Cool, Classic Gravity Waves Over Delaware Coast Monday

Clouds showing well defined gravity waves over
Bethany Beach, Delaware on Monday. 

 I'm on a getaway and spending a few days on the Delaware coast. We arrived in Bethany Beach Monday under gray skies that spit bits of rain.  

But even the gloomy sky was interesting.

A warm front to the south Delaware set up what are known as gravity waves in the atmosphere. Winds aloft from the south were forced to ride up and over the warm front, which sort of acted as a block to the wind flow.

The set up was kind of like how water flows over a submerged rock in a fast-flowing river. Have you ever noticed when the water in that river flows over that rock, there's a series of waves in the water that continue well past the rock?

The rock set up that series of repeating waves. A blockage in the atmosphere, be it a mountain or a weather front, can do the same thing. So you have waves in sky, Up where we live in Vermont, gravity waves are very common as air flows over mountains. 

The gravity waves I saw in Bethany Beach were a little different than I'm used to seeing because the space between the peaks and valleys of the waves, so to speak, was longer than what I see in mountainous Vermont. The Bethany Beach sky wasn't super unusual, but new to me. 

By the way,the air has to be rather stable in general to support gravity waves. By stable, I mean the temperature in the atmosphere does not increase very fast with height, or at all. If the air were unstable, with temperatures cooling quickly with height, there wouldn't be waves. As the air starts to go up over the blockage, it would keep going up instead of sinking again.  In that case, you'd end up with a band of showers and thunderstorms.

The warm front ended up going through, leaving us in Bethany Beach to enjoy a partly sunny, unseasonably warm Tuesday.

Here's the video of those neat gravity wave skies over coastal Delaware. As always, many people on mobile devices will need to click on this hyperlink to see it. To see the video clearly, click on the arrow, then the YouTube logo. 

Otherwise, here's the video: