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Ridges and Troughs

A few posts ago, Jason asked: "What is the difference between a ridge and a trough?" (this can be found under the "comments" link)

Ridges, are basically elongated areas of high atmospheric pressure. You will see high pressure on surface maps, represented by a big blue H.

I call high pressure our "fair weather friend" because we tend to see quiet weather when we are dominated by a strong high. Clear to partly cloudy skies are usually the rule.

When the ridge occurs at higher altitudes, it can still affect our weather here at the surface.

Ridges can act as "blocking" mechanisms if they are strong enough... kind of acting as a shield, as storms cannot penetrate them.

Upper level ridges can bring warm spells in the winter months, and also very hot weather in the summertime. These ridges are shown on weather maps as air moving north, then south. In the image below, there is a strong ridge over the western US.

On the other side of things... that same image above has a large trough over the eastern half of the country. Troughs are represented by air digging south and then turning north on an upper level weather map.

And a trough is the exact opposite of a ridge... it's an elongated area of relatively low atmospheric pressure. On the surface map, we see the big red "L" as low pressure.

When we're stuck in a trough, we expect cooler than normal temperatures... and sometimes active weather. The coldest air in a trough is on the West side of the trough... and the clouds and rain/snow are typically on the East side!

Hope that answers your question!
Jamie

Posted by at March 3, 2005 5:42 PM

Comments

Posted by: Sara at March 4, 2005 5:11 PM