Satellite data is one of the more essential forecasting tools. The satellite in use over the western U.S. is the GOES - West Satellite located 22,500 miles above the equator. This satellite is geostationary, meaning that it rotates along with the earth so that it is always over the same place on the earth. Thus it provides nearly continuous images of the earth. Three basic images are generated from this satellite: visible, infrared and water vapor imagery.
Visible imagery is like a camera snapshot from space, recording reflected visible light from the earth’s surface. All clouds are white. The image goes black as the sunsets.
Infrared images are actually measurements of temperature, rather than reflected light as in visible satellite images. Warmer objects appear darker than colder objects. Infrared images from polar orbiter satellites are used to map sea surface temperatures (SST) over the oceans.
Water vapor images are useful for pointing out regions of moist and dry air in the upper half of the atmosphere. Dark colors such as black and dark grey indicate dry air while bright colors such as white or light grey indicate moist air.