeENSOneutralPh6.thumb.png.a3bde5ae1167c3cf896f67d66bb1b2c6.png Phase 7: 1147573541_MJOcompositeENSOneutralPh7.thumb.png.caf01c8ed170680753557cfa66db2592.png

Some way to go and also bearing in mind the forecasts at the moment suggest low amplitude, but could the MJO offer a glimmer of hope of a pattern change in a couple of weeks time? One to keep an eye on.

  • Like 3
Link to post
Share on other sites

Indian Ocean Dipole (IOD) Update

A quick update on the IOD which as well as casting an influence on UK winter prospects (see my previous post) is having a major impact on other aspects of global weather. Typical of a +IOD impact, the southern two-thirds of Australia sees below average rainfall and above average temperature. It’s therefore not surprising that following this years very strong +IOD Australia is experiencing a severe drought, bushfires and yesterday (17th Dec) recorded a record high temp of 40.9C.

Meanwhile a record-breaking tropical cyclone season has just finished in the North Indian Ocean with 8 storms, several severe. Using the ‘total energy’ measure of this years cyclones, 2019 was nearly 5 times greater than an average year, setting a new record.

Fortunately the +IOD is gradually fading with the latest update showing a considerable fall from the record positive value of +2.1C back in Oct/Nov. But at +0.8C is still above the threshold value of +0.4C so, for now, still ongoing.

15th Dec update: 1045680868_IOD15DecUpdate.thumb.png.a7e10fdd4c43529e8c4b758ee6d5ec81.png

Source: http://www.bom.gov.au/climate/enso/indices.shtml?bookmark=iod

  • Like 3
Link to post
Share on other sites

Disappointing developments with progression of the MJO this week. For some weeks it has been the strong Indian Ocean Dipole (IOD) interfering with MJO development. The IOD continues to substantially weaken as we move through December and is expected to become neutral in January. So last week's forecasts that a weak MJO event would continue to progress eastward through the COD and finally emerge end-Dec in the Western Pacific Phase 6 and 7 at reasonable amplitude gave hope that the start of January could see some high latitude blocking develop in our neck of the woods. The sudden change in direction of progress shown by both GEFS and ECM on the latest RMM Phase diagram is indicative of interference from Rossby Wave activity, with the MJO dropping back into the neutral zone in week 2.

GEFS 676937394_MJOGEFS23Decto06Jan.thumb.gif.cb304dd9e0af0af5c12a5d17c4f23d72.gif ECM 1325729587_MJOECM23Decto06Jan.thumb.gif.49339a0cd303ee7880ea1c1576e01dfc.gif

Source: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/clivar_wh.shtml

Going forward there remains uncertainty, although the OLR forecast (brown is clear sky & dry, green cloud & convection) to 19th Jan suggests renewed MJO activity may develop in January. It also confirms the fading IOD over the Indian Ocean.

2135530636_MJOOLRforecast23Decfor19Janmarked.thumb.jpg.45ef2cd6a015bd48bc41dfaf04de4a1c.jpg

Source: https://ncics.org/portfolio/monitor/mjo/

Edited by Blessed Weather
Links added.
Link to post
Share on other sites

Teleconnections Update - 31st Dec 2019

Indian Ocean Dipole (IOD)

The IOD has continued its sharp decline during December with a latest reported value from the Australian Met (BOM) for w/e 29th December of +0.3C, bringing the index into the 'neutral' zone (-0.4 to +0.4C). Although strangely their narrative suggests a latest value of +0.6C and anticipated drop to neutral in January, contradicting their chart which clearly states +0.3C:

497362515_IODWklyIndex29Dec2019.thumb.png.25eb3b3af4306300aab7e8c057f431ff.png

Source: http://www.bom.gov.au/climate/enso/indices.shtml?bookmark=iod

Madden Julian Oscillation (MJO)

With the IOD finally losing its influence, the latest NOAA/CPC MJO update reports:

"For the first time since September, there are indications that the positive Indian Ocean Dipole (IOD) is not anchoring the upper-level pattern over the western Indian Ocean."

This is more encouraging going forward as the strongly positive IOD has been significantly interfering with (subduing) MJO activity in the last couple of months.

NOAA confirm that Rossby Wave interference contributed to the fact that the recent movement through Phase 7 was brief and at low amplitude. Latest forecasts from both GEFS and ECM project a weak MJO to move through the Western Pacific and weaken again as it traverses the Western Hemisphere in the COD (neutral zone) before strengthening and re-emerging in Week 2 over the Maritime Continent. Forecasts to 13th January:

GEFS 1316097739_MJO_GEFSBC_member30Decto13Jan.thumb.gif.bb74db22a630e419e36bd077af50519d.gif ECM 678801999_MJOECMF_30Decto13Jan.thumb.gif.dbd5b4d55cc5a219332197815ee0fd1d.gif

Source: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/clivar_wh.shtml

MJO Phases 4 and 5 composites for January (ENSO neutral) would suggest a Euro High. For high latitude blocking we would want to see a quick progression through to favourable Phases 6, 7, 8 and 1. But that's getting way ahead of ourselves.

