NZ Weather Forum

Part 5 of the SSW now pushing into SE OZ and should be into the Tasman in around 24 hours. This one is fascinating as it’s the first in the sequence to create a Tasman cut off low. 540 line will reach around 32 degrees south of the equator but this time in the middle of the Tasman. Hard to know the exact impact until it circulates but a robust wet north easter might be on the way for the weekend around parts of the NI, with a moisture advection scenario for the SI following but that depends on the low position. It seems that the cut off low will keep the ridge west and allow a 6th cold wave to penetrate NZ in its wake. That will be 6 in 16 days to affect NZ if it lines up.

I just read a dooms day long term forecaster is warning for mass flooding in Auckland in the coming fortnight and for councils to prepare now. I’m not quite sure about that myself but it’s certainly an interesting atmospheric set up for the start of June across the country

David wrote:2.8C min here earlier. I see parts of rural NW Auckland and rural SE (around Hunua) dipped just below 0C this morning.

Cambridge didn't get below about 2C this morning despite clear sky must have been in a corridor of more breeze.

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An intense blue sky here today caused by the dry polar air and no clouds.

No frost here this morning, certainly noticed the cold.

Plenty of snow for 29th May on the SI Alps showing on the 2.30pm sat pic.

Does anyone (maybe Nev) know what the record minimums for official sites in Auckland are for May? I'm sensing they could be under threat tomorrow morning if the breeze drops.

Cyclone Tracy wrote: ↑Tue 29/05/2018 15:06 Does anyone (maybe Nev) know what the record minimums for official sites in Auckland are for May? I'm sensing they could be under threat tomorrow morning if the breeze drops.

I think Ardmore Aero's May record is -2.9C and Whenuapai Aero's is -2.3C, both set on May 28, 2014. Also on that day, Albany got down -1.3C, along with 0.9C at Akld Aero (equal lowest) and 0.4C at Mangere (2nd lowest after -0.3C in 1964).

Thanks for the temperature information, Nev. I did not realise how cold it could get in Auckland as it is often quoted as having a 'semi-tropical' climate.

Another NIWA tweet stated that the minimum of 0.8*C on Tuesday morning at Whangarei was its third lowest ever in May, although it does not state how long the record is.

https://twitter.com/NiwaWeather/status/ ... 2356440064

Another of their tweets gives a minimum of -6.0*C at both Ranfurly + Middlemarch on the SI, but a MetService tweet trumps them with a minimum of -6.5*C at Mount Cook Airport. Nice to see a bit of competition in the weather industry.

Simon Culling wrote: ↑Tue 29/05/2018 21:43 Thanks for the temperature information, Nev. I did not realise how cold it could get in Auckland as it is often quoted as having a 'semi-tropical' climate.

Auckland is not in the subtropics. I believe lattitude 32 is start of the subtropics but there seems to be a lot of definitions for it.

Most of those locations Nev lists are on the rural outskirts of Auckland. For some reason the Auckland isthmus does not have an official climate station these days. I think the Auckland domain would be a good spot to start a new one.

According to Niwa Auckland Airport has an annual average 8.7 ground frosts a year and 0.1 air frosts. Sheltered low lying parts, particularly west and south Auckland would have more frost while elevated or very coastal locations would have less frost. Ardmore and Whenuapai are quite rural.

3C currently at Grey Lynn and ice on tops of cars.

The lowest May air temp recorded at Albert Park (central Auckland) was 2.0C. The all time min was -0.1C in the month of June. There was an average of 4.2 ground frosts a year there. data 1909 to 1980.

NZstorm wrote: ↑Wed 30/05/2018 07:01 3C currently at Grey Lynn and ice on tops of cars.

1.7C in Howick this morning, icy cars and roofs and a few patches of light ground frost. Brrr.

A couple of PWS around Hunua/Ararimu showing -1C.

Generally speaking that's colder than most parts of chch

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Down to 3.7c here this morning. Impressive nocturnal surface cooling with a 17c sea surface temperature very close to my PWS.

