Snowfall vs. IOD vs. ENSO in the Western Himalaya:

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A 20-Year Case Study (2004–2024)




Introduction

Western Himalayan snowfall is primarily delivered by western disturbances (WDs)—moist low-pressure systems originating in the Mediterranean that track eastward into the Indian subcontinent. Their frequency and intensity are strongly shaped by large-scale climate modes such as the El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). ENSO phases alter the subtropical jet stream and moisture transport, while IOD phases modulate precipitation patterns in the Indian Ocean basin. Climate change adds further complexity by warming the atmosphere and reducing long-term snowpack.

This case study analyses notable winters from 2004 to 2024, correlating ENSO and IOD phases with snowfall outcomes using scientific papers, satellite datasets, and climate reporting.

How ENSO and IOD influence Western Himalayan snowfall


La Niña and western disturbances

La Niña episodes are often associated with strengthening of the subtropical jet, which can help more western disturbances reach northern India. In many La Niña winters, this leads to colder conditions and the potential for frequent snowfall events.

However, La Niña does not guarantee abundant snow. Some La Niña winters deliver intense cold but very little precipitation—often because the IOD is negative or moisture availability is limited.
The 2021–22 winter, for instance, saw regular disturbances but inconsistent or patchy snowfall distribution.

El Niño and snow droughts

Strong El Niño events warm the eastern Pacific and weaken westerlies, often suppressing the penetration of western disturbances.
During the 2023–24 El Niño, mountain passes like Zojila received only 6–7 feet of snow instead of the usual 30–40 feet.
The India Meteorological Department attributed the dry spell to a near-complete absence of WDs during key weeks of winter.

Climate researchers also note a long-term decline in WD activity, with El Niño winters amplifying this drying tendency.

Indian Ocean Dipole

Satellite and reanalysis studies show that:

  • Positive IOD → lower temperatures, higher precipitation, expanded snow cover across High Mountain Asia.

  • Negative IOD → reduced precipitation and weaker westerlies.

The 2018–19 winter, despite being a weak El Niño year, saw unusually heavy snowfall across several Himalayan regions—likely because of a strong positive IOD and a supportive NAO pattern.

Conversely, the 2021–22 La Niña coincided with a negative IOD, reducing moisture and limiting large storm totals even though disturbances were frequent.

Case Study: 20 Winters (2004–2024)

Below is a distilled summary of ENSO/IOD phases and observed snowfall outcomes from major winters. 

Winter (DJF)ENSO (ONI)IOD phaseObserved snowfall / notes
2004–05El Niño (weak)Neutral/–Moderate snowfall; no exceptional WD activity reported.
2005–06La Niña (moderate)NeutralColder winter; moderate snow; supportive westerlies.
2006–07El Niño (weak)NegativeDry winter in northwest Himalaya; weak disturbances.
2007–08La Niña (strong)Likely positiveHeavy snow spells and strong disturbances; widespread cold.
2008–09La Niña → NeutralNeutralModerate snowfall.
2009–10El Niño (strong)NegativeVery dry winter; WD suppression; similar to 2023–24.
2010–11La Niña (moderate)NeutralMultiple heavy spells; Rohtang closed early; active WDs.
2011–12La Niña → NeutralNeutralMixed snowfall; patchy distribution.
2012–13NeutralNeutralAverage season.
2013–14NeutralNeutralModest snowfall.
2014–15El Niño (weak)NegativeBelow-average snow across HP & Uttarakhand.
2015–16El Niño (strong)NegativeVery dry winter; rain replacing snow at lower elevations; WD suppression.
2016–17La Niña (weak)NeutralCold winter; moderate snow; some local heavy storms.
2017–18La Niña (weak)NeutralStrong early-season snowfall in multiple regions; sustained snow cover in some valleys.
2018–19El Niño (weak)PositiveRemarkably heavy snowfall season; positive IOD + NAO boosted moisture and storm strength.
2019–20Neutral → positive IODNeutral/positiveHeavy early spells; normalised later.
2020–21La Niña (moderate)NeutralCold winter; moderate snowpack.
2021–22La Niña (moderate)NegativeFrequent disturbances but limited total accumulation due to restricted moisture.
2022–23La Niña (weak)NeutralMixed conditions; declining precipitation trend continues.
2023–24El Niño (strong)NeutralExtremely dry; Zojila snow only ~6–7 ft vs normal 30–40 ft; IMD flagged lack of WDs.

Discussion and Key Insights

1. ENSO alone cannot predict Himalayan snowfall

The winter of 2018–19 proves that a weak El Niño can still produce massive snowfall if aided by a positive IOD and NAO.


Meanwhile, 2021–22 shows that a La Niña can still result in underwhelming totals if the IOD is negative.

Teleconnections are interactive, not linear.

2. Western disturbances are the decisive factor

Snowfall depends most directly on WD frequency and moisture load.


Dry El Niño years like 2009–10 and 2023–24 were marked by a collapse in WD activity.

Long-term observational research indicates:

  • WDs are declining in frequency/intensity.

  • Precipitation is shifting from snow to rain.

  • Snowfall seasons are ending 1–2 weeks earlier.

3. Positive IOD reliably boosts snow potential

A strong positive IOD cools the Indian Ocean and enhances moisture availability.


This helps:

  • strengthen WDs

  • increase snowfall

  • expand snow-cover area

The 2018–19 season is a prime example.

4. La Niña winters favour event-based snowfall

La Niña often brings cold, sharp snowfall events—not necessarily high seasonal totals.

Examples:

  • 2010–11 had repeated heavy spells.

  • 2017–18 had intense early-season storms.

If the IOD is negative, La Niña winters may turn cold but dry.

5. Climate change now modulates all teleconnections

Long-term studies report:

  • 16–86% decline in seasonal snowfall across Himachal Pradesh.

  • Lower-elevation snowfall dropping dramatically.

  • Increasing likelihood of rain-on-snow events.

  • Faster melting and reduced snowpack stability.

Teleconnections now operate on a warmer baseline, amplifying extremes.

Conclusion

Two decades of data reveal that western Himalayan snowfall depends on the dynamic interplay between ENSO, IOD, NAO, WD activity, and climate change.
Patterns include:

  • La Niña → colder winters with event-driven snowfall.

  • El Niño → drier winters, especially when WDs weaken.

  • Positive IOD → increased snow and moisture, sometimes overpowering ENSO.

  • Negative IOD → reduced snowfall even during La Niña.

  • Climate change → declining WDs, reduced snowpack, earlier melt.

Ski-tourers, mountaineers and planners must therefore monitor phenomenon, not ENSO alone, to anticipate Himalayan snow conditions in future winters.

Sources 

  • Bureau of Meteorology IOD data

  • NOAA Oceanic Niño Index

  • NDTV climate reports on western disturbances and snow droughts

  • HimachalScape reporting on WD-linked snowfall events

  • CCB (Consortium for Capacity Building) commentary on La Niña winters

  • IMD winter precipitation analyses

  • MDPI satellite analysis of snow cover vs. IOD

  • DRDO & IMD snow trend studies

  • Peer-reviewed studies on ENSO/WD interactions in the western Himalaya

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