Relevance: GS I (Geography – Climate) & GS III (Disaster Management) | Source: IMD / The Hindu

1. The Human Context: White & Grey

North India is witnessing a dual weather extreme.

• The White: The Himalayas (Kashmir, Himachal) are blanketed in heavy snow, turning landscapes into a “winter wonderland” for tourists but a logistical nightmare for locals (e.g., the critical Srinagar-Jammu National Highway closure).
• The Grey: The plains (Punjab, Delhi) are soaked in rain, a sharp contrast to the usual dry winter. This phenomenon is driven by an active Western Disturbance (WD).

2. The Science: What is a Western Disturbance?

It is not a local monsoon wind; it is a traveler from the West.

• Origin: WDs are extra-tropical storms originating in the Mediterranean Sea.
• The Journey: Driven by the Subtropical Westerly Jet Stream, they travel eastward across Iran, Afghanistan, and Pakistan to hit India.
• Moisture: They pick up moisture from the Mediterranean, Caspian, and sometimes the Arabian Sea. When they hit the Himalayas, they are forced up (Orographic Lift), causing snow in the mountains and rain in the plains.

3. Boon or Bane?

• Liquid Gold (Boon): For farmers, this winter rain is critical for Rabi crops, especially Wheat (which needs cool, moist soil). For the rivers, the snow is a “savings account”—recharging glaciers that feed the Ganga and Indus in summer.
• The Challenge (Bane): Excessive snow cuts off essential supplies (food/medicine) to remote valleys. Unseasonal hail can destroy delicate cash crops like Saffron and Apples.

UPSC Value Box

Q. With reference to the Indian climate, the term “Western Disturbances” refers to:

1. Tropical cyclones originating in the Bay of Bengal during the retreating monsoon season.
2. Extra-tropical storms originating in the Mediterranean region that bring winter rainfall to North India.
3. Dust storms from the Thar Desert that affect the Gangetic plains in summer.
4. The easterly jet streams that drive the onset of the Southwest Monsoon.