I was out on my balcony on an ordinary afternoon, looking for some fresh air. Then I noticed a series of steadily existing but constantly evolving frisbee-like clouds over the Rocky Mountains far away. I firmly believe that this was an excellent opportunity for the Cloud Second assignment. So, I got my camera ready and decided to record the evolution of the clouds by taking photos at a rate of one per second. The camera took more than 3,000 photos in a row, which meant that about 50 minutes of cloud evolution was recorded. I stitched these photos together at 60 fps to create a clear and smooth time-lapse video of 6000 × 4000 pixels.

This series of photos was taken starting at 16:35 and ending at 17:31 on Nov 1, so I found the Skew-T diagram from Grand Junction at 00Z on Nov 2 (18:00 in Boulder on Nov 1). From the Skew-T diagram, we know that CAPE = 0, indicating that the atmosphere was stable. Also, the two curves in the Skew-T diagram came close together starting at 5750 meters and separated at about 12,000 meters, which is consistent with the thick cloud stretching upward in the video. After searching, the frisbee-shaped cloud I focused on would be Altocumulus lenticularis.

• Place: Boulder
• Time: 16:35 – 17:31, Nov 1
• Direction of the cloud: South-southwest
• Camera: Sony ZVE10 Mirrorless Camera & Tamron 18-300mm f/3.5-6.3 Di III-A VC VXD Lens for Sony E
• Focus length: 78 mm (35mm equivalent: 117mm)
• Resolution: 6000 × 4000
• ISO: 100
• Aperture: f/5
• Shutter speed: 1/640s at 16:35, 1/320s at 17:31. The shutter speed has been slowed down by the camera’s automatic algorithm as the sky gets darker.