Western Disturbance

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Western Disturbance is the term used in India, Pakistan, Afghanistan and Nepal to describe an extratropical storm that brings sudden winter rain and snow to the northwestern parts of the Indian subcontinent. This is a non-monsoonal precipitation pattern driven by the Westerlies. The moisture in these storms usually originates over the Mediterranean Sea and the Atlantic Ocean. Extratropical storms are a global, rather than a localized, phenomena with moisture usually carried in the upper atmosphere (unlike tropical storms where it is carried in the lower atmosphere). In the case of the subcontinent, moisture is sometimes shed as rain when the storm system encounters the Himalayas.

Western Disturbances are important to the development of the Rabi crop in the northern subcontinent, which includes the locally important staple wheat.

[edit] References

• PBS Savage Planet feature on extratropical storms, http://www.pbs.org/wnet/savageplanet/02storms/01extratropical/indexmid.html
• Western disturbance news report, http://timesofindia.indiatimes.com/articleshow/1600979.cms
• USA Today article on extratropical storms, http://www.usatoday.com/weather/wstorm.htm
• "Westerlies to hit northwest back to back," http://www.blonnet.com/2007/03/08/stories/2007030801481200.htm