thunderstorms Flashcards
what are the commonly found weather hazards in thunderstorms?
lightning, icing, turbulence, and
severe precipitation.
how do thunderstorms form?
- warm, humid air at low levels, a steep temperature lapse rate through at least 10,000 feet, and a suitable trigger action for vertical currents.
what is the composition of a thunderstorm?
composed of a great number of individual clouds called cells which
have merged together.
These cells are constantly forming and dissipating, absorbing air from the environment. So in a Cb ,clouds will be in different stages
what are the three stages of a thunderstorm?
growth, mature and decay
what happens in the growth stage of a thunderstorm?
As moist air rises sufficiently high from the Earth’s surface, it is cooled to the dew point.
Condensation begins and cloud forms. Latent heat is given off so the rising air cools at a lower rate once saturation with water vapour is reached.
Air is drawn into cloud cells at the bottom of the cloud, it’s continuous release of latent heat through progressive condensation of it’s water content, causes the updraught to become stronger as it ascends.
what is the main feature of a thunderstorm in the growth stage?
The strong up draught.
The speed increases with altitude - the downdraughts travel at a slower rate.
what happens in the mature stage of a thunderstorm?
With a continued updraught, a large amount of snowflakes and raindrops accumulate in the upper part of the cloud.
the droplets become too large to be supported by the updraughts in the cloud and they fall as precipitation.
The force of the precipitation falling through the cloud, exerts drag on the updraughts, forcing the air back down.
in the mature stage of a thunderstorm what marks the initial wave of downdraughts?
The initial wave of downdraughts is marked by a squall or series of strong gusts and is often followed by heavy precipitation.
what happens in the upper part of a cloud in the mature stage, above the freezing point (0 degree isotherm)
cloud is still developing
what happens in the mature stage of the cloud reaches the top of the tropopause or if a lower temperature inversion exists?
cloud development will cease and the cloud top will spread out to form an anvil shape, pointing in the direction of the upper winds.
at the mature stage of a thunderstorm the up and down draughts can create what?
windshear
why should light or any aircraft avoid thunderstorms?
because they will most likely experience things such as turbulence, heavy precipitation, electrical effects (lightning), severe icing, turbulence/downbursts and damage to instruments.
how does the mature stage of a thunderstorm cause lightning?
Lightning can occur once ice crystals form in the developing cloud.
generally the upper part of the cloud that is positive and the lower part that is negatively charged. When the potential differences between the two become critical, a discharge takes place which neutralizes the electrical field.
This lightning discharge may be within the cloud, between the clouds or from cloud to Earth.
what is thunder?
the heat generated from this discharge causes a sudden expansion of air along the path taken
by the lightning. This is heard as thunder
what happens in the decay stage of a thunderstorm?and what happens if certain conditions are right?
As precipitation increases, the rising warm air weakens and reduces the vertical development of the cloud.
The combined efforts of intense precipitation and horizontal development eventually result in the cloud disintegrating into low irregular lumps of Stratus.
If conditions are right during the mature stage, new Cumulonimbus cloud may propagate itself from the original
