UP Rain Extreme: The Interaction of a Deep Depression and Western Disturbance

Gist Uttar Pradesh witnessed an intense three-day wet spell causing widespread devastation, including 62 fatalities and severe flooding across most districts. The anomaly occurred due to a complex meteorological interaction between a retreating deep depression from the Bay of Bengal and an incoming Western Disturbance. For a civil services aspirant, this event perfectly illustrates how the collision of tropical and extra-tropical weather systems can trigger extreme precipitation anomalies, even as the southwest monsoon begins its standard withdrawal. Background Depressions are organised low-pressure weather systems that form when localized heating causes air to warm, become less dense, and rise. This rising action draws warm, moist air towards the centre, which subsequently cools and condenses to produce strong winds and heavy rainfall. Western Disturbances WDs are extra-tropical cyclones driven by the interaction of polar and tropical winds, originating in regions beyond Afghanistan and Iran . These east-moving weather systems gather moisture from large water bodies including the Mediterranean Sea , Black Sea , Caspian Sea , and the Arabian Sea . The subtropical westerly jet stream —a fast-moving, high-altitude air current flowing…