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NZ @ Noon

A few further showers dotted central and eastern parts of this North island this morning but a few comments to WeatherWatch said they’re generally insignificant.

Reports have come in of some showers moving through Palmerston North, Dannevirke, Tokoroa and eastern areas of the North Island but in some cases as soon as it hit the ground, it then very quickly dried up.

One commented how Wellington missed out on any showers and further south how Christchurch had yet again escaped even drizzle overnight from the front passing through.

Temperatures have also taken a hit over central and eastern areas of the North Island in the wake of the southerly wind.
Wellington, Rotorua, Napier and Gisborne have remained in the mid teens so far today which is a considerable drop from the heat of yesterday, especially for the eastern cities.

The South Island has generally seen blue skies with just some morning cloud and the odd light shower about the southern coast.
It was a cool to cold night for many areas but with the sunshine this morning temperatures have steadily climbed across many parts of the south.

Sunshine hours

As we’ve reported here at WeatherWatch, February was a very sunny month with numerous centres well above normal sunshine hours.

Contibutor, John Haylock of Taranaki, has given us a breakdown of sunshine hours for New Plymouth.

New Plymouth Airport has recorded 330.4 hours of sunshine in February (following 303.8 in January).
This February total is only just shy of the record monthly sunshine total in New Zealand which, according to NIWA, is 336 hours in Nelson in December 1934 and 335 in Taupo in January 1950.
However, the New Plymouth February 2013 total is remarkable because it was recorded in February – with only 28 days instead of 31 – and days that are noticeably shorter than either December or January.
This is highly likely to be a February record total for New Zealand and may well be a record for the highest percentage of possible sunshine hours in a month in New Zealand.
With the shorter days and 28 day month it is probably the equivalent of close to 400 hours sunshine in December or January.

If it had been a leap year, last Friday’s all day sunshine would have added enough hours on to break the all time record for a month.

It has been a very sunny last 12 months.

In the year to the end of February, New Plymouth has had 2645 hours of sunshine (2433 last year plus the extra 212 hours in Jan-Feb this year compared to last) – more than the North Island annual record of 2,588 in Napier in 1994 and not far behind the all time New Zealand record of 2,711 in Nelson in 1931.

Apart from the rain on 4th February it has been sunny every day – and like much of the country, it is very dry. The first half of March looks like having a lot more sunshine. More records could be broken.

We’ll keep an eye out thanks John and we appreciate the information.

Hompage image of New Plymouth, where sunshine has been abundant in recent times.


John Haylock on 5/03/2013 5:12am

RW – thank you for your comments. I agree that any extreme readings should be taken with a degree of scepticism, especially when there has been a change in measuring equipment and that change appears to accompany a change in long term values.

Of course, there are three possibilities.

1. The reading is correct
2. The old equipment was incorrect
3. The new equipment is incorrect

At the moment all we can do is assume the reading is correct relying on those in charge of preparing and calibrating the equipment to have done their job. It was certainly an incredibly sunny month in New Plymouth – there was only one genuinely cloudy day. This is borne out by the the MetService forecasts – based on the ununsual weather systems in place they forecast sunshine almost every day. Simply based on an analysis of those forecasts you would conclude it was a record breaking month – and that is continuing at the moment – wall to wall sunshine today. Look at our current 10 day forecast. Based on that it is likely we will have high levels of sunshine in March as well.

New Plymouth has had very unusual weather and that level of sunshine is certainly possible (and yes it was Perth-like with regard to sunshine – not in temperature though!) By the way I am still curious about whether 330.4 hours in February in New Plymouth beats Blenheims 231 hours in July as a record percentage of what’s possible – you didn’t actually answer that question – and I’m not sure how to work it out.

The next most obvious possibility is that the old equipment was incorrect and that we are now measuring the correct amount of sunshine on properly calibrated equipment. If so – we may have to readjust our perceptions about sunshine levels in various parts of the country. To me the possibility of the old equipment being incorrect is more likely than the third possibility that the new equipment is incorrect.

I have no way of actually knowing which of those three possibilities has actually happened. However as I said at the beginning the 330.4 hours in February in New Plymouth is an official reading (which ties in with the observation that it has been very, very sunny) and for now we have to assume it is correct.

RW on 5/03/2013 7:38am

The real answer is that these 2 different types of equipment measure different things. The Campbell-Stokes equipment is set to measure “bright” sunshine by a level of intensity that etches a mark on a special card. For decades data recorded this way was centrally checked at Met Service, and I believe it gave very sensible comsistent results given the various climatologies. Your “old” equipment at NP Aero produced a period average 1972-2011 of around 2200 hours, somewhat higher than the previous numbers obtained at Marsland hill, as might be expected. This number is equivalent to Gisborne and not much lower than Napier’s, hence I would be very suspicious of anything that suddenly lifted that average substantially, as it seems right to me.

