Shop Windows to the Universe

The Winter 2010 issue of The Earth Scientist includes a variety of educational resources, ranging from astronomy to glaciers. Check out the other publications and classroom materials in our online store.
Weather map showing an occluded front
Click on image for full size
Windows to the Universe image by Lisa Gardiner

Occluded Fronts

Sometimes a cold front follows right behind a warm front. A warm air mass pushes into a colder air mass (the warm front) and then another cold air mass pushes into the warm air mass (the cold front). Because cold fronts move faster, the cold front is likely to overtake the warm front. This is known as an occluded front.

At an occluded front, the cold air mass from the cold front meets the cool air that was ahead of the warm front. The warm air rises as these air masses come together. Occluded fronts usually form around areas of low atmospheric pressure.

There is often precipitation along an occluded front from cumulonimbus or nimbostratus clouds. Wind changes direction as the front passes and the temperature changes too. The temperature may warm or cool. After the front passes, the sky is usually clearer and the air is drier.

On a weather map, like the one on the left, an occluded front looks like a purple line with half triangles and half semicircles along it pointing in the direction that the front is moving. It ends at a low pressure area shown with a large ‘L’ on the map, and at the other end connects to cold and warm fronts.

Last modified August 12, 2009 by Lisa Gardiner.

Shop Windows to the Universe Science Store!

Cool It! is the new card game from the Union of Concerned Scientists that teaches kids about the choices we have when it comes to climate change—and how policy and technology decisions made today will matter. Cool It! is available in our online store.

Windows to the Universe Community

News

Opportunities

You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

Cumulonimbus

Cumulonimbus clouds belong to the Clouds with Vertical Growth group. They are generally known as thunderstorm clouds. A cumulonimbus cloud can grow up to 10km high. At this height, high winds will flatten...more

Nimbostratus

Nimbostratus clouds belong to the Low Cloud (surface to 2000m up) group. They are dark gray with a ragged base. Nimbostratus clouds are associated with continuous rain or snow. Sometimes they cover the...more

Wind

Wind is moving air. Warm air rises, and cool air comes in to take its place. This movement creates different pressures in the atmosphere which creates the winds around the globe. Since the Earth spins,...more

Weather Fronts

When a front passes over an area, it means a change in the weather. Many fronts cause weather events such as rain, thunderstorms, gusty winds, and tornadoes. At a cold front passes there may there may...more

Types of Thunderstorms

There are two main types of thunderstorms: ordinary and severe. Ordinary thunderstorms are the common summer storm. Ordinary thunderstorms last about one hour. The precipitation associated with them is...more

Supercell Thunderstorms and Squall Lines

A supercell thunderstorm is a huge rotating thunderstorm. It can last for several hours as a single storm. These storms are the most likely to produce long-lasting tornadoes and baseball-sized hail. Tornadoes...more

Thunder and Lightning

Lightning is the most spectacular element of a thunderstorm. In fact it is how thunderstorms got their name. Wait a minute, what does thunder have to do with lightning? Well, lightning causes thunder....more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA