1.2.3.8. The highest ever measured thunderstorms

The strongest updrafts reach the tropopause and produce overshooting tops. The highest thunderstorms in the world have been recorded in the tropics, where the tropopause is the highest (15-18 km). Thunderstorms reaching 20-22 km high have been recorded there. The July 23, 2010 Vivian, South Dakota severe supercell thunderstorm, which produced the world record hailstone … Read more

1.2.3.7. Mammatus clouds

Mammatus clouds form on the underside of a thunderstorm’s anvil. The name mammatus comes from the Latin word mamma, meaning “udder” or “breast”. They appear as pouch-like structures protruding from underneath the anvil. Mammatus clouds are gentle downdrafts – sinking cool air – descending from the anvil, that form, evolve and dissipate over a time … Read more

1.2.3.5. Overshooting top

Overshooting tops develop on thunderstorms that have particularly strong updrafts. Overshooting tops typically develop on Cumulonimbus capillatus incus clouds. The updraft punches through the equilibrium level (and thus the anvil), rising higher due to its momentum, despite not being buoyant anymore. An overshooting top is usually short-lived, several tens of seconds, up to several minutes. … Read more

Thunderstorms

typical thunderstorm

In this section we are going to take a general look at thunderstorms. What is a typical thunderstorm. We will take a thunderstorm apart into its basic components and how they make the thunderstorm work. Typical thunderstorm – Cumulonimbus capillatus incus   The most distinctive and typical cloud shape associated with thunderstorms is Cumulonimbus capillatus … Read more

Types of convective clouds – from fair-weather clouds to thunderstorms

convective cloud types

Convection forms distinct types of clouds. Convective clouds are divided into two types (genera): cumulus and cumulonimbus. Each successive type and species display more vertical development as a result of more convective energy being available. The more convective energy is available, the higher the convective cloud will reach. In terms of how high convection goes, … Read more

Convective initiation – how thunderstorms start

convective initiation

Initiation of convection   On a warm day, convection begins when the air close to the surface warms enough to become buoyant and start rising. This process is called free convection. The temperature at which free convection begins is called the convective temperature. When the convective temperature is reached on a clear, hot, and humid … Read more

Atmospheric instability

As air near the ground heats, it becomes more and more unstable and becomes more and more likely to rise convectively. We now take a look at when the atmosphere is stable, less stable, and unstable, what that actually means, and how convection initiates. STABLE AND UNSTABLE ATMOSPHERE – INSTABILITY   Atmospheric stability is the … Read more

Buoyancy and phase changes in water

buoyancy

Convection is driven by buoyancy. So we will first define an air parcel. We are going to be using this term a lot. An air parcel is an imaginary volume of air. It can be at any altitude, any temperature, any pressure. Keep this concept in mind. The fundamental physical phenomenon behind thunderstorms is convection. … Read more