ECMWF have...

NZ Thunderstorm Soc · Mon 05/07/2004 22:35

ECMWF have a fat, juicy winter high moving onto the country later this week.

..about time too. Save this bout of westerlies for the spring??? - please

JohnGaul
NZTS

Andy · Unread post by **Andy** » Tue 06/07/2004 07:28

nice and frosty

Manukau heads obs · Tue 06/07/2004 08:49

when comparing winter temperatures, maybe only weather stations on the coast line,or out at sea, should be used, to get away from the nature or more or less anticyclones giving more or less inland frosts affecting the average temperature for the winter....i.e it would then be a better reflection of the average temperature ?

jeffsweather · Unread post by **jeffsweather** » Tue 06/07/2004 09:51

Not sure how NIWA and others calculate the average given the difference between coastal and inland stations. In the UK, the CET (Central England Temperature) has been measured since 1659. On this page
http://badc.nerc.ac.uk/data/cet/
there is a link to to a map of the area covered. There are stations near the coast at Bristol but all the rest are inland.

Perhaps there would need to be 2 CNZT's, one for the north and one for the south. With the southern alps dividing west and east, it's probably not that easy either.
Also there are large areas of NZ that don't have of long term weather stations.

At this site http://www.metoffice.com/research/hadle ... a/CET.html
it says "note that since 1974 the data have been adjusted by 1-2 tenths Â°C to allow for urban warming."

I wonder if this has been done for urban stations in NZ?

spwill · Unread post by **spwill** » Tue 06/07/2004 11:23

Yes, a High for the weekend

. Christchurch should do well out of it with several days fine weather there from Saturday. Auckland is a lot more exposed so just a day or two of fine Weather here from Sunday.

Manukau heads obs · Tue 06/07/2004 11:35

i actualy dont like the way of the using the max and min temperature to get a average...
because that maximum temperature might only have been for 10 minutes, and the rest of the day might have been quite a bit less....
same for the night....often the temperature can incrase in the middle of the night, and stay much higher than the minimum reached (like if the wind gets up, cloud moves over, etc).
i.e using the max/min sort of assumes a nice temperature curve, but that not real life...

spwill · Unread post by **spwill** » Tue 06/07/2004 16:04

Yes, I agree Brian.
Example, its a lot warmer up here in the North compared to the South Island than temperatures sometimes suggest. The 10 am temp in Auckland is often close to our max temp for the day , summer and winter. Thats certainly not the case in the South Island where the thermometer is always on the move especially in summer.

Michael · Unread post by **Michael** » Tue 06/07/2004 16:19

Just boring durnial ranges here all the same year round just about

NZstorm · Unread post by **NZstorm** » Tue 06/07/2004 16:36

Brian wrote

actualy dont like the way of the using the max and min temperature to get a average...

I agree. I have always thought it was a bit balmy to base a mean temperature around two extremes. I have wondered wether the median temperature would be more representative as an average.

And I take spwill's point, comparing a mean temperature from say Christchurch with a mean temperature from Auckland, is not comparing apples with apples. The diurnal temperature regimes of the two cities are quite different.

GraemeWi · Unread post by **GraemeWi** » Tue 06/07/2004 18:18

If I were to design a method of getting an 'average' temperature, I would take the days readings at whatever interval they are done at and use sigma smoothing on the data before doing an average. That way the extremes are smoothed out of the base data and the average would be more 'true'.

Doing a straight average between the high and low gives a statistically ugly number. Using the standard methods of evaluating the result, the 'average' would be discarded.

Cheers,

G

tich · Unread post by **tich** » Tue 06/07/2004 21:29

Another thing about working out average tempertaures in NZ - is it taken into account, in spring and autumn, the fact the beginning of a month will be warmer or colder than the end. Let's say a hypothetical NZ station has an average daily maximum of 20C in April. Knowing that the end of April is naturally colder than the beginning, would an 18C maximum on April 1st be regarded as 2C below normal, and then would another 18C maximum on April 30th be judged as 2 degrees below normal?

Michael · Unread post by **Michael** » Tue 06/07/2004 21:56

We may get an hour or two of sunshine between the showers if the rest of the country get another week of blue skies

spwill wrote:Yes, a High for the weekend . Christchurch should do well out of it with several days fine weather there from Saturday. Auckland is a lot more exposed so just a day or two of fine Weather here from Sunday.