Infrared satellite imagery measures the temperature of the closest reflecting surface as observed from the satellite. Geosynchronous satellites are in orbit 22,500 miles above a fixed point at the earth. Clouds appear white in the image; the brightness of the cloud depends on the temperature of the cloud. Higher clouds, which are colder, appear bright white. Lower clouds, which are warmer, appear gray. Land and oceans appear gray or black in the image. The warmer the temperature of the land or water, the darker the feature looks on the image.
Infrared satellite images can be viewed 24 hours per day, since the temperature is being measured. Land temperature varies between night and day, which can be seen in IR satellite images taken at night versus during the day. Very low clouds, such as stratus and fog, are sometimes difficult to see in IR imagery, as the temperature is very close to the nearby land temperature.
Maps are valid at different intervals, depending on the satellite. Generally, images are taken every 15-30 minutes for GOES imagery, every one-three hours for GMS imagery, and every three-six hours for Meteosat imagery. Map valid time indicates the time the image was taken. Maps are created generally 15-30 minutes after the valid time of the image.
Visible satellite imagery is a picture taken by the satellite. Therefore, it needs sunlight on the viewing surface for anything to be seen.
For this reason, visible satellite images are only useful during daylight
hours. Visible images show various clouds and land features very differently
than infrared images. Clouds that appear bright white are thick and are
reflecting sunlight. High, thin clouds appear opaque, whereas low clouds
Maps are valid at different intervals, depending on the satellite. Generally, images are taken every 15-30 minutes for GOES imagery, every one to three hours for GMS imagery, and every three-six hours for Meteosat imagery. Map valid time indicates the time when the image was taken. Maps are created generally 15-30 minutes after the valid time of the image. Visible images are only created during local daylight hours.
Severe Thunderstorm/Tornado Watch Areas
Surface Freezing Line
This map combines Infrared Satellite imagery with NEXRAD Radar Base Reflectivity. The valid times for the satellite image and base reflectivity might not be exactly the same because as the data does not always coincide, but they are normally within 30 minutes of each other.
Maps are available every 15 minutes and contain the latest GOES IR satellite image combined with the latest NEXRAD Base reflectivity mosaic. Radar mosaic is typically more current than the corresponding satellite image.