Cloudscapes Around Sumatra, Indonesia. Postcard

July 18, 2021 - Panoramic, west-looking photograph of cloudscapes around Sumatra, one of Indonesia's largest islands. The image also shows the smaller, neighbouring Bangka and Belitung Islands, the Java Sea, and the west coast of Borneo (far right margin, above the solar panel). The long, bright clouds, generated by thunderstorms, cast dark shadows on the land and sea below. The brightest zone of the Sun's reflection on the water (sunglint) highlights the narrow strait between Sumatra and the islands. Singapore is hidden beneath a thunderstorm. On the day this photo was taken, winds were blowing from the northeast (right to left in this view). After crossing the Java Sea, the moist air would have risen as it was heated. Such heating likely caused thunderstorms to form over each island. The tops of some of the storms were sheared off by winds to form clouds with flattened upper surfaces; these are called anvil clouds. Winds can extend anvils across great distances, making long, narrow tails. The big anvil that starts over Bangka Island stretches about 200 kilometres (120 miles) across Sumatra into the Indian Ocean. Other anvil clouds formed where air was forced to rise over the high Barisan Mountains on Sumatra's southwest coast (far left). Small cumulus clouds also formed over the small line of Mentawai Islands (top left). Cloud-free zones appear over the Java Sea and the Indian Ocean.