UP Rain: When Two Weather Systems Interact, Pg17

Key Highlights:

• Uttar Pradesh experienced an intense three-day wet spell from Friday to Sunday, receiving 66.5 mm of rainfall against a normal of 7.6 mm.
• This excessive rainfall led to flood-like situations in 56 out of 75 districts, resulting in 62 deaths, 46 injuries, and damage to over a thousand houses.
• The India Meteorological Department (IMD) attributed the heavy rains to the interaction of a deep depression and a Western Disturbance (WD).
• The event occurred as the southwest monsoon continued its withdrawal across north and northwestern India.

UP Rain Fury.jpg

Detailed Insights:

• The deep depression originated over the Bay of Bengal, crossed the North Andhra Pradesh-South Odisha coast, and weakened over north-eastern Madhya Pradesh and south-eastern Uttar Pradesh.
• A low-pressure system forms when localized heating causes warm, moist air to rise, cool, and condense into clouds and precipitation.
• Depressions are organized low-pressure systems that produce strong winds and heavy rain, gradually weakening into well-marked low-pressure areas.
• Western Disturbances (WDs) are east-moving, rain-bearing wind systems that originate beyond Afghanistan and Iran, gathering moisture from various seas.
• These are extra-tropical cyclones, formed by the interaction of polar and tropical winds, and are carried by the subtropical westerly jet stream.
• As WDs encounter the Himalayas, they rise and cool, bringing cloudy weather, rain, and thunderstorms, particularly to north and northwest India.
• The IMD noted that the current Western Disturbance was present as a trough high in the atmosphere over northwestern India.

Scientific/Technical Concepts Involved:

• Deep Depression: An organized low-pressure weather system characterized by strong winds and heavy rainfall.
• Western Disturbance (WD): An extra-tropical storm originating in the Mediterranean region, bringing sudden winter rain to the northern parts of the Indian subcontinent.
• Low-pressure system: An atmospheric region where the pressure is lower than its surroundings, causing air to converge, rise, and often lead to precipitation.
• Subtropical westerly jet stream: A high-altitude, fast-moving air current that flows from west to east, influencing the movement of weather systems like Western Disturbances.