New Zealand Weather

[Kiwi]

 

[Kiwi]

Vince Cocurullo Mayor of Whangarei

"6:30am update Mon 13th Feb 2023

We have had heavy rainfalls last night along with high winds. NRC Rainfall gauges have recorded over 200mm in the last 24 hours.

Metservice still have Whangarei and Northland in Red Zone for More Heavy rain and High winds, until Tuesday evening Wednesday Morning. https://www.metservice.com/maps-radar/rain/forecast/3-days"

[karyo]

I woke up at 7am with the sound of heavy rain and it is continuing up to now with no breaks. The wind is picking up too. 

The worst rain is forecast to be from late afternoon onwards and it will coincide with gale force winds. Hawkes Bay is expected to get 150mm on coastl areas with up to 400mm on the hills so some flooding is certainly likely.

This is my first ever cyclone so I am quite excited but I hope there won't be too many problems in my area and that the electricitry won't cut off.

Edited February 12, 2023 by karyo

[crimsone]

 

I’d quite like to sleep now. West Auckland isn’t fun right now.

[stodge]

Mrs Stodge's mother is in Greenmeadows, near Napier and Hastings, in the Hawkes Bay region.

First thing, she is fine - she is in a retirement village which didn't get flooded and she didn't have to evacuate. The village has no power apart from a generator at the main building which is powering the kitchen where they are working overtime to make meals and hot drinks for the residents and they have Wi-Fi.

Hopefully @Karyo is okay but the power went off across the whole of Hawkes Bay on early Tuesday morning (local). The main sub station serving Napier and Hastings is submerged and it may be several days before power is restored. This morning, authorities are saying up to a week.

Gabrielle has been an extraordinary weather event with the LP centre moving SE from just east of Cape Reinga down the coast through the Hauraki Gulf and passing to the north of the East Cape. To the south of it (remember we are in the Southern Hemisphere) very strong E'ly winds battered the east coast of the North Island and very heavy rain accompanied the gale across the east and north of North Island with the heaviest falls in Coromandel, around Gisborne and in Hawkes Bay.

There are severe thunderstorms forecast today for the Bay of Plenty as an upper level residual trough passes west to east.

Winds gusted to 130 km per hour in the far north and around 90 km per hour at Napier. I've not seen accumulated rainfall numbers but would expect 200-300mm to have fallen quite widely and perhaps up to 400mm in the Ruahine Ranges and the Esk Valley.

So far, five people are confirmed dead and there are serious concerns this figure will rise as the authorities reach areas which are currently inaccessible.

[karyo]

That was quite a wild experience! After a wild night of rain and wind i woke up to find no electricity or WiFi signal on Tuesday.  The house I was staying in thankfully didn't get damaged but there was a lot of flooding in Napier and Hastings and fallen trees. Napier still has no electricity but the flood waters a receding now. The Art Deco festival which was scheduled fir this weekend has been cancelled, this is a huge economic loss for the city.

Thankfully, the airport is not affected so I am leaving for Melbourne today.

Something I have to highlight is how well local people are dealing with this disaster. I queued at the local supermarket for an hour on Tuesday and despite the mile long queue nobody was agitated or disorderly. People were chatting to each other and keeping the spirits reasonably high. Also, with no traffic lights in operation, the traffic on the roads appears to work fine with drivers being curtious and letting other cars in the traffic. 

[stodge]

Mrs Stodge's mother got her power back after six days last Monday.

The disaster has left a deluge of silt covering the land including the valuable agricultural soil. Unfortunately, eleven people are confirmed dead with eight still missing.

Roads remain closed and bridges remain down cutting off access to many areas but it's improving slowly.

Looking at the latest GFS it seems the next cyclones forming off New Caledonia and Vanuatu will stay to the north of the North Island but that doesn't mean no impact from wind and rain. 

[stodge]

I’m back in New Zealand for a couple of months visiting Mrs Stodge’s family in Napier and elsewhere.

We arrived yesterday to very hot conditions in Hawkes Bay with Napier the warmest place in NZ at 33c and strong sunshine barely mitigated by a strong W’ly airflow between HP to the north of New Zealand and LP encroaching from the south and southwest. 

