File:Cloud Streets over the Atlantic Ocean (MODIS 2023-12-22).jpg

English: Wintry air returned to New England in the last days of autumn 2023, bringing a chill to the region just before the winter solstice. The cold and dry northwesterly wind not only nipped noses as nighttime temperatures dipped as low as 26°F (-3.3°C) in southern Maine, but it also created beautiful, parallel rows of clouds over the Atlantic Ocean.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Aqua satellite captured a true-color image of these cloud streets off the East Coast of the United States on December 20, the day before the Northern Hemisphere winter solstice.

“Cloud streets” describe cumulus clouds that line up in organized rows parallel to the direction of the wind. They form when cold, dry air blows over a relatively warm and moist water body, such as the Atlantic Ocean. A more detailed explanation is that cloud streets occur when columns of heated air—thermals—rise through the atmosphere and carry heat away from the ocean surface. The moist air rises until it hits a warmer air layer (a temperature inversion) that acts like a lid. The inversion causes the rising thermals to roll over on themselves, forming parallel cylinders of rotating air. On the upward side of the cylinders (rising air), water vapor condenses and forms clouds. Along the downward side (descending air), skies remain clear.

Although the New England states experienced the coldest temperatures on the East Coast on December 20, low temperatures were below freezing along the coast at least as far south as Charleston, South Carolina, which is located on the Atlantic Coast near the lower edge of this image. Note that the cloud streets start a bit offshore. This is because the cold air mass needs some time and distance moving over the water to pick up enough moisture for cloud formation.