I received this letter in my inbox with this attached photo.
“We are currently on a Regal Princess cruise (that left Galveston a few weeks back) visiting the Azores (Portugal) where we came across this unusual cloud formation. May you recognize such and tell us what it may represent?” - Paul Lyle, Galveston
The mystery was afoot; I’d seen these kinds of clouds before but never by themselves. I needed more information, so I wrote Paul back in haste and asked, “What is the exact location, date, and time you took the photos? Were the clouds stationary?”
His response: “The first photo I sent was taken on 4/11/25 at 3:47 p.m., Ponta Delgada, Azores (Portugal), and the clouds were stationary. The second photo sent was taken at 6:40 p.m. (same date) from the same island/location as we were sailing away.”
After that, I had all the information I needed.
With the help of Alan Sealls, a retired broadcast meteorologist and cloud expert, the investigation began. Like a Sherlock Holmes mystery: Holmes and Watson were on the case!
I’ll let Alan decide which one of us is Holmes and Watson. 😂
We started by going to a NASA satellite worldview. This is what we discovered for April 11 and the matching times. I’ve underlined the city, Ponta Delgada, and pointed arrows to the clouds. You’ll notice the clouds don’t look like the others in the area.
Mystery Solved - These are orographically induced gravity wave clouds or stratocumulus lenticularis clouds.
Now take a look at this wide satellite view of the Azores.
Orographically induced wave clouds form when strong winds blow across mountains, causing the air to rise, cool, and then sink in waves on the other side.
As the mountains disrupt the wind, clouds form at the tops of the waves, creating smooth-looking clouds that often look like ripples in the sky or cloud streets. I looked at other dates and these gravity waves are common in the Azores because of the mountain topography.
Here is a graphic example of how they form. Notice how the mountains disrupt the wind flow.
Can these ever form in Houston?
They can but it’s rare. One of these moments was captured last year from Greenway Plaza. SHF sent this photo to click2pins.com. What an incredible shot! It’s like the streets above are mimicking the Houston streets below.
Two other meteorologists helped find the answer to this question. Thank you, Matt Miller and Amy Metz.
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