Meteorology: Understanding the Atmosphere            Ackerman and Knox

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A feature of interest on these satellite images is the appearance of mountain waves as the strong southwesterly flow of the southern branch of the subtropical jet impinged upon the Sierra Nevada mountain range. The GOES-9 water vapor and visible imagery below shows these waves as they develop during the day, just to the lee of the snow-capped peaks in eastern California. Note how a dark cloud-free band (a "foehn gap") becomes better-defined on the water vapor images (19:00-19:15 UTC), about 30 minutes before the first appearance of visible wave cloud billows (about 19:30-19:45 UTC). This water vapor signature of rapid subsidence can be used for short-term forecasting of mountain wave clouds and their associated turbulence.

GOES-9 water vapor

GOES-9 water vapor image

(Java animation)

GOES-9 visible

GOES-9 visible image

(Java animation)