Coldest recorded NZ temperature

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shovelopikis
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Coldest recorded NZ temperature

Unread post by shovelopikis »

When will we ever see the Ophir/Ranfurly records broken?

and what sort of set up would need to be in place for it to break it (or get close to it)?

what sort of set up created those ones in the first place?
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Re: Coldest recorded NZ tempreture

Unread post by Michael »

Dry Anticyclonic weather and high pressure and southerly flows in winter
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Re: Coldest recorded NZ tempreture

Unread post by jamie »

what are they?

Hamilton has a record min of -9 or -10, i forget the exact figure but i just wonder what kind of set up would be required to achieve that.

What we do need to remember is that we are warming year on year. So the longer we go without breaking it the harder it will be to break it, but in saying that, the warmer the world gets, the more volatile the weather becomes so in the bad outbreaks it could be quite possible.
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Re: Coldest recorded NZ tempreture

Unread post by David »

jamie wrote:Hamilton has a record min of -9 or -10, i forget the exact figure but i just wonder what kind of set up would be required to achieve that.
I thought that -10 was an observer error
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Re: Coldest recorded NZ tempreture

Unread post by NZ Thunderstorm Soc »

jamie wrote:
What we do need to remember is that we are warming year on year. So the longer we go without breaking it the harder it will be to break it, but in saying that, the warmer the world gets, the more volatile the weather becomes so in the bad outbreaks it could be quite possible.
I would agree with that. 8)
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Re: Coldest recorded NZ tempreture

Unread post by RWood »

The Ranfurly temperature was not a reasonable representation of the town or area, as I soon figured out on looking at more detailed records. The site for several years was clearly in a sun-starved frost pocket, and the mean jumped up quite a lot after a site change.
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Re: Coldest recorded NZ tempreture

Unread post by cbm »

David wrote:
jamie wrote:Hamilton has a record min of -9 or -10, i forget the exact figure but i just wonder what kind of set up would be required to achieve that.
I thought that -10 was an observer error
I conducted a small invesitagtion into that a year or two ago, but didn't get round to sharing any results. I pulled as much data as I could find from Clifo.

Have put raw data and basic stastical analysis up here:

https://sites.google.com/site/ruakuraextememinimuns/

There are always asumptions that you have to make, such as the climate is stationary over the period of data, effects of site and equipment etc. There is a branch of stats called Extreme Value theory used to predict extreme minimuns for crop farming. However, I believe that as these values are already the extreme values of each year, they are more likely to be normally distributed? I did some basic stats at uni but I'm not qualifed in the field and welcome any critique of my stastical analysis.

Overall, based on the data, I believe now that the value of -9.9 is much more likely than not to have been an error. Was it actually a grass minimum? The chances of it occuring naturally in the 1 dataset of 73 years that we have would appear to be in the 1 in tens of thousands range.

At the time I tried to find if any other sites in the Central to Upper North Island recorded anything unusally low on the date in question but the data just didn't seem to be there.
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Re: Coldest recorded NZ tempreture

Unread post by melja »

If you drop the Ranfurly one out then Ophir at -21.6 would be next then.
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Re: Coldest recorded NZ tempreture

Unread post by David »

cbm wrote: I conducted a small invesitagtion into that a year or two ago, but didn't get round to sharing any results. I pulled as much data as I could find from Clifo.

Have put raw data and basic stastical analysis up here:

https://sites.google.com/site/ruakuraextememinimuns/

There are always asumptions that you have to make, such as the climate is stationary over the period of data, effects of site and equipment etc. There is a branch of stats called Extreme Value theory used to predict extreme minimuns for crop farming. However, I believe that as these values are already the extreme values of each year, they are more likely to be normally distributed? I did some basic stats at uni but I'm not qualifed in the field and welcome any critique of my stastical analysis.

Overall, based on the data, I believe now that the value of -9.9 is much more likely than not to have been an error. Was it actually a grass minimum? The chances of it occuring naturally in the 1 dataset of 73 years that we have would appear to be in the 1 in tens of thousands range.

At the time I tried to find if any other sites in the Central to Upper North Island recorded anything unusally low on the date in question but the data just didn't seem to be there.

I suppose the normal assumption is not too badly violated (apart from the -10 value) if you plot the observations with a normal distribution curve superimposed:
extreme-minimums-distribution.png
From a few calculations I did using the data table in your link, I find that the chance of a sample of 73 random normal values containing at least one value as far below the mean as in the Ruakura case to be approximately 1 in 33,000.

Not exactly the same numbers that you have there, but of similar magnitude. Overall I come to the same conclusion as you! :smile:
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Re: Coldest recorded NZ tempreture

Unread post by David »

cbm, just another note:

If you drop -9.9 from the sample and use the non-suspect data only, you find the chance to be more like 1 in 29,000,000 :lol:
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Re: Coldest recorded NZ tempreture

Unread post by matttbs »

So now you guys have me wondering, what is the real all time low for Hamilton?
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Re: Coldest recorded NZ tempreture

Unread post by David »

matttbs wrote:So now you guys have me wondering, what is the real all time low for Hamilton?
I can't say for sure, but possibly the -6.7C in 1912 is the lowest
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Re: Coldest recorded NZ tempreture

Unread post by jamie »

Yea seems to be a mistake for sure. Glad i know now.

I had a dig back through just now and its a shame a bunch of stations only started 1946 and 1949. The best i found was Rotorua and Tauranga, which had -4.? and -2.6 respectively.

I wonder if it is supposed to be -4.9. Depending on who wrote the number on the paper, they might have written their 4's similarly to a 9.

