Western Disturbances impact on rain and snowfall: Basics Explained

Western disturbances, the only source of rainfall and snowfall in the hills of north India during winter, non-monsoonal precipitation, have been showing a declining trend in intensity in the past few years and this year is no exception. It rings an alarm bell not only for Rabi crops but also for the availability of water in the mountains. Experts attributed this anomaly to climate change.


Western Disturbances (WD) are low-pressure areas, extratropical storm originating,  embedded in the Westerlies-the planetary winds that blow from west to east between 30 and 60° latitude. The disturbance travels from the “western” to the eastern direction. Disturbance means an area of “disturbed” or reduced air pressure. Equilibrium exists in nature due to which the air in a region tries to normalize its pressure. In the term “extra-tropical storm”, a storm refers to low pressure. “Extra-tropical” means outside the tropics. As the WD originates outside the tropical region, the word “extra-tropical” has been associated with them.

They originate in the Mediterranean region, travel westward, and enter India loaded with moisture, where the Himalayas obstruct them, causing rain and snow over northern India. The moisture in these storms usually originates over the Mediterranean Sea and Atlantic Ocean. WDs are important to the development of the Rabi crop in the northern subcontinent They gradually travel across the middle east from Iran, Afghanistan, and Pakistan to enter the Indian sub-continent. Western Disturbances are low-pressure systems, embedded in western winds (westerlies) that flow from west to east.

 Moreover, Western disturbances, specifically the ones in winter, bring moderate to heavy rain in low-lying areas and heavy snow to mountainous areas of the Indian Subcontinent. They are the cause of most winter and pre-monsoon season rainfall across northwest India. Precipitation during the winter season has great importance in agriculture, particularly for the rabi crops.


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