Today (Friday) has been a very different day. Still sunny and dry (it has been a dry spring and Hawkes Bay is under water usage restrictions with gardens only allowed to be irrigated every other day) but much fresher with a maximum of 24c.

The HP to the north has migrated west over the Tasman Sea and with LP persistent to the south we have a SE’ly flow over Hawkes Bay which will likely shift more SW tomorrow keeping us pleasant at 23c.

Sunday seems to be turning more unsettled as the HP fades and a new area of LP develops over the south of the Tasman. Unlike the Antarctic LPs, this will swing the airflow back to a warm and humid NW’ly and there’ll be rain for the South Island on Sunday spreading to the North Island on Monday. As is often the case, orographic rainfall will develop over the Southern Alps with up to 150mm forecast

[stodge]

Quite a soaking for much of New Zealand in the next 36 hours or so though the heaviest rain will be over the southern and western coasts of the South Island. The core LP, currently over the western Tasman will deepen significantly and move SE to be about 950 MB by Monday. The resulting complex series of frontal systems will cross New Zealand tomorrow and Monday - it’s analogous to an LP moving past NW Scotland and a series of fronts crossing the UK.

There are warnings of embedded thunderstorms in the south and western coastal areas tomorrow.

As happens in the UK, areas to the east of higher ground will receive less rain and will benefit from Foehn type conditions so 30c here in Hawkes Bay, 27c in Christchurch and other parts of the east of the South Island compared to 17-19c on the western coasts.

The rain moves away Monday into Tuesday and a slack pressure regime takes over.

GFS 00z suggests further into FI we’ll start to see a hint of more tropical type developments from the north and north west but currently they are forecast to move into the Tasman rather than across the north of New Zealand but that’s all speculation for now.

[stodge]

Monday morning here in Aotearoa and in Hawkes Bay the westerly wind continues to blow augmented by the high ground to the west which funnels the wind down into the bay. We were supposed to reach 30c yesterday but only got to 27c as more cloud developed.

No rain as yet - we may get a sprinkle this morning with temperatures in the low 20s. 

The overall Synoptics have a deepening area of LP well to the south of the South Island. The LP looks to be slow moving for the next 36 hours before starting to fill and move away towards the far southern ocean.

The westerlies will ease but the HP remains out over the islands and in the Tasman a brief HP cell looks set to be replaced by a broad shallow trough coming off Australia. The current GFS suggests that trough will move across the North Island later in the week and over the weekend so in Hawkes Bay that could mean a wet spell with easterlies. Further into FI, we stay in a westerly pattern with HP in the northern Tasman and LP approaching the far south of the South Island but all speculation.
 

[Metwatch]

Everytime I look at charts for Australia / New Zealand, it always confuses me at first as the pressure systems winds rotate the opposite direction to the northern hemisphere!

Majority of low lying areas of NZ has a similar climate to England; oceanic climate. However winters are generally a bit milder than what we are used to. The mountains are much larger in NZ as well. so there is a more pronounced rain shadow effect, particularly for the south island.

 

Edited December 9, 2024 by Metwatch

[stodge]

 Metwatch Many thanks and you are quite correct.

New Zealand sits between 34 and 47 degrees south - Napier is just shy of 40 degrees south so the same latitude as Madrid and Ankara.

Cape Reinga sits at 34 degrees south and the far north - Northland - has sub tropical elements in its climate. It is vulnerable to ex-tropical cyclones coming south east from New Caledonia and Vanuatu - Gabrielle in February was a particularly severe example. These storms can produce copious amounts of rain and severe winds for the far North, Bay of Plenty and Hawkes Bay.

The main sources of weather are the Tasman and the Southern Ocean. Strong storms in the Southern Ocean rarely reach New Zealand even in winter but the cold fronts sweep north east and introduce what’s called a “southerly change”. It’s analogous to a Polar Maritime NW’ly for us. Under clear skies, frost can develop in winter even in Hawkes Bay. The winter storms produce snow to high ground and lower ground in the South Island. In summer, they mean a significant drop in temperature as the PM airmass takes over.

