Odd Lenticular Clouds Gave Vermont Skies A Unique Appearance, Followed By Other Rare Clouds Days Later

Lenticular clouds over South Burlington,
 Vermont last Thursday.

 During last week's relatively warm weather, the sky over northwest Vermont began to look a little like some odd fuzzy spaceships were overhead.  

These were lenticular clouds. They happen from time to time mostly over mountainous areas. They're some of the weirdest and most picturesque clouds you can get. 

To understand how these clouds form, think about a fast flowing river. You'll often see the water flow up and over a submerged rock, then there are waves downstream that sort of echo the wave that was over the rock. 

That's what's going on in the atmosphere. Air is flowing up and over a mountain, then you get those waves downstream. Those lenticular clouds you're seeing are the peak of the waves. When air rises to form the peak of the wave, moisture condenses and forms those smooth, rounded clouds. 

This, by the way, is a demonstration why meteorologists are basically physicists specializing in fluid dynamics. The air flows like a fluid, and acts that way. Meteorologists need to understand how these processes work to help that forecast the weather. 

Last Thursday, when these lenticular clouds appeared, winds from the southwest were flowing over the Adirondacks, and the subsequent waves appeared overhead in northwestern Vermont. 

Another view of lenticular clouds over South Burlington,
 Vermont last Thursday.

This made for a very pretty, unique sky, but these lenticular clouds weren't as spectacular as sometimes seen near larger mountains. 

Places like the fairly isolated volcanic peaks in the Cascades of Washington State produce some really wild lenticular clouds. Those can be multi-layered, almost resembling giant wedding cakes from outer space.  

In these areas, like the Cascades, people have actually called the authors because the lenticular clouds really do look like spaceships. People who didn't know any better have thought that's what they really were.  

Lenticular clouds certainly don't happen every day here in Vermont. So it is a treat when we do get them. So I certainly enjoyed last Thursday afternoon's skies. 

Video: Views of the lenticular clouds over northwestern Vermont on October 19. Click on this link to view the video, or, if you see the image below, click on that:

ASPERITAS SIGHTING

A few days later, this past Tuesday, we were treated to another fairly rare cloud called asperitas. It's an overcast with weird wave and sort of swirl patterns associated with it. 

Scientists aren't exactly 100 percent sure how they form. They're often near convective thunderstorms, but sometimes form in much calmer conditions.  The ones we had overhead in Vermont Tuesday came with no major weather.  There were sprinkles around, but certainly no heavy showers or storms. 

Asperitas clouds form over Georgia, Vermont Tuesday. 

The weather that we had Tuesday consisted of warm, moist air flowing from the Gulf of Mexico interacting with weak disturbances in the atmosphere. This has led to those small batches of light showers that have been coming through for the past few days. 

These clouds actually need a stable layer in the atmosphere where the air doesn't mix much. Small disturbances, like pebbles thrown into a pond, can jostle the air enough to create these clouds. 

Although asperitas is often associated with inclement weather, rain for some reason does not fall from these clouds, despite their unstable appearance. These clouds often look ominous, but no need to hide in the basement if you seem them. They don't harm anything. 

The asperitas clouds I saw Tuesday were not nearly as dramatic as they can get.  Sometimes, like some spotted over northern New Hampshire in April, can be incredibly wild.