Latest Key Factors
- -IOD (Most neg since 2022)
- -PDO
- RECORD WARM NORTH PACIFIC
- DEVELOPING LA NINA
- +AMO WITH COLD BLOB S OF GREENLAND
We’re increasingly likely to observe at least WEAK La Nina conditions through late autumn and early winter.
3 KEY DRIVERS: La Nina, Easterly QBO, -IOD
Latest equatorial Pacific SSTA’s show La Nina conditions developing.
The important region to watch is for ENSO status is 3.4
Model Projection
Examples of Easterly QBO years:
- Recent years that have been identified as having the easterly phase include 1987, 1992, 1994, 1996, 1998, 2001, 2007, 2010, 2015, 2016, 2018, and 2020.
While it is not possible to provide a comprehensive list of all years with both an easterly Quasi-Biennial Oscillation (QBO) and weak La Niña, some winters that featured these combined conditions include:
- 1984–1985: A weak to moderate La Niña occurred during this winter. It was an easterly QBO year.
- 2008–2009: A weak La Niña was present during this period, which coincided with an easterly QBO.
- Winter 2022–2023: This winter featured both an easterly QBO and weak La Niña conditions.
Several studies have confirmed that the influence of the QBO on the polar vortex is most pronounced during La Niña events, while it is weaker during El Niño periods.
AI Overview
EASTERLY QBO & WEAK LA NINA YEARS
An easterly QBO phase is linked to a higher frequency of La Niña events, while weak La Niña years tend to be associated with this easterly QBO phase as well, according to modeling and observations. This means that when the Quasi-Biennial Oscillation is in its easterly phase (QBOE), there’s a greater likelihood of a La Niña event occurring, and consequently, an increase in weak La Niña years might be more prevalent during these QBOE periods.
Understanding the Components
- Quasi-Biennial Oscillation (QBO): This is a cyclical variation of stratospheric winds above the equator, with winds blowing from the east (easterly phase, QBOE) and then from the west (westerly phase, QBOW).
- La Niña: A climate pattern where ocean surface temperatures in the eastern and central Pacific Ocean are cooler than average.
The Relationship
- Easterly QBO (QBOE) and La Niña: Research and models show a tendency for more La Niña events to occur when the QBO is in its easterly phase.
- Weak La Niña Years and QBOE: The observed relationship is not perfectly consistent over time but generally suggests that the easterly QBO phase is linked to a higher frequency of La Niña events. When these La Niña events are less intense or weaker, it can also align with the active periods of the QBO easterly phase.
How it Matters
- Weather Impacts: The QBO influences the Atlantic jet stream, affecting our weather.
- Stratospheric Warming: An easterly QBO phase, for example, can contribute to a weaker jet stream and a higher chance of Sudden Stratospheric Warming (SSW) events, which can lead to colder winters in Northern Europe.
-IOD YEARS
AI Overview
Recent years with significant negative Indian Ocean Dipole (IOD) events include 2021 and 2022, with a prolonged multi-year event lasting for 19 months, and brief occurrences in 2020 and 2024. A potential negative IOD was also noted as developing in 2025. These events differ in length and strength, with the 2021-2022 event being historically long and strong.
Key Negative IOD Years:
- 2021-2022: This was a multi-year, unprecedented event, marking the first time a negative IOD persisted for 19 months, coexisting with a triple-dip La Niña.
- 2020: A brief, weak negative IOD occurred but quickly returned to neutral.
- 2024: Another short-lived negative IOD was observed before the index returned to neutral.
- 2025: A negative IOD was developing and predicted to be stronger in the latter half of the year, following a brief negative phase in the previous year.
What a Negative IOD Means:
- During a negative IOD, westerly wind anomalies become more prevalent in the tropical Indian Ocean.
- This leads to changes in sea surface temperatures (SSTs), with warmer waters near Indonesia and cooler waters in the eastern Indian Ocean.
- For Australia, a negative IOD generally brings above-average rainfall, which can be a positive thing for producers.
Factors Influencing Negative IOD Events:
- La Niña: The triple-dip La Niña event from 2020 to 2022 was a key factor in sustaining the multi-year negative IOD event.
- Monsoon Activity: Changes in the Indian Summer Monsoon can also influence the occurrence of negative IODs.
Recent and multi-year negative IOD events
- 2021–2022: A notable multi-year negative IOD event occurred from 2021 to 2022, which lasted for an unprecedented 19 months. It developed alongside a multi-year La Niña event (2020–2022).
- 2022: Declared a negative IOD year, following the weaker event in 2021.
- 2021: A negative IOD year that was weaker than the following year’s event.
- 2016: An extreme negative IOD, considered the strongest event since 1980 according to some datasets.
- 2010: A strong negative IOD event that, combined with a strong La Niña, caused severe flooding in Australia during the 2010–2011 season.
- 1998: Another notable negative IOD year.
- 1996: A negative IOD event that followed a period of no negative events since 1980.
- 1992: A negative IOD event observed prior to the 1996 event.
NOTE: STRONG +IOD linked to STRONGER POLAR VORTEX / -IOD linked to WEAKER POLAR VORTEX
Closest Global SSTA matches with current.
2025
2020
2022
Interesting how La Nina’s with WQBO’s favour -NAO’s more than EQBO’s.
YEARS WITH: Weak La Nina, East QBO, -IOD
95-96 Weak La Nina, East QBO, -IOD
00-01 Weak La Nina, East QBO, -IOD (Like this year, followed a solar max the previous year)
05-06 Weak La Nina, East QBO, -IOD
08-09 Weak La Nina, East QBO
17-18 Weak La Nina, East QBO
20-21 East QBO (similar SST profile)
Here’s how the above winters looked together at 500mb! Wow!
North Pacific Warm & Atlantic Cold BLOB Is Back?
The famous cold North America, stormy Europe winter of 2013-14 was blamed on the presence of these anomalous warm and cold pools in both northern ocean basins. Commencing in 2013 and maturing through 2014 and 2015, eventually ending in 2016.
Incidentally, while North America observed frequent cold outbreaks between 2013 and 2016, it’s was predominantly MILD in Europe…
Latest SST’s vs same time in 2013, 2014, 2015
2013
2014
2015
2016
Resulting winters?
Excerpt from The Weather Outlook:
2013-14
Much milder than average. The UK mean winter temperature was 5.2°C, which is 1.5°C above the average.
2014-15
Close to average. The UK mean winter temperature was 3.9°C, which is 0.2°C above the average.
2015-16
Very mild. The third warmest in the series from 1910. The UK mean temperature was 5.5C, which is 1.8C above the average.
2016-17
Very mild. The UK mean temperature was 5.0C, which is 1.3C above the average.
Tweet from Ethan Sacoransky (14th Sep)
If we take the six closest years since 2010 to the current Pacific sea surface temperature anomalies, we get a blend of 2013–14, 2017–18, 2020–21, 2021–22, 2022–23, and 2024–25.
Corresponding 500 geopotential to same years above.
Early Siberia snow and cold, One of Highest Arctic Sea Ice Mins Since 2014, Weak PV?
Unusually Weak Early Polar Vortex?
This is speculative but, could unusually strong ridging within higher latitudes (Canada, Scandinavia, Russia) from troposphere present frictional effects into lower stratosphere? Projected (by models) uptick in tropical activity and stronger storms within Northern Hemisphere increasingly a threat of HL blocking?
SUMMARY
Position of the cool pool over the Eq Pac could be critical to WHERE the rising motion is positioned…
IF La Nina was to weaken by warming over the central Pacific, there is potentially for the MJO to shift from Indian Ocean/MC to central Pacific (phase 7-8-1) which would support more high lat blocking & more importantly Greenland blocking!
Some studies support La Nina + WEST QBO can lead to -AO/NAO’s and EAST QBO’s -AO But +NAO!!
Watch the Winter Update livestream Youtube!
What are the models suggesting?
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