Page 285 - PPL-engelsk 2025

Meteorology

Mature stage

The cloud begins to produce precipitation. Cold air is carried down with

precipitation from the cloud.

This weakens the updrafts, which eventually become downdrafts.

The top of the CB reaches the tropopause (30,000 – 60,000 feet). The cloud

experiences heavy turbulence. Thunderstorms can be severe.

Near the ground, there is heavy rain and strong gusty winds. Hail and ice hail

are also likely. The precipitation will gradually spread more and more, and when

the updrafts have disappeared throughout the convection cell, the final stage

begins.

The middle stage lasts about 30 minutes.

Dissipating stage

The energy supply has stopped, and the cell begins to dissipate.

Only downdrafts remain. Precipitation ceases as the downdrafts weaken. The

temperature approaches that of the surrounding air, and the cloud slowly

dissolves. It can either disappear completely or leave small amounts of

stratified clouds.

The final stage lasts about 15 minutes.

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3.6.5 Wind gradient and wind gusts during takeoff and landing

As you saw earlier, the wind can change during the approach to a runway. This

applies to both strength and direction.

Conditions such as CB clouds often bring wind squalls. Wind squalls are a

sudden increase in wind speed that lasts for a few minutes and then subsides.

Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 285