|
|
| Clear daytime skies favor severe thunderstorm development -
On many summer days when the sky is clear in the morning, cumulus clouds develop during midday and can
cover much of the sky by midafternoon, when the day’s maximum temperature is reached.
These cumulus clouds can develop further into towering cumulus and cumulonimbus
clouds if the atmosphere is conditionally unstable, bringing showers and thunderstorms to
an area where the morning had been clear and sunny.
Wherever a pre-existing cloud cover is present during the morning, the solar heating of the surface is reduced,
so the development of showers and thunderstorms is less likely. In the animation, note the clear area over
Kansas and Nebraska, and the preexisting cloud cover to the east and north.
A line of strong thunderstorms develops in the clear area
in midafternoon (around 2000 UTC), at the time of maximum heating of the ground. The explosive development occurred
in a conditionally unstable atmosphere, with the lifting triggered by solar heating and focused by a “dry-line”
boundary. Several of these storms actually produced tornadoes. You will notice that thunderstorms did
not develop in the area with preexisting cloud cover, where the solar heating of the ground was weaker.
|
|
