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Chennai's July Paradox: Clouds Above, Dry Ground Below
19 Jul
Summary
- Chennai experiences cloudy but dry weather in July due to the Western Ghats blocking monsoon rains.
- Nighttime rains in Chennai occur when residual moisture reaches the city and cloud tops destabilize.
- Evening thunderstorms in southern Tamil Nadu result from colliding sea breezes and hot, dry westerlies.
In July, Chennai experiences cloudy conditions without rain. This phenomenon is attributed to the Western Ghats mountain range. Southwest monsoon winds, laden with moisture from the Arabian Sea, release their water over Kerala after hitting the Ghats.
As the air descends the eastern slopes towards Tamil Nadu, it warms and dries, leaving Chennai in a rain shadow. The city typically awaits the northeast monsoon in October for substantial rainfall. However, residual moisture from strong monsoon activity on the west coast can reach Chennai by evening or night, leading to light to moderate showers.
Additionally, cool sea breezes from the Gulf of Mannar and Palk Strait collide with hot, dry westerlies over southern Tamil Nadu, particularly Ramanathapuram. This collision violently pushes air upward, forming cumulonimbus clouds and causing localized evening thunderstorms, driven by significant stored atmospheric energy.
