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Wed, 23 Oct 2019
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Strange Skies

Cloud Grey

Noctilucent clouds light up night skies over the Netherlands

This is a good time of year to look up at the sky after sunset and before sunrise. Around the start of the astronomical summer on June 21st, there is a good chance that you will encounter the weather phenomenon noctilucent clouds.

The shiny clouds could be seen all over the Netherlands on Wednesday night and Thursday morning.
NLCs over The Netherlands
© Via Twitter@pcb1970pcb
Noctilucent clouds over Uithoorn, Netherlands.
Noctilucent clouds are created by tiny ice crystals forming on dust particles. "When the sun is down for us and it gets dark, the clouds are still lit by the sun. This makes it look like these clouds are shining in the dark", Weerplaza writes about the phenomenon. Because it is often quite windy in the Netherlands this time of year, the glowing clouds may also look like they're dancing, according to the weather service.

Shining clouds are a quite rare phenomenon, only appearing a few days in the year. If you missed it last night, there is still a chance of noctilucent clouds in the coming weeks.


Comment: See also:


Sun

Sun halo shines above St. John's, Newfoundland

Sun halos over St. John's, NL
© Jeremy Morgan
This year we've seen a sugar maple moon, a super wolf blood moon - even a rare super worm moon, which apparently is a thing. Now we've got a solar halo.

If the sun is visible where you are on Friday, you might notice a strange ring around it. The ring is called a 22-degree halo, because its radius is about 22 degrees around the sun or the moon. The rings are caused by light refraction or splitting through very thin upper level or cirrus clouds made of ice crystals, and can be seen as an indication of coming precipitation.

Weather folklore says a ring around the moon means rain is coming soon, and that does sometimes play out because cirrus clouds do come a day or so ahead of some low-pressure systems, which can bring precipitation, according to Texas A&M.

Potential rain sounds like a regular weather day in Newfoundland and Labrador, you might think - but apparently we're not the only ones seeing a halo right now.


Rainbow

'Fire rainbows' seen across southeast Michigan

Circumhorizontal arc over Dearborn, MI
© Kara Gavin
Circumhorizontal arc over Dearborn, Michigan on Wednesday
Photos of colorful clouds over Michigan and other nearby states have been circulating social media this week.

Sometimes this phenomenon is referred to as a "fire rainbow," but the meteorological term is a "circumhorizontal arc."

The colors come from scattered sunlight through horizontal plates of ice crystals. Circumhorizontal arcs usually are seen in the afternoon on a sunny day. Cirrus clouds (the wispy clouds) are made of ice crystals, since the clouds are so high up. The ice crystals that make up these clouds can refract light from the sun when at a steep angle greater than 58°.

Comment: On June 12th, circumhorizontal arcs were seen in Pennsylvania, Virginia and Ontario, Canada:


Rainbow

'Rainbow colored clouds' seen over northern Virginia

Circumhorizontal arc over VA
© Nora Lee Henderson
There wasn't any rain midday Wednesday, so you know it's not a rainbow. But some of the clouds did turn a vibrant!

These rainbow colored clouds are called a circumhoriztional arcs, or rather part of the arc.

While they're not exactly rare around our area, the circumstances have to be just right.

They can only happen certain times of the year (late spring through early fall) and during the midday because the sun has to be high enough in the sky.

The sunlight has to enter clouds made of flat, plate-shaped ice crystals at a steep angle. The ice crystals have to be oriented horizontally for this to work.

Cloud Grey

Circumhorizontal arc lights up southwestern Ontario sky

Circumhorizontal arc over ON, CA
© Lori Dunn
Chatham, Ontario
This particular arc only lasted a few minutes before disappearing completely.

Southwestern Ontario was graced with a rare treat Wednesday afternoon when a circumhorizontal arc, or 'fire rainbow', lit up the sky.

Social media erupted with images of the rainbow, with many people asking for clarification on what they were seeing. The phenomenon - dubbed a "fire rainbow" by a Washington journalist in 2006 - is formally known as a circumhorizontal arc and while rare in Canada, it isn't unheard of.

The conditions have to be just right for the arcs to appear. The effect can occur when the sun travels through tiny ice crystals in the atmosphere, but the sun has to be high in the sky -- at least 58 degrees -- which is why they're most likely to occur in the afternoon.

Camera

'Fire rainbows' appear across central Pennsylvania

Circumhorizontal arc over central PA
© Laurie Makie
Folks across Pennsylvania caught a glimpse of a rare colorful spectacle in the sky Wednesday - a "fire rainbow."

The textbook name for a "fire rainbow" is circumhorizontal arc, the colors in the sky have nothing to do with fire.

This rare view happens when sunlight hits thin, wispy white clouds at just the right angle.

In order for this to happen, the sun has to be high in the sky, which happens midday.

Sunlight enters ice crystals, which are tiny pieces of ice that make up a cloud, and then gets bent.