The Tasman is where most of New Zealand’s weather originates - unlike the Atlantic of course, there’s a large land mass not far to the west so you don’t get the intensity of LP found in the North Atlantic or Southern Ocean. Indeed, it’s often quite a slack area of pressure but complex troughs do develop and if, in winter, they phase with energy from a storm in the Southern Ocean, they can develop rapidly.

The other synoptic feature worth mentioning is the semi-permanent HP over the central southern Pacific Ocean. It’s a huge cell analogous to the Azores HP in our part of the world. In the summer it ridges west across northern New Zealand and can lead to fine and settled conditions especially across the North Island. It tends to withdraw east in winter allowing south west winds to sweep right through the north.

The west and southwest of the South Island suffers from orographic rainfall and, as you say, the Southern Alps creates a rain shadow which means places like Christchurch, Ashburton and Timaru experience Foehn like conditions and can be the warmest and driest parts of the country. A similar effect occurs in Hawkes Bay due to the high ground to the north and west.

[stodge]

Wednesday afternoon in Aotearoa and it’s a glorious afternoon in Napier with sunshine and light winds. We reached 26c and it was, so I’m told, a typical Hawkes Bay summer’s day.

Synoptically the North Island is under a transient ridge of HP but pressure is falling over South Island and the Tasman and the trough will cover the whole country with rain or showers tomorrow. 

However, from Friday we are forecast two fine days in Napier with 29c on Friday and 27c on Saturday. Not 100% convinced as we will be between shallow areas of LP to the west and east of the North Island so I’d have thought a storm wouldn’t be impossible in the Ranges though the prevailing light winds might keep us fine.

Next week is looking very different at this stage - GFS suggests a new LP will form at the top of North Island which will draw in an E’ly flow to Hawkes Bay and that usually means rain or showers and we could have 3-4 days of unsettled conditions. The rain will be very welcome albeit I suspect the quantity won’t do much to alleviate the overall. Daytime maxima nearer 20c so cool for the time of year.
 

 

[TillyS]

Thanks for this @Stodge and others

The only things I would like to add, if I may as an amateur to your professional knowledge are these:

1. Although relatively close to each other, the meteorology of Australia and New Zealand are chalk and cheese. The two countries are very different in lots of other ways too but the weather is one of them. I’ve left Sydney in shorts and t-shirt to arrive in Queenstown to a virtual Scottish winter. A couple of days ago it was 33C in Sydney and 13C in Queenstown: not uncommon.

2. I don’t think NZ weather is very like the UK at all. There are several reasons for this. One is the huge variation between North Island and South Island, and also within the islands. For complex topographic reasons and prevailing weather patterns there are variations in NZ temps, wind, and precipitation that you just don’t get, or get very rarely, in the UK. Weather in NZ is staggeringly complex and varied on any given day: a weather forecasting nightmare although they are very good at it. Furthermore, as you rightly say the mountains are much higher. Britain simply doesn’t have the kind of Alpine barrier that NZ South Island has. And again the variations this yields are extraordinary. As you say, the rain shadow is amazing. So parts of Otago and the Canterbury plains are the driest in the country (as you said!).

3. That Alpine terrain on South Island is something else again. The nearest you get to the distinctive conditions would be the Scottish Highlands but that doesn’t come anywhere near close. You have to be exceptionally careful tramping (= hiking) in NZ as a result. Not just the South Island but also, for example, the Tongariro crossing. The precipitation on the western side of the Alps is something else. Milford Sound gets something like 9 metres of rain a year!!!! It’s the wettest inhabited place on earth I believe. In the mountains you really can get 4 seasons in a day, and have to be extremely careful as a result. There is simply nothing remotely comparable to this in the UK.

4. The Big big big added factor in all this is the Southern Ocean. Much of NZ actually sits south of Australia. The Southern Alps cop it from the Roaring Forties and when those storms roll across to the south, the resultant weather swings can be truly amazing. You can go from summer to winter in the blink of an eye.

I’m only really touching on this subject because I do find NZ weather to be absolutely fascinating. I can honestly say I’ve never seen a country like it for head-scratching meteorology. It is an astonishing place.

