Western Disturbances

• Western Disturbances are mid-latitude storms that develop north of the Tropic of Cancer
• Also known as extra-tropical cyclones or winter storms/blizzards
• Coined by an Indian Meteorologist for the weather phenomenon propagated from the West
• Low-pressure systems embedded in western winds that flow from west to east
• Form over the Mediterranean Sea and travel over Iran, Iraq, Afghanistan, and Pakistan before entering India
• Moisture gets trapped when they come up against the Himalayas, resulting in precipitation in the form of snow and rain over Northwest India
• Average of 4-5 western disturbances form during the winter season, with varying rainfall distribution and amount
• The word ‘Western’ refers to the direction from which they originate with regard to India
• ‘Disturbance’ refers to the unstable or disturbed air within the low-pressure systems
• Sometimes they can extend up to 15 degrees north, resulting in rainfall over north Maharashtra, Gujarat, and the entire Madhya Pradesh to the south.

Formation of western disturbances

• Western Disturbance originates in the Mediterranean Sea as extra-tropical cyclones
• High-pressure area over Ukraine and neighboring countries causes intrusion of cold air from Polar Regions towards an area of relatively warmer air with high moisture
• Change in pressure generates favorable conditions for cyclogenesis in the upper layer of the atmosphere, promoting the formation of an eastward-moving extratropical depression in the sea
• These disturbances gradually travel across the Middle East from Iran, Afghanistan, and Pakistan before entering the Indian subcontinent.
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Impact

• Western Disturbances cause winter and pre-monsoon season rainfall in North-West India
• This phenomenon is associated with cloudy sky, higher night temperatures, and unusual rain
• India gets around 5-10% of its total annual rainfall from Western Disturbances
• They bring moderate to heavy rain in low lying areas and heavy snow to mountainous areas during winter
• Parts of North India depend on snow and rain from Western Disturbances for winter crops like wheat
• They start declining after winter and can help activate monsoon in certain parts of northwest India during summer
• Weak Western Disturbances are associated with crop failure and water problems
• Strong Western Disturbances can help avoid problems associated with water scarcity.
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Casualties

• While Western Disturbances are not typically associated with disasters, in recent years there have been instances where they have caused disastrous events during the summer and monsoon seasons. For example:
  • The 2010 cloudburst in Leh, where 71 towns and villages were damaged and 225 people died, was caused by Western Disturbances.
  • In September 2014, the Kashmir region suffered disastrous floods across many of its districts, resulting in over 200 deaths, which were also caused by Western Disturbances.
  • Expert opinions are divided regarding the 2013 floods in Uttarakhand, where over 5000 people were killed after three days of incessant rainfall. While some believe that the floods may have occurred due to interactions between Western Disturbances and the summer monsoon, others argue that Western Disturbances and monsoon occur in completely different time frames.
• It is important to note that while Western Disturbances are generally beneficial for precipitation and agriculture in North India, they can also bring intense weather events that may cause disasters, especially when interacting with other weather systems or local geographical conditions. It is crucial to monitor and understand the behavior of Western Disturbances and their impacts to better prepare and mitigate risks associated with extreme weather events.