The EWSs are supposed to measure incoming levels of solar radiation and count quantities above a certain threshold. If you like to provide an email address, I can forward the email from Philip Eden, which won’t give you any joy re the safety of assessing the different results obtained by the two methods.

The sites that I have “picked on” above have been producing data for a while now, so I’m not just shooting off comments prematurely. The 330.4 hours would be about 87% of the recordable, at the least. I repeat, NIWA needs to check calibrations. The “proof” for NP will at least in waiting for more observations, not just the 330.4, which I would regard as strictly provisional.

Incidentally, the “official” averages to 1950 were used for a decade or so, but then they realised that with no central checking before 1935 there were a a variety of problems with older records from various sites and these were not used in the updated averages to 1960. The older records turned out to be too optimistic in various cases, and because of that and the fact that the 1930-50 epoch was sunnier than is typical for much of the country, Yearbooks and other monthly/annual reports based on the “old” averages were rather misleading – at one stage it was asserted that every year 1948-1956 in the North Is was cloudier than normal. My point – what might seem “official” can change.

Footnote: 2 of NP’s days in Feb. gave totals of 0.0 and 7.7, so the other 26 are claiming 322.7, which is 12.4 per day. That is a phenomenal amount of sun. We shall see (also note – 2 of the days with 13 hours towards the end of the month were flagged as estimated/suspect).

John Haylock on 5/03/2013 9:53pm

Thanks RW.

Having done some further research it seems the total daylight hours in New Plymouth during February were 382.1. So 330.4 hours (if correct) would be 86.47% of possible.

By the way I agree on the couple of suspect days towards the end of the month. They were days with quite a bit of high cloud around, though there was still sun shining through the cloud. I was a little suprised with the reported figures on those two days. I am confident the rest of the month was correct though.

By the way there is quite a bit of cloud around today and as I write there is a shower of rain on the horizon out to sea north of New Plymouth. That’s been a very rare sight lately – I think it will miss us though.

And I fully agree that it would be good for NIWA to check calibrations.

RW on 5/03/2013 11:20pm

Hi John – high cloud is one of the issues with EWSs – eg the Kipp & Zonen being used here – Eden makes reference to it. They easily over-record weak filtered sunshine. Tony Trewinnard of Blue Skies believes sun measurement is far less objective than that of temperature or rainfall – Canterbury has quite a bit of high cloud, and guess what? EWSs installed there are all showing big leaps in readings over the CS ones.

The article I link to here mentions that these instruments can show calibration drift even when new – only underlining the need for regular checks.

What I don’t want to see in the “new” sun climatology is an unnatural rearrangement of relative sunniness. As an example, I suspect that when Napier converts to an EWS,it may get a big boost which might put it to the top of the list. But that’s just a guess…

RW on 5/03/2013 12:44am

John Haylock’s comment is very interesting. However, I am sceptical of the extremely high values New Plymouth has been getting since “going EWS”. It is a matter of record that a large number of NZ sites have shown very significant increases in sunshine values post-conversion, regardless of the weather conditions prevailing, and almost every month new “highs” are being reported – but almost exclusively at EWSs. I would respectfully suggest that New Plymouth would have been capable of recording 80-84% of the possible sunshine during a remarkable February – which is as high as any place in NZ has ever managed. This would result in a total of about 305-310 hours – still high enough to beat NZ’s leap February record! – but 330 is just not credible to me – that’s getting into Perth territory. BTW, to get 400 hours in Dec or January, even in more southern places, would be more akin to about 87% of possible – I don’t accept that could happen with our current climatology.

For the record, the highest % of possible recprded at a NZ site with good exposure was the 84% at Blenheim in July 1952, when it recorded a remarkable 231 hours.

