Friday, 13 March 2015

A Blizzard Blankets Mauna Kea

On March 12, 2015, a blizzard warning was in effect on the Big Island of Hawaii. That's not a misprint; it has been snowing in Hawaii. Snow is not unprecedented on tropical peaks, but it is uncommon.

In the past week, the National Weather Service has issued several snowstorm and blizzard warnings for summits higher than 3,400 meters (11,000 feet) on the Big Island. The latest forecast called for freezing fog, strong winds, and blowing snow with possible accumulation of 5–10 centimeters (2–4 inches).

This storm could add to the total snowfall on Mauna Kea, which already had some accumulation from storms in the first week of March. The Operational Land Imager (OLI) on Landsat 8 captured a view of the snow-capped summit on March 10, 2015 (top); it was nearly bare on February 22 (bottom). Use the image comparison tool to see the changes.

The shape of the March 10 snow cover mimics the size of the hole in the clouds on February 22, which is not just a coincidence, according to atmospheric scientist Dale Durran. The location of the edge of the snow is closely tied to the elevation at which the temperatures get cold enough for precipitation to fall as snow. At the same time, Durran noted that the location of the edge of the clouds (bottom image) marks the upward limit—also in elevation—for clouds that build from low altitudes toward the top of the peak. In general, clouds build upward during the day as the sunlit ground heats air near the surface and produces gentle, up-slope breezes and convection.

The snow storms and blizzard warnings led to the closure of the road to Mauna Kea’s summit and astronomical observatories, and leading some astronomers to spend a day at the beach. News stories also noted that the blizzard delayed construction of a new, 30-meter telescope.
NASA Earth Observatory image by Joshua Stevens, using Landsat data from the U.S. Geological Survey. Caption by Kathryn Hansen.
Landsat 8 - OLI