ENSO Updates (2007 thru 2023)

[Ntxw]

This is the first weekly strong value. Assuming gradual warming continues in the Fall we could see ~2.0C in October or November. This is for the weekly, ONI is tougher for a 3 month average. 1.7 to 1.9C for OND seems doable.

[Kingarabian]

Nino 3.4 goes up to +1.5C and the GFS is showing a strong CPAC trade burst. Will be an interesting event to study in future years.

[cycloneye]

BoM has not declared El Niño

The Bureau's El Niño Alert continues, with El Niño development likely during spring. When El Niño Alert criteria have been met in the past, an El Niño event has developed around 70% of the time.

Sea surface temperatures (SSTs) in the tropical Pacific are exceeding El Niño thresholds and have continued to warm slightly over the last fortnight. Climate models indicate further warming of the central to eastern Pacific is likely, with SSTs remaining above El Niño thresholds until at least early 2024.

The 90-day Southern Oscillation Index (SOI) is presently just below El Niño thresholds, while trade winds and Pacific cloudiness have not yet demonstrated sustained El Niño patterns. Overall, atmospheric indicators suggest the Pacific Ocean and atmosphere are not yet consistently reinforcing each other, as occurs during El Niño events. El Niño typically suppresses spring rainfall in eastern Australia.

The latest weekly Indian Ocean Dipole (IOD) index is +1.05 °C. This is the second week it has been above the positive IOD threshold of +0.40 °C. However, before an IOD event is declared, several more weeks of the IOD index above the positive IOD threshold are required. Climate models suggest a positive IOD is likely for spring. A positive IOD typically decreases spring rainfall for central and south-east Australia and can increase the drying influence of El Niño.

The Madden–Julian Oscillation (MJO) is currently weak or indiscernible. Most surveyed models forecast a strengthening pulse to move over the Maritime Continent or Western Pacific in the coming days. If this pulse moves into the Western Pacific and remains relatively strong it may assist El Niño development by weakening trade winds.

http://www.bom.gov.au/climate/enso/

[dexterlabio]

I remember it being discussed here before that in an El Niño base state, the Pacific is conducive to spawn storms without the aid of MJO. Currently the Atlantic is certainly favored, but while the Pacific is supposedly in the unfavorable phase, a flurry of storms are now being observed with Saola on the cusp of being a Cat5.

Could this be a sign of the El Niño base state finally setting up?

[Ntxw]

There is indeed an outbreak of WPAC cyclones. For the next ~2 weeks up until ~10th of Sept the tropical forcing is crossing the IO-MC (active Atlantic and start of WPAC). It will move out into the open Pacific beyond that point. The trade surge starts out near the IDL and be replaced sometime thereafter, concurrent with background Nino base state setting in.

In terms of the eastern ENSO regions, once again that area will not feel much in the way of trades relative to the long range forecasting. The next two months is looking more like the typical +ENSO forcing you would expect closer to the IDL and CPAC.

[Ntxw]

IDL forcing is on the way and sinking MC. The CPAC regions in mid-September should fall in line with what we would expect for an El Nino of recent times. If this verifies, it would likely stick the background forcing in place and allow the MEI, RONI, and SOI to all follow in line.



This is supported by the movement of warmest water from west of the IDL east to the IDL itself.

[zzzh]

JJA ONI = 1.1, though I expect a much weaker MEI.

[cycloneye]

The CPC weekly update has Niño 3.4 up to +1.6C.

Niño 4 1.1ºC
Niño 3.4 1.6ºC
Niño 3 2.3ºC
Niño 1+2 3.2ºC

https://www.cpc.ncep.noaa.gov/products/ ... ts-web.pdf

[zzzh]

MEI 0.4

[dexterlabio]

^wow so based on MEI 2014 wasn't El Nino year, and 1997 El Nino was far stronger than 2015

[Iceresistance]

SOI index is really tanking

[Kingarabian]

Subsurface warmth has recovered nicely below the EPAC. Strength wise, CFS thinks this is about it for this event.

We are in the middle of September now so it won't be long before we enter the NHEM winter season. Up in the air if typical El Nino winter effects will occur with a subpar atmosphere coupling.

