Western Disturbances

Western Disturbances
 

News: Recently large parts of the country experienced hailstorms which were also accompanied by torrents of rain.
 

What led to the hailstorms and rains?
 The primary reason was that of multiple Western Disturbances (WD), several other WD related weather systems and many troughs, which are extended low pressure areas, formed due to the interaction of the WDs and associated systems with winds blowing in from the eastern part of India, primarily BOB.
 A warming Arabian Sea could also be responsible for the intense storm activity and rain.
 The IMD also cited a strong subtropical westerly jet stream, a band of winds that circles the subtropical regions of the planet in the upper layers of the troposphere, as a reason for the storm activity. This was further aided by the incursion of moisture-laden winds from the Bay of Bengal and the lowering of the freezing level in the atmosphere, which helped in the formation of hail.
 Recent studies have also shown that the warming of the Arctic and the Mediterranean Sea means that Western Disturbances are striking India less in winter and more in summer; with catastrophic consequences on crops, cropping patterns and crop productivity.
 The hail and rains have led to extensive damage to standing crops in many states, such as Maharashtra, Rajasthan, Punjab, Haryana and Gujarat. 

What are Western Disturbances?
 Western disturbances are extra-tropical storms that originate in the Caspian or Mediterranean Sea, which is an area of low pressure & bring sudden showers(non-monsoonal), snow and fog to northwest India.
 The westerly jet stream is responsible for bringing WD from Mediterranean region in to the Indian subcontinent.