General July Weather

[David]

Howick - Stats from my station for July 2018:

Mean temp 10.5C
Mean daily max 15.0C
Mean daily min 6.4C
Highest temp 17.5C (26th)
Lowest temp 0.6C (4th)
Total rainfall 140.6mm
YTD rainfall 1122mm

[Bradley]

Looks like Christchurch (botanical gardens site) has just recorded its warmest ever July maximums since records began in 1864 with an average max of 14.0C

[TonyT]

Looks like Christchurch (botanical gardens site) has just recorded its warmest ever July maximums since records began in 1864 with an average max of 14.0C

Gardens data isn't usually filed till about 10 days into the next month. More likely its Niwa's contaminated Riccarton data invalidly being compared with the Gardens long term record.

[Nev]

^ Christchurch Gardens comment was from MetService posted on Facebook…

[Nev]

MetService July 2018 Summary

Frequent and unsettled northwesterlies prevailed across the South Island during July, resulting in above average rainfall for western areas of the South Island, but drier than usual conditions along the east coast. For the North Island, a mixture of prevailing westerlies and a ridge of high pressure produced well below normal rainfall for Gisborne, Hawkes Bay and the Wairarapa. In these regions, July rainfall totals ranked in the lowest handful (typically the 4th-6th driest July in the records). It was also relatively dry for Northland and the Bay of Plenty. Rainfall was close to normal elsewhere, with the exception of Kapiti, Horowhenua and Manawatu, where it was wetter than normal.

July temperatures were well above average across most of the South Island, as well as for the lower North Island. Elsewhere, monthly temperatures were closer to average.

Jul 2018 Climate Anomaly Maps ℅ NIWA.gif

Some very preliminary July 2018 figures for the main centres:

Code: Select all

July 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       14.7  +0.2     6.5  -0.8    10.6  -0.3     99   72%    144  110%
Auckland Aero           15.3  +1.0     7.4  -0.1    11.3  +0.4    124   93%
Tauranga Aero           15.1  +0.6     6.4  +0.3    10.7  +0.4     93   73%    n/a   n/a
Hamilton Aero           14.2  +0.4     3.8  +0.2     9.0  +0.3    133  103%
Hamilton, Ruakura       15.5  +1.7     3.4  -0.6     9.5  +0.6    116   99%    133  105%
Wellington, Kelburn     12.6  +1.2     7.8  +1.5    10.2  +1.3    128   93%    110   92%
Christchurch Aero       13.5  +2.6     1.1  +0.5     7.3  +1.5     24   37%    156  123%
Dunedin, Musselburgh    12.0  +2.0     3.7  +0.6     7.8  +1.3     30   52%    117  106%
Greymouth Aero          11.6  -0.5     5.6  +1.5     8.6  +0.5    301  152%     82   77%

Edit: Amended Wgtn & Chch T-maxs & T-means

[melja]

Have to say this month really did go against a lot of predictions from some people round here.

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[Razor]

^ Christchurch Gardens comment was from MetService posted on Facebook…

I was talking with the staff who look after the site in the gardens...this is 'unofficially' true

[NZ Thunderstorm Soc]

Only got 13.8mm of rain here for July and I think Levels got less than that.

[TonyT]

Have to say this month really did go against a lot of predictions from some people round here.

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I'm happy to put my hand up. Medium range data (and my interpretation of it) was well off the mark this month. I interpreted the forecast anomalies to mean more easterly airflow (and therefore less sunshine, and therefore cooler temperatures). Instead we got westerly flows, which were for the most part weaker than we often see (so an easterly anomaly was correct), but westerly nonetheless, so sunshine hours were up and temperatures also. I guess the one thing I did see correctly was weak or non-existent southerly airflows, and I did say at the end of June that we had probably seen the coldest part of the winter then. Like I said in an earlier comment, the atmosphere is smoking some strange backy at the moment and there are puzzling outcomes on both short term (day to day forecasting) and longer term (seasonal trends) time scales. El Nino looking less likely now, as SST anomalies in the Nino zones have dropped back closer to zero this week. No sunspots for 23 days, and 33 of the last 34 spotless. We live in interesting times.

[melja]

I wasn't going to name names Tony but I do follow your comments very closely on here and FB and noticed it haha

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[RWood]

I see Metservice are stating that Christchurch Gardens had an average July Tmax of 14.0C, its highest in a very long record. Napier did pretty well for sun - even with the usual caveats on sunshine measurement, 199 hours is a very good tally for a NZ location (though Blenheim reported a remarkable 231 hours in July 1952).


Oops - didn't note the earlier discussion. Will see how up to date the Gardens daily max/min data is on CliFlo.

Edit - nothing beyond July 1 there yet. If Gardens were about 0.4C higher than the Aero as a first guess that would give a result of about 13.7C - let's see.

[Nev]

^ I've amended the mean T-maxs I had for Wgtn and Chch in the table above.

So it looks like Chch Aero's 13.5C was its equal-highest (with 2013), Musselburgh's 12.0C its 2nd equal highest (after 2013), Akld Aero's 15.3C its 3rd equal-highest, and both Ruakura's 15.5C and Kelburn's 12.6C their 4th highest.

[RWood]

^ I've amended the mean T-maxs I had for Wgtn and Chch in the table above.

So it looks like Chch Aero's 13.5C was its equal-highest (with 2013), Musselburgh's 12.0C its 2nd equal-highest (after 2013), Akld Aero's 15.3C its 3rd equal-highest, and both Ruakura's 15.5C and Kelburn's 12.6C their 4th highest.

Then if one adds 0.4C to the Chch Aero mean (a guess based on the difference between the 30-year means) then a fortuitous rounding could give the Gardens its 14.0C mean.

[Nev]

Here's NIWA's preliminary, 'July 2018 National Climate Summary'.

July 2018 was NZ's 5th-warmest July on record (behind 1998, 2000, 2005, and 2013).


The national average temp of 8.9C was 1.1C above normal.

The month's highest temp of 22.3C was recorded at Kaikoura on the 21st, while the lowest temp of -7.6C was recorded at Middlemarch on the 13th.

Lots of near-record high temps (and no record low temps), including Dunedin's 2nd highest July mean-temp and Wellington's 3rd highest.

Note that NIWA's Mangere temps used for Auckland look suspiciously way too low, especially when compared to nearby sites like Auckland Aero.

[tunster]

Instead we got westerly flows, which were for the most part weaker than we often see (so an easterly anomaly was correct), but westerly nonetheless,

Actual anomalies for July show a westerly anomaly at 1000hPa and 500hPa, not an easterly anomaly.

[TonyT]

Instead we got westerly flows, which were for the most part weaker than we often see (so an easterly anomaly was correct), but westerly nonetheless,

Actual anomalies for July show a westerly anomaly at 1000hPa and 500hPa, not an easterly anomaly.

Ah well, more busted than Joseph Parker then.