That means Hamilton's true lowest temp is -6.7 in 1912?
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Re: Coldest recorded NZ tempreture

Unread post by cbm »

David wrote:cbm, just another note:

If you drop -9.9 from the sample and use the non-suspect data only, you find the chance to be more like 1 in 29,000,000 :lol:

I did consider that :). Saw that doing so would drop sigma down to 0.9 but didn't recalculate the odds. Left it in based on the prinicpal that it made the case stronger, ie. standard dev was still only 1.1 even with it in.
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Re: Coldest recorded NZ tempreture

Unread post by cbm »

jamie wrote:Yea seems to be a mistake for sure. Glad i know now.

I had a dig back through just now and its a shame a bunch of stations only started 1946 and 1949. The best i found was Rotorua and Tauranga, which had -4.? and -2.6 respectively.

I wonder if it is supposed to be -4.9. Depending on who wrote the number on the paper, they might have written their 4's similarly to a 9.

That means Hamilton's true lowest temp is -6.7 in 1912?
Taking the thought to be invalid -9.9 out, that at about 2.5 sigma from mean is at about the 0.25 percentile, so chance of a dataset of 73 years containing a value that low or lower is about 1 in 5. Statistically at least then, much more plausible.
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Re: Coldest recorded NZ temperature

Unread post by shovelopikis »

does anyone have any more info on the ranfurly or ophir event?
like more detailed reports instead of main stream media reporting laymans terms...

eg how many days was it a southerly for? what was the HPa readings if any, or was it freezing fog for a good week...ophir gets it a lot but ranfurly a lot less since its higher elevation
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Re: Coldest recorded NZ temperature

Unread post by spwill »

shovelopikis wrote:does anyone have any more info on the ranfurly or ophir event?
With the Ophir event there was snow cover after a very cold southerly outbreak. I would say the southerly was followed by a lingering High bringing clear skies/ light winds and night time cooling. The very dry polar air will have helped with night cooling , the snow cover acting as a blanket trapping ground heat below.
Ophir has an altitude of 305m and sits in a valley, this will have also played a part.
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Re: Coldest recorded NZ temperature

Unread post by RWood »

spwill wrote:
shovelopikis wrote:does anyone have any more info on the ranfurly or ophir event?
With the Ophir event there was snow cover on the ground after a very cold southerly outbreak. I would say the southerly was followed by a lingering High bringing clear skies/ light winds. The very dry polar air will have helped with night time cooling , the snow cover acting as a blanket trapping ground heat below.
Ophir has an altitude of 305m and sits in a valley, this will have also played a part.
Spot on. The Climate Digest pub. notes a very cold southerly snowy outbreak - to low levels - in the south from 28 June, followed by a ridge. Moa Creek at a higher elevation is not far away and often recorded lower minima than Ophir, but I don't think it had any data for that period.

Something similar and even more spectacular in some aspects occurred in July 1968 after very heavy snowfalls at the end of June. Tara Hills near Omarama had snow cover for the whole of the month and had a Tmean for the month of -4.9C, which was 6.3C below average.
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Unread post by melja »

Would the long term snow cover help the cooling by reflecting all the sun and heat? Rwood?
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Unread post by RWood »

melja wrote:Would the long term snow cover help the cooling by reflecting all the sun and heat? Rwood?
Yes, indeed. The snow cover at TH was "never less than 5 1/2 inches" for that month, and had a big effect. It lasted a short time into August, but long enough for the mean temp. there to be about 0.9C below normal while areas without snow cover had a warmer than average August.

The met. summaries for November 1967 noted that mean temps for the month were greatly depressed by the exceptional snowfall covering the ground for quite a while in the affected areas. There was a sharp change in the temperature anomalies north of a well-defined line in the SI.
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Re: Coldest recorded NZ temperature

Unread post by bpo »

The odds of temperatures that low or even lower occurring again in the foreseeable future are staggeringly small.
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Re: Coldest recorded NZ temperature

Unread post by tunster »

bpo wrote:The odds of temperatures that low or even lower occurring again in the foreseeable future are staggeringly small.
I was at a conference last year with a speaker from Oxford who had run a [email protected] like programme for climate. One of the interesting findings was comparing the likelihood of notable UK weather months in modern times compared with in the 1960s.
December 2010 (second coldest ever) was found to be half as likely to occur now as in the 60s.
November 2011 (second warmest ever) was found to be 62 times more likely to occur now as in the 60s.


These are Birmingham's stats for December 2010:
http://www.wunderground.com/history/air ... atename=NA

The 19th is particularly staggering: a max of -4C and a minimum of -15C!
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Re: Coldest recorded NZ temperature

Unread post by Nev »

A few snippets regarding the latest our most extreme temp records...
'New Zealand's extreme weather record' - NZ Hearld

The World Meteorological Organisation (WMO) is considering a report of a -25.6C temperature at Ranfurly on July 17, 1903, which if accepted would become the coldest ever recorded temperature for the Oceania region…

In the meantime, Mr Macara [NIWA] is now working on second report for the WMO, on New Zealand's highest temperature of 42.4C recorded at Rangiora on February 7, 1973.

The WMO presently lists 42.2C recorded at Tuguegarao, Philippines, on 29 April, 1912 as the highest ever recorded Oceania temperature…

(full story...)
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Re: Coldest recorded NZ temperature

Unread post by Manukau heads obs »

woa, Phillippines 42.2C?
would have been a fair amount of humidity?
or was it in recorded in the lee of some ranges, e.g fohn Effect?
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Re: Coldest recorded NZ temperature

Unread post by Bradley »

That article has the highest temperature ever recorded in the world as 56.7c, 10 July, 2013 at Furnace Creek Ranch, California. That has to be a type surely? I thought it was in 1913 that temperature was recorded? Even that temperature is suspect, from what I've read the highest reliable temperature ever recorded in the world was around the 54-55C mark in Death Valley achieved with a proper Stevenson Screen
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