General October Weather

[NZ Thunderstorm Soc]

Another fine day with some cloud.
Today's maximum was 17.5C.

[NZ Thunderstorm Soc]

Another fine day with some cloud.
Today's maximum was 18.3C

[spwill]

Convergence zones over Otago, Canterbury and the upper North Island tomorrow may generate a heavy shower or two.

Good to have the mainly fine weekend here.

[David]

Wonder when the next rainy system will come through. Hasn’t rained here since the 6th and very little in the 10 day outlook

[TonyT]

Wonder when the next rainy system will come through. Hasn’t rained here since the 6th and very little in the 10 day outlook

Last few days of this month might yield something, next favourable period looks to be the third week of November. MJO very much favours east to northeast airflow for the next 4 weeks.

[cbm]

I posted these to the photographs topic yesterday. Wondering if I did capture something quite rare as this seems "upside down" compared to every other Kelvin-Helmholtz photo I can find.

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[Nev]

I posted these to the photographs topic yesterday. Wondering if I did capture something quite rare as this seems "upside down" compared to every other Kelvin-Helmholtz photo I can find.

I can only assume that in this case the faster moving layer of air is below the relatively more stable layer above, rather than the other way round in say an inversion layer, which are often associated with Kelvin-Helmholtz Instability clouds.

Below is another example of an 'upside-down' KHI cloud...
https://epod.usra.edu/blog/2012/10/mari ... louds.html

[mikestormchaser]

Canterbury plains is heating up! Classic signs of instability spreading over from the west this evening. Nice castalanus altocumulus overhead. Beautiful calm evening! Can Smell blossom in the air

[cbm]

"I can only assume that in this case the faster moving layer of air is below the relatively more stable layer above, rather than the other way round"

Yes. I gathered that too. Which by itself must be less common that having faster winds at higher altitude.

Thanks for finding another example of what a photographer considered upside down KH. However looking closely I think the KH is the regular way up on that one, just the thin slice of clear sky creates an optical effect that makes it possible to see it the other way up.

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[NZ Thunderstorm Soc]

Canterbury plains is heating up! Classic signs of instability spreading over from the west this evening. Nice castalanus altocumulus overhead. Beautiful calm evening! Can Smell blossom in the air

Looking a wee bit interesting, Mike but nothing much to "Wet your pants" over.
Warm day here today with scattered mid range cloud and light east to SE wind.
20.3C here today.

[jamie]

Re the upside down KH cloud. Yea I snapped some pics too. Seemed odd and I can’t recall seeing upside down ones before. Was quite spectacular as annoying as that cloud was blocking the sun all day.
Brian also snapped some pics looking back this way.


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[Nev]

Thanks for finding another example of what a photographer considered upside down KH. However looking closely I think the KH is the regular way up on that one, just the thin slice of clear sky creates an optical effect that makes it possible to see it the other way up.

Not sure about 'the thin slice of clear sky'? The KHI in that San Francisco pic looks to be curling from the underside of the 'Marine Layer Cloud' to me, which is highlighted by the sun's rays from behind the cloud being refracted at both the base of the cloud (saturation level) and the top of the cloud (inversion layer).

Also curious to know what the date and time of your pic was? Would be interesting to see a sounding for that day.

[cbm]

Thanks for finding another example of what a photographer considered upside down KH. However looking closely I think the KH is the regular way up on that one, just the thin slice of clear sky creates an optical effect that makes it possible to see it the other way up.

Not sure about 'the thin slice of clear sky'? The KHI in that San Francisco pic looks to be curling from the underside of the 'Marine Layer Cloud' to me, which is highlighted by the sun's rays from behind the cloud being refracted at both the base of the cloud (saturation level) and the top of the cloud (inversion layer).

Also curious to know what the date and time of your pic was? Would be interesting to see a sounding for that day.

I see what you are saying now, you are saying the brightly lit strip both above and below the marine layer cloud is water droplets i.e part of the cloud that is being illuminated. I was seeing the bottom bright strip as being a gap between the bottom of a near to the camera marine layer cloud and the top of a more distant cloud formation that had a KH pattern along its top extent. If it's the former then yes this KH is also upside down and I guess the photographer at the time was best placed to judge that.

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[cbm]

Here are the details of the photo. I actually took 6 shots but the first 5 were quite simillar.

