Enroute Icing

### Produced by The COMET® Program

### Step 1: Diagnosing Locations of Icing » Satellite Data » Cloud Phase and Icing Potential RGB

The Cloud Phase and Icing Potential RGB product is made from visible and shortwave and longwave IR channels, and helps locate fog and low clouds. You can infer the presence of supercooled cloud liquid from the vertical temperature structure in the low cloud area.

When the RGB is enhanced with color, you can see where low cloud tops are at supercooled temperatures. In the product:

- Land and water are darker gray
- Water clouds above freezing are white
- Water clouds between -22° and 0°C are light to dark blue
- Ice clouds are dark to light blue-green

Generally, lower, warmer (but still subfreezing) clouds are in liquid form when higher clouds are not present.

The product is useful for distinguishing high-altitude ice clouds from lower-altitude water clouds. However, it has some limitations. Because it uses reflected SW IR solar radiation, it is less useful at night unless supercooled water areas are highlighted using cloud top temperature (as they are in this case). In wintertime polar latitudes where darkness predominates, aviation forecasters can use the 24-hour Microphysics RGB product and other polar-orbiting imagery. For more on the 24-hour Microphysics RGB product, visit the Short-term Prediction Research and Transition Center (SPoRT) website.

The example below is from the animation for the case. As you can see, the area outlined in red has ice clouds; the area in yellow has supercooled cloud water; the area in white has above-freezing cloud water; and the area in gray has ice clouds near the ice/supercooled water threshold.

View the Cloud Phase and Icing Potential RGB animation, which goes from approximately 00 to 1302 UTC 26 Feb. Make a mental note of areas where supercooled cloud, which is conducive to icing, may exist.