What are these clouds?! We’re receiving lots of photos like these today! A lovely & somewhat uncommon display of “stratus undulatus” clouds – wavy, rippling patterns formed from atmospheric instability as air masses collide, with vertical wind shear present, creating this wave appearance similar to ocean waves. Photos are of Seabrook, NH, from Michael Dowe; Merrimac, MA, from Lori Howe, both via our Noyes’ 1DegreeOutside weather app; and the final from X user @MartyMcFLYS.

What Are Stratus Undulatus Clouds?

Stratus undulatus clouds are part of the stratus family, typically forming in the lower to middle levels of the atmosphere. Their characteristic wavy patterns are caused by atmospheric instability, often where two different air masses meet or wind flows create shearing layers. The result is a sky that looks like a rolling, textured sea of clouds!

How Do These Clouds Form?

These clouds form when stable layers of air are disrupted by turbulence or wind shear, leading to the undulating, wave-like patterns we see. This is typically caused by interactions between different weather systems or changes in wind direction with altitude.

How Common Are They in New England?

While New England is no stranger to a variety of cloud types, stratus undulatus clouds are relatively rare here, particularly in such striking, visible formations. However, the region’s shifting weather patterns and occasional atmospheric instability make them possible, especially during transitions between weather systems.

What Do These Clouds Indicate About the Weather?

Stratus undulatus clouds often signal a change in weather, since they are formed in the clash of airmasses and the midst of shifting wind direction and speed aloft. They can be a precursor to an approaching weather front or atmospheric disturbance – in today’s case, the latter, with a disturbance approaching from the west and ushering warmer, more humid air into New England aloft, colliding with our preceding cooler, drier air.  You can usually bet, when you see these, more unsettled weather is on the way in the short-term.

Thank you to everyone who shared their photos with us! Keep your eyes on the sky for more unique weather phenomena, and don’t forget to share your captures with us via the “Send to Us” tab in our Noyes’ 1DegreeOutside Weather App, our Community Gallery here on the website or via social media.