Sun

'Superflares' could threaten Earth says study

Superflare
© NASA, ESA and D. Player
An artist's depiction of a superflare on an alien star.
Astronomers probing the edges of the Milky Way have in recent years observed some of the most brilliant pyrotechnic displays in the galaxy: superflares.

These events occur when stars, for reasons that scientists still don't understand, eject huge bursts of energy that can be seen from hundreds of light years away. Until recently, researchers assumed that such explosions occurred mostly on stars that, unlike Earth's, were young and active.

Now, new research shows with more confidence than ever before that superflares can occur on older, quieter stars like our own-albeit more rarely, or about once every few thousand years.

The results should be a wake-up call for life on our planet, said Yuta Notsu, the lead author of the study and a visiting researcher at CU Boulder.

If a superflare erupted from the sun, he said, Earth would likely sit in the path of a wave of high-energy radiation. Such a blast could disrupt electronics across the globe, causing widespread black outs and shorting out communication satellites in orbit.

Notsu will present his research at a press briefing today at the 234th meeting of the American Astronomical Society in St. Louis.

"Our study shows that superflares are rare events," said Notsu, a researcher in CU Boulder's Laboratory for Atmospheric and Space Physics. "But there is some possibility that we could experience such an event in the next 100 years or so."

Scientists first discovered this phenomenon from an unlikely source: the Kepler Space Telescope. The NASA spacecraft, launched in 2009, seeks out planets circling stars far from Earth. But it also found something odd about those stars themselves. In rare events, the light from distant stars seemed to get suddenly, and momentarily, brighter.

Researchers dubbed those humungous bursts of energy "superflares."

Rainbow

Circumhorizontal arc a sign summer is right around the corner in Seattle, Washington

Circumhorizontal arc over Tacoma, WA
© Mark Coates
Circumhorizontal arc spotted in Tacoma, WA on June 9, 2019.
A pretty sight in the clouds this weekend is a sure sign that summer is on the way -- and you don't even need to look at the weather forecast.

Mark Coates snapped these photos of a colorful cloud outside a Tacoma grocery store Sunday afternoon. "I have never seen a more beautiful cloud, it was the colors of the rainbow," Coates said. "The weather was pretty clear, no rain around."

Officially named "circumhorizontal arcs" (or more informally sometimes known as "fire rainbows" - although they have nothing to do with fire...or actual "rain"bows) -- the colors caused by ice crystals in the thin cirrus clouds being at just the correct angle to refract the sunlight into the colors of the prism.

These colorful clouds are fairly rare sights in the mid-latitudes, because they can only occur when the sun is 58 degrees or higher above the horizon. For the Pacific Northwest, that pretty much relegates any sightings to around 6 weeks either side of the summer solstice.

Cloud Grey

Huge outbreak of noctilucent clouds occur in Europe, US

NLCs over Oregon
© Andrew Robb
Last night, a huge outbreak of noctilucent clouds (NLCs) occurred as tendrils of frosted meteor smoke were sighted in Europe and the USA as far south as Oregon and Utah. "What a surprise," says Andrew Robb of Beaverton OR. "It's been almost 10 years since I've seen NLCs here in Oregon. They're back!"

Robb took the picture, above, just after sunset on June 8th. "NLCs stretched the length of the whole horizon," he says. "Their rippling waves and other structures were fascinating."

NLCs are Earth's highest clouds. Seeded by meteoroids, they float at the edge of space more than 80 km above the planet's surface. The clouds are very cold and filled with tiny ice crystals. When sunbeams hit those crystals, they glow electric-blue.

Normally, NLCs are confined to polar regions, but this year people are seeing them at middle latitudes, too. Last night alone the clouds appeared in Utah, Minnesota, Wisconsin, Washington, Montana, Iowa, Oregon and Maine. Electric-blue ripples also blanketed much of northern to central Europe. This is what sunrise over Poland looked like on June 9th:
NLCs over Poland
© Marek Nikodem

Comment: Photos of noctilucent clouds in Minnesota and Wisconsin:

NLCs in WI
© Tim Purington
Noctilucent clouds in Hammond, Wisconsin
NLCs in MN
© Chelsea Langlais
Noctilucent clouds in Forest Lake, Minnesota



Cloud Grey

Londoners left baffled by rare 'black hole' cloud formation

Asperitas clouds over London
© Twitter
Asperitas clouds over London were branded a 'creepy' sight by some social media users.
Londoners were treated to a rare cloud formation which gathered over the capital.

Pictures taken in south London showed clouds which resembled a ''black hole'' according to one social media user.

The unusual sight saw a flurry of images posted on Twitter accompanied by various descriptions which ranged from ''creepy cloud'' to ''what the hell is this?'

Twitter user Iain Mellis captured a wave-like formation in the centre of the capital.

The clouds were identified by experts as Asperitas, a rare formation which was only recently given a name.


Comment: Actually, 'undulatus asperatus'. It's so new, it was only first proposed as a type of cloud formation in 2009...