Western disturbances are the seasonal features during winter months influencing weather conditions over northern parts, both mountains and plains. The induced cyclonic circulations accompanying the primary one result winter rainfall across states of Rajasthan, Punjab, Haryana and Delhi. Western disturbance and the induced system together increase the spread and intensity of weather hazards like thunderstorm, lightening, squall, rain and fog. Northern weather systems move from west to east, across Indo Gangetic plains, from Punjab to Uttar Pradesh & Bihar.
Down south, northeast monsoon activity, largely affecting Tamil Nadu & Puducherry, Kerala & Mahe and Lakshadweep also intrudes to reach Karnataka and Andhra Pradesh. Easterly waves, trough in the easterlies and off shore cyclonic circulations become the regular weather systems affecting these parts. All these equatorial systems move from east to west.
In normal cases, the central parts of the country, spanning across Gujarat, lower half of Madhya Pradesh, Konkan & Goa, Maharashtra, South Chhattisgarh, Odisha and North Telangana remain far from the reach of weather systems of north and south, both. Very little weather activity is observed over these parts between November and February. All these are counted as fair weather states during this period.
Any weather activity over north India on account of winter systems and over South Peninsula due to northeast monsoon, is quite obviously considered seasonal. Extension of these north and south arms in to the central parts, comprise the ‘unseasonal’ activity, invariably harmful for the crops and the work force.
Unseasonal weather activity is a result of opposing weather systems getting aligned along the same longitudes. The juxtaposing of westerly and easterly systems resultantly trigger ‘phase locking’, also called interaction between the opposing streams of westerlies and easterlies. Such a situation resulted unseasonal and unprecedented hailstorm and thunderstorm over Gujarat on 26thNovember 2023. There was a fatal loss of more than 20 lives and enormous damage to the standing kharif crops. The inclement weather activity spilled over to complete Maharashtra and some parts of Chhattisgarh and north Telangana. Similar conditions recurred and spread over to Madhya Pradesh.
Western disturbance is moving across the mountains, associated with induced cyclonic circulation over North Rajasthan and Punjab. Also, there is trough in the easterlies extending from Kerala to North Madhya Maharashtra. The interaction between the mid level westerlies and lower level easterlies will result unseasonal weather activity over Madhya Pradesh and Maharashtra, for the next 3 days. The weather activity will include scattered thunderstorms, lightening strikes and hailstorm at few places. Eastward extension of this unseasonal activity may also cause similar conditions over some areas of north Chhattisgarh, Southeast Uttar Pradesh and adjacent parts of Jharkhand and Bihar.