Monday, March 31, 2008

The roll and rumble of ‘cauliflower’ clouds

The roll and rumble of ‘cauliflower’ clouds

Bangalore: Non-meteorologists call them ‘cauliflower’ clouds. Meteorologists say they are ‘cumulonimbus’ clouds. The aviation industry says they are a ‘hazard’ to flying.
The city received heavy rain right through March, thanks to the formation of cumulonimbus clouds. Pilots and weathermen at HAL airport are on their toes during the premonsoon months — March, April and May — to gauge changes in weather.
“At HAL airport it’s rush hour during these months. Apart from flashing regular weather bulletins, radars at the airport keep an eye on vertical cloud formations, so that the flying machines can avoid those violent clouds,’’ senior meteorologist, Indian Meteorological Department, B Puttanna, told The Times of India.
Cumulonimbus clouds are a product of vertical cloud formation, having capacity to elevate up to 15 km above sea level.
They cause sudden downpours coupled with thunder. A slight mistake by a weatherman, and an aircraft can run into a cloud system with thunder activity.
“Above five km from sea level, the temperature falls to zero degrees Celsius and above 10 km it might even recede to minus 40. These are the only clouds which can shower hailstorms and initiate thunder activity,’’ the officer added.
Aircraft pilots have no problem negotiating cumulonimbus clouds, but try to avoid it. “Once the aircraft cuts through these clouds, it will experience turbulence which is an atmospheric instability causing gusty air currents. Since the temperature outside the aircraft is low there will be ice formation on the vehicle’s skin which could damage the controllers,’’ an Indian Air Force pilot explained.
The officer pointed out that there are weather monitoring agencies in the West which cut through a tropical storm to gauge weather parameters.
But passenger airlines avoid such turbulence by doing a ‘dog leg’ (taking diversion before the cumulonimbus cloud). The turbulence can cause extreme stress and discomfort to passengers.
This apart, special care is taken in the case of long-distance international flights, which fly at higher altitudes. For instance, ATR aircraft fly above 16,000 feet. International flights can climb up to 40,000 feet.


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