RAMMB Satellite Case Studies

What the GOES imagery shows us over Colorado & Kansas

When inspecting the cloud fields using the 10.7 micrometer (Ám) imagery, notice how the lower clouds are warm, while the higher clouds and thunderstorm tops are cold. Also notice that the low-level cumulus, which are small and bright in the visible (VIS) imagery, and warm in the 10.7 Ám infrared (IR), can be seen in all imaging channels except the 6.7 Ám IR (mid-level water vapor-sensitive) channel. This is because the signal at 6.7 Ám comes from water vapor that is located in the middle and upper layers of the atmosphere, above the height of the low-level cumulus.

The normal imaging frequency for GOES is every 15 minutes. This special research data set contains periods when imagery was taken at 15-min., 1-min. and 30-sec. intervals. Create animated loops from the image sequences at the different time intervals and note the differences in your ability to follow cloud features and to observe thunderstorm development. Notice how the cumulus clouds can be followed much easier with the more frequent-interval imagery, due to their relatively short life-span. Notice too how small-scale features at the thunderstorm tops, such as waves and overshooting tops, can be observed more easily with more frequent-interval imagery.

The thunderstorms in the central Plains exhibit a noticeable degree of organization and have formed in preferred (expected) locations. The main activity is associated with an east-west aligned warm front in central KS, a low pressure area in eastern CO and a low-level convergence zone (often called a dry-line) which stretches from western KS into western TX. Use both single images and loops to study these boundaries and the storm development along them.

It is instructive to observe the thunderstorms using all the imager's channels and at very frequent intervals. Note how the overshooting tops in the VIS imagery correspond with colder areas in the anvil at 10.7 and 6.7 Ám. These regions represent the location of active updraft areas of the thunderstorms and will be associated with regions of radar echo. See how the anvils of the thunderstorms extend downwind from the cold, overshooting area and that, above some of the anvils, there are long plumes of cloud. These long cloud plumes seem to emanate from the updraft area and, when they are long and continuous, indicate a long-lived thunderstorm as their generator. Longer-lived storms are often severe, when other atmospheric conditions allow.

Notice how the clouds appear differently in the 3.9 Ám channel imagery. Higher, cirrus clouds are dark, while lower, cumulus clouds are bright. This is a complex subject which is covered in some detail in the CIRA-RAMM Team's GOES 3.9 Ám Channel Tutorial.

Track the motion of the different thunderstorms using the animated imagery. See how the large storm, which develops in central CO, moves more to the south than the other storms in the region? Such anomalous storm motion (often termed a "right mover") may indicate the existence of a storm with severe weather associated with it; in this case, a tornado.