General March Weather

[RWood]

The Indian summer continued through March, being very warm overall. Normal rainfall was a bit of a mixed bag, being especially wet in parts of north Otago, Westland and Tasman, while notably dry in north Canterbury. Sunshine also very unevenly disbursed…

Mar 2015 Climate Anomaly Map ℅ NIWA.gif

Some very preliminary March 2015 figures for the main centres:

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March 2015 Average Temps, Rainfall and departures from their 1981-2010 normals ℅ NIWA

Site                      T-max °C       T-min °C       T-mean °C    Rainfall mm

Auckland, Mangere        24.2  +1.8     16.0  +1.4     20.1  +1.6      86  100% 
Auckland Aero            24.3  +1.7     15.9  +1.0     20.1  +1.3      73   97% 
Tauranga Aero            22.8  +0.3     14.7  +0.9     18.8  +0.6      77   80%
Hamilton Aero            24.1  +1.2     11.7  +0.7     17.9  +1.0      73   87% 
Hamilton, Ruakura        24.5  +1.8     13.0  +1.6     18.7  +1.6      60   76% 
Wellington, Kelburn      19.9  +0.8     13.7  +1.1     16.8  +1.0      54   64% 
Christchurch Aero        20.5  +0.2     10.5  +0.9     15.5  +0.6      40   86% 
Dunedin, Musselburgh     17.9  +0.6     10.9  +0.7     14.4  +0.7      47   74%
Greymouth Aero           20.1  +1.2     13.2  +2.2     16.6  +1.7     358  202% 

Note that most of Westland's roughly double normal rainfall fell in just a few days near the beginning of the month; overall it was also exceptionally sunny and warm.

Kelburn rainfall much higher according to MetService dailies - were you getting airport data there?

Re West Coast, the usual caveat about EWSs applies - I want to see the manual readings from Greymouth & Hokitika (Franz Josef has been broken for ages now) ...

Edit: looks like about 85mm for Kelburn.

[Dale]

Greymouth & Hoki do not surprise me.. what we copped here the other morning.. and afternoon, the figures tally.

[Nev]

Kelburn rainfall much higher according to MetService dailies - were you getting airport data there?

Re West Coast, the usual caveat about EWSs applies - I want to see the manual readings from Greymouth & Hokitika (Franz Josef has been broken for ages now) ...

Edit: looks like about 85mm for Kelburn.

Yes, you're right. Kelburn was missing 30.8mm for the 17th (to 9am). Have amended chart on my original post overleaf. (Chch Aero might also possibly be out by a few mm.)

[Nev]

Thought these reformatted MetService weekly March rainfall maps were also interesting (although not sure how many sites they're based on). Shows heavy rain in the first week for the west of the S.I. and lower N.I.. And heavy rain in the third week for the east and north of the N.I. - mostly ℅ TC Pam around the 16th and 17th…

MetService March weekly rainfall maps.gif

[NZstorm]

Auckland the warmest centre by far in March.

Just for the record Grey Lynn recorded 103mm.

[RWood]

Greymouth & Hoki do not surprise me.. what we copped here the other morning.. and afternoon, the figures tally.

Juts to clarify, I was referring to sunshine data (G & H have both manual and EWS recordings of that).

[jamie]

Auckland the warmest centre by far in March.

Just for the record Grey Lynn recorded 103mm.

Am I seeing it wrong then? Isn't Hamilton basically the same avg temp as Auckland?

Similar rainfall here. Rains came a month earlier than last year thank god

[NZstorm]

Auckland the warmest centre by far in March.

Just for the record Grey Lynn recorded 103mm.

Am I seeing it wrong then? Isn't Hamilton basically the same avg temp as Auckland?

Auckland averaging 3C warmer minimum. Thats quite a big margin over a month.

[Nev]

Here's NIWA's preliminary, 'March 2015 National Climate Summary'.

A warm month for all regions, and patches of wet and dry throughout New Zealand.


The national average temp of 16.7C was 1.0C above normal.

The month's highest temp of 32.1C was recorded at Hanmer Forest on the 5th, and the lowest of -2.4C recorded at Pukaki Aero on the 19th.


Quite a few Auckland sites included in March's near-record temps.

