An astronaut aboard the International Space Station took this photograph of a massive vertical cloud formation—known to meteorologists as cumulus castellanus—above Andros Island.

These towering columnar clouds are part of the genus cumulonimbus. The cloud name castellanus comes from the similarity to the crenellated towers or turrets of medieval castles. The International Cloud Atlas (World Meteorological Organization) classifies clouds of this type as either Altocumulus castellanus or Stratocumulus castellanus, depending on the base cloud height from which they develop. Regardless of the nomenclature, these clouds develop due to strong vertical air movement typically associated with thunderstorms.

Part of the Bahamas archipelago, Andros Island is divided by large estuaries into three sections. North Andros, Central Andros, and South Andros are each comprised of several smaller islets and cays that are connected by smaller estuaries. Together, Andros Island is the largest in total area (2,300 square miles or 6,000 square kilometers) of all 700 islands in the Bahamas.

Astronaut photograph ISS048-E-38518 was acquired on July 19, 2016, with a Nikon D4 digital camera using a 420 millimeter lens, and is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center. The image was taken by a member of the Expedition 48 crew. The image has been cropped and enhanced to improve contrast, and lens artifacts have been removed. The International Space Station Program supports the laboratory as part of the ISS National Lab to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption by Andi Hollier, Hx5, JETS Contract at NASA-JSC.