What’s happening

The Western Himalayan region—Uttarakhand, Himachal Pradesh, Jammu and Kashmir, and Ladakh—went through an exceptionally harsh monsoon in 2025 (late May to early September). There were very heavy rains, flash floods, landslides, cloudbursts, and storms. These were made worse by unusual wind patterns in the atmosphere and by the way different weather systems “met” and strengthened each other.

Weekly rainfall pattern (June–September 2025):

• Many weeks had “large excess” rainfall (more than 60 percent above normal).
  
• Himachal Pradesh had six such weeks; in the first week of July rainfall was around 195 percent above normal.
  
• Ladakh showed extreme percentage spikes (for example the week ending 27 August), largely because its usual weekly rainfall is tiny—so even a few showers translate into a very large percentage.
  
• Jammu and Kashmir and Uttarakhand also had several weeks of excess, with some dry weeks in between—so the season swung between too much and too little.
  

Key concepts at a glance

• Western Disturbance: A low-pressure weather system that forms near the Mediterranean Sea and travels across Iran and Pakistan into north India. It brings spinning winds aloft and “lift” in the atmosphere, which can intensify rain over mountains.
  
• Monsoon Low/Depression and the Monsoon Trough: During monsoon, low-pressure centres move along a long “trough” stretching from Rajasthan to the Bay of Bengal. When this trough sits farther north than usual, the main moisture conveyor points straight at the Himalayan slopes.
  
• Subtropical Jet and Rossby Waves: High-altitude rivers of fast westerly winds guide weather systems. When global warming in the Arctic reduces the temperature difference between pole and equator, these wind rivers become wavier and slower. Systems linger longer over one place, increasing rainfall there.
  
• Heating of the Tibetan Plateau: Strong summer warming above the Plateau helps air rise and spread out at high levels. That outflow aloft behaves like a gentle vacuum, encouraging more rising air and sustained rain just to its south and west—over the western Himalayas.
  
• Low-Level Jet from the Arabian Sea: Near the surface, strong south-westerly winds carry very moist air from the Arabian Sea into north India. Warm seas mean more water vapour and more efficient rain.
  
• Precipitable Water: The total amount of water vapour in a column of air. Warmer seas raise this value, so the same storm can drop much more rain.
  
• Intraseasonal Pulses (Madden–Julian Oscillation and Boreal Summer Oscillation): Natural 30–60 day “on–off” cycles that make convection stronger for a couple of weeks and then weaker. When an “on” phase meets a western disturbance, rainfall spikes.
  
• Orographic Lift: When moist winds hit a mountain wall, they are forced upward. The air cools quickly; water vapour condenses; rainfall jumps. This is the heart of Himalayan cloudbursts.
  
• Upper-level Divergence: Outflow of air high up in the sky. It helps air to keep rising from below, supercharging rainfall.
  
• Antecedent Wetness and Saturation-Excess Runoff: If soils are already wet, they cannot absorb more. Even moderate rain then runs straight into streams and rivers, causing flash floods.
  
• Debris Flow versus Landslide: A landslide is the failure of a slope. A debris flow is a fast, thick slurry of mud and rocks rushing down a channel after intense rain.
  
• Alluvial Fan and Floodplain: Natural spread-out deposits at valley mouths and flat river terraces. These are natural flow paths. Building here invites damage.
  
• Paraglacial Landscape: Recently deglaciated high-mountain terrain that is young, loose, and unstable.
• Dam “Rule Curve”: The operating guide that tells when to store and when to release water. Updating it for current extremes reduces downstream flood risk.

Why 2025 turned extreme 

The big picture: The Himalayas behave like a giant wall. In 2025, three ingredients repeatedly lined up over this wall: 

• (1) a lot of moisture in the air, 

• (2) very strong lifting of that moist air, and 

• (3) weather systems that moved too slowly or stalled. 

When moisture, lift and time-over-one-place are all high together, ordinary rain becomes explosive downpours. Then our choices—where and how we build—turn natural hazards into human disasters.

A) What changed in the atmosphere and the oceans?

1. More western disturbances, and some unusually stubborn ones

What are Western Disturbances (WDs)?

Western Disturbances are weather systems (low-pressure areas) that form over the Mediterranean region and travel eastward toward India via the westerly jet stream in the upper atmosphere.

They bring moisture-laden winds that cause rain or snow in north and northwest India, mainly during winter and spring.

What’s unusual in 2025

Normally, WDs weaken or become infrequent during the monsoon months (June–September), as the southwest monsoon winds dominate.

But in 2025, 49 western disturbances were recorded even during monsoon months, which is abnormally high.

Mechanism behind the unusual WDs

There are two main parts to this:

Classical Western Disturbances

• From near the Mediterranean Sea.
  
• Move eastwards along the subtropical westerly jet stream.
  
• Typically cause rain in northern India in winter/spring.
  

But this year, they continued into summer, likely due to persistent westerly flow patterns and atmospheric blocking over Europe and Central Asia.

  Cut-off Low Systems

• These are cold-core low-pressure systems that break away (“cut off”) from the main westerly jet stream.
  
• Once detached, they move slowly and linger longer because they’re no longer steered by fast upper winds.
  
• Being cold at the core, they destabilize the air, making it rise easily — this “lift” fuels prolonged and heavy rainfall.
  
• When they interact with moist monsoon air, the result is intense and widespread rain.
• Western disturbances usually dominate winter and spring. In 2025, an unusually large number (49) affected the monsoon months themselves.
  

