Western disturbance

Western disturbance

Subject: Geography

Context: Delhi saw fewer Western Disturbance event this year and this has led to February temperature 7 degree above normal.

Concept:

• Towards the end of February, temperature usually starts rising, however, this is dependent on the number of Western Disturbances. There was 1 Western disturbance around February 5 this year and none after that.
• A Western Disturbance is a weather pattern associated with sudden winter rain and snow in northwest India, which plays an important role in bringing down the temperatures.

About Western disturbance

• It is an extra-tropical storm (low pressure winds embedded in western winds (westerlies) that flow from west to the east) which originates in the Mediterranean region
• Why name Western disturbance (WD): 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.
• WD is associated with the rainfall, snowfall and fog in northern India.
• After travelling over Iran, Iraq, Afghanistan and Pakistan to northern India it comes with the cloud along with rain and snow. The moisture which WDs carry with them comes from the Mediterranean Sea and/or from the Atlantic Ocean.
• In India, WD eventually come up against the Himalayas and get blocked, as a consequence, the moisture gets trapped and precipitation is shared in the form of snow and rain over Northwest India and sometimes, other parts of North India
• Once it is more intense in the Indian Region, they can extend even upto 15 degree north, resulting into rainfall upto north Maharashtra, Gujarat and the entire Madhya Pradesh
• The WD is the cause of the most winter and pre-monsoon season rainfall across North-West India, moderate to heavy rain in low lying areas and heavy snow to mountainous areas of the Indian subcontinent.
• It has significance in in agriculture particularly for rabi crops including wheat.
• Extra-Tropical Cyclones are also called as winter storms and blizzards.