This is a GOES visible channel image from 2017-01-27, about 9 a.m. local time. It's the Atlantic coast of the US. The coast is visible towards the bottom of the image. The scale is large.

This question is referring to the wavy structures that appear in the clouds. Are these 'gravity waves'?

enter image description here


2 Answers 2


These are rotor clouds, and are manifestations of "Lee Waves", a particular kind of internal "gravity wave" (better defined as "buoyancy effect").

Forced convection helps form these clouds as warm, moist air is forced upward by both wind from behind and the mountain barrier in front. The upward movement forces cooling and condensation of vapor into clouds. Once past the mountain barrier, this instability dissipates it's momentum through a series of less intense waves as a function of distance away from the mountain range. The clouds themselves are "standing": they do not move, but are constantly regenerated by the windward moist air mass; nor do they build increasingly larger as they are dissipated on their lee side.

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    $\begingroup$ +1 but note that in meteorology, convection refers to any kind of upward motion, regardless of the driving force. $\endgroup$ Commented Jan 30, 2017 at 19:25
  • $\begingroup$ Indeed, glossary.ametsoc.org/wiki/Convection $\endgroup$ Commented Jan 30, 2017 at 23:21
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    $\begingroup$ I would not have thought that there were so many types of convection in meteorology. Thanks for making the answer better.... $\endgroup$ Commented Jan 31, 2017 at 15:30
  • $\begingroup$ @knobScratcher I will explain the reason for the downvote later after I have formulated my own answer. These are not rotor clouds. $\endgroup$
    – user1066
    Commented May 14, 2017 at 7:03

No, these are cirrocumulus clouds displaying an undulating pattern like fish scales, giving way to the name mackerel clouds or mackerel sky. The clouds can form ahead of a warm front and are generally a reliable indicator that weather is going to change within a day or so.

  • $\begingroup$ Downvote: The question was referring to the wavy patterns, not where the clouds come from. $\endgroup$ Commented Jan 30, 2017 at 14:56
  • $\begingroup$ Are these clouds exhibiting gravity waves? No! $\endgroup$ Commented Jan 30, 2017 at 15:10
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    $\begingroup$ Well, OP is asking about physics, you're answering with phenomenology. That's not an answer. $\endgroup$ Commented Jan 30, 2017 at 15:12
  • $\begingroup$ The physics of these clouds have nothing to do with 'gravity waves'. Air mass mixing and convection explains the pattern the clouds exhibit. $\endgroup$ Commented Jan 30, 2017 at 15:15
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    $\begingroup$ -1 IMO these are almost certainly topographically-forced gravity waves. The pattern seems to begin exactly east of the Appalachians, and the wave crests are parallel with the mountain range. You are correct that the convection explains the pattern, but the convection here forms due to gravity waves. $\endgroup$ Commented Jan 30, 2017 at 15:31

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