Clouds of the Day -When the Clouds Are Flat - Tuesday, November 21, 2023

When clouds are flat they are called Stratus. Low level flat layered clouds are named Stratus. Middle level flat layered clouds are Altostratus, and higher level Stratus are Cirrostratus. The clouds in the photo below are Altostratus because the cloud base is above 6,500 feet but below 20,000 feet.

How do you estimate the height of cloud bases? Practice makes perfect. Compare the clouds you see with cloud photos. Compare the cloud photos on this website with what you see in your sky. Compare the relative sizes of the cloud formations with what is in your sky as a first guess. In the future I will be including a photo of the sky as shot with a 50 mm lens. That photo will give you the best rendition of the sky as seen with the human eye. Photos that are zoomed in or zoomed out are not how clouds look to us naturally. Hopefully that will give you a better idea of how cloud sizes will look to you without telescopic or wide angle lenses.

You may also purchase our Weather Briefing Cloud ID chart. The description is on our homepage.

Altostratus

Another way is to look at your local National Weather Service website. If you have an airport nearby there may be an hourly observation available. The websites for each NWS region vary somewhat but if you can locate the current weather observation, note the time. It will usually be near the top of each hour. You should see a three-day hourly history of observations. The form may look like the one below.

Count over 6 columns from the left to see the sky condition. On this sample the first row has CLR in it, meaning the sky is clear. Looking down the column the third row shows BKN034. Just put three zeros at the end of 034 and you will get 03400 which would be 3,400 feet. Use that for your local cloud base height. CLR means the sky is clear, SCT means scattered clouds, BKN means broken clouds, and OVC means the sky is overcast.

Happy hunting. The format below use used in the Central Region of the National Weather Service. Your regional may not provide the same detail as below.