Important Geophysical Phenomena

GS-1

4.WESTERN DISTURBANCE

• According to the India Meteorological Department (IMD), awestern disturbance is likely to affect the Himalayan regionsoon.

• The disturbances will result in fairly widespread light to moderate snowfall and rainsin the plains of Jammu.

IMPORTANT POINTS:

• Western Disturbance (WD), labelled as an extra-tropical storm originating in the
• Mediterranean,is an area of low pressurethat 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.
• Disturbancemeans an area of “disturbed” or reduced air pressure.
• Equilibrium exists in nature due to which the air in a region tries tonormalise its pressure.
• In the term “extra-tropical storm”, storm refers to low pressure. “Extratropical”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 carrywith them comes from the Mediterranean Sea and/or from the AtlanticOcean.
• 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, hailstorms and cold waves killing people, destroying infrastructure and impactinglivelihoods.
• Exper t opinion on western disturbances is divided regarding the 2013 floods in Uttarakhandin which over 5000 people were killed, after three days ofincessant rainfall.

SOURCE: DTE