Why in news?

More than 100 people died in powerful thunderstorms that struck Uttar Pradesh, with Prayagraj, Mirzapur, and Bhadohi among the worst-hit districts.

These storms, known as Andhi, are a common pre-monsoon weather phenomenon in northern India, typically occurring between April and May, sometimes extending into July. They are usually accompanied by dust storms, thunder, lightning, rain, and occasionally hail.

While many such storms are mild, stronger ones with wind speeds exceeding 90 kmph can cause severe destruction by uprooting trees, collapsing structures, toppling poles, and causing lightning-related deaths.

What’s in Today’s Article?

• Thunderstorms: Formation, Characteristics and Life Cycle
• Why This Thunderstorm Event Was More Destructive?
• Thunderstorm Forecasting: Successes and Limitations

Thunderstorms: Formation, Characteristics and Life Cycle

• A thunderstorm is a rain-bearing weather event accompanied by thunder. Since thunder is produced by lightning, all thunderstorms involve lightning.
• Thunderstorms are primarily the result of convection, which is the upward movement of warm, moist air in the atmosphere.
• Thunderstorms are most common during spring and summer, especially in the afternoon and evening, though they can occur throughout the year depending on atmospheric conditions.
• Key Conditions for Thunderstorm Formation
  • Three essential ingredients are required for the formation of a thunderstorm:
    • Moisture - Adequate moisture in the atmosphere provides the water vapour needed for cloud formation and precipitation.
    • Unstable Rising Air - The air must be unstable, meaning that once it starts rising, it continues to rise because it remains warmer and lighter than the surrounding air.
    • Lifting Mechanism - A trigger or “nudge” is needed to push warm air upward. This can be caused by: Surface heating by the sun; Hills or mountains; Collision of warm and cold air masses; Interaction between wet and dry air masses.
• How Does a Thunderstorm Form?
• The sun heats the Earth’s surface, warming the air above it.
• This warm air rises and carries moisture upward through convection. As the air rises, it cools, and the water vapour condenses to form clouds.
• As the cloud grows vertically into colder regions of the atmosphere, ice particles form.
• Collisions among these ice particles generate electrical charges, eventually leading to lightning.
• The rapid heating caused by lightning produces shock waves heard as thunder.
• Thunderstorm Life Cycle
  • Developing Stage
    • Marked by the formation of a cumulus cloud
    • Strong upward air movement (updraft) dominates
    • Cloud grows vertically into a towering cumulus
    • Little or no rainfall, though occasional lightning may occur
  • Mature Stage
    • Most intense and dangerous stage
    • Rain begins to fall, creating a downdraft
    • Updraft and downdraft coexist
    • Formation of a gust front due to spreading cool air
    • Associated with: Heavy rainfall; Hail; Frequent lightning; Strong winds; Tornadoes
  • Dissipating Stage
    • Downdraft becomes dominant
    • Warm moist air supply gets cut off
    • Rainfall gradually weakens
    • Lightning may still remain a threat

Why This Thunderstorm Event Was More Destructive?

• Unusually Powerful and Widespread Storms - The recent thunderstorms in Uttar Pradesh were far stronger than typical pre-monsoon events, with at least eight districts recording wind speeds above 100 kmph, reaching 130 kmph in some areas.
• Meteorological Conditions Behind the Event - Pre-monsoon thunderstorms in northern India are usually triggered by intense surface heating and moisture-laden winds.
  • This time, temperatures crossed 45°C, while strong southeasterly winds carried abundant moisture from the Bay of Bengal deep into northwestern Uttar Pradesh.
• Atmospheric Instability Triggered Severe Storms - At the same time, western disturbances brought cool, dry air in the upper atmosphere, while warm, moist air remained near the surface. This sharp contrast created intense atmospheric instability—a classic condition for severe thunderstorms.

Thunderstorm Forecasting: Successes and Limitations

• The IMD had forecast thunderstorm activity in advance, but underestimated the maximum wind speeds.
• Initial forecasts predicted winds up to 60 kmph, later revised to 70 kmph, while nowcasts projected 80–90 kmph. However, some districts recorded winds exceeding 100 kmph.
• According to the IMD, the overall forecast was timely and reasonably accurate.
• A strong observation network of around 2,400 weather stations in Uttar Pradesh has improved forecasting accuracy, though efforts are ongoing to better predict extreme intensity.
• Unlike cyclones, thunderstorms do not follow a clear directional path and occur as scattered, multiple events across wide areas.
• This makes large-scale evacuation impractical, limiting disaster response options mainly to early warnings and preparedness.