Labour weekend - not looking good as usual

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Thunder
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Unread post by Thunder »

Good point Brian, we did win the rugby. Dam good game it was to!! :D
If the atmosphere is not unstable then it doesnt matter how many potential trigger conditions there are - you could get all the people in New Zealand to stand in a field and blow upwards while farting at the same time and you still wouldn't make a cloud (except one of methane). If I can offer a word of advice, you stormchaser guys need to be thinking stability all the time, rather than worrying about temperatures and wind directions. Those factors only come into play once you have an unstable atmosphere to support a convective cloud.

If I can use an example, think of a marble and a perfectly round, semi-spherical pudding basin. Put the marble inside the pudding basin and no matter where you start it rolling from, or what direction you nudge it in, it will always end up stopped in the bottom of the pudding basin. Thats what a stable atmosphere does to any convection - it damps it out. Now, turn the pudding basin upside down and try to balance the marble on the top - if you are very lucky you might just get it to balance, but the slightest movement or breath of wind on it will send it rolling down the side of the pudding basin to end up goodness knows where. That is an unstable atmosphere - a little push is all it needs to accelerate and end up somewhere unpredictable, and convection just keeps spiralling upwards (until it meets a stable layer).

To extend the analogy, you might find it more useful to keep looking out for the shape of the pudding basin in the sky today, than worry whethere the marble will balance on the top.
To the point indeed....I'll definately keep all this in mind. I guess this has something to do with it but I did note that on the 1st page of this thread that the upper air was warmer than I'd like.

I did find the bowl however in one of my previous storm day photo's and convection took off! hehe.
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Michael
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Unread post by Michael »

Well its raining looks like Gales to follow tommorrow to cap it off :evil: :( :cry: :-({|=
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TonyT
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Unread post by TonyT »

Aaron J Wilkinson wrote:I did find the bowl however in one of my previous storm day photo's and convection took off! hehe.
But did you loose your marbles...? :lol: [/b]
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Unread post by Thunder »

Well done. :D
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Aaron Wilkinson
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Unread post by NZ Thunderstorm Soc »

Manukau heads observer wrote:
all you canty people should be all happy today, you won the NPC !!
(thunderstorm or no thunderstorms, you should be happy, LOL )
:) :D :shock: 8)
Did we win that football game :(
That's a shame.
I hate Canterbury rugby, as they and their supporter's are so one eyed :evil:

...anyway, the Pudding-Bowl theory, Tony, did you make that up?
Sounds impressive :lol:
Wait to you hear about my Metallic Pedal-Car theory :?: :? :lol: :lol:

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Unread post by Manukau heads obs »

no gales michael, wind easing away to stuff all today

we missed all the action here in the auckland area....not by much though,,,,the cb's kept on going down the coastline...just south of Waiuku...i.e the King country/taranaki/manwatu got heaps of cb's and thunderstorms...and rotorua area too

the next low coming off australia now might be more promising!
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TonyT
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Unread post by TonyT »

NZ Thunderstorm Soc wrote:...anyway, the Pudding-Bowl theory, Tony, did you make that up?
Sounds impressive :lol:
Wait to you hear about my Metallic Pedal-Car theory :?: :? :lol: :lol:

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Its not a theory, just a way to try to explain the difference between an unstable system and a stable system - I read it somewhere a long time ago and have used it in talks a few times. It makes a good demonstration if you actually get two objects that shape and show people how one is stable and the other not.

I once did a talk to several hundred grape growers where I was trying to show them how chaos theory limits the predictability of day to day weather forecasting, using a basket ball and a rugby ball as examples of predictable and unpredictable systems - that went down really well. :)
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Unread post by Manukau heads obs »

so, have you lost your marbles or not?
there is other spins to it too:
that once you get rain, you get latent heat released, which warms the air, and makes it rise more, but then warmer air can hold more moisture, and so the RH drops a bit....but also that the rain cools the air below the cloud, and that can reduce the updraft, and if the cloud is stationary, and blocks alot of sun heatin of the ground, then it kills iteself, but that does not apply for colliding sea breezes of upligt off terrain....
i.e there are quite a few feeb back systems,,,some einforce, some dont, etc etc
and then you can have wind shear,,,,i,.e the whole thing can topple over a bit...and that can affect the downdraft/updraft feed backs, etc
dang
i have lost my marbles i think
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Unread post by 03Stormchaser »

The only notable note too come out of yesterday was the dew point got to one of its highest, if not its highest this season 14C
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Unread post by tich »

Rained at Arthurs Pass until about midafternoon, then cleared to variable cloud (and the odd little spit). Cloudy this morning; a shower about 5AM. Still forecast to rain; I thought it was going to clear, but the front must've slowed down. Not cold enough for snow.
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NZstorm
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Unread post by NZstorm »

Back from 4 sun drenched days in the South Island Riviera....Dunedin.
Had to go down there for a wedding. I did notice in the Otago Daily Times this morning that Dunedin's total sunshine for the year to date was only 1000 hours. Was that a misprint :?

Flat stratocumulus from Dunedin to Auckland, but a bit of t/cu over the Bay of Plenty/Coromadel.

I think the pudding bowl/marbles theory is a good way to explain stability versus instability. But also, in NZ we can end up with neither stable nor unstable air, rather conditionally unstable. Air that is currently stable but with sufficient heating, the atmosphere could be rendered unstable.
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NZstorm
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Unread post by NZstorm »

Got some weak showers over Auckland now from what must be sea breeze convergence. Temp has dropped from 21C to 18C.
tich
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Unread post by tich »

Showers returned to Arthurs Pass from about midday. I climbed as high as about 1300m about Noon - there was a light shower then, but only liquid; no sign of fresh snow. (plenty of existing snow above about 1400m, and remains of avalanches as low as about 1000m)

No more precip east of about Castle Hill, but very thick mist at Porters Pass about 4PM. Cloudy with higher cloud for Canty plains; sun starting to show in Chch now.
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Unread post by Andy »

Some low cloud this morning but burning off quickly to clear blue skies.

A cracker 25.2 degrees around 1600 :)
tich
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Unread post by tich »

sun starting to show in Chch now.
Of course the sun isn't shining at this hour, but much of the cloud has cleared in Chch this evening.
tich
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Unread post by tich »

Looking at weather maps, I can see why the weather didn't clear up in the mountains as it was originally expected to do. The front and southerly came through Sunday afternoon, but it seems like a portion of it broke off and stayed over Westland/Buller, while the main front continued northeast over NZ. Even though the peice of the front (and resultant small trough) seemed to be weak when it broke off, it still gave more showers to Westland and Arthurs Pass.
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