Enroute Icing

### Produced by The COMET® Program

### Step 1: Diagnosing Locations of Icing » Satellite Data » Visible

Visible imagery shows daytime cloud coverage. It can help with icing forecasts by showing:

- Cloud brightness, which increases with cloud opacity, water content, and RH
- Clear to cloudy and cloudy to clear transitions near the front and back edges of icing areas
- Potential convection that looks like “lumpy” cloud areas

When using visible imagery with temperature data from Skew-T diagrams and other sources, we can see where there may be supercooled water. If you can see through a cloud layer to the surface, the icing threat is likely to be minimal.

An obvious limitation to using conventional visible imagery is that it’s only available during daytime. It’s also hard to distinguish visible cloud from snow, although other satellite channels or products can help with this.

Here’s the VIS image from 13:03 UTC 26 February 2011. The sun is just rising in the Chicago CWSU service area, but we can still see suggestions of visible cloud.