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I noticed an unusually fast moving cloud this morning.

My questions:

  • What is the average velocity of a cloud on Earth?

  • What is the greatest ever recorded cloud velocity?

  • What factors affect the velocity of a cloud? (e.g. do they experience inertia?)

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Clouds move with the wind, so the cloud velocity is just the wind velocity. The recent storm in the Philipines reached wind velocities of 200 mph, though the higest speed reported is apparently 253 mph.

The fastest moving clouds known are on Neptune, where the winds reach 1340 mph.

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It looks like there can be a difference of up to 5 m/s between cloud velocity and wind velocity (http://journals.ametsoc.org/doi/abs/10.1175/1520-0450%281976%29015%3C0010%3AWEFCMP%3E2.0.CO%3B2 ).

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  • $\begingroup$ cheers, if the rule is to deviate from wind-speed by +/-5m/s then that's pretty simple! $\endgroup$ – hello_there_andy Nov 30 '13 at 16:07
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    $\begingroup$ Well, I just found one old source, there may be other data out there, so please take this with a grain of salt:-) $\endgroup$ – akhmeteli Nov 30 '13 at 16:22
  • $\begingroup$ That reference compares cloud speed as measured from a satellite camera, versus wind speed measured at cloud base and various altitudes within clouds. A cloud is not a solid object. It is suspended droplets, and it can be vaporizing on one side and condensing on another, all as a function of altitude, temperature, and humidity. There is also considerable vertical motion. One thing I'm very skeptical of: droplets having velocity of $5 m/s$ relative to the air they are suspended in. $\endgroup$ – Mike Dunlavey Nov 30 '13 at 20:02
  • $\begingroup$ @Mike Dunlavey: In principle, such relative velocity is no big deal, for example, if there are some forces acting on the droplets, caused, e.g., by gravity (although this is vertical), electric charges, convective effects, etc. Even without forces, initial velocity relative to the air will persist for some time if drag to mass ratio is relatively low. $\endgroup$ – akhmeteli Nov 30 '13 at 21:46

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