What is Bow Echo?
The recent storm that struck Delhi showcased a unique phenomenon known as a bow echo. This meteorological event was visually represented on weather radar as a crescent shape. Bow echoes are because they often precede severe windstorms. During the Delhi storm, wind speeds reached up to 100 km/h. Understanding bow echoes is crucial for predicting severe weather events.
What Is a Bow Echo?
A bow echo is a radar signature of a line of thunderstorms that appears bowed or curved. This formation can range from 20 km to 100 km in length and typically lasts between three and six hours. The term “bow echo” was introduced in the 1970s by meteorologist Ted Fujita.
Formation Process of Bow Echoes
Bow echoes form when rain-cooled air descends to the ground and spreads out, creating a gust front. This gust front is a boundary between the cooler air and warmer moist air at the surface. The warm air is pushed upwards, leading to the formation of new thunderstorms. This cycle continues, causing the bow shape as airflow bends the storm system.
Characteristics of Bow Echoes
Bow echoes are commonly associated with severe weather conditions. They can produce damaging straight-line winds and are often linked to derechos, which are long-lived bow echoes. The process involves a series of thunderstorms that maintain strength through continuous formation and reinforcement of rain-cooled air.
Historical Occurrences in India
Bow echoes are not rare in India. A notable instance occurred on May 31, 2022, over Delhi and Noida, with winds reaching 100 km/h. Similar formations have been recorded during thunderstorms in other regions, such as Odisha.
Relation to Derechos
A derecho is weather event that arises from a bow echo or multiple bow echoes. It is characterised by strong winds and can travel extensive distances. If a bow echo produces widespread wind gusts exceeding 58 mph (93 km/h) and travels over 250 miles (400 km), it is classified as a derecho.
Impact on Weather Forecasting
Meteorologists closely monitor bow echoes due to their potential for severe weather. Understanding their formation and behaviour helps improve forecasting accuracy. Advanced radar technology aids in identifying these phenomena, allowing for timely warnings and preparedness.
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