The MODIS instrument on NASA’s Terra satellite collected this natural-color view of cloud streets over the ocean off of New England and the Canadian Maritimes on January 24, 2011.
South of the loosely packed ice in the northern part of the sea, parallel rows of clouds line up along the north-south axis of the wind. These “streets” of clouds form when cold air blows over the warmer, moister air that sits over the water.
Perhaps the most impressive of cloud formations, cumulonimbus (from the Latin for “pile” and “rain cloud”) clouds form due to vigorous convection (rising and overturning) of warm, moist, and unstable air. Surface air is warmed by the sun-heated ground surface and rises; if sufficient atmospheric moisture is present, water droplets will condense as the air mass encounters cooler air at higher altitudes. The air mass itself also expands and cools as it rises due to decreasing atmospheric pressure, a process known as adiabatic cooling. This type of convection is common in tropical latitudes year-round and during the summer season at higher latitudes.
At mid- and high latitudes during the winter, clouds often form neat, parallel rows. Called cloud streets, these formations can persist for hundreds of kilometers if the land or water surface underneath is uniform.
Strong winds gusted over the Gulf of Mexico on December 16, 2007, and though the wind is invisible in these photo-like snapshots, its presence is written in the clouds and on the surface of the water.