Western Disturbances

Definition

Extratropical (mid-latitude) low-pressure storm systems that originate over the Mediterranean and Caspian Sea region and travel eastward, steered by the subtropical westerly jet stream, to bring winter rain and snow to north-west India.

Key points

• They are non-monsoonal: they bring rain in the winter season (broadly December to March), unlike the south-west monsoon of summer.
• They are guided across Iran, Afghanistan, and Pakistan into north India by the subtropical westerly jet stream.
• They cause winter rain over Punjab, Haryana, and the western Himalayas, and snowfall in Jammu and Kashmir, Himachal Pradesh, and Uttarakhand.
• This winter rain is vital for the rabi crops, especially wheat, in the north-western plains.
• Strong western disturbances can trigger avalanches, cold waves, and flash floods in the hills; the snow they deposit feeds the Himalayan rivers.

Why it matters for CAPF

The Mediterranean origin, the jet-stream steering, the winter season, and the benefit to the rabi wheat crop are recurring climatology facts; the avalanche and cold-wave angle links to disaster management in border areas.

Common confusion

Western disturbances (winter, from the Mediterranean, north-west India) versus the south-west monsoon (summer, from the Indian Ocean); they help the rabi (winter) crop, not the kharif crop; they are extratropical, not tropical, systems.

Parent note

indian monsoon and climate