Strong northerly winds frequently blow across Greenland, carrying cold, relatively dry polar air out across the Greenland Sea. As the air passes over the moist, warmer waters, conditions are right for cloud formation. As a result, the Greenland Sea is often cloud-filled.

The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA's Aqua satellite passed over the region on April 5, 2012 and acquired this true-color image of a typically cloud-filled sky over the Greenland Sea. It also captured the image of a beautiful von Karman vortex street trailing on the leeward side of Jan Mayen Island.

Jan Mayen Island sits about 300 miles (500 km) east of central Greenland, and about 400 miles (600 km) west of North Cape, Norway, positioning it an area prone to both clouds and wind. The island is dominated by the Beerenberg volcano, which rises 7,470 feet (2,277 m) on the northeastern end.

This tall, ice-capped mountain forms a formidable barrier to wind flow. When a strong wind slams against the tall, immovable volcano, the air becomes quite turbulent, and forms a swirling pattern as it passes by. These swirls form a beautiful and predictable pattern, known as a von Karman vortex street.

Credit: Jeff Schmaltz, MODIS Land Rapid Response Team, NASA GSFC Click to enlarge. (1.5 mb)



The Hurricanes: Science and Society Webinar Series

Hurricanes: Science and Society is hosting a five-part webinar series in this spring. The webinar series will provide participants with an opportunity to "meet" some of the country's top hurricane scientists and introduce a range of hurricane topics from the basics of hurricane science to advances in forecasting hurricanes to preparing for an approaching hurricane.

Each of the five one hour webinars will have leading members of the hurricane research and forecasting fields discussing their research and answering questions from the "audience." Target audiences include instructors of high school and undergraduate level courses and informal science educators. However, citizens of all ages are welcome to tune in.

Today's Weather Activity

Welcome to JetStream, the National Weather Service Online Weather School. This site is designed to help educators, emergency managers, or anyone interested in learning about weather and weather safety.

The information contained in JetStream is arranged by subject; beginning with global and large scale weather patterns followed by lessons on air masses, wind patterns, cloud formations, thunderstorms, lightning, hail, damaging winds, tornados, tropical storms, cyclones and flooding. Interspersed in JetStream are "Learning Lessons" which can be used to enhance the educational experience.

You are free to use the materials in any manner you wish. We welcome your feedback on this project. Your input will greatly assist others in teaching the "hows" and "whys" of weather. Not sure where to begin? Click to see all topics in JetStream in the Topic Matrix. Contact Us:

Steven Cooper Steven.Cooper@noaa.gov
Deputy Regional Director, NWS Southern Region Headquarters, Fort Worth, Texas

Dennis Cain Dennis.Cain@noaa.gov
a.k.a. "Professor Weather", NWS Fort Worth, Texas