A string of thunderstorms, or squall line, is visible in this low-oblique, south-looking photograph taken over the Atlantic Ocean just southeast of Bermuda. A squall line can be severe, causing high winds, torrential rainfall, and possible tornadoes. The passing squall line marks the replacement of warm moist air with cooler, drier air. When a cold front progresses eastward off the east coast of the United States, a narrow band of convective thunderstorms often continues eastward across the Atlantic Ocean. These thunderstorms can be intense, rising to heights in excess of 40 000 feet (12 200 meters) as seen in this photograph. While these storms pose no threat to land, they are of great concern to marine interests because of the potential development of strong gusty winds, heavy rainfall, and waterspouts.