2. The jet stream lingered; the Plateau heated strongly

• With the Arctic warming faster than the rest of the planet, the pole-to-equator temperature difference shrank. The subtropical jet stream became wavier and slower, retreating northward later than usual.
• Strong summer heating of the Tibetan Plateau helped maintain outflow aloft, which in turn locked in rising motion over the western Himalayas.

3. The monsoon conveyor shifted north

• The main monsoon lows and depressions travelled farther north than they typically do, steering the deepest moisture into the hills rather than central India.
  
• Warmer waters in the Arabian Sea and changing temperature contrasts over West Asia strengthened low-level convergence, bringing the monsoon systems into direct overlap with western disturbances.
  

4. Warmer Arabian Sea, fatter clouds

• Higher sea-surface temperatures mean more water vapour and more efficient rainfall.
  
• Strong south-westerly winds piled this moisture against the Siwalik and Lesser Himalaya—the first mountain walls—causing intense dumping.
  
• When an intraseasonal “active” phase matched the arrival of a western disturbance, rainfall peaked.
  

B) Why cloudbursts and landslides multiply in mountains

• Orographic turbo-charge: Steep slopes force air up fast; it cools and condenses explosively. Warm-rain processes (raindrops merging) plus ice-phase processes (hail and graupel growth) give very high rain rates over very small areas.
  
• Storms that park in place: Ridges and valleys can hold storm cells nearly stationary, so a 30-minute downpour sits right above one basin.
  
• Fragile ground and steep rivers: Thin, fractured mountain soils and rocks, already wet from previous spells, fail easily. Short, steep catchments flush water quickly. Sediment from slope failures blocks culverts and bridge spans, backing up water and suddenly raising flood levels.
  
• Why Ladakh’s percentages shot up: The normal rainfall is tiny. A few strong events carried across high passes create huge percentage anomalies. Bare, coarse surfaces with little vegetation mean instant runoff and gully erosion—even modest rain becomes hazardous.
  

C) Human actions that magnify damage

• Cutting slopes and building on river edges: Road cuts without proper benches and retaining structures remove the “toe” that supports slopes, open cracks in rock layers, and place homes and shops in natural flow paths such as alluvial fans and floodplains.
  
• Hydropower and linear projects: Blasting, tunnel drainage, and dumping of excavated rock destabilise hillsides. If dams release water only to meet power peaks (rather than for safety), downstream floods worsen.
  
• Fast urban growth and pressure from tourism: Paved surfaces speed runoff; drains clog with waste; temporary camps appear on low terraces; and one landslide can sever the only evacuation road in a valley.
  

What to do 

Plan by risk, not by plot boundary

• Create no-build buffers along rivers. Enforce landslide-susceptibility zoning based on slope angle, rock type, drainage density, and past slide history.
  
• Adopt a Himalayan Building Code: slope-safe foundations, proper back-drainage behind retaining walls, and keep debris-flow corridors open—do not build across them.
  

Stabilise slopes; let water and sediment pass safely

• Use bio-engineering (deep-rooted native plants), proper benching, and toe protection on road cuts.
  
• Install debris traps and check dams in slide-prone gullies. Size culverts and bridges for sediment-laden flood flows, not just clear water.
  

Turn forecasts into timely action

• Densify the network of Doppler weather radars and automatic rain-gauges. Base warnings on rainfall intensity plus duration plus soil wetness.
  
• Prepare village-level standard operating procedures with simple colour-coded triggers (close schools and roads, move machinery, evacuate low terraces) and hold annual drills.
  

Operate dams for extremes, not for averages

• Update dam operating curves to reflect recent extreme rainfall. Coordinate releases across cascades of dams.
  
• Run regular sediment management to reduce the raising of riverbeds and backwater effects that worsen floods.
  

Restore natural buffers

• Protect and revive riparian green belts and wetlands; ban construction on alluvial fans.
  
• Carry out micro-watershed afforestation with native species to slow runoff and bind soils.
  

Build institutions and open data

• Create a multi-state Himalayan Risk Platform that shares live rain, river, landslide, and road status data.
  
• After each event, conduct forensic hydrology and geotechnical audits and publish loss-and-damage ledgers so that lessons translate into fixes.
  

Exam Hook

Key takeaways 

• Extreme outcomes arise when very moist air, strong lifting over mountains, and slow or stalled systems happen together.
  
• The overlap of western disturbances with north-shifted monsoon lows focused rain on the Himalayan slopes.
  
• A wavier, slower high-altitude jet stream and strong Tibetan Plateau heating helped storms linger.
  
• Mountain “physics” plus fragile terrain create cloudbursts, debris flows, and flash floods.
  
• Where and how we build often decides whether heavy rain stays a hazard or becomes a disaster.
  

Mains Question:
“Explain the atmospheric and oceanic drivers behind the 2025 Western Himalayan extremes and evaluate the human factors that magnified losses. Propose a region-specific resilience plan covering land use, infrastructure design, early warning, dam operations, and ecosystem restoration.”

Prelims (MCQ):

Q. Which combination best explains frequent Himalayan cloudbursts?
A. Weak monsoon, cold Bay of Bengal, strong easterly winds
B. High precipitable water, orographic lifting over mountains, outflow of air aloft that aids rising motion, and slow storm movement
C. Low precipitable water, strong sinking motion, fast storm movement
D. Trade-wind inversion, sea fog, and katabatic winds
Answer: B

One-line wrap:
Very heavy rain may be unavoidable; very heavy loss is not—keep people out of flow paths, keep slopes stable, and turn forecasts into swift action.

Source: Down to Earth