Should some or all of March be considered summer?

Plato · Unread post by **Plato** » Thu 26/02/2015 18:37

As we come to the "official" end of summer, it doesn't really feel summer is ending. Indeed, in most of the country (population-wise at least) March is warmer than December, and early March is probably warmer than early December everywhere.

I understand in the USA and some other places, summer and winter are defined astronomically, thus summer starts on the summer solstice and ends on the autumn equinox, while winter begins on the winter solstice and ends on the spring equinox.

For summer I think this would be pretty good for us. For one I think it would help a little with holiday-making decisions, e.g. to help people understand that Christmas-New Year is really more like "early summer" and if viable a later trip could give better weather.

However, for winter it's not quite as good. The seasonal lag for winter tends to be much shorter (anyone know why this is?) and for most places June 1 - August 31 is a better measure of winter. The exception is possibly the ski season, for which June 22 - September 22 tends to line up rather well, although "spring skiing" conditions tend to predominate at the end of that.

Flutterbye · Unread post by **Flutterbye** » Thu 26/02/2015 21:18

I agree but for many people, it's cut and dried that the 1st of December is the first day of summer. They can't understand the solstice/equinox thing.

RWood · Unread post by **RWood** » Thu 26/02/2015 22:41

Depends on what elements you consider important. I have 30-year temperature means for over 100 stations in each island, over 220 in all. For the North Is, the average of the means favours March over December by 0.10C; for the South Island, December beats March by 0.43C. For NZ over all 220+ stations, December wins by 0.19C.

Most extreme differences: Cape Reinga Mar-Dec about 1.3C; Alexandra and Cromwell Mar-Dec about -1.5C.

For sunshine, March is relatively sunnier by a moderate margin, but of course with the shorter days the average sunshine hours are lower.

For rainfall, there are difficulties in "averaging" with such a skewed distribution, but over the populated zones March should come out as drier.

Manukau heads obs · Fri 27/02/2015 08:32

RWood, when is on average, the warmest period of summer?
I see often people say first week of Feb, but I suspect it might be more the last week of Jan?

spwill · Unread post by **spwill** » Fri 27/02/2015 10:02

March is a better weather month here than December.

RWood · Unread post by **RWood** » Fri 27/02/2015 13:39

spwill wrote:March is a better weather month here than December.

I have some tables which approximately give the warmest fortnight for a number of sites, will dig them out later.

Plato · Unread post by **Plato** » Fri 27/02/2015 14:51

RWood wrote:Depends on what elements you consider important. I have 30-year temperature means for over 100 stations in each island, over 220 in all. For the North Is, the average of the means favours March over December by 0.10C; for the South Island, December beats March by 0.43C. For NZ over all 220+ stations, December wins by 0.19C.

I think March would win if you weighted the sites by population. I imagine the places with warmer Decembers are mostly sparsely populated inland sites, whereas the coastal sites (which include the major cities) typically have warmer Marches. Also, another easily-overlooked factor are water temperatures (relevant for water-based recreational activities) which I believe are decidedly warmer in March everywhere (I think sea temperatures even reach their peak in March).

Furthermore, if we're looking at changing to astronomical summer, the relevant comparison would not all of December to all of March, but 1st-21st December to 1st-21st March. By leaving out the warmest third of December and the coldest third of March, I'm guessing nearly everywhere would have the warmer March.

RWood · Unread post by **RWood** » Fri 27/02/2015 18:22

Plato wrote:
RWood wrote:Depends on what elements you consider important. I have 30-year temperature means for over 100 stations in each island, over 220 in all. For the North Is, the average of the means favours March over December by 0.10C; for the South Island, December beats March by 0.43C. For NZ over all 220+ stations, December wins by 0.19C.
I think March would win if you weighted the sites by population. I imagine the places with warmer Decembers are mostly sparsely populated inland sites, whereas the coastal sites (which include the major cities) typically have warmer Marches. Also, another easily-overlooked factor are water temperatures (relevant for water-based recreational activities) which I believe are decidedly warmer in March everywhere (I think sea temperatures even reach their peak in March).

