A New Kind Of Cloud?

[Mondy]

http://news.bbc.co.uk/today/hi/today/newsi...000/8076805.stm B)

[NL]

Asperatus.... like the sound of that...Undulatus Asperatus i think should be its full title.

Certainly look like one or two have been photo-shopped to give such vivid colours but still

excellent images.

[dogs32]

http://news.bbc.co.uk/today/hi/today/newsi...000/8076805.stm

surely thats photo shopped

[Harry]

I've seen these types of clouds (or something similar) many times before - most notably I have observed them before or after heavy thunderstorms, either early morning or evening time. The two which really stick out are:

1. The morning after severe thunderstorms in Minnesota (WHICH I SLEPT THROUGH ARRRRGHH!!!)

2. Another occasion was before a severe thunderstorm here, I think in July 07!

They are quite mystical looking, and all my recollections are very calm, warm and humid conditions at the time of seeing them!

[VillagePlank]

The guy who wrote Cloudspotting did a late night show not so long ago, and he took this to the RMS to be listed ... seems like it's worked

[Thundery wintry showers]

Oddly enough I was wondering about the classification of this type of cloud... as recently as the Bank Holiday weekend in Tyne & Wear, when such clouds developed shortly before heavy showers moved in from the SW. In my experience they do tend to be associated with deep instability and thunderstorms in the vicinity- consistent also with Harry's observations.

I wonder if they can arise by extension of the well-known altocumulus castellatus? I certainly notice a trend for them to come about as altocumulus castellatus grows.

[J07]

The second image in that show was taken in NZ. Googling Alpine Village Inn suggests that it was in Hanmer Springs, an inland location at moderate altitude (400m I think). No further information is forthcoming, which is a shame as I would like to know what condition led to that display.

Contrary to the above posts, I speculate that it is some form of wavecloud, it looks kind of similar to altocumulus lenticularis. That formation is extremely common in NZ, so the question is what was different in this case. Who knows.

[full_frontal_occlusion]

I've seen these types of clouds (or something similar) many times before - most notably I have observed them before or after heavy thunderstorms......

2. Another occasion was before a severe thunderstorm here, I think in July 07!

July '07 sounds spot on. I made a mental note after noticing 'unusual' clouds whilst driving through Hampshire on my way to the International Air Tatoo. That was on Sunday, July 15. Rain held off mercifully, but I believe the Midlands took a pasting.

Might be worth looking at the synoptic archives for that day.

ffO.

[Paul Sherman]

http://www.stormtrack.org/forum/showthread.php?t=19272

This is quite Interesting to me, a few months ago (Mar09) I was looking on the above thread on Stormtrack and the exact same cloud formation was discussed over there, obviously the photos in the above Link have not been massively Overexposed by Photoshop, but the consensus was a form a Wave Cloud, on the day the pictures were taken over Dallas a Severe Thunderstorm was located about 100 Miles South and sent "Gravity Waves" Northwards towards the DFW Area.

Just a thought ?

[MAF]

i did post this link in the review section. but will post it here too. i think the cloud pictured above has been recognised by the CAS

http://cloudappreciationsociety.org/collectors-handbook/

[karyo]

I've seen these types of clouds (or something similar) many times before - most notably I have observed them before or after heavy thunderstorms, either early morning or evening time. The two which really stick out are:

1. The morning after severe thunderstorms in Minnesota (WHICH I SLEPT THROUGH ARRRRGHH!!!)

2. Another occasion was before a severe thunderstorm here, I think in July 07!

They are quite mystical looking, and all my recollections are very calm, warm and humid conditions at the time of seeing them!

I agree and I have also seen those clouds on a number of occassions when I was still living in Greece. They were associated with frontal thundery activity in the summer months. Conditions were always calm (no wind) and moist.

I have a feeling that they are more common in mountainous locations as I've never seen them in the islands.

Karyo

[J07]

http://blog.metservice.com/pages/asperatus/

Written by: Bob McDavitt on Jun 4th, 2009 (0 Comments)

ASPERATUS?

Clouds: Their changing shapes often occur over a time-scale and space-scale that we humans can not always fully appreciate unless we use time-lapse photography.

In the international cloud naming scheme used to describe and identify clouds, there are ten basic characteristic cloud FORMS or TYPES or genera (nouns): Cirrus, Cirrostratus, Cirrocumulus, Altostratus, Altocumulus, Nimbostratus, Stratocumulus, Stratus, Cumulus, and Cumulonimbus.

To further describe clouds there are several accepted and defined adjectives covering 14 cloud species (shape and structure), 9 varieties (arrangement and transparency), 9 supplementary features, and two words (genitus, mutatus) describing growth. Click here for a table of these words.

