General May Weather

[melja]

I would think it was foggy and also that area of NZ is also the greatest distance from the ocean too.

One observation coming into winter round these parts(Rangiora) is no dew at all with concrete in shaded areas being dry still and my car has been dry all week too.

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[Andy]

Central has been under a layer of fog since Wednesday this has caused the low max temps.

[Cyclone Tracy]

133mm for May, year to date 655mm.

Daily mean temperature 14.7c, average is 14c. Last 3 mornings of May were under 5c, that has never happened before in May here on my records.

[RWood]

Don't necessarily need freezing fog to have very low maxima: to requote part of the monthly summary for July 1968:

"In Southland, Otago and inland Canterbury temperatures were mainly 2F-5F below average, with greatest departures in the high country, where this was the coldest month since July 1938. Elsewhere they were mainly close to average. The snowfalls on the last 4 days of June on the high country of both islands and to low levels in the South Island persisted for the first 4 days of July, and there were further falls about 10-12 July and on the 25th. Frosty conditions, especially during the first half of the month, allowed little opportunity for snow cover to melt over the greater part of the South Island. On the hills to the southwest of Mossburn at 2000 ft the depth was reported as 2 ft, and 10 ft in the drifts, and it remained frozen there for 3 weeks. Very severe conditions were experienced, even at quite low altitudes, where a continuous snow cover persisted. For example Tara Hills, Omarama (alt. 1600’) had snow lying for the whole month, never less than 5.5” in depth. The mean temperature of 23.2F (-4.9C) was the lowest ever recorded in New Zealand for a month below an altitude of 3000’. On 8 days the maximum failed to reach 32F (0C), the lowest maximum being 20F (-6.7C) on the 14th. The minima fell just below 0F (-17.8C) on the 6th, 7th and 14th. [All this despite ample sunshine of 143 hrs; the month’s temperature departure was 11.2F (6.2C)]."

[Simon Culling]

Thanks for your detailed response, Rupert. Much appreciated.

A number of observers reported fog in Middlemarch as the reason for the low temperatures there on this occasion and that the sun finally came out on Friday. However, as the account above suggests, it can remain very cold in this area, even with plenty of sunshine, under the right conditions.

If I recall correctly, such conditions prevailed in June 2015 when -20*C was recorded at Pukaki Airport.

[Nev]

A generally warm start to May 2018 was counted by a relatively chilly end…

MetService May 2018 Summary

Unsettled weather continued through May. Frequent lows over the Tasman Sea produced several northeasterly rain events over the North Island, but these were interspersed by periods of stormy westerlies over the country. At the end of the month, a persistent and extremely cold southerly regime kicked in, before being replaced by a very frosty winter High. This ended the run of unusually mild temperatures that had persisted through the first three weeks of the month.

It was wetter than usual May for western areas of the North Island, and also for the north of the South Island. In contrast, rainfall was below average along the east coast of both Islands, with the Kaikoura Coast being the exception.

May 2018 Climate Anomaly Maps ℅ NIWA.gif

Some very preliminary May 2018 figures for the main centres:

Code: Select all

May 2018 Average Temps, Rainfall, Sunshine and departures from 1981-2010 normals ℅ NIWA

Site                     T-max °C      T-min °C      T-mean °C     Rain mm      Sun hrs

Auckland, Mangere       18.0  +0.5    10.7  +0.3    14.4  +0.4    100   92%    174  121%
Auckland Aero           18.1  +0.7    11.5  +0.9    14.8  +0.8     97   89%
Tauranga Aero           18.1  +0.8    10.1  +0.8    14.1  +0.8     71   64%     n/a  n/a
Hamilton Aero           17.3  +0.5     7.3  +0.9    12.3  +0.7    146  136%
Hamilton, Ruakura       18.5  +1.6     7.2  +0.3    12.8  +0.9    125  130%    166  121%
Wellington, Kelburn     14.4  +0.1     9.7  +0.7    12.1  +0.4    125  112%    117*  88%
Christchurch Aero       14.6  +0.3     4.5  +0.8     9.6  +0.6     58  101%    132   94%
Dunedin, Musselburgh    13.4  +0.7     4.9  -1.0     9.1  -0.2     38   59%    132  121%
Greymouth Aero          14.1  -0.4     7.3  +0.2    10.7  -0.1    187   95%    115  112%

* Wellington missing 1 day of sunshine data.

[RWood]

Thanks for your detailed response, Rupert. Much appreciated.

A number of observers reported fog in Middlemarch as the reason for the low temperatures there on this occasion and that the sun finally came out on Friday. However, as the account above suggests, it can remain very cold in this area, even with plenty of sunshine, under the right conditions.

If I recall correctly, such conditions prevailed in June 2015 when -20*C was recorded at Pukaki Airport.

You're welcome Simon. I think conditions were indeed clear and sunny at Pukaki throughout that cold spell in 2015. Re Middlemarch, fog is probably less common than in the Alexandra basin as its winter sunshine hours are higher (though for some unknown reason the yearly totals are considerably less than I would expect - perhaps a horizon issue).

[RWood]

A generally warm start to May 2018 was counted by a relatively chilly end…




Some very preliminary May 2018 figures for the main centres:

Code: Select all

May 2018 Average Temps, Rainfall, Sunshine and departures from 1981-2010 normals ℅ NIWA

Site                     T-max °C      T-min °C      T-mean °C     Rain mm      Sun hrs

Auckland, Mangere       18.0  +0.5    10.7  +0.3    14.4  +0.4    100   92%    174  121%
Auckland Aero           18.1  +0.7    11.5  +0.9    14.8  +0.8     97   89%
Tauranga Aero           18.1  +0.8    10.1  +0.8    14.1  +0.8     71   64%     n/a  n/a
Hamilton Aero           17.3  +0.5     7.3  +0.9    12.3  +0.7    146  136%
Hamilton, Ruakura       18.5  +1.6     7.2  +0.3    12.8  +0.9    125  130%    166  121%
Wellington, Kelburn     14.4  +0.1     9.7  +0.7    12.1  +0.4    125  112%    117*  88%
Christchurch Aero       14.6  +0.3     4.5  +0.8     9.6  +0.6     58  101%    132   94%
Dunedin, Musselburgh    13.4  +0.7     4.9  -1.0     9.1  -0.2     38   59%    132  121%
Greymouth Aero          14.1  -0.4     7.3  +0.2    10.7  -0.1    187   95%    115  112%

* Wellington missing 1 day of sunshine data.

Not missing in the daily Metservice reports, must look into that. The Wellington data somewhat obscures the dismal run over the last 3 weeks of the month, after a sunny start.

Incidentally some data recovery efforts must have been made for April, as many AWS sites in the monthly stats. seem to be complete.

[NZstorm]

(though for some unknown reason the yearly totals are considerably less than I would expect - perhaps a horizon issue).

Too near the coast I think. The area probably sits under wave clouds in a NW as well.

[RWood]

(though for some unknown reason the yearly totals are considerably less than I would expect - perhaps a horizon issue).

Too near the coast I think. The area probably sits under wave clouds in a NW as well.

Yes, the wave cloud idea sounds good. Still a big drop from the values you get further west inland, especially Cromwell.

[spwill]

Middlemarch is not true Central Otago, it has quite a lot of exposure to the east coast, there is not much block to the east. Yes, the wave cloud is a feature in that area.