Hole-punch clouds were observed on Tuesday the 3rd of October 2017 over Northern Zealand which is north of Copenhagen in Denmark? It was reported by DMI:
_http://www.dmi.dk/nyheder/arkiv/nyheder-2017/oktober/fly-slog-hul-i-nordsjaellands-morgenhimmel/ said:
"The clouds - or the phenomenon - called a hole-punch cloud," says climatologist and DMI's cloud expert John Cappelen.
"The English name implies that someone or something has punched a hole in the cloud cover. I'm leaning most to a plane passed through the deck of altocumulus. It is the typical story of the kind of cloud holes," says senior climatologist.
Water, there is water, even when it ought to be ice
A hole occurs because cloud droplets in the altocumulus layer has been liquid water, but hypothermic. They have had a temperature below 0°C without being frozen to ice.
"The interference from a plane provokes freezing of the supercooled cloud droplets. The drops suddenly changed phase from a liquid to a solid; from water to ice. Ice crystals then sprinkled out of the cloud, have formed a featherlike ice cloud and left a gap," explains John Cappelen.
The feather cloud in the middle is actually the falling snow also called virga or fall stripes.
On the basis of the time stamps on the photos, DMI has received Tuesday morning, it is most likely that there have been (at least) three hole-punch-clouds on the game. They were then moved from the southwest to the northeast by the relatively strong wind.
The DMI article refers to an article:
_http://science.sciencemag.org/content/333/6038/77 said:
Formation and Spread of Aircraft-Induced Holes in Clouds
Andrew J. Heymsfield1,*, Gregory Thompson1, Hugh Morrison1, Aaron Bansemer1, Roy M. Rasmussen1, Patrick Minnis2, Zhien Wang3, Damao Zhang3
Science 01 Jul 2011:
Vol. 333, Issue 6038, pp. 77-81
DOI: 10.1126/science.1202851
Abstract
Hole-punch and canal clouds have been observed for more than 50 years, but the mechanisms of formation, development, duration, and thus the extent of their effect have largely been ignored. The holes have been associated with inadvertent seeding of clouds with ice particles generated by aircraft, produced through spontaneous freezing of cloud droplets in air cooled as it flows around aircraft propeller tips or over jet aircraft wings. Model simulations indicate that the growth of the ice particles can induce vertical motions with a duration of 1 hour or more, a process that expands the holes and canals in clouds. Global effects are minimal, but regionally near major airports, additional precipitation can be induced.
If it was a plane, or rather planes, because they say there were at least three holes why did they not check the data and flight plan to see if any of the ones could have done it, taking flight routes, flight levels and known cloud altitude into consideration?
The Wikipedia call them fall streak holes: as the hole appears because something begins to fall.
_https://en.wikipedia.org/wiki/Fallstreak_hole said:
A fallstreak hole (also known as a hole punch cloud, punch hole cloud, skypunch, cloud canal or cloud hole) is a large gap, usually circular or elliptical, that can appear in cirrocumulus or altocumulus clouds. Such holes are formed when the water temperature in the clouds is below freezing but the water, in a supercooled state, has not frozen yet due to the lack of ice nucleation. When ice crystals do form, a domino effect is set off due to the Bergeron process, causing the water droplets around the crystals to evaporate: this leaves a large, often circular, hole in the cloud.[1]
It is thought that the introduction of large numbers of tiny ice crystals into the cloud layer sets off this domino effect of fusion which creates the hole. The ice crystals can be formed by passing aircraft, which often have a large reduction in pressure behind the wing- or propeller-tips. This cools the air very quickly, and can produce a ribbon of ice crystals trailing in the aircraft's wake. These ice crystals find themselves surrounded by droplets, and grow quickly by the Bergeron process, causing the droplets to evaporate and creating a hole with brush-like streaks of ice crystals below it.
What if the sudden freezing of the cloud droplets was caused by and inrush of cold air from above? Might that also be possible?
From the session of March 23, 2013 there was:
https://cassiopaea.org/forum/index.php/topic said:
[…]Q …(L) Oh yeah, we were driving home from the fabric store the other day, and as we were coming along, we saw every single kind of cloud in the sky. There were roll clouds to the southwest, there were high cirrus clouds, there were buttermilk-looking clouds, mare's tails, and then there was a really peculiar circular cloud that looked like a big oval smoke ring in the sky. (Andromeda) And it was in an area where it was raining and sunny at the same time. (L) It was pouring rain, the sun was shining, it was just the most bizarre thing. And every kind of cloud that is listed in cloud lists was in the sky all at the same time. It was bizarre. Any comment on our circular cloud and the other...?
A: Smoke ring, eh?
Q: (Andromeda) That's what I said! It looks like something had happened there in that area, because besides that smoke ring cloud, there was another cloud that almost had like a hole in it. This one was one that was more like a ring, and then by it was one that had the circular thing.
A: Punched from upper atmosphere air burst.
Q: (Perceval) Is that what most of those hole-punch clouds are?
A: Yes.[/b]
Q: (Perceval) Those have been around for like decades. (Kniall) It's literally a smoke ring. (L) But coming from the other direction. (Perceval) And they come up with all sorts of fancy explanations for how they form that have nothing to do with the actual cause. […]
The question thus is if the hole-punch clouds over Northern Zealand were caused by a plane as the expert climatologist think, or following the suggestion of the C's by three upper atmospheric air bursts, which would need the help of an astronomer and a physicist rather than an climatologist. If it was a plane, why did at least three appear at about the same time. Might it have been a break up of an incoming meteoroid, see _https://en.wikipedia.org/wiki/Meteoroid and meteor air bursts _https://en.wikipedia.org/wiki/List_of_meteor_air_bursts
If there was upper atmospheric bursts one might expect cold air to be pushed down and provide cooling of the droplets, and as fragmentation is common for incoming objects, I tend to favour a hypothesis involving upper atmospheric air bursts as an explanation for the appearance of at least three hole-punch clouds over Northern Zealand on the morning of October 3rd.
Screen shots from the page of DMI are attached.
My first thought was that these are perfect conditions for building a snowman but I'm not so sure I would be so happy to build one in September! 
)... so i'm considering for tomorrow to go somewhere for some dippin' an' Vit D collectin'
. I guess temperature there was around 27°C. Watched sunset, sent greetings to Sun and DCM and Laura while sun gazing (a sort of)...
) and Earth Changes are definitely on the up. 
