Rare “noctilucent” clouds appear over the SF Bay Area | Hacker News Reader

Rare “noctilucent” clouds appear over the SF Bay Area

sfgate.com

123 pointsindus41 comments

Feels an apposite thread in which to share a link to the Cloud Appreciation Society: https://cloudappreciationsociety.org/

(my copy of The Cloudspotter's Guide, their first publication - written by one of the society's founders - is in the bookshelf next to me as I type)

Great link, and a superlatively germaine usance of the locution "apposite"! :)

I came here to post the same as I love this so much. Their newsletter brings joy, I can highly recommend it.

Noctilucent clouds are the only natural-occuring ice on the planet that isn't hexagonal, instead having mostly cubic crystals, which are stable in the low temp/low pressure environment. Cubic ice is very similar to hexagonal, unlike some of the more exotic ices that exist in high pressure and/or high temp environments in places like Europa's mantle.

"they will first arrive us in form of invisible clouds" ~Aldous Huxley

Beautiful, but source?

https://www.google.com/search?q=%22they+will+first+arrive+us...

I can't find anything in Google Books either. I'm assuming it should be "arrive as", but this is either a translation of something or a misattribution.

I live in SF and didn't see the clouds that morning... but did see the rocket launch. Even though it's relatively tiny in the sky being over 200 miles away, still very cool. I was able to see the initial boost phase (surprisingly clearly), the stage separation, the second stage continuing on its way and some of the booster maneuvering for landing... just illuminated dots on the sky with some faintly visible exhaust plume.

The reported "clouds" probably didn't really become visible until later, well after I went back inside.

These clouds are only visible before sunset or after sunrise. They're very weak and make themselves visible when the surface is in the shadow, but they are not thanks to their impressive an highly unusual altitude (they're well well above all weather).

FYI, you have a typo. It should be “Before sunrise or after sunset”

I caught such on camera about 10-12 years ago in southern Sweden. Though curious enough for me to go get my camera, at the time they didn't strike me as rare as I had seen them form before.

They're not especially rare at these latitudes (I live in southern Finland, ~61°N). You see them fairly frequently on summer nights, rocket launches or not. But what is interesting that nobody seems to have written anything about them until the 20th century, which could indicate that suitable condensation nuclei did not exist in the upper atmosphere before humans started emitting them.

I have the same feeling that these are not very uncommon. My guess is, as I'm also from Sweden, is that the period of time the sun is in the right position for this is much longer at these latitudes.

I'm certain Iv'e seen clouds like these many times, at least 5 times if not more.

> I have the same feeling that these are not very uncommon

The article explicitly states the rarity is at the given latitude:

“Such clouds are very rare at this latitude and also in winter…”

Naturally they chose to over-emphasize the rarity aspect in the headline, otherwise no-one would bother clicking.

Considering how common they're in southern Finland, I'd say you'd only need to get a bit north of Stockholm/Göteborg to see them fairly regularily.

On the right latitudes 60+ these can be seen each year in the months around summer solstice during the short nights. Here's a timelapse over 2 hours if you want to see how some types of them move through the sky https://imgur.com/gallery/PlyifNr

I've been often surprised at how many "cloud nerds" are in the US, that know so many of the Latin classification terms for different cloud formations. In Europe it seems to be a much more niched thing, and I've never heard anyone discuss clouds at this level.

Is it a subject for which importance is placed in school?

I grew up in the United States. I have a vivid memory of learning the words for clouds (e.g., cumulus, stratus, cirrus, etc) at the age of six in the first grade. We didn't need to able to spell them, but we had to be able to identify them by matching pictures of the clouds with the words.

German, I somewhat remember that as well from primary school 30 years ago. Not sure about the exact details, though.

I'd guess because they have tornadoes and cyclones in the USA?

Also, big federal agencies in USA (like NASA) have a sizable education/outreach budget. NOAA would be no exception, a quick search returns $34M.

It’s more because of America’s unique farming legacy.

Wouldn't say importance, but I do recall a class where some of the different types of clouds and weather patterns were mentioned. Well, it was either class or a Discovery Channel program, back when they still did educational things.

These days it's probably curious youtubers mentioning these things. I probably underestimate how educational youtube and co are. Mind you, it's superficial knowledge at best, and with the rapid fire distractions going on, it'll be in the one ear and out the other.

I experimented with visual ray cloud busting for a while.

Get concentrated up with meditation first. Then find a likely target (fluffy yet defined. Isolated...). Lay sharpened gaze upon the cloud. Starts to break up in a minute.

I could swear I have seen clouds like those a million times. However, it is interesting to know clouds could be rare.

Unless you live near the Arctic Circle these are quite rare to see. I thought I saw something similar from sunny Florida and it turned out to be regular cirrus clouds getting lit up by the sun.

Also, a 2D picture doesn't give you the depth information to see that these are really, really far away. Like I've seen meteor showers and have no doubt the altitude they are at. These cloud formations are about that height (50-100km)

I suspect they could mean they are rare in SF Bay or USA. Noctilucent clouds are not that uncommon in higher latitudes.

If you’d see them every day, once a day, you’d have to be 2739 years old.

I see them at least once or twice a year. Mammatus on the other hand...

Would love to see a proper, fully fledged Mammatus. Also a decent Asperatus.

—- are you saying they’re not rare - or you didn’t see them? - don’t understand this comment—-

I parsed that as "I'm pretty sure I saw them many times, so these particular clouds can't really be rare" + "it never occurred to me that some cloud types could be actually so rare to be news if you so see them".

This is one of my favourite sites on noctilucent clouds:

http://www.nightskyhunter.com/Noctilucent%20Clouds.html

It describes what they are, how they differ from normal clouds, and how to recognise them.

Can we call them "rare" or even "clouds" if they were from a rocket launch?

Rare is the new normal. Every day it's record hot, cold, wet, dry, wind... That's how it is where I am (southern IL). The weather has become crazy.

I think the Space X rockets regularly produce these when they are launched at twilight.

Cool coincidence this happening right before the 6.something earthquake.

You can see these in LA after the SpaceX launches. Quite cool!

Seems silly, you could probably find another specific set of cloud criterion and label it rarest clouds in the world.

At best, these are rare in the context of SF norms. They are also more common than described, just that normally they go unobserved. We only really notice them at dawn when they get hit by sunlight early due to altitude.

The category is not an arbitrary one, primarily because they are higher than other weather phenomena, being in the mesosphere. In fact, there is a hypothesis that they did not occur (or perhaps only occasionally even by the standard of their current rarity, such as after large volcanic explosions) until the industrial revolution.

they've botched spraying the chems tbh.

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