What are Western disturbances
A Western Disturbance is an extra-tropical storm originating in the Mediterranean region that brings sudden winter rains to the northern parts of the Indian subcontinent, extending east to northern parts of Bangladesh and southeast Nepal.
It is a non-monsoon rainfall pattern which is driven by westerly winds. The moisture in these storms usually originates from the Mediterranean Sea, the Caspian Sea and the Black sea to the higher layers of the atmosphere, and then in the form of sudden rain and snow. It falls on North India, Pakistan and Nepal. For Rabi crops in North India, especially for wheat, these storms are very necessary.
How is the Western Disturbance formed?
- These disturbances originate in the Mediterranean region.
- A high pressure area consolidates over Ukraine and the surrounding neighborhoods, allowing cooler air from the polar regions to enter a region of relatively warm air with high humidity.
- This creates favorable conditions for cyclogenesis in the upper atmosphere, which promotes the formation of an eastward moving extra-tropical depression.
- Traveling at speeds up to 12 m/s (43 km/h; 27 mph), it travels towards the Indian subcontinent until the Himalayas stop its impact. The depression weakens rapidly over the Himalayas.
- Subtropical western jet streams and western disturbances are embedded in the mid-latitudes.
Monsoon effects of western disturbances
After winter, the number of these disturbances starts decreasing. During the summer months of April and May, it spreads throughout northern India. The southwest monsoon current moves from east to west in the northern Himalayan region. Unlike this disturbance, which moves from west to east over North India, resulting in an increase in the pressure of the cold pool of air. It helps in activation of monsoon over parts of North West India. This is the reason why pre-monsoon rainfall occurs especially in northern India.
What is the importance and effect of western disturbances?
- Due to western disturbances, especially in winters, moderate to heavy rains occur in low-lying areas and heavy snowfall in mountainous areas of the Indian subcontinent. This cause most of the winter and post-monsoon rainfall in Northwest India.
- Rainfall during the winter season is of great importance in agriculture, especially for rabi crops as the crops grow faster only due to winter rains. Among them, wheat is one of the most important crops, which helps in meeting the food security of India.
- On an average, four to five Disturbances are formed during the winter season. The distribution and quantity of rainfall varies with each disturbance.
- Excessive rainfall due to these disturbances can cause crop damage, landslides, floods and avalanches.
- It sometimes brings cold wave conditions and dense fog over the Indo-Gangetic plains. These conditions remain stable till the onset of Western Disturbance.
- When a disturbance spreads over the whole of Northwest India before the onset of Monsoon, the region sees a temporary progress of the Monsoon current.
Frequently asked questions:-
Western disturbances cause rainfall in which state of India?
The cause of rainfall in North India’ states eg. Jammu and Kashmir, Punjab, UT Chandigarh, Haryana, UT Delhi, Rajasthan, Himachal Pradesh, Uttar Pradesh, Uttranchal etc.
is its any effect on monsoons
where does this storm originate from
From Mediterranean region