Western disturbance

In the case of the Indian subcontinent, moisture is sometimes shed as rain when the storm system encounters the Himalayas.

This generates favorable conditions for cyclogenesis in the upper atmosphere, which promotes the formation of an eastward-moving extratropical depression.

Traveling at speeds up to 12 m/s (43 km/h; 27 mph), the disturbance moves towards the Indian subcontinent until the Himalayas inhibits its development, upon which the depression rapidly weakens.

Excessive precipitation due to western disturbances can cause crop damage, landslides, floods and avalanches.

The southwest monsoon current generally progresses from east to west in the northern Himalayan region, unlike western disturbances which follow a west to east trend in north India with consequent rise in pressure carrying cold pool of air.

[citation needed] The interaction of the monsoon trough with western disturbances may occasionally cause dense clouding and heavy precipitation.

A Western Disturbance over Northern India and Pakistan in November 2012
A western disturbance moving east towards the Indian subcontinent. It can be seen as a cloud patch originating from the Black Sea , progressing east thereafter.
A strong western disturbance affecting the northern parts of the Indian subcontinent in February 2013. Such disturbances bring substantial amount of rainfall and are a threat to lives and property.