It’s not every day the official National Weather Service forecast from Honolulu, HI calls for freezing rain and snow in parts of Hawaii, but that’s what happened 19 February 2012 for the Big Island. Mauna Loa and Mauna Kea both received snow over the last 24 hours, and VIIRS shows both volcanoes are covered with the white stuff.
True color image of the island of Hawaii from VIIRS, taken at 23:16 UTC, 19 Febraury 2012
False color (or "pseudo-true color") image of the island of Hawaii from VIIRS at 23:16 UTC, 19 February 2012
The top image is an RGB composite of moderate resolution channels M3 (blue), M4 (green) and M5 (red). As these channels observe radiances in the blue (0.488 μm), green (0.555 μm) and red (0.865 μm) portions of the visible spectrum, respectively, the image represents what the human eye sees, and is thus a “true color” representation.
The bottom image is an RGB composite of high resolution channels I-1 (blue), I-2 (green) and I-3 (red). These channels observe radiances centered on 0.64, 0.86 and 1.61 μm, respectively. As a result, differences in the optical properties of liquid droplets and ice particles at these wavelengths allow liquid and ice clouds (and snow) to be distinguished more easily. Liquid clouds appear white (or a dirty, brownish-white), while ice clouds appear blue. The snow on top of Mauna Loa and Mauna Kea stands out as a deeper blue. Vegetation still shows up as green, and barren ground as brown, producing an image that may be called “pseudo-true color”.
Both peaks, which are more than 13,600 ft above sea level, receive snow during most winters. The Mauna Loa observatory, at 11,100 ft above sea level, averages 3.7 inches of snowfall each year. While there are many observatories on Mauna Kea with weather stations, none of them seem to collect routine snowfall information. You can find the latest webcam imagery of Mauna Kea by clicking here to find out how much snow there is in the tropical paradise now. Aloha!