[Iceresistance]

New Weekly ENSO just came out

Niño 4 1.1ºC
Niño 3.4 1.6ºC
Niño 3 2.2ºC
Niño 1+2 2.6ºC

https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf

[cycloneye]

The Aussies officially declared El Niño.

l Niño
An El Niño has been declared and is underway.

Any three of the following criteria need to be satisfied:
Sea surface temperature: Temperatures in the NINO3 or NINO3.4 regions of the Pacific Ocean are 0.8 °C warmer than average.

Winds: Trade winds have been weaker than average in the western or central equatorial Pacific Ocean during any three of the last four months.

SOI: The three-month average Southern Oscillation Index is –7 or lower.

Models: A majority of surveyed climate models show sustained warming to at least 0.8 °C above average in the NINO3 or NINO3.4 regions of the Pacific until the end of the year.

Oceanic indicators firmly exhibit an El Niño state. Central and eastern Pacific sea surface temperatures (SSTs) continue to exceed El Niño thresholds. Models indicate further warming of the central to eastern Pacific is likely.

Broadscale pressure patterns over the tropical Pacific reflect El Niño, with the 90-day Southern Oscillation Index (SOI) at −7.7. Recent trade wind strength has been generally close to average, but was slightly weaker than average across the tropical Pacific in August 2023 for the first time since January 2020.

Overall, there are signs that the atmosphere is responding to the pattern of SSTs in the tropical Pacific and coupling of the ocean and atmosphere has started to occur. This coupling is a characteristic of an El Niño event and is what strengthens and sustains an event for an extended period. Climate models indicate this El Niño is likely to persist until at least the end of February. El Niño typically leads to reduced spring and early summer rainfall for eastern Australia, and warmer days for the southern two-thirds of the country.

A positive Indian Ocean Dipole is underway. The Indian Ocean Dipole (IOD) index is +1.25 °C for week ending 17 September. This is its fifth week above the positive IOD threshold (+0.40 °C). The longevity of this trend, combined with the strength of the dipole being observed and forecast, indicate a positive IOD event is underway. All models predict this positive IOD will persist to at least the end of spring. A positive IOD typically leads to reduced spring rainfall for central and south-east Australia.

http://www.bom.gov.au/climate/enso/index.shtml

[LarryWx]

Now that Sep exact model ONIs are out, I can derive the exact changes from the prior month’s runs:

Model: new peak/months (change in peak)

BoM: +2.87/DJF (0.00)

Met-France: +2.69/NDJ (+0.03)

Euro: +2.24/NDJ (-0.16)

JMA: +2.06/NDJ (-0.16)

UKMET: +1.96/DJF (-0.04)

CFSv2: +1.83/NDJ (-0.28)



AVG: +2.28/between NDJ and DJF (-0.12)

[WalterWhite]

Now that Sep exact model ONIs are out, I can derive the exact changes from the prior month’s runs:

Model: new peak/months (change in peak)

BoM: +2.87/DJF (0.00)

Met-France: +2.69/NDJ (+0.03)

Euro: +2.24/NDJ (-0.16)

JMA: +2.06/NDJ (-0.16)

UKMET: +1.96/DJF (-0.04)

CFSv2: +1.83/NDJ (-0.28)



AVG: +2.28/between NDJ and DJF (-0.12)

Most models expect this winter to feature a Strong El Niño, which virtually guarantee a La Niña next year.

[cycloneye]

CPC Weekly update:

The latest weekly
SST departures are:
Niño 4= +1.2ºC
Niño 3.4= +1.7ºC
Niño 3 2=+1.0ºC
Niño 1+2= +2.8ºC

https://www.cpc.ncep.noaa.gov/products/ ... ts-web.pdf

[Iceresistance]

Weekly update came out yesterday

Niño 4 = +1.1°C
Niño 3.4 = +1.5°C
Niño 3 = +2°C
Niño 1+2 = +2.8°C

https://www.cpc.ncep.noaa.gov/products/ ... ts-web.pdf

[weeniepatrol]

https://psl.noaa.gov/enso/mei/

MEI data for AS came in at +0.6.

[Iceresistance]

https://psl.noaa.gov/enso/mei/

MEI data for AS came in at +0.6.

I forgot, what does a Positive MEI mean? An El Nino?