On almost every weathercast on the nightly news, there is either a still satellite photo or more likely a satellite animation depicting cloud elements looking down from space. The two main types are Visual and Infrared. A visual image is taken by a standard camera and is basically what we would see if we were on a satellite looking down to earth. The infrared camera records images in a different light spectrum that relates to temperature. After some practice, interpretation of the images becomes easier to determine what kind of cloud you are looking at and what weather they will likely produce.

The images below were all taken at the same time – noon PST on April 3, 2011. The first photo is a visual shot, the next two are infrared using two different ways to show temperatures, one using grey scale and the other false colour. Look at the legend on the side of the image to determine the temperature. Normally the colder the cloud top temperature, the more intense the type of weather is being experienced under the cloud. However it is not quite so simple as this as sometimes the infrared image is showing cloud top temperatures of high cirrus type clouds when there is little if any cloud below it.

The visual shot below shows fairly milky looking cloud extending from the Pacific towards Vancouver Island. This is normally associated with cirrus type cloud. To the north there is what appears to be lower topped cloud over Haida Gwaii. Notice that this cloud has a banded appearance. Checking out the weather at the surface, Port Hardy is showing overcast skies but with no rain falling. Sandspit is reporting light showers. So the bands or lumpiness on the satellite photo is likely indicating convective buildups. The cloud over Port Hardy isn’t thick enough to produce any rain.

Notice way off to the east over southern Alberta. There is a lot of what appears to be cloud but Calgary is showing mostly sunny skies on the surface report. So what do you think the white  area might be showing? If you were in Calgary yesterday you experienced a late season snowstorm. So what appears to be cloud is actually fresh snow. If you look at a satellite animation it is easier to understand as the snow area isn’t moving or changing shape.
(Click on the images to get a larger view).

The ‘grey scale’ image below doesn’t have as much detail on it as it is a lower resolution image than the visual picture – 4 km versus 1 km on the Vis. The bright white cloud shows up quite well over the Pacific indicating cold topped cloud. The snow over southern Alberta is still evident but it is much easier to see on the visual shot.

Finally on the ‘false colour’ image below, it is easy to see that the cloud tops west of Vancouver Island are quite cold. Using the legend on the bottom of the photo, the tops are in the range of minus 45 to minus 55.

Each photo is useful both for a diagnosis of the current weather situtation and as a forecast tool. It is always a good starting point to look at satellite images. ‘Ground proofing’ by checking current weather observations on the surface, analysing RADAR and computer prognosis charts are other tools in the forecast process.