I’m not picking on New Plymouth here, as the following should make clear. There are NZ stations where the conversions have been consistent with older values – these include Kaitaia, Dargaville, North Shore (probably – but only after a scale-down adjustment), Mangere, Hamilton, Dannevirke, Gisborne (again after some fiddling I suspect), Takaka, Blenheim, Mt Cook, Akaroa (probably), Tekapo (marginal), Dunedin (marginal). But then there are the “offenders” – the worst is lower on the sun scale – Balclutha is getting 300-400 hours more than its manual site ever did, and is completley lacking in credibility. Others, all with large increases, include Greymouth, Hokitika, Ashburton, Te Kuiti, Ohakune, Cheviot, Rangiora and Paraparaumu – this latter is in my region and it just ain’t that sunny – both manual and EWS are still going and there’s a big discrepancy. Then of course there’s the case of table-topper Whakatane – still phony in my view. You don’t turn a 100-150 hour deficit relative to Nelson & Blenheim, maintained over 4 decades or so, into parity or even surplus with no climatological reason to support it! I think NIWA needs to look at instrument adjustments but this would not be a small task and I’m not holding my breath.

The EWS conversion in the UK – which has a lot of climatological expertise – has been a vexed business and is still not really resolved. I have an email I solicited from Philip Eden, an acknowledged expert, on the whole issue.

Just to show I am not just picking on EWS readings – the manual equipment at Invercargill has been reporting anomalously high values – with no occurrence of lowered rainfall or the like for correlative value – for about 15 years. I simply don’t trust the readings, which even average about 100 more hours than those at its EWS.

There’s an Australian who is obsessed with NZ rainfall and sun stats, who posts on an overseas forum. He simultaneously thinks the In’gill figures are OK, but has turned his intellectual???! searchlight on New Plymouth’s readings. He’s bound to write to NIWA. But in fact he doesn’t understand NZ climatologies at all.

John on 5/03/2013 12:21am

I think the Metservice might be having trouble with the thermometer in Oamaru. Here’s today’s noon recordings:

Oamaru Town

at Noon Tuesday 5 Mar 2013
•Temperature: 45°C
•Wind Speed: 7km/h
•Wind Direction: E
•Rainfall (last hr): 0.0mm
•Humidity: 64%
•Pressure: n/a

Guest on 4/03/2013 11:25pm

Check out
On 53.4 degrees C at 12.24pm!!!

Ian Cooper on 5/03/2013 8:12pm

Very interesting comments regarding various historical sunshine records etc by RW.

Records for the Turitea Met Station near Massey University at Palmerston North show similar trends to those that RW mentions. For instance the sunniest decade was the 1940’s with an aggregate of 18,632 hours and in 2nd place was the 1930’s with 18,497 hours. The main difference that I see between those two decades and the subsequent ones was the increase in spring sunshine hours, the exception being from the late 1960’s to the late 1970’s. The 1980’s were the dullest on record despite Mt Pinatubo doing its worst to make the early 1990’s our darkest on record. The 1980’s period starting in 1977 through to 1993 were characterised by very dull winters compared to the earlier decades in the recorded period. What were the climatic differences in all of these decades? Quite simply it was either strongly La Nina which sees improved sunshine prior to Christmas on the west coast, or strongly El Nino which sees an increase in the westerly flow and subsequent cloud cover up against the spinal divide.

One very interesting year was 1935. Still the sunniest for that site, and yet up until the infamous 2004, 1935 was the wettest on record since 1928! When we look at the sunny months of 1935 they fit neatly in between the wet months. As is often the case with record breaking years there were no record breaking months in either sunshine or rainfall. The driest year, 2007, is another classic exampe of that. There are exceptions of course, 2004 being the best example with the wettest month ever recorded here in the wettest year.

I believe, but have no proof at the moment that the Turitea site is not EWS and therefore the sunshine recorder is still the same as it has always been. The data for the past decade seems to bear this out. This February was the first month here to exceed 250 hours since March 2003 which was during the last major drought in our region.

With January being the 5th sunniest and February being the 3rd equal sunniest for Palmerston North it will only take an above average March to diplace 1957 as the best J-F-M sunshine total. At the moment that looks a distinct possibility, as does the relentless march of this La Nada influenced drought, one that bears remarkable similarities to those of 1977-78 and 2002-03 for my region.

RW on 7/03/2013 10:17pm

Hello Ian. Are you aware that the data published for Palmerston North has been EWS since mid-2002? I can recall after checking with NIWA that the instrument isn’t (or at least wasn’t initially) mounted as high as the old C-S one, and I think the sunshine totals have suffered slightly as a consequence (intercomparison with Paraparaumu and Wellington and also with the relatively recent prior records from the manual equipment shows some deterioration). So perhaps you should be recording even more sun that has been shown lately, unless the equipment issue I mentioned has changed again.

Yes, the Nino/Nina status may be a big player for you, though one cannot rule out some variability in the standard of reading/measuring using C-S – the central checkcing that was done for many years was very useful in that regard, but stopped somewhere in the 80s.

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