Furthermore, if we're looking at changing to astronomical summer, the relevant comparison would not all of December to all of March, but 1st-21st December to 1st-21st March. By leaving out the warmest third of December and the coldest third of March, I'm guessing nearly everywhere would have the warmer March.

The list of sites where December is warmer - apart form the 2 already given - includes Wanaka, Fairlie, Christchurch, Wairoa, Taihape, Havelock Nth, Queenstown, Ashburton, Napier, Waipukurau, Taumarunui, Motueka, Masterton, Gisborne, Timaru, Gore, Balclutha, Blenheim, Taupo, Takaka, Invercargill, Waimate, Dannevirke, Oamaru, Whakatane, Rotorua, Nelson, Dunedin and Kaikoura, with approximate dead heats at Palmerston North and Paraparaumu. I'm sure residents of many of these places would be offended at being described as living in sparsely populated areas.

Personally I will never consider March to be part of summer, because the day-lengths are not great enough. Water temperatures are far less important to me than the available amount of daylight.

I am happy with the DJF version of summer, but it's a matter of personal taste.

Often overlooked is the fact that for the central regions of NZ at least, Marches in the last 15-20 years have been more settled and sunny than really long term records show.

RWood · Unread post by **RWood** » Fri 27/02/2015 22:31

Manukau heads obs wrote:RWood, when is on average, the warmest period of summer?
I see often people say first week of Feb, but I suspect it might be more the last week of Jan?

When I look at the temperature means collections the data looks too "lumpy" at the 1-week and 2-week running averages - for most of several dozen sites there is not a clear peak period. But things look better using 3-week averages, so I computed a few of them.

Approx. warmest periods: Owairaka 28-1 to 17-2 Kelburn 25-1 to 14-2 Napier 14-1 to 3-2 Gisborne 16-1 to 5-2 Ch'ch Aero 16-1 to 5-2 Kaitaia 25-1 to 14-2 Alexandra 15-1 to 4-2 New Plymouth Aero 28-1 to 17-2.

All averages computed from quite long periods of time (but collected several years ago, so nothing later than 2008). Data is raw data, only for time spans that don't include any significant site changes.

Manukau heads obs · Fri 27/02/2015 22:46

looks like nw fohn winds in December in eastern areas a factor re those warmer December compared to march

RWood · Unread post by **RWood** » Fri 27/02/2015 22:57

Manukau heads obs wrote:looks like nw fohn winds in December in eastern areas a factor re those warmer December compared to march

Certainly sounds like a contributing element.

Nev · Unread post by **Nev** » Sat 28/02/2015 07:27

Manukau heads obs wrote:looks like nw fohn winds in December in eastern areas a factor re those warmer December compared to march

Or it could just be the much longer daylight hours and higher-angle sun in December resulting in more daily heat build-up? Chch Aero for example, with a mean-temp of 15.8C in Dec and 14.9C in Mar, gets about 25% more daylight-hours in Dec than in Mar.

Also, during Chch Aero's 61 year history, it has recorded temps of 30.0C or more 57 times in December, compared to 40 times in March (Jan 142, Feb 123). Interestingly, it has never recorded 30.0C+ in April, but has done 8 times in November.

From this NIWA list of 29 main towns and cities and their mean-temps (although figures may differ by a few points compared to CliFlo data), 10 have warmer Marches (top group), 18 have warmer Decembers (bottom group), while Tauranga is about the same...

Code: Select all

Mean monthly air temperature (°C) for the 1981-2010 period. 	