[RWood]

Here's NIWA's preliminary, 'March 2015 National Climate Summary'.

A warm month for all regions, and patches of wet and dry throughout New Zealand.


The national average temp of 16.7C was 1.0C above normal.

The month's highest temp of 32.1C was recorded at Hanmer Forest on the 5th, and the lowest of -2.4C recorded at Pukaki Aero on the 19th.


Quite a few Auckland sites included in March's near-record temps.

Nev, do you think you could prevail on NIWA to catch up on the missing 30.8mm rain reading for Kelburn? I'm sick of contacting them and/or MetService to plug the holes with the manual sunshine readings (2 were missing at the end of the month but turned up after I contacted NIWA, having previously contacted MetService who explained why the first of the 2 didn't appear and fixed that matter at their end). As the monthly report stands, it is misleading re Kelburn rainfall ...

[Bradley]

The Indian summer continued through March, being very warm overall. Normal rainfall was a bit of a mixed bag, being especially wet in parts of north Otago, Westland and Tasman, while notably dry in north Canterbury. Sunshine also very unevenly disbursed…

Mar 2015 Climate Anomaly Map ℅ NIWA.gif

Some very preliminary March 2015 figures for the main centres:

Code: Select all

Mar 2015 Average Temps, Rainfall and departures from their 1981-2010 normals ℅ NIWA

Site                      T-max °C       T-min °C       T-mean °C    Rainfall mm

Auckland, Mangere        24.2  +1.8     16.0  +1.4     20.1  +1.6      86  100% 
Auckland Aero            24.3  +1.7     15.9  +1.0     20.1  +1.3      73   97% 
Tauranga Aero            22.8  +0.3     14.7  +0.9     18.7  +0.5      77   80%
Hamilton Aero            24.1  +1.2     11.7  +0.7     17.9  +1.0      73   87% 
Hamilton, Ruakura        24.5  +1.8     13.0  +1.6     18.7  +1.6      60   76% 
Wellington, Kelburn      19.9  +0.8     13.7  +1.1     16.8  +1.0      85  100% 
Christchurch Aero        20.5  +0.2     10.5  +0.9     15.5  +0.6      40   86% 
Dunedin, Musselburgh     17.9  +0.6     10.9  +0.7     14.4  +0.7      47   74%
Greymouth Aero           20.0  +1.1     13.1  +2.1     16.6  +1.7     358  202% 

Note that most of Westland's roughly double normal rainfall fell in just a few days near the beginning of the month; overall it was also exceptionally sunny and warm.

Edit: Amended Wgtn rainfall. And updated Anomaly Map.

Nev do you happen to know why NIWA has said above that the average March minimum for Christchurch Aero is 9.6C when it is quite clear based on their own long term data since the site opened in 1954 that it is 10.0C? Am I missing something here?

[Nev]

Nev do you happen to know why NIWA has said above that the average March minimum for Christchurch Aero is 9.6C when it is quite clear based on their own long term data since the site opened in 1954 that it is 10.0C? Am I missing something here?

Bradley, all 'normals' are based the last 30-year decadal averages (as per the table's heading), which is standard meteorological practice, not the life of the site, which can vary by a few years to over 100 years. The exception being NIWA's national 7-series temp, which is based on 1971-2000 normals.

RWood, yes I did notice the summary's Kelburn March rainfall shortfall. Although I am tempted to query NIWA, perhaps in this instance, it might be better coming from a piqued Wellingtonian…

[NZ Thunderstorm Soc]

My readings from here in WM. for March.

Ave temp 15.6°C
Ave Minimum 10.6°C
Ave Maximum 20.7°C
Minimum 5.2°C on 20th
Maximum 28.7°C on 2nd
Rainfall 45.8mm

Highlight being the thunderstorm on the 13th where there was only a few heavy drops here but down the road towards Templeton, it absolutely poured.

[Bradley]

Nev do you happen to know why NIWA has said above that the average March minimum for Christchurch Aero is 9.6C when it is quite clear based on their own long term data since the site opened in 1954 that it is 10.0C? Am I missing something here?

Bradley, all 'normals' are based the last 30-year decadal averages (as per the table's heading), which is standard meteorological practice, not the life of the site, which can vary by a few years to over 100 years. The exception being NIWA's national 7-series temp, which is based on 1971-2000 normals.