Edited December 11, 2024 by TillyS

[TillyS]

And the sun can shine in Milford Sound … I took these on a gin clear day

Edited December 11, 2024 by TillyS

[TillyS]

On 10/12/2024 at 03:26, stodge said:

trong storms in the Southern Ocean rarely reach New Zealand even in winter but the cold fronts sweep north east and introduce what’s called a “southerly change”. It’s analogous to a Polar Maritime NW’ly for us.

Just for anyone who hasn’t been to NZ, the difference is that there these swings are much more sudden and way more dramatic. And relentless too: when Spring weather continues in NZ you can get these two-day wild swings occurring week after week.

I know you know all this Stodge, and much more than I do. I’m just posting this out of fascination. There are lots of reasons for going to New Zealand and dramatic weather is one! It’s way more dramatic than Britain which is very bland by comparison.

[stodge]

 TillyS You’re not wrong of course.

Even in midsummer we went from 33c to 24c in just 24 hours as the wind shifted from NW to SW behind a cold front.

Just to update the previous, Thursday’s rain is caused by a mass of moist unstable air from the sub tropical regions moving SE across the North Island. Far to the south, there’s another small LP just off Fiordland so Southland is also due rain and showers.

The clue is in the 850s which GFS has for Hawkes Bay at +16 tomorrow and Friday so in any sunshine to the Lee of the hills on Friday, I reckon we’ll easily see a humid and sticky 31c. 

The analogue for us would be a thundery LP moving up from France towards southern Britain.

[stodge]

Friday late afternoon in Napier and it’s been another glorious day of cloudless skies and unbroken sunshine. The temperature reached 31c but due to be a notch cooler over the weekend.

Yesterday’s disorganised area of rain and showers crossed the northern half of North Island with the main rain around Northland, Auckland and the Bay of Plenty. We had a spell of morning rain in Hawkes Bay but the afternoon was dry, cloudy and humid.

Hardly any wind yesterday but a fresh westerly today to augment the fire risk but the wind is due to slacken after today and for tomorrow and Sunday we’ll pick up an onshore easterly in the afternoon and evening.

Synoptically, it’s a slack pattern with a weak ridge over the north of New Zealand but that looks set to change as a new HP forms over the southern Tasman and pressure falls to the north east of New Zealand to the south of the Cook Islands and Tonga and two separate shallow areas of LP merge. GFS suggests this will happen by midweek and between that and an HP to the south east, we’ll get a prolonged spell of onshore winds into Hawkes Bay next week so I’m expecting more unsettled and cooler conditions with rain or showers from Monday.

[Metwatch]

Interesting to hear about the frequent and rather strong temperature swings often seen in the country. I can't think of many other places where these swings in temperatures are masked by monthly climate averages, perhaps some parts of USA where you can get very strong cold fronts, then it warms back up in a few days?

Would love to experience a month or 2 in NZ to feel what it's like as it would be quite a change from the much smaller varations in temperatures i'm used to here!

[stodge]

Actually we’ve had a change of sorts today - despite cloudless skies, an easterly onshore wind developed from the Pacific this afternoon and has pegged our maximum to 25c after yesterday’s scorcher of 31c. The humidity has reduced which has raised the fire risk substantially - the nearby parks and reserves are closed and helicopters are up monitoring any grass fire outbreaks.

Tomorrow looks a similar day but the synoptic pattern is changing. We’ve enjoyed a ridge over the North Island from the huge Pacific HP cell but pressure is now falling to the north and the ridge will decline back east. Meanwhile a new HP will form over the Tasman and build across the South Island. Between the two a shallow trough will form across the North Island and showers look likely on Monday in the instability and with an onshore drift on the east coast I’m expecting a downpour or two.

I think Tuesday will be better as the HP builds and the east coast of North Island will be in a SE’ly flow with the main LP over the Chatham Islands.

From there, the latest GFS suggests an area of LP to the north east of New Zealand will dominate the North Island weather with an E’ly flow and unsettled conditions to the end of the week and into FI the cooler more unsettled theme dominates as a new LP forms in the Tasman and extends the trough across the whole of the North Island.

Conversely, the South Island, which has had plenty of rain, will do well out of the synoptic set up with HP just off the east coast and dry conditions.

