2 Hours in the Life of the Prairie Sky on Friday, October 18, 2019

Heading to winter means big changes overhead. Sometimes they happen quickly. Let’s look at a 2 hour “snapshot” of the sky over northeast Iowa last Friday. The following images are photos taken Friday afternoon, October 18, 2019. The photos show the variety of cloud formations that appeared in a matter of two hours. The sky came alive as clouds changed shape and texture almost minute-by-minute.

Most of the United States resides under the Westerlies. The Westerlies is a west to east river of air found between 30 and 60 degrees north latitude. (For those living in the Southern Hemisphere you have your own westerlies between 30 and 60 degrees south latitude.). During the summer the core of the Westerlies is found near the United States - Canada border. It extends around the entire hemisphere at roughly the same latitude.). The Westerlies are weak during the summer with wind speeds at about 30,000 feet ranging between 20 and 70 mph. During the winter the Westerlies drop south, often flowing across the southwest United States to the region from the Carolinas to northern Florida. The speeds in the core reach often exceed 100 mph and can top 150 mph.

Why does this matter? The westerlies carry storms and fair weather around the hemisphere. As the winds aloft become more energetic during fall, clouds change dramatically! The photos below show some unusual shapes and patterns that formed and dissapated in a few tens of minutes. Check them out and if you live under the westerlies look for rapid weather changes as winter approaches. Temperature will rise and fall during autumn but the over-all trend will be down.

Cirrus and altocumulus, Cedar Falls, Iowa. Photo by Craig Johnson

Looking at the same clouds A few minutes later. Same The clouds have moved to the right. Photo by Craig Johnson

More altocumlus. Photo by Craig Johnson

Cirrus streamers with different textures. Photo by Craig Johnson

Cirrocumjlus, Cirrus fibratus, and altocumulus, Photo by craig Johnson. Notice the cloud patterns.

Cirrus again. Notice the banding. This formation has both Cirrus fibrates and Cirrus uncinus. Photo by Craig Johnson.