LOCATION                JAN     FEB     MAR     DEC
-----   -----   -----   -----   -----   -----   -----	
Kaitaia                 19.5    20.0    18.6    17.9
Whangarei               19.9    20.2    18.8    18.5
Auckland                19.1    19.7    18.4    17.8
Hamilton                18.4    18.8    17.1    16.9
New Plymouth            17.8    18.0    16.8    16.3
Wanganui                18.3    18.5    17.1    16.9
Palmerston North        17.8    18.3    16.4    16.2
Wellington              16.9    17.2    15.8    15.4
Westport                16.3    16.7    15.3    15.0
Hokitika                15.6    16.0    14.5    14.4

Tauranga                19.4    19.6    18.0    18.0 

Rotorua                 17.7    17.9    16.0    16.2 
Gisborne                19.2    19.1    17.5    18.1 
Taupo                   17.0    17.1    14.9    15.6 
Napier                  19.5    19.4    17.7    18.4 
Masterton               18.1    17.7    16.3    16.4 
Nelson                  17.8    17.9    16.1    16.4 
Blenheim                18.0    17.6    15.8    16.5 
Kaikoura                16.4    16.4    15.1    15.2 
Christchurch            17.5    17.2    15.5    16.1 
Mt Cook                 14.7    14.8    12.3    12.8 
Lake Tekapo             15.2    14.8    12.4    13.2 
Timaru                  15.9    15.5    13.8    14.4 
Milford Sound           14.7    14.8    13.3    13.4 
Queenstown              15.8    15.6    13.0    14.0 
Alexandra               18.0    17.4    14.9    16.3 
Manapouri               14.7    14.3    12.1    13.0 
Dunedin                 15.3    15.0    13.7    13.8 
Invercargill            14.2    13.9    12.5    13.0

P.S. Although the US popularly use astronomical dates for their so called "official seasons", the NWS/NOAA use the same meteorological calendar dates that many other countries like us use.

Dean. · Unread post by **Dean.** » Sat 28/02/2015 07:44

The nights and mornings have that autumn feel already down this way

Orion · Unread post by **Orion** » Sat 28/02/2015 08:02

I learned as a child, and have always considered, that November - December - January is "summer" because of length of daylight hours - disregarding that infernal "daylight saving".
Thus the solstices and equinoxes fall approximately in the middle of the seasons, where they belong. In my opinion.

NZstorm · Unread post by **NZstorm** » Sat 28/02/2015 08:14

March is very much a summer month in my opinion.

RWood · Unread post by **RWood** » Sat 28/02/2015 09:06

Nev wrote:
Manukau heads obs wrote:looks like nw fohn winds in December in eastern areas a factor re those warmer December compared to march
Or it could just be the much longer daylight hours and higher-angle sun in December resulting in more daily heat build-up? Chch Aero for example, with a mean-temp of 15.8C in Dec and 14.9C in Mar, gets about 25% more daylight-hours in Dec than in Mar.

Also, during Chch Aero's 61 year history, it has recorded temps of 30.0C or more 57 times in December, compared to 40 times in March (Jan 142, Feb 123). Interestingly, it has never recorded 30.0C+ in April, but has done 8 times in November.

From this NIWA list of 29 main towns and cities and their mean-temps (although figures may differ by a few points compared to CliFlo data), 10 have warmer Marches (top group), 18 have warmer Decembers (bottom group), while Tauranga is about the same...
Code: Select all
Mean monthly air temperature (°C) for the 1981-2010 period. 	

LOCATION                JAN     FEB     MAR     DEC
-----   -----   -----   -----   -----   -----   -----	
Kaitaia                 19.5    20.0    18.6    17.9
Whangarei               19.9    20.2    18.8    18.5
Auckland                19.1    19.7    18.4    17.8
Hamilton                18.4    18.8    17.1    16.9
New Plymouth            17.8    18.0    16.8    16.3
Wanganui                18.3    18.5    17.1    16.9
Palmerston North        17.8    18.3    16.4    16.2
Wellington              16.9    17.2    15.8    15.4
Westport                16.3    16.7    15.3    15.0
Hokitika                15.6    16.0    14.5    14.4

