Wednesday, January 10, 2007

Word Of The Week

tramontane

In weather reports, we often hear about the mistral and the tramontane. The mistral we recognize as the wind that blows southward down the Rhône valley toward the Mediterranean Sea. It blows hard and for days on end such that homes in Provence were built with their backs to the wind and windows that open southward. Windows on the north side of these houses are small and few, to keep out the wind.

But what of the tramontane ? It, too, is a wind. It blows southeastward along the foot of the Pyrénées mountains through the Languedoc and the Roussillon regions of France. Both of these winds are the result of cool air being forced through the valleys by high pressure to the north and west, squeezed between mountain ranges, toward a low pressure system over the Mediterranean. In the case of the mistral, it's the Alps on the east and the Massif Central on the west.

The tramontane is pressed between the Massif Central on the northeast and the Pyrénées range on the south. Like water through a narrowing gorge, the wind's course is narrowed such that the air picks up speed and blows hard and steady over the land until it is released to the open space over the sea.

In the image above (click on it for a larger view), A stands for anticyclone, or high pressure, and D stands for dépression, or low pressure (image from www.educnet.education.fr).

These winds normally blow in the summer, but it is not unheard of for them to pick up at any time depending on relative pressure and temperature conditions. Film at eleven.

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