Cumulus congestus (Cu con) is the most developed stage of cumulus before becoming cumulonimbus. It features towering columns exceeding 6,000 metres in height, with sharp, cauliflower-shaped tops indicating vigorous updrafts.
Precipitation and evolution
Unlike cumulus humilis, congestus already produces moderate to heavy showers of short duration. However, its top has not yet glaciated (no ice crystals), which distinguishes it from cumulonimbus. When the top begins to flatten or become fibrous, the cloud is transitioning into cumulonimbus calvus.
Forecasting importance
On unstable days, cumulus congestus indicates a high risk of thunderstorms within 1–2 hours. Updrafts can reach 15–25 m/s, creating severe turbulence for aviation.