Phase 5 Composite: 2118582580_MJOPhase5ENSONeutral.thumb.png.55dc02e35071baa196ec9c104451dc55.png

Source: https://www.meteonetwork.it/models/mjo/

Southern Oscillation

The SOI index is a measure of the sea level pressure differences occurring between the western and eastern tropical Pacific Ocean (Tahiti and Darwin, Australia) and is indicative of El Niño or La Niña conditions. The SOI correlates well with changes in ocean temperatures across the eastern tropical Pacific with prolonged periods of negative (positive) SOI values coinciding with abnormally warm (cold) ocean waters typical of El Niño (La Niña) episodes. Therefore sustained negative values of the SOI below −7 typically indicate El Niño conditions while sustained positive values above +7 typically indicate La Niña. Values between +7 and −7 generally indicate neutral conditions. The index (mean) for the 30 days ending 22nd December was -4.5 thus indicating continuance of ENSO neutral conditions.

SOI index: 1817086305_SOIIndex29Dec2019.thumb.png.0933ed4605d25787f047e2471a384175.png

Source: http://www.bom.gov.au/climate/enso/#tabs=SOI

The generally accepted threshold for El Nino (La Nina) is a SST temp anomaly greater than +0.5C (-0.5C) per month where the monthly measure is a 3-month running mean. The threshold must be exceeded for 5 consecutive monthly measures. (Although other definitions are used, for instance Australian BOM use a 0.8C threshold).
For interest, here's the latest weekly SST values for ENSO regions:

1847656393_ENSOSSTtempsperweekDec2019.thumb.jpg.ab4503ab1feb9758cb35c6e5b6c99040.jpg

Source: http://www.bom.gov.au/climate/enso/#tabs=Sea-surface

Multi-model forecasts suggest ENSO will remain neutral for the foreseeable future:

1216030752_ENSOmodelforecastsfromDec2019.thumb.jpg.f8dba2562bdc38a2596ccf19795d0cb4.jpg

Source: https://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/

Edited by Blessed Weather
Typo and tidied up ENSO definition.
  • Like 5
Link to post
Share on other sites
37 minutes ago, Blessed Weather said:

Teleconnections Update - 31st Dec 2019

 

Thanks for the update.

So all eyes onto late January, when the MJO should be making its way into 7-8-1, if indeed it does and at a decent amplitude. IDO will have become neutral as will ENSO, lower solar minimum.

Will the PV simply overwhelm everything?

 

  • Like 1
Link to post
Share on other sites

Observed Relationships Between Sudden Stratospheric Warmings and European Climate Extremes

Quote

Abstract

Sudden stratospheric warmings (SSWs) have been linked with anomalously cold temperatures at the surface in the middle to high latitudes of the Northern Hemisphere as climatological westerly winds in the stratosphere tend to weaken and turn easterly. However, previous studies have largely relied on reanalyses and model simulations to infer the role of SSWs on surface climate and SSW relationships with extremes have not been fully analyzed. Here, we use observed daily gridded temperature and precipitation data over Europe to comprehensively examine the response of climate extremes to the occurrence of SSWs. We show that for much of Scandinavia, winters with SSWs are on average at least 1 °C cooler, but the coldest day and night of winter is on average at least 2 °C colder than in non‐SSW winters. Anomalously high pressure over Scandinavia reduces precipitation on the northern Atlantic coast but increases overall rainfall and the number of wet days in southern Europe. In the 60 days after SSWs, cold extremes are more intense over Scandinavia with anomalously high pressure and drier conditions prevailing. Over southern Europe there is a tendency toward lower pressure, increased precipitation and more wet days. The surface response in cold temperature extremes over northwest Europe to the 2018 SSW was stronger than observed for any SSW during 1979–2016. Our analysis shows that SSWs have an effect not only on mean climate but also extremes over much of Europe. Only with carefully designed analyses are the relationships between SSWs and climate means and extremes detectable above synoptic‐scale variability.

Plain Language Summary

Sudden stratospheric warmings (SSWs) are rapid warming events that occur tens of kilometers above the Earth's surface in the Northern Hemisphere. They are often associated with cold winter weather at the surface in the Northern Hemisphere, but previously, the connection between SSWs and cold extremes has been made using reanalyses and models rather than observational data. We performed the first comprehensive analysis of the link between SSWs and climate extremes in Europe. We found that winters with SSWs are substantially colder than average in areas like Scandinavia. Below‐average temperatures tend to precede SSW events, but the intensity of cold extremes, such as the coldest night of the month, tends to be strongest after the SSW event. Precipitation tends to decrease in northern Europe in winters with SSWs, but in southern Europe the aftermath of an SSW is often associated with more precipitation and an above‐average number of wet days. The 2018 SSW, for which the subsequent surface cold event was referred to as “The Beast from the East,” exhibited stronger cold anomalies in extreme indices over northwest Europe than any SSW in the 1979–2016 period. Through this analysis we found a link between SSWs and European wintertime climate extremes.

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JD030480

  • Like 2
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...