There has recently been a call from the Cloud Appreciation Society of the United Kingdom to ask The Royal Meteorological Society to apply to the World Meteorological Organization to officially add a new variety or species of cloud to the international scheme. The new word is “ASPERATUS”, after the Latin word for rough, and is intended to be used as an adjective to describe those clouds whose underbellies look like the surface of choppy sea.

This story was covered in the UK here and here and then in NZ by Radio NZ National on the Panel.

Photo credit to Bill Slater, taken near Hanmer Springs on 2 March 2005 and winner of the Met Society Photo competition, shows an example of what ASPERATUS implies. Bill explains “It was a fine day and we first noticed some round disc like clouds at fairly high altitude. We commented that they were like flying saucers. Then as we reached Hanmer Springs we started to see these swirls and dangling clouds, looking back towards the Lewis Pass… no rain ever fell.”

“Asperatus” clouds form when there are two (or more) layers of air of differing density, one sitting on the other. The cooler and higher layer is cloudy and the other layer is clear. The boundary between these layers may occasionally get knocked up, but will return downwards thanks to gravity and then may go further down but will return back up thanks to buoyancy. This creates a wave-like surface along the cloud base, and we call these gravity waves because the returning force is gravity and buoyancy.

Yes, the waves on the surface of the sea are a good example of this process.

Another good example is when moist air blows over a range of mountains and makes a system of mountain wave clouds. In New Zealand this often happens, and people in Canterbury call the mountain wave clouds “the northwest arch”.

At first individual Altocumulus lenticularis clouds form, but as a front approaches, upper-level moisture increases and middle and high clouds combine to produce an arch cloud comprising Altocumulus, Altostratus, and Cirrostratus. This arch cloud displays a very sharp edge near the mountains and often there is an arch of clear sky immediately downstream of the mountain divide.

We can cope with the current naming scheme and use Altocumulus lenticularis to describe the NW arch clouds, but it would also be useful to have the extra variety or species word “ASPERATUS” especially when there are undulations in the cloud base.

The MetService cloud poster already has a special photo devoted to the NW arch cloud. At present it is just classified as “Northwest Arch Ac/As/Cs”, but if the word “ASPERATUS” is officially accepted then we are ready and waiting.

If you are coming to the National Fieldays at Mystery Creek 10-13 June then pass by the MetService display in the main pavilion and ask for your own complimentary full-sized cloud poster.

Tags: clouds

Edited June 5, 2009 by J07

[Thundery wintry showers]

Does anyone know if there's any truth behind the association with thunderstorms? I guess it might stem from the association with turbulent air, since thunderstorms develop in conditions of extreme instability, and cumulonimbus clouds by definition feature a lot of turbulent air.

Edit: obviously they aren't exclusively associated with storms because I could swear that there are some outside Exeter right now! Photos to come in the Photography forum.

Edited June 5, 2009 by Thundery wintry showers

[J07]

Does anyone know if there's any truth behind the association with thunderstorms? I guess it might stem from the association with turbulent air, since thunderstorms develop in conditions of extreme instability, and cumulonimbus clouds by definition feature a lot of turbulent air.

Edit: obviously they aren't exclusively associated with storms because I could swear that there are some outside Exeter right now! Photos to come in the Photography forum.

Look at the post above. No thunderstorms in those situations.

[Snowyowl9]

I`ve never seen clouds quite like those, July 2007 was something similar that one evening,but if there nothing to do with thunderstorms and were only seen abroad,they look very dreamlike the first 2 especially.

[sammie]

I've seen them here but never with a thunderstorm (we hardly get them here so I supose thats why haha) more frontal activity. I just assumed it was tubulence in the air from being forced up the hills around where I lived since the cloud base is relativly low.

[Thundery wintry showers]

I think I saw those clouds in Exeter as recently as last night:

Not as spectacular, but all bone fide with no image manipulation used at all!

As far as thunderstorms go it was somewhat ironic, as there was no thundery activity associated with those clouds last evening but there was then a potent, if localised, thunderstorm at 8-9am this morning.

[Snowyowl9]

Oh yes I`ve seen those clouds types TWS just not like those surreal DRX and J07 pics,it`s also like mamma cloud undulation in altocumulus, but this is more wavery.

Edited June 6, 2009 by Snowyowl9

[Cookie]

a new cloud you can't be cirrus

[Thundery wintry showers]

Come to think of it, perhaps the association with thunderstorms stems from confusion with the cumulonimbus pannus (a series of layers of fractal cloud that often form around, and shortly preceding, significant thunderstorms). Those can end up having a similar appearance.

[Snowyowl9]

I saw these clouds late today like your photos TWS, seem to get better cloud formations from the east all too rare on a clear day like today,it`s usually hazy from that direction.

Edited June 7, 2009 by Snowyowl9