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NACREOUS CLOUD ALERT: Auroras aren't the only colors in the polar sky. Observers around the Arctic Circle are reporting vivid, iridescent nacreous clouds, which form in the stratosphere during the coldest months of northern winter. "Once seen they are never forgotten," says Marketa Stanczykova who photographed these specimens outside Reykjavik, Iceland, on Jan. 4th. Another onlooker in Reykjavik, Albert Jakobsson, describes how "the beautiful colors played in the clouds and kept going for about one and half hour after sunset."
WEEKEND AURORA WATCH: NOAA forecasters estimate a 30% chance of geomagnetic activity during the next 24 hours. High-latitude sky watchers should be alert for scenes like this:
Timo Newton-Syms of Ruka, Finland, took the picture on Jan. 7th when a solar wind stream hit Earth's magnetic field. "The auroras where widespread and visible despite passing clouds and light pollution from the nearby ski slopes," he says. The same stream of solar wind continues to buffet Earth's magnetic field, and is the source of the expected geomagnetic activity this weekend.
more images: from Maxim Letovaltsev of Murmansk, Russia; from Mike Alexander of the Galloway Astronomy Centre, Glasserton, SW Scotland, UK; from Kjetil Skogli of Grøtfjord, Tromsø; from Martin McKenna of Maghera, Co. Derry, N. Ireland; from Bernt Olsen of Tromsø, Norway; from Frank Olsen of Tromsø, Norway;
TRIPLE PUNCH HOLE CLOUDS: "I've lived by the sea for many years, but never seen anything like this," reports Wesley Tyler of Myrtle Beach, South Carolina. "On Friday, Jan. 7th, there were three punch hole clouds in the same place." He grabbed his camera and recorded the phenomenon:
Considered a mystery for many years, punch hole clouds appear on rare occasions all over the world, sometimes attracting widespread attention, e.g., the famous Moscow UFO cloud of 2009. Recently meteorologists have penetrated the mystery: punch holes form when airplanes fly through thin layers of high altitude clouds. If water droplets in the cloud are supercooled (below freezing but still liquid), they can suddenly turn to snow when shocked by the passage of the plane. This mini-snowstorm occurs over a circular area much wider than the airplane itself.
Not all flights through banks of clouds will produce snow. According to Wired Magazine, only about 7.8 percent of the Earth’s surface is covered with clouds at the right elevation for supercooled droplets to form. Because jet aircraft don’t generally cruise at those altitudes, they may only form hole-punch clouds when they take off or land.
The apparition of three rare cloud-holes in one small area suggests a busy airspace around Myrtle Beach. Indeed, the Myrtle Beach International Airport is just miles from where the photo was taken. Or maybe punch hole clouds are still a bit of a mystery after all....
Solar Eclipse Photo Gallery
December 2010 Aurora Gallery
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