The Accumulated Cyclone Energy – the ACE index – is a metric that is used to express the energy used by a tropical cyclone during its lifetime. The calculation takes a tropical cyclone’s maximum sustained winds every six hours and multiplies it by itself to generate the values. The total sum of these values is … Read more
How high into the sky can thunderstorms develop – what are the highest even measured thunderstorms? The strongest updrafts reach the tropopause and produce overshooting tops. The highest storms 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. … Read more
Mammatus clouds form on the underside of a thunderstorm’s anvil. Their name 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 span … Read more
A back-sheared anvil is the expression for a cumulonimbus anvil that spreads against (upwind) into relatively strong winds (jet stream) aloft. Anvil vs. wind As the anvil is forming, it is under the influence of upper-level winds. Typically as you go higher in the troposphere, winds increase. Under stable conditions with high pressure, winds in … Read more
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
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
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
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 is a condition where the Earth’s atmosphere is generally considered to be unstable. 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, … Read more
The warmer air has a lower density than colder air. This makes it buoyant, making it rise. As the air parcels are rising, the moisture this air contains begins to condense and form cumuliform clouds. Those are a result of moist convection. This is what makes hot air balloons rise. If we take a parcel … Read more