UKMet is the first model to get quite excited about the weekend's cut off low on the 12Z run with a 979 hPa cyclonic surface low just east of the upper north island by the end of the weekend.

melja wrote: ↑Wed 30/05/2018 09:23 Generally speaking that's colder than most parts of chch

I wouldnt say most parts, Port Hills and along the beach areas maybe, but thats only due to that horrible cold wind off the sea

Umm no real Frost this morning Richard in Chch with cloud until around 7.30. Most auck city surrounds recorded colder over night temps than Chch.

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We bottomed out at 1.1 at 8am this morning

melja wrote: ↑Wed 30/05/2018 14:54 Umm no real Frost this morning Richard in Chch with cloud until around 7.30. Most auck city surrounds recorded colder over night temps than Chch.

Ok so you are only talking about this morning

Of course haha, was referring to the guys In Auckland giving there overnight minimum.
The 0.8C in Whangarei Tuesday is also impressive given chch has only had 1 day lower than this in the last 30 days.

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-2 deg out in Sheffield this morning. Which is quite rear in some respects as Chch city generally gets colder frost temps than us. On many occasions we get to about -2 just after dusk but then get a light breeze which pushes the temp back to above freezing. Yet the areas around Glen tunnel and Colgate in the valley can get very cold frosts as they dont get that breeze like us being more open here i suppose.

-2 with freezing fog. Bloody pea soup. 2nd day in a row with freezing fog.


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talbotmj15 wrote: ↑Wed 30/05/2018 19:10 -2 deg out in Sheffield this morning. Which is quite rear in some respects as Chch city generally gets colder frost temps than us. On many occasions we get to about -2 just after dusk but then get a light breeze which pushes the temp back to above freezing. Yet the areas around Glen tunnel and Colgate in the valley can get very cold frosts as they dont get that breeze like us being more open here i suppose.

There's a number of locations around where katabatic winds pretty much stop all frosts too, but give me a calm frosty morning over putting up with a wind that goes right through ya. One of the strongest katabatic winds i know of is at whats called locally as Maori galley where the Hurunui river passes through a narrow gorge, that spot only gets two directional winds, up the river and down the river.

Chilly start again with 1.4C on my station this morning.

Despite the cold finish I think we have had a good May here, a warm feel for the first 3 weeks and quite a lot of the rain coming through at night which is reflected in the higher sunshine hrs for the month.

4.2c overnight here. 3 mornings in a row under 5c in May. A touch unusual you could say.

5th system of the SSW now showing a circulation centre on the 3pm sat pic near Lord Howe Island. This system fascinates me the most of the sequences with its associated flow on affects north and south of the Tasman. It possibly will hold back the ridge for a polar surge from a 6th system next week but I'm also spotting something very interesting for this newly formed Tasman low on some models. A possible Meteorological 'butterfly effect' on the tropics after it has gone. Needs a thorough examination before taking too seriously though...I will come back on this subject after that exam is done

I think this low pressure sequence might need its own thread soon....

Part 2 of my post associated with the affects on the tropics -

SSW system 5 and 6 is triggering a potential Tropopause cold breach over New Caledonia in a week’s time. GFS & EC have both picked it up in the upper atmosphere….. Still a long way to go but an out of season Tropical depression is one scenario from such a set up. Even if it only causes a tropical disturbance, this could feed into the mid latitudes. The last time a tropical system transitioned during June into the mid latitudes as a XTC and affected NZ was June 1958. The system was unnamed (before naming) and called 32P to the best of my research. Rare event you could say. Keeping an eye on that one…

Latest GFS and EC ensemble on that topic

NIWA mentioned in a tweet that the maximum temperature on Friday (31st May) was -2.6*C at Lauder (Otago) and -1.0*C at Middlemarch. The former is apparently a record for May in a record stretching back to 1924.

https://twitter.com/NiwaWeather/status/ ... 1884120064

Are these low temperatures the result of cold air pooling under an inversion? This part of Otago looks topographically to be a valley surrounded by hills on all sides, so when the sun is low (i.e. mid Winter) and cold air gets trapped in this way, it just gets colder and colder until the inversion breaks.