Interesting fact about noctilucent clouds (pictured below) making their way further south than ever in known history... check out the write-up below that appeared July 6, 2011 on
SpaceWeather.com
ELECTRIC BLUE CLOUDS: When noctilucent clouds (NLCs) first appeared in the 19th century, they were a high-latitude phenomenon. You had to travel toward the poles to see their electric-blue glow. Not anymore. Just this past weekend, NLCs spilled over the Canadian border into the lower United States as far south as Denver, Colorado. Flying 33,000 feet over the Mile High City on July 2nd, Brian Whittaker snapped this picture from the window of a passenger jet:
Whittaker is a long time observer of NLCs from planes flying much further north. "I was amazed to see them at 39 degrees latitude over the USA," he says.
Another long time observer, University of Colorado atmospheric sciences professor Richard A. Keen was located just underneath the storm clouds in Whittaker's photo. "Rats!" says Keen. "I was watching for NLCs, but all I saw was rain."
During the peak of the display on July 1-2, NLCs were seen in Washington state, Oregon, Montana, North and South Dakota, Minnesota, Colorado and Kansas. Keen notes that the sightings in Colorado (lat 39.8N) and Kansas (lat 38.9N) are among the most southerly sightings ever. "The lowest-latitude sighting I know of was by Craig Coutlee in Ignacio, Colorado on June 22, 1999, the same day as my sighting near Boulder," recalls Keen. "Craig was at 37.1N latitude, just north of New Mexico."
The latest outbreak continues a trend in recent years of NLCs spreading to ever-lower latitudes. Is this a sign of climate change? Some researchers think so. Sky watchers everywhere are encouraged to be alert for electric blue just after sunset or before sunrise; observing tips may be found in the 2011 NLC gallery.
