Key Factors

• Current Global state (ocean & land temperature anomaly)

The planet is without doubt a warmer place now than a decade ago and currently in a steep warming trend unlike anything seen in the modern era.

For the last time the earth dipped below average you have to go all the way back to 2014, at the end of a series of ‘cooler years’ following the 2008 solar minimum and ahead of a rise to a new ‘warm benchmark’ in 2016, courtesy of the most recent Super El Nino and surpassing the spike in the wake of the previous Super of 1997.

It’s safe to say we’re now surpassing 2016 with a new 2023 benchmark. Ocean and atmosphere is very warm, record warm and you can blame anything, CO2, underwater volcanoes, hunga tonga etc etc.

September 2023 appears to have reached yet another global temperature plateau.

ERA5 global temperature anomaly:
September 2023: +0.93°C
September 1940: -0.63°C

compared to a 1991-2020 climatology or average/normal pic.twitter.com/YGT5KZuSIc

— Ryan Maue (@RyanMaue) October 6, 2023

Trying to understand what created the huge September 2023 global temperature anomaly, and we need to look at weather time-scale features substantial enough to affect the overall global temperature.

Since we know the annual cycle pretty well, on average, the Earth is warmest… pic.twitter.com/Dhv1M3L6hW

— Ryan Maue (@RyanMaue) October 5, 2023

CLIMATE: Different view of global temperature — instead of "anomaly from climatology" — here's the actual value showing the annual cycle.

Earth varies from 13°C to 17°C (55°F to 63°F)

We're on a downslope until early January as winter descends on the Northern Hemisphere.📉 pic.twitter.com/tpTLViQRDh

— Ryan Maue (@RyanMaue) October 4, 2023

All the warming we may have now, I know there is always another side to this and it’s not quite as clear cut as what many would have you think! Been here before, long before we were here? Absolutely!

What impact could a warm ocean and atmosphere have on the 23/24 winter? I believe it’s possible that because of the warmer world, some of the traditional drivers/teleconnections (below) may not deliver quite as clear of a signal as they once would.

• Current overall global sea surface temp anomaly/record warm AMO/ cold PDO?

We continue the trend for ‘warmest’ AMO on record while we still continue with the cold or negative PDO, likely a hangover from the La Nina.

• Past summer upper air pattern (lot’s of blocking)

While one of Europe and Northern Hemisphere’s ‘warmest summer’s and year’s on record and 8th warmest for UK, it’s worth noting that there has been considerable blocking within the mid & high latitudes through much of 2023.

Warmer oceans, atmosphere, transition from 3-year La Nina to El Nino, Hunga Tonga the cause? WILL THIS CONTINUE?

Worth looking back at past spring/summers with a firm -NAO pattern. The stand out perhaps to 2023 is 2009.

Linkage Between ENSO-IOD-MJO

• Type of El Nino (Ocean says East/Atmosphere says Modoki?)

While the tropical Pacific has strongly warmed in the east from the beginning of 2023 and steadily warmed westwards through spring and summer, so the atmosphere has been slow to catch up. Likely due to the triple Nina and this in turn has held the -PDO signal in the N Pacific.

The 2023 El Nino as of October 2023 is ‘strong’ based on SST’s, however the atmosphere has been stop-start with not a particularly clear walker circulation evident. This could be a simple delay with Nino traditionally peaking in December or could prove significant down the road if this were to continue.

During a developing El Nino, the MJO can weaken or become masked as atmosphere begins to feel the change in SST profile beneath. It can also help drive on the development process if the MJO remains active within the Pacific.

An active Pacific MJO (phase 6-7-8) drives WWB’s (westerly wind bursts) across the equatorial Pacific ocean surface and forces sub-surface Kelvin Waves (warm water pools beneath the equator) to push west to east with these westerlies.

This graphic shows a cross section of the Pacific and flip in SST anomaly from October 2022 to September 2023.

Now check out the 850mb wind anomalies with blue representing strong and persistent EWB’s or easterly wind bursts, oranges are WWB’s.

While the below graphic represents a global cross-section of 850mb wind anomalies, note the strong westerly wind bursts (WWBs) representative of the active phase of the MJO near the dateline, these help reverse the mean winds (typically easterly) and drive warm sub-surface water from maritime continent to South America.

The stop-start nature of these WWB’s are evident and is evidence of a slower atmospheric response to the Nino and sluggish MJO through the Pacific.

Essentially the OCEAN is displaying strong El Nino conditions while ATMOSPHERE is displaying more of a moderate with rising cell of the Walker Circulation showing up more over the Nino 3.4 region (modoki) rather than all the way to Nino 1.2 (near S America).

It’s worth having a close look below at this graphic showing the difference in atmospheric state over the entire tropical belt and see the difference in the Walker Circulation with La Nina, Neutral and El Nino.

 

THE WALKER CELL pretty much interlinks all three of the major tropical oscillations (El Nino-IOD-MJO) and this is WHY the tropics really can hold the cards when it comes to GLOBAL WEATHER from pole to pole!

The critical question as of mid-October is this… with the ocean displaying a STRONG El Nino but the atmosphere is saying no, it’s moderate and much more central based (within the atmosphere), what happens from mid-October to mid-December.

Will the atmosphere and walker cell respond to the strong oceanic El Nino? In other words force the upward branch of the walker circulation east, creating an almost continuous cell of rising air between the dateline and South America which would then drive a stronger jet over N Pacific-N America and N Atlantic as seen in 1982-83, 1997-98 and 2015-16? or will it remain as is now.

Recent SST trends within the all important Nino regions 1.2 and 3.4.

Wow a notable drop in temperature in region 1.2 between Aug 31st and Oct 12th.

3.4 holding steady.

The above charts are a clear indication for cooling in the east and warmth holding in the central region.