RWood, yes I did notice the summary's Kelburn March rainfall shortfall. Although I am tempted to query NIWA, perhaps in this instance, it might be better coming from a piqued Wellingtonian…

Thanks Nev, missed that heading - thanks for clearing that up!

[RWood]

Nev do you happen to know why NIWA has said above that the average March minimum for Christchurch Aero is 9.6C when it is quite clear based on their own long term data since the site opened in 1954 that it is 10.0C? Am I missing something here?

Bradley, all 'normals' are based the last 30-year decadal averages (as per the table's heading), which is standard meteorological practice, not the life of the site, which can vary by a few years to over 100 years. The exception being NIWA's national 7-series temp, which is based on 1971-2000 normals.

RWood, yes I did notice the summary's Kelburn March rainfall shortfall. Although I am tempted to query NIWA, perhaps in this instance, it might be better coming from a piqued Wellingtonian…

Thanks Nev, missed that heading - thanks for clearing that up!

I would be careful about calculating a mean from the long-term records - the site history notes in CliFlo make it clear that instruments got moved around a fair bit and prior to using a later good open exposure there was a significant period when heat generating objects like a building were much too close (or possibly literally underneath at one point I suspect). That could explain why the latest 30-year means for Tmin at CHC are lower than the older ones, which is not at all typical of the NZ sites.

[Nev]

I would be careful about calculating a mean from the long-term records - the site history notes in CliFlo make it clear that instruments got moved around a fair bit and prior to using a later good open exposure there was a significant period when heat generating objects like a building were much too close (or possibly literally underneath at one point I suspect). That could explain why the latest 30-year means for Tmin at CHC are lower than the older ones, which is not at all typical of the NZ sites.

Compared with Chch Gardens, the Chch Aero figures seem to be fairly robust. Probably more likely that the lower T-mins and higher T-maxs are indicative of less cloud. The corresponding lower rainfalls and higher sunshine hours tend to add some weight to that scenario…

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Chch Aero - 30-year averages

March           T-max°C  T-min°C  T-mean°C    Rain     Sun
1941 - 1970       19.3      9.9     14.6      ---      168
1951 - 1980       19.7     10.2     15.0       61      161
1961 - 1990       20.1     10.3     15.2       58      169
1971 - 2000       20.1     10.0     15.1       56      183
1981 - 2010       20.3      9.6     14.9       46      191

P.S. Agree that Canterbury's climate wouldn't be a very good representation of overall national trends.

[RWood]

I would be careful about calculating a mean from the long-term records - the site history notes in CliFlo make it clear that instruments got moved around a fair bit and prior to using a later good open exposure there was a significant period when heat generating objects like a building were much too close (or possibly literally underneath at one point I suspect). That could explain why the latest 30-year means for Tmin at CHC are lower than the older ones, which is not at all typical of the NZ sites.

Compared with Chch Gardens, the Chch Aero figures seem to be fairly robust. Probably more likely that the lower T-mins and higher T-maxs are indicative of less cloud. The corresponding lower rainfalls and higher sunshine hours tend to add some weight to that scenario…

Code: Select all

Chch Aero - 30-year averages

March           T-max°C  T-min°C  T-mean°C    Rain     Sun
1941 - 1970       19.3      9.9     14.6      ---      168
1951 - 1980       19.7     10.2     15.0       61      161
1961 - 1990       20.1     10.3     15.2       58      169
1971 - 2000       20.1     10.0     15.1       56      183
1981 - 2010       20.3      9.6     14.9       46      191

P.S. Agree that Canterbury's climate wouldn't be a very good representation of overall national trends.

Good point, though things are complicated slightly by the fact that the exposure was improved significantly about 1976 - TonyT mentioned that some good while back. It's certainly the case that the annual sunshine means at the airport show a step change around then. Nevertheless it still looks as if things have got a little sunnier ...

[RWood]

RWood, yes I did notice the summary's Kelburn March rainfall shortfall. Although I am tempted to query NIWA, perhaps in this instance, it might be better coming from a piqued Wellingtonian…

Have done so now - but it's annoying to have to keep reminding these organisations. Perhaps one day sanity will return and there will only be one "body".