[Summer8906]

 TillyS @stodge Interesting that even an island location considerably further away from a continental landmass than the UK is, and with that continental landmass (Australia) being much smaller than Eurasia, has more dramatic temp swings than in the UK and other parts of NW Europe.

 

Edited December 14, 2024 by Summer8906

[stodge]

 Summer8906 There’s a clue to the south in the huge cold block that is Antarctica.

Even in midsummer there is a vast pool of cold air over the icecap and as the cold air tries to flow north and interacts with the warmer air and water we get the chain of LP which dominate the far Southern Ocean. Each of these LP has cold air in its circulation and as the cold front moves up New Zealand from the south west it brings this, admittedly modified, Polar Maritime air.

If you look at the GFS 3D global map and view the 850s in this part of the world there’s a real contrast between the heat of northern and Western Australia and the tropics and the much cooler southern waters.

This means 850s of +8 or +12 from sub tropical air over New Zealand are replaced by 850s of zero to +4 as the colder air add takes over and that’s a big move in temperature - larger than you see in the UK but nothing compared to the continental landmasses.

Edited December 15, 2024 by stodge

[stodge]

Sunday evening here - yet another fine and sunny day. We reached 26c with an afternoon.

However, significant change is now underway. A warm front is set to bring heavy rain to Northland and Bay of Plenty and Hawkes Bay will likely get some welcome rain in the afternoon.

HP builds across South Island on Tuesday but with LP persisting to the east, we’re due a SE flow so more showers are likely for us on Tuesday while most of the rest of the country is fine. By Wednesday, a deepening area of LP will move south west towards the North Island and with the HP moving south east a broad E’ly flow will cover both islands. The likelihood for Hawkes Bay is windy and unsettled conditions from midweek with rain or showers at time.

GFS is showing 850s of +16 and +20 for the east coast of North Island on Christmas Eve so we could be roasting with the turkey.

 

[Summer8906]

 stodge Interesting. Perhaps one of the big problems with the contemporary Northwestern European climate (as opposed to the perhaps more interesting late 20th-century climate) is how watered-down a lot of the Pm airmasses actually are, a product of the anomalously high SSTs of recent times, I suspect. Conversely the tropical maritime air is generally cloud-laden and often drizzly, hence max temps are often not that high (indeed, in summer, Tm air tends to bring daytime maxima no better than average due to the high cloud amounts). So the two airmasses don't have much contrast and temps don't change that much, also the cold fronts tend not to be strong - again often drizzly. On the other hand the Pm airmasses are so modified that they often don't produce classic Pm conditions.

In the 80s it seemed to be different, we got more strong cold fronts and more in the way of cold Pm air - but that was before climate change kicked in.

If I had to suggest one thing that would probably improve the NW European climate significantly, it would be a significant lowering of the SSTs. We could still get heatwaves (because heatwaves are always associated with air flowing in on a long land track) but we'd get "real" Pm airmasses and stronger contrasts on cold fronts. Arguably our problem is not so much the presence of the Atlantic, but the anomalously warm waters for our latitude.

On another matter do you get much in the way of thunderstorms in NZ? And is Wellington really as equable as the mean temps suggest, or does the 21-22C midsummer max come from rapid alternations between say the mid-teens and the mid-to-high twenties?

Edited December 15, 2024 by Summer8906

[stodge]

 Summer8906 I don’t disagree with a word of your first three paragraphs. There’s some interesting research on changes in SSTs in the Southern Ocean which would be worth a read.

The SSTs around New Zealand range from 10-12c in the south to 16-18c off the north of the North Island.

The waters further south are obviously colder but are warmer than the ice around Antarctica itself and that helps fuel the chain of storms which move west to east round the huge continent in the Antarctic Circumpolar Current (ACC).

The storms pass well to the south of Australia and New Zealand in summer but are further north in winter and as they move SE past the South Island the cold front moves NE and pulls in the cold Antarctic air which moves right up the country even to Hawkes Bay and Auckland.

I’ve no view on thunderstorm frequency but I imagine they would occur to higher ground. Tornadoes, while rare, have occurred.

Wellington is known for its windy conditions as it sits in the funnel between the two islands and the crossing of the Cook Strait is notorious for being rough whether on a ferry or in a plane.