Äikeserakud

Äikeserakud, also known as thunder cells or cumulonimbus incus, are a specific type of cumulonimbus cloud that has developed a distinctive anvil shape. This anvil, or incus, forms when the rising updraft of the storm cloud reaches the stratosphere, where the air is much colder and more stable. The moisture in the updraft can no longer rise, so it spreads out horizontally, creating the characteristic flat, spreading top of the anvil.

These clouds are the forerunners of thunderstorms and are associated with severe weather phenomena. They can produce heavy rainfall, lightning, thunder, hail, and strong winds, including tornadoes. The presence of an anvil is a strong indicator that a powerful thunderstorm is in progress or has recently been active. The anvil can extend for hundreds of kilometers downwind from the main storm cell, often outrunning the visible cloud base below.

The formation of the anvil is a result of the dynamic processes within the cumulonimbus cloud. The intense updraft, driven by powerful convection, carries moist air to very high altitudes. When this air encounters the tropopause, the boundary between the troposphere and the stratosphere, it is forced to spread out. Ice crystals and water droplets within the cloud are then carried by upper-level winds, shaping the anvil. Observing the development and orientation of an äikeserakud can provide clues about the wind patterns at high altitudes and the overall severity of the storm.