Mid-air turbulence causes Air India's Phuket-Delhi flight to drop 300 feet: Why monsoon airspace is unlike any other

On Tuesday, an Air India flight from Phuket to Delhi encountered brief mid-air turbulence, causing the aircraft to drop 300 feet in altitude. Ten passengers and four crew members were taken for medical checks upon landing in Delhi, but there were no serious injuries. The incident highlights the unique challenges of flying through monsoon airspace in August.

Monsoon turbulence is distinct from other types due to the convective nature of the air masses involved. In August, the monsoon trough sits across the Gangetic plain, feeding warm, wet air into the Bay of Bengal. This results in deep convection, with cumulonimbus towers reaching up to 16 kilometers and mesoscale systems spanning hundreds of kilometers.

Turbulence in this context occurs in three main categories: convective, clear-air, and mountain-wave. Convective turbulence, the primary concern here, is generated by thunderstorms with their updrafts and downdrafts. Clear-air turbulence arises from vertical wind shear at cruising altitudes, while mountain-wave turbulence is caused by air being forced over high terrain.

During monsoon flights, aircraft can encounter mature thunderstorms or the turbulence extending hundreds of kilometers downwind of a storm's anvil. Monsoon airspace is particularly challenging because mature cells can reach altitudes where airliners cruise, and the clear air around and above a storm can still contain turbulence.

Aircraft typically receive three layers of information about potential turbulence: onboard weather radar, pilot reports (PIREPs), and meteorological advisories. However, onboard radar misses certain types of turbulence, PIREPs may have gaps in less busy airspace, and advisories provide general areas of expected hazards rather than specific locations. Despite these limitations, most monsoon turbulence can be anticipated and avoided through these systems.