Where we’re at now compared to past in Nino 3.4 (central).

JAS 2023: 1.3C (?)

JAS 2015: 1.9C (warm winter)

JAS 2009: 0.6C (cold winter)

JAS 2004: 0.5C (mixed winter)

JAS 2002: 0.9C (cold spells)

JAS 1997: 1.9C (Super Nino, warm winter)

CANSIPS 3-month SST forecast

CFSv2

• IOD (Strongest positive since 2019?)

From Wikipedia

The IOD involves an aperiodic oscillation of sea-surface temperatures (SST), between “positive”, “neutral” and “negative” phases. A positive phase sees greater-than-average sea-surface temperatures and greater precipitation in the western Indian Ocean region,^{[dubious – discuss]} with a corresponding cooling of waters in the eastern Indian Ocean—which tends to cause droughts in adjacent land areas of Indonesia and Australia. The negative phase of the IOD brings about the opposite conditions, with warmer water and greater precipitation in the eastern Indian Ocean, and cooler and drier conditions in the west.

The IOD also affects the strength of monsoons over the Indian subcontinent. A significant positive IOD occurred in 1997–98, with another in 2006. The IOD is one aspect of the general cycle of global climate, interacting with similar phenomena like the El Niño-Southern Oscillation (ENSO) in the Pacific Ocean.

The IOD phenomenon was first identified by climate researchers in 1999.^[1][2]

An average of four each positive-negative IOD events occur during each 30-year period with each event lasting around six months. However, there were 12 positive IODs between 1980 and 2009, and no negative events between 1980 and 1992. The occurrence of consecutive positive IOD events is extremely rare with only two such events recorded, 1913–1914 and the three consecutive events from 2006 to 2008 which preceded the Black Saturday bushfires. Modelling suggests that consecutive positive events could be expected to occur twice over a 1,000-year period. The positive IOD in 2007 evolved together with La Niña, which is a very rare phenomenon that has happened only once in the available historical records (in 1967).^[3][4][5][6] A strong negative IOD developed in October 2010,^[7] which, coupled with a strong and concurrent La Niña, caused the 2010–2011 Queensland floods and the 2011 Victorian floods.

In 2008, Nerilie Abram used coral records from the eastern and western Indian Ocean to construct a coral Dipole Mode Index extending back to 1846 AD.^[8] This extended perspective on IOD behaviour suggested that positive IOD events increased in strength and frequency during the 20th century.^[9]

COMBING BOTH +IOD & EL NINO WALKER CIRCULATION

As you can probably gather, the IOD being in a positive state actually just continues or perhaps completes a westward extension, another limb of the Walker Circulation, an Indian Ocean version of El Nino. Unfortunate for Indonesia and Australia as this simply enhances the drought/heat pattern here.

It’s thought that the record strong +IOD in autumn/early winter of 2019 may well have enhanced the strength of the stratospheric polar vortex, powering a super-charged zonal jet stream which then flooded N America and Europe with mild oceanic air. However while the 2019-20 may have been very mild with a powerful -90C PV, we didn’t have an El Nino.

The rare 3-straight +IOD’s between 2006-08 coincided with El Nino in late 2006, La Nina in 2007 and weak L Nina 2008. Interestingly these were largely mild winters.

In October 2010 a strong -IOD coincided with a strong La Nina. We of course had the record cold December of 2010 but winter turned very MILD thereafter.

MORE ON THE IOD IN THE NEXT UPDATE!

• MJO

Both El Nino and IOD are working together and this ‘typically’ favours a phase 8 and 1 of the MJO.

Depending on amplitude, these are favourable for high latitude blocking.

Outgoing Longwave Radiation (OLR) & Past Warm Winters

2006 (+IOD)

2015-16 (Super El Nino)

2019-20 (record strong IOD)

Cold winters

2009-10

Unfortunately there are warm and cold winters with BOTH favourable and unfavourable MJO’s and this I believe proves that this cannot be solely relied on as a guide to a particular NH pattern. Strength of a particular phase is one thing but this proves you must not leave ANY stone unturned. In other words look at everything rather than focus on just one or two particular drivers. I recon a strong to super, firmly ‘east based’ Nino would overwelm the pattern all other drivers.

WILL COMPARE PAST YEARS WITH OTHER CLIMATE DRIVER COMBINATIONS IN NEXT UPDATE!

• QBO (easterly)

An easterly QBO (zonal wind blowing within the equatorial stratosphere) can also increase the chance of a slowdown of the polar vortex and jet stream and even increase the probability of an SSW.

• Arctic Sea Ice (6th lowest)

 

• Stratospheric Polar Vortex & Eurasian Snow Cover

At this point, not a great deal to say with regards to the PV. Perhaps some warming over Siberia with a slight push but overall the vortex strengthens over or near the pole through the rest of Oct.

Now

End of Oct

Forecast as per latest ECMWF

As one would expect, we’re beginning to see the white patches develop and spread over northeast Russia. I am not a particularly big fan of the theory that steep and early increases in snow cover leads to more of a -AO/NAO winter pattern and what the heck, I might as well join in.

It's October, my favorite month! So of course I discuss Eurasian #snow cover extent (including first plot of the year) & the implications for winter. Also there isn't one but two possible polar vortex (PV) disruptions in the coming weeks. Blog now public: https://t.co/Gg8N2KHLUk pic.twitter.com/ewv90Vw7Ni

— Judah Cohen (@judah47) October 5, 2023

The thing is we’re ahead of some years and behind in others regarding Eurasian snow cover. Some early starts have proved a +AO/NAO and non-winter and other years where it’s been slow, a decent winter and therefore I struggle with this idea.

Tags: el nino, featured, indian ocean dipole, IOD, madden julian oscillation, mjo, winter 2023-24, winter update