Formation of a Thunderstorm

Formation of a Thunderstorm

1. 1st Developing/Cumulus Stage

   • During the development of the cumulonimbus cloud, updrafts move air aloft, allowing condensation to take place throughout the ascent of the convective currents.

2. 2. Mature stage

   • During this stage, water drops start to fall through the cloud, drawing air down with them. Although it is dependent on the shape ofthe storm and the prevailing wind gradient, this downdraft is often in the middle of the cloud/storm, surrounded on all sides by strong continuing updrafts, which are providing further fuel for the storm. During this stage, downdrafts can reach 3000 ft/min, and updrafts can reach 5000 to 6000 ftlmin. The mature phase of a cumulonimbus cloud is also the most hazardous stage of its thunderstorms.
     • In short, the dangers include a. Torrential rain b. Hail c. Severe turbulence d. Severe icing e. Windshear and micro bursts f Lightning

3. 3. Decaying stage

   • This is the final stage of the cumulonimbus cloud. It starts with the end ofthe thunderstorm, which is marked by the end of continuous rain and the start of sporadic showers, sometimes as virga due to a temperature inversion beneath the cloud base, which can still cause a marked windshear. At the higher levels it may take on the familiar anvil shape as upper winds spread out under the tropopause. An anvil can have marked downward vertical currents beneath it, which cause a strong windshear that also should be avoided.

4. Thunderstorms are associated with cumulonimbus clouds, and there may be several thunderstorm cells within a single cloud. Therefore, we first have to examine how a cumulonimbus cloud starts to form. Four conditions are required for a cumulonimbus cloud to develop:

   • 1. A high moisture content in the air.
   • 2. A trigger lifting action (or catalyst) to cause a parcel of air to start rising. The four main lifting actions are a. Convection b. Turbulence c. Frontal d. Orographic
   • 3. Adiabatic cooling of the rising air.
   • 4. A highly unstable atmosphere so that once the air starts to rise, it will continue rising. Effectively, the environmental lapse rate (ELR) must be greater than the saturated adiabatic lapse rate (SALR) for over 10,000 ft.

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