Raekuurot

Raekuurot are a meteorological phenomenon described in Finnish as hail events that form and fall during convective thunderstorms. The term covers single or multiple hail occurrences and is often associated with thunder, and sometimes strong winds and lightning.

Formation occurs in cumulonimbus clouds when strong updrafts lift water droplets into subfreezing regions, causing them to freeze and grow into hailstones. As hailstones are carried through the cloud, they accrue additional ice layers. When their weight exceeds the supporting updraft, they fall to the ground as hail. The size and duration of raekuurot depend on atmospheric instability, moisture, and wind shear.

Characteristics vary widely. Raekuurot can range from light hail showers to severe events with large hail and damaging winds. They may develop quickly within a thunderstorm and last from a few minutes to longer during persistent convective activity.

Impacts include damage to crops, vehicles, roofs, and windows, as well as hazards to people and animals. Economic losses from raekuurot are common in regions with frequent severe hail. Mitigation measures include timely weather warnings, protective coverings for vulnerable assets, and appropriate insurance coverage.

Forecasting and monitoring rely on weather radar, satellite data, and numerical models to identify hail cores within storms and issue warnings. Radar detection of hail is not perfect and depends on storm structure and ambient conditions.

Geographically, raekuurot occur wherever thunderstorms form, with higher frequency in regions of strong convective activity. In Finland, they are more common in spring and summer when thunderstorm activity is elevated.