How big to clouds get? I often see a jet fly through
some clouds dwarfing the jet.
The answer to your question depends somewhat on how you define cloud. But a
case can be made for some of the clouds being huge. For instance along a
warm front warm air (being lighter than the cold air) climbs over the cold
air. As it does so it cools to the dew point and a cloud forms. The cloud
can be as long as the front... hundreds of miles.
Typically clouds do not grow vertically above about 20,000 or 30,000 feet (4
to 6 miles), but compared to an airplane that is still large. One type of
cloud - the cumulonimbus - grows vertically to heights of 60,000 or 70,000
feet (12 to 14 miles). Those are the large storms we call thunder heads.
On the other side of the spectrum even the "steam" coming off a cup of
coffee is a cloud. That one is quite small and short lived, but still
technically a cloud.
Cloud size depends on several factors...the type of cloud, the amount of
moisture in the air at the level the clouds are forming, the amount of
"mixing" or turbulence at the cloud level, and others. But the stratus type
of clouds, are arrayed in a continuous sheet, and can stretch for thousands
of miles. If you look at a visible satellite picture, you can see clouds
stretching completely across the United States, especially in the
Wendell Bechtold, meteorologist
Forecaster, National Weather Service
Weather Forecast Office, St. Louis, MO
Clouds come in a large range of sizes, from only
a few feet across for the smallest puffy, fair
weather, cumulus cloud to gigantic in the case of
a huge cumulonimbus thunderstorm cloud (which can be
several miles across).
Then again, if you have a cloud cover, like on a
grey winter day, the cloud can extend for several
hundred miles north, south, east, and west.
David R. Cook
Atmospheric Physics and Chemistry Section
Environmental Research Division
Argonne National Laboratory
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Update: June 2012