Western Disturbance | 18 Jan 2021
Why in News
According to the India Meteorological Department (IMD), a western disturbance is likely to affect the Himalayan region soon.
- The disturbances will result in fairly widespread light to moderate snowfall and rains in the plains of Jammu.
Key Points
- Western Disturbance (WD), labelled as an extra-tropical storm originating in the Mediterranean, is an area of low pressure that brings sudden showers, snow and fog in northwest India.
- The meaning of WD lies in its name.
- The disturbance travels from the “western” to the eastern direction.
- These travel eastwards on high-altitude westerly jet streams - massive ribbons of fast winds traversing the earth from west to east.
- Disturbance means an area of “disturbed” or reduced air pressure.
- Equilibrium exists in nature due to which the air in a region tries to normalise its pressure.
- The disturbance travels from the “western” to the eastern direction.
- In the term “extra-tropical storm”, 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.
- A WD is associated with rainfall, snowfall and fog in northern India. It arrives with rain and snow in Pakistan and northern India. The moisture which WDs carry with them comes from the Mediterranean Sea and/or from the Atlantic Ocean.
- WD brings winter and pre-monsoon rain and is important for the development of the Rabi crop in the Northern subcontinent.
- The WDs are not always the harbingers of good weather. Sometimes WDs can cause extreme weather events like floods, flash floods, landslides, dust storms, hail storms and cold waves killing people, destroying infrastructure and impacting livelihoods.
- Expert opinion on western disturbances is divided regarding the 2013 floods in Uttarakhand in which over 5000 people were killed, after three days of incessant rainfall.