8.30 Thunderstorms

8.30.2 State the three conditions required for the development of thunderstorms.

Thunderstorms are defined as one or more electrical discharges indicated by lighting or thunder. This is due to a build up of static electricity caused mainly by friction.

Requirements           

•  
• An atmosphere that is unstable through a deep layer
• An adequate supply of moisture from below
• A Trigger action which causes the initial upsurge of the unstable air

8.30.4 Describe the three stages in the life-cycle of a thunderstorm.

Three stages of thunderstorms

Growing stage

• 15-30 minutes
• 10,000 – 15,000 ft
• Rate of growth up to 2000 ft / min!!
• Latent heat released by condensation – increasing instability.
• Precipitation suspended in updraughts.

Mature Stage

• 15-20 minutes
• 25,000 – 40,000 ft
• Rain on the leading edge.
• Downdrafts at leading edge (first gust)
• Maximum development at the anvil.

Decaying Stage

• Downdraughts and rain beneath entire thunderstorm.
• Rain less intense.
• Anvil becomes widespread.