High-Resolution Image

This image, acquired on Memorial Day, May 31, 2004, by the MODIS instrument onboard the Terra satellite, shows a well-defined low pressure system. The center of the system was over Wisconsin and Minnesota, not visible on this image, and was the source of stormy weather in Maryland that day. A low pressure system typically has a warm and a cold front associated with it. The two fronts come together and become an occluded front. An occluded front is a complex boundary between warm, cool and cold air.

Warm fronts tend to be more stretched out, and also move more slowly. The warm front can be seen on this image as a wide band of cloud stretching across the image. Cold fronts are more compact and form a narrower line. Cold fronts move faster, and eventually catch up to the warm front, and the two fronts come together. The cold front can be seen in this image as an arc stretching along the image on the left, with clear sky to the left of it. This systemÕs warm and cold front merged to form an occluded front over Michigan.

The two fronts together bring with them a wide range of cloud types. Cirrus Ð thin feathery clouds made of ice crystals can be seen along the top part of the image. The warm front contains stratus and nimbostratus clouds within it. Those clouds are shaped like great sheets, are made of water drops, and produce the steady rain seen over Maryland that morning. The cold front contains large cumulus clouds that eventually grow to become lines of thunderstorms. A large thunderstorm can be seen in the lower left corner of the image.

(Submitted by Gala Wind, L-3 GSI)