General July Weather

einzack · Unread post by **einzack** » Tue 25/07/2017 15:28

Couple of cracking days yesterday and today. 14.5°C yesterday and then 16.7°C today.
A lovely change after the string of very chilly temps we've had for what seems like forever up until now.
I know it won't last, but you gotta enjoy it when it comes!

cbm · Unread post by **cbm** » Tue 25/07/2017 15:45

Car is reading 12C in Omarama. Locals are saying it is mild for time of year.

Sent from my GT-N7100 using Tapatalk

mattyj46 · Unread post by **mattyj46** » Thu 27/07/2017 15:54

Weather watch noting this time next week we could be more severe weather warnings issued for wind, rain and snow

NZstorm · Unread post by **NZstorm** » Thu 27/07/2017 20:24

Looks to be a low risk of thunder/hail over Auckland city tomorrow afternoon if convergence can get its act togeather.

einzack · Unread post by **einzack** » Fri 28/07/2017 08:24

The lock on my car was frozen this morning, so I couldn't get in. First time for that. Temp on station recording 1.6°C, but the other car, once I'd manage to get inside, read -2°C and roads very icy and slippery.

Area51 · Unread post by **Area51** » Fri 28/07/2017 17:42

Spot on re convergence. Lightning around South Auckland area at present.

David · Unread post by **David** » Sat 29/07/2017 07:49

The coolest morning of the year here so far on 1C. Looking cold tonight too, maybe 0C

Nev · Unread post by **Nev** » Sat 29/07/2017 08:36

4.2C here this morn.

I see Mt Cook Aero got down to -13.3C.

spwill · Unread post by **spwill** » Sat 29/07/2017 09:17

A nice looking convergence line over east Ak yesterday afternoon.
While July has been wet, it has been an uneventful Winter in Auckland so far, no extremes.
See if we can get a light frost here tomorrow morning.

jamie · Unread post by **jamie** » Sat 29/07/2017 09:17

I see MetService are picking -4 here tonight. Should be our best frost of the year.

Razor · Unread post by **Razor** » Sat 29/07/2017 18:02

jamie wrote:I see MetService are picking -4 here tonight. Should be our best frost of the year.

Same! Glad I'm watching the footy from in front of the fire

Orion · Unread post by **Orion** » Sun 30/07/2017 08:41

Posting from Orewa Beach: observing some fine mares' tails to the north.

spwill · Unread post by **spwill** » Sun 30/07/2017 08:45

The coldest morning of the year for NZ, frost from Northland to Southland.

spwill · Unread post by **spwill** » Mon 31/07/2017 08:47

We managed to escape frost here this morn, a fine day to finish July.

Temperature/sunshine near average here for July but wetter than normal.
2 days with thunder and 1 frost at my place.

Orion · Unread post by **Orion** » Mon 31/07/2017 12:52

My flight from Auckland to Christchurch this afternoon was quite bumpy at times: message from the Flight Deck was of an unforecast jetstream at around 30,000'.

tunster · Unread post by **tunster** » Mon 31/07/2017 22:42

Orion wrote:My flight from Auckland to Christchurch this afternoon was quite bumpy at times: message from the Flight Deck was of an unforecast jetstream at around 30,000'.

Was that Air NZ 535?

NZstorm · Unread post by **NZstorm** » Tue 01/08/2017 07:36

I see that frost Sunday morning was a record low temp for Grey Lynn weather station. 0.1C. Station has been operating since about 2002 I think.

Orion · Unread post by **Orion** » Tue 01/08/2017 08:50

tunster wrote:
Orion wrote:My flight from Auckland to Christchurch this afternoon was quite bumpy at times: message from the Flight Deck was of an unforecast jetstream at around 30,000'.
Was that Air NZ 535?

Yes, why do you ask?

Nev · Unread post by **Nev** » Tue 01/08/2017 11:24

The lower edge of the subtropical jetstream extended right down to the west of the South Island around midday yesterday, with SSW winds above 30,000 ft over Auckland/Northland of more than 150 km/h by the looks. That lower edge gradually weakened and later retracted. Meanwhile, westerly surface winds at Akld Aero around midday were only about 10 km/h. So not surprised you you hit turbulent headwinds after ascending …

SH Jet Stream Analyses - Jul 31, 00z.gif

SH Jet Stream Analyses - Jul 31, 12z.gif

(Source)

GFS NZ 300 mb Winds - Jul 31, 00z.png

Orion · Unread post by **Orion** » Tue 01/08/2017 12:48

Thanks Nev

Nev · Unread post by **Nev** » Tue 01/08/2017 16:40

MetService July 2017 Summary

Frequent lows were centred over New Zealand during July. Not surprisingly, the month was unusually volatile and very wet for most regions, excluding the West Coast of the South Island. Extreme weather events were characteristic of the month of July. An unusually cold outbreak on July 12/13 produced snowfalls to low levels across the South Island and also brought heavy snow to the lower and central North Island. Flooding rains occurred across the eastern South Island on the 21st, and State of Emergency declarations were issued for Otago, including Dunedin and Oamaru, as well as for Timaru and Christchurch.

Jul 2017 Climate Anomaly Maps ℅ NIWA.gif

Some very preliminary July 2017 figures for the main centres:

Code: Select all

July 2017 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       15.0  +0.5     8.0  +0.7    11.5  +0.6    190  138%    126   96%
Auckland Aero           14.6  +0.3     7.8  +0.3    11.2  +0.3    178  134%
Tauranga Aero           14.4  -0.1     6.3  +0.2    10.3   0.0    124   96%    n/a   n/a
Hamilton Aero           13.9  +0.1     4.2  +0.6     9.0  +0.3    160  124%
Wellington, Kelburn     11.5  +0.1     6.4  +0.1     8.9   0.0    230  168%     97   81%
Christchurch Aero       10.0  -0.9     1.0  +0.4     5.5  -0.3    159  246%     93   73%
Dunedin, Musselburgh     9.5  -0.5     2.6  -0.5     6.1  -0.4    157  274%    100   91%
Greymouth Aero          11.7  -0.4     4.4  +0.4     8.1   0.0    229  116%    128  119%

Lowest temps included -14.6C at Lake Tekapo (760m) and -13.7C at Mt Cook Aero (660m) on the 29th.

Edit: Amended Chch Aero's T-min departure. And updated maps

tunster · Unread post by **tunster** » Tue 01/08/2017 16:57

Orion wrote: Yes, why do you ask?

I went looking for PIREPs after your post and found one from Air NZ 535 of severe turbulence over the upper SI in the range of 29,000ft to 34,000ft.
As the jet core was either over the upper SI at that time, or a little further west (it varied with height), my guess for the reason behind the turbulence is strong horizontal wind shear close to or just east of the jet core.

Not sure what the "unforecast" jetstream means though. The high level charts issued by Kansas did not include that particular jet, probably because they do not include every single jet streak, they tend to focus on the persistent, large ones (like the bulk of the STJ which was to the north of NZ yesterday). I'm guessing that is what the pilot meant, because both the jet and the possibility of severe turb above 25,000ft was mentioned in the Sitbrief issued by NZ that morning.

Pilot reports are so very important because otherwise it's not possible to know for sure when things like icing and turbulence actually occur. Syntopically, the right sort of set up can be identified, and hence flagged for potential, and you can identify some tell tale signs in radar and satellite imagery, but without a bonafide report you never actually know for sure whether it happened or not......

TonyT · Unread post by **TonyT** » Tue 01/08/2017 17:49

Nev wrote:
MetService July 2017 Summary

Frequent lows were centred over New Zealand during July. Not surprisingly, the month was unusually volatile and very wet for most regions, excluding the West Coast of the South Island. Extreme weather events were characteristic of the month of July. An unusually cold outbreak on July 12/13 produced snowfalls to low levels across the South Island and also brought heavy snow to the lower and central North Island. Flooding rains occurred across the eastern South Island on the 21st, and State of Emergency declarations were issued for Otago, including Dunedin and Oamaru, as well as for Timaru and Christchurch.

Jul 2017 Climate Anomaly Maps ℅ NIWA.gif
Some very preliminary July 2017 figures for the main centres:
Code: Select all
July 2017 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       15.0  +0.5     8.0  +0.7    11.5  +0.6    190  138%    126   96%
Auckland Aero           14.6  +0.3     7.8  +0.3    11.2  +0.3    178  134%
Tauranga Aero           14.4  -0.1     6.3  +0.2    10.3   0.0    124   96%    n/a   n/a
Hamilton Aero           13.9  +0.1     4.2  +0.6     9.0  +0.3    160  124%
Wellington, Kelburn     11.5  +0.1     6.4  +0.1     8.9   0.0    230  168%     97   81%
Christchurch Aero       10.0  -0.9     1.0  -0.4     5.5  -0.3    159  246%     93   73%
Dunedin, Musselburgh     9.5  -0.5     2.6  -0.5     6.1  -0.4    157  274%    100   91%
Greymouth Aero          11.7  -0.4     4.4  +0.4     8.1   0.0    229  116%    128  119%
Lowest temps included -14.6C at Lake Tekapo (760m) and -13.7C at Mt Cook Aero (660m) on the 29th.

The Christchurch figures have been calculated incorrectly, if the mean max is -0.9 from normal and the mean min is -0.4 from normal then the mean must be -0.65 from normal, not -0.3 as stated.

Nev · Unread post by **Nev** » Tue 01/08/2017 18:01

TonyT wrote:The Christchurch figures have been calculated incorrectly, if the mean max is -0.9 from normal and the mean min is -0.4 from normal then the mean must be -0.65 from normal, not -0.3 as stated.

Thanks Tony, was a bit rushed...

Chch Aero's average T-min of 1.0C should be 0.4C above normal (not 0.4C below normal). Have amended my original post/table.

Orion · Unread post by **Orion** » Tue 01/08/2017 19:47

Thanks, tunster.
It was an interesting experience

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