Western Disturbances

Western Disturbances News

Warm winters: Recently, the temperature reached 28.4 degrees Celsius which is the second-highest maximum temperature for December from 2015 onwards, as per IMD data.

• The average maximum temperature from December 2 to 6 this year was 26.06 degrees Celsius, a notch higher than the long-term average of 25 degrees for these dates from 1981 to 2010.

Reason: These above normal maximum temperatures have mostly been on account of fewer western disturbances affecting Delhi this year.

• Western disturbances bring rain and snow over the hills, and more moisture to the plains. The cloud cover results in higher minimum temperatures at night and lower day-time or maximum temperatures.

What are Western Disturbances?

• About: They are extratropical storms that originate in the Mediterranean region which brings sudden winter rain to the north-western parts of the Indian sub-continent.
• Travelling path: They originate in the Caspian Sea or the Mediterranean Sea and gradually travel across the middle-east from Iran, Afghanistan and Pakistan to enter the Indian sub-continent.
• Important characteristics:
  • They are a non-monsoonal precipitation pattern which is driven by the westerlies.
  • These extratropical storms are a global phenomenon. They may happen during any season, not necessarily in monsoon.
  • This phenomenon usually carries moisture in the upper layer of the atmosphere, unlike their tropical counterparts where the moisture is carried in the lower layer of atmosphere.
  • The western disturbances are embedded in the mid-latitude subtropical westerly jet stream.
  • They travel at speeds up to 12 m/s (43 km/h; 27 mph).

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