An extratropical cyclone created this sprawling, comma-shaped swirl of clouds over Hudson Bay. The Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite acquired the image on August 10, 2016. The storm intensified on August 9, reached peak strength on the 10th, and weakened by August 11.
Extratropical cyclones have cold air at their cores, and they are fueled by interactions between masses of cold and warm air masses. Mature extratropical cyclones like this often feature comma-shaped cloud patterns that are the product of 'conveyor belt' circulation. While heavy precipitation is often present near the low-pressure head of the comma, a slot of dry air usually trails the west side of the tail.