Photos were taken from here looking WSW.
Dropped pin
https://maps.app.goo.gl/wtCZ67b2PUYvoGAD7

[jamie]

IMG_1856.jpg

IMG_1857.jpg

My pics of it. Sorry for crap foreground. Was busy having evening beers so I didn’t bother to go for a better vantage point.


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[cbm]

IMG_1856.jpg
IMG_1857.jpg
My pics of it. Sorry for crap foreground. Was busy having evening beers so I didn’t bother to go for a better vantage point.


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Yours look like were taken just on sunset. I first noticed it at about 6pm so it lasted at least 1.5hrs.
In case anyone is interested here is every photo I took in full resolution.
https://drive.google.com/file/d/1V2OgaK ... sp=sharing

[harleyb]

Here's that same cloud formation taken from further south. You can see wave patterns in the underside of the clouds which may be the same wave phenomenon but viewed from a different angle? A lovely sight at sunset anyway. That cloud edge had stayed put pretty much all day.

20221015_200950.jpg

[NZ Thunderstorm Soc]

Good capture of the upside down KH clouds. I have only seen them down here the other way up.
....anyway it was a day of clagg and a dull grey weather day down here with light winds and the occasional drizzle.
Maximum of 12.5C for today with 0.5mm of drizzle. I see there might of been a thunder clap or 2 down heard down Otago way this afternoon.
Probably the same clagg weather tomorrow when the southerly comes through on the next front.

[David]

A welcome 10mm here since 4pm yesterday

[Nev]

Mod Note: See new thread for today's Canterbury T-storms.

[cbm]

Here's that same cloud formation taken from further south. You can see wave patterns in the underside of the clouds which may be the same wave phenomenon but viewed from a different angle? A lovely sight at sunset anyway. That cloud edge had stayed put pretty much all day.

20221015_200950.jpg

Yeah. That may well be the same KH formation but not as easy to see from that angle. Presume that is looking North or Nor North west? Either that or the formation/pattern extended hundreds of km.

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[NZ Thunderstorm Soc]

Mainly fine overnight and this morning with light easterly but wind more southerly from noon with some moderate cloud buildups occurring with pleasant temperatures here and fine skies to the east.
I was at lunch in town when the front went through around 2pm,and it came onto wintry hail with the odd grauupel falling as well.
Only 1.2mm for today.
Temperature drop occurred with today's maximum dropping from 18.6C prior to the change, down to 10C by 3pm.
From then a cool southerly wind and cloud moved across and hang around for the rest of the day.
Fine evening.

[harleyb]

Here's that same cloud formation taken from further south. You can see wave patterns in the underside of the clouds which may be the same wave phenomenon but viewed from a different angle? A lovely sight at sunset anyway. That cloud edge had stayed put pretty much all day.
20221015_200950.jpg

Yeah. That may well be the same KH formation but not as easy to see from that angle. Presume that is looking North or Nor North west? Either that or the formation/pattern extended hundreds of km.

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Yes, I was looking WNW, I'm guessing your pic was looking more SW. Probably the same process happening in the same cloud feature, though probably a couple of hundred km away from the part of it that you saw.
It was interesting how the high cloud edge stayed where it was for most of the day, a perfect balance between the low to the east pushing the high cloud "upstream" towards the west with the net result being a boundary that didn't move much at all. A bit like a wind ripple standing still against a current. Very cool.

[cbm]

Yeah. That may well be the same KH formation but not as easy to see from that angle. Presume that is looking North or Nor North west? Either that or the formation/pattern extended hundreds of km.

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Yes, I was looking WNW, I'm guessing your pic was looking more SW. Probably the same process happening in the same cloud feature, though probably a couple of hundred km away from the part of it that you saw.
It was interesting how the high cloud edge stayed where it was for most of the day, a perfect balance between the low to the east pushing the high cloud "upstream" towards the west with the net result being a boundary that didn't move much at all. A bit like a wind ripple standing still against a current. Very cool.

My shots were taken facing only slightly South of West, basically West so we can't have been looking at the same clouds but perhaps the formation/boundary was hundreds of km long.



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[NZ Thunderstorm Soc]

A mainly fine day with a near frost this morning and some weak unstable looking cloud to the west this afternoon.
Today's maximum was 18.6C with a bit of a NE blowing.