Cloud Streets in the Gulf of Mexico
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Cloud Streets in the Gulf of Mexico

December 20, 2007

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. The top image, captured by the MODIS on NASA's Aqua satellite on the afternoon of December 16, shows long rows of clouds called cloud streets that are combed into a sweeping curve by the northwest wind. The clouds formed when cold, dry air blowing out of the northwest encountered warm, moist air over the gulf. The fast-moving cold air chilled the moist air until the water vapor condensed into clouds that followed the wind's path.

In addition to the long vertical lines that align with the wind direction, clusters of waves cut across the clouds parallel to the shore. These lines are the waves created when the cold, dry air collided with and rose over the mass of warm, moist air. Like the waves that rise and fall through water after it hits a retaining wall, these waves ripple across the front of the cold air mass where it clashes with the stable, warm air. The dark horizontal lines are cloud-free areas where the oscillating cold air dips into the warmer air beneath it. The air is too warm in the trough of the waves for clouds to form.

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