Tauranga                19.4    19.6    18.0    18.0 

Rotorua                 17.7    17.9    16.0    16.2 
Gisborne                19.2    19.1    17.5    18.1 
Taupo                   17.0    17.1    14.9    15.6 
Napier                  19.5    19.4    17.7    18.4 
Masterton               18.1    17.7    16.3    16.4 
Nelson                  17.8    17.9    16.1    16.4 
Blenheim                18.0    17.6    15.8    16.5 
Kaikoura                16.4    16.4    15.1    15.2 
Christchurch            17.5    17.2    15.5    16.1 
Mt Cook                 14.7    14.8    12.3    12.8 
Lake Tekapo             15.2    14.8    12.4    13.2 
Timaru                  15.9    15.5    13.8    14.4 
Milford Sound           14.7    14.8    13.3    13.4 
Queenstown              15.8    15.6    13.0    14.0 
Alexandra               18.0    17.4    14.9    16.3 
Manapouri               14.7    14.3    12.1    13.0 
Dunedin                 15.3    15.0    13.7    13.8 
Invercargill            14.2    13.9    12.5    13.0 
P.S. Although the US popularly use astronomical dates for their so called "official seasons", the NWS/NOAA use the same meteorological calendar dates that many other countries like us use.

I loaded my 220+ sites from CliFlo and results look the same as yours.

RWood · Unread post by **RWood** » Sat 28/02/2015 09:08

Orion wrote:I learned as a child, and have always considered, that November - December - January is "summer" because of length of daylight hours - disregarding that infernal "daylight saving".
Thus the solstices and equinoxes fall approximately in the middle of the seasons, where they belong. In my opinion.

Interesting point. As I value sunshine a lot I could even adopt that definition, or if data were analysed more deeply, the sunniest 90-day (approx.) timespan which would be displaced very slightly later I suspect. May come back on that ...

to update - to within an hour's precision the sunniest (among equals) 90-day period here that is closest to the period with the most daylight is 7 November to 4 February, so from that viewpoint I get another definition of summer.

spwill · Unread post by **spwill** » Sat 28/02/2015 10:00

Manukau heads obs wrote:looks like nw fohn winds in December in eastern areas a factor re those warmer December compared to march

I agree with this. It is pattern that ultimately controls our weather and December occasionally sees the Spring westerlies hanging on and is the reason why March weather is better in Auckland in general to December weather.
Eastern SI generally has its best weather in the westerly pattern.

NZ Thunderstorm Soc · Thu 19/03/2015 20:30

Well at the moment, it seems likely, as February was cooler here than January.
As Daniel said, the anticyclones seems to be less influential so more warmer weather should be on the cards for this month.

EDIT: Well Cyclone Pam has put a bit of a change with that.

melja · Unread post by **melja** » Fri 20/03/2015 17:47

Having had the fire on the last 3 nights and the frosts in the south im not sure March could be a summer month round here

Dean. · Unread post by **Dean.** » Fri 20/03/2015 17:51

melja wrote:Having had the fire on the last 3 nights and the frosts in the south im not sure March could be a summer month round here

No,summer well and truly disappeared a couple of weeks ago for these parts !

jamie · Unread post by **jamie** » Fri 20/03/2015 18:50

Not here is hasn't. Well you could say it's on the out.

Dean. · Unread post by **Dean.** » Fri 20/03/2015 23:03

jamie wrote:Not here is hasn't. Well you could say it's on the out.

Looking to a warming trend the next two weeks,hopefully we rid of these 4 degree nights for a month or so

NZstorm · Unread post by **NZstorm** » Sat 21/03/2015 08:30

I have been in Dunedin this week and it has been winter
down here! Pam became a cold air dredge in the southern ocean.

NZ Thunderstorm Soc · Sat 21/03/2015 12:10

NZstorm wrote: Pam became a cold air dredge in the southern ocean.

That's what I thought as well, here.

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