ClimateWatch: How AUGUST is shaping up as official El Niño announcement draws nearer (+16 Maps & Video)

As of August 2, El Niño was still not officially with us – but the latest update from the Bureau of Meteorology (BoM) continues to place our part of the world in an “El Niño Alert” – meaning it’s arrival is imminent.

BoM’s statement issued on August 1st says El Niño development is considered “likely in the coming weeks” – and this is despite the current lack of atmospheric response to sea temperatures rising in the eastern Pacific.

There are two parts to measure El Niño – sea surface conditions at the equator and then the atmospheric response to that which links it up. While sea surface conditions are well above normal in the equatorial Pacific near South America (classic strong El Nino set up) the atmosphere around New Zealand and Australia is yet to fully link up. Climate drivers like El Niño and La Niña can take many months to form and ease – they don’t develop rapidly like the weather does, so this big time frame is normal.

In the past an El Niño “Alert” lead on to an El Niño event developing around 70% of the time, according to BoM research. In America NOAA scientists say it has already arrived as it starts to impact their weather. But not here in New Zealand or in Australia – with both Niwa and BoM saying an announcement is still in the coming weeks.

What’s making it a little messier for NZ is the fact we have a local marine heatwave still carrying on – usually El Niño brings cooler sea surface temperatures to our side of the Pacific. Not only that, but in the western equatorial Pacific it’s still warmer than usual…and that’s more like La Niña, El Niño’s opposite.

NZ has westerlies off and on coming up – but the easterlies are still in the mix this month too, along with northerlies. That’s what we mean by being in a neutral and chaotic set-up and not yet El Niño driven.

EL NINO RECAP
Sea surface temperatures (SSTs) in the tropical Pacific are exceeding El Niño thresholds, with climate models indicating this is likely to continue at least through to the end of the year. In the atmosphere, however, wind, cloud and broad-scale pressure patterns mostly continue to reflect neutral ENSO conditions – according to BoM. This means the Pacific Ocean and atmosphere have yet to become fully coupled, as occurs during El Niño events. El Niño typically suppresses winter–spring rainfall in eastern Australia and northern and eastern New Zealand.

New Zealand remains in a NEUTRAL and therefore chaotic weather pattern – being driven mostly by high pressure zones out of Australia, but with low pressure zones or rainmakers in between these highs which are mostly affecting the southern coastal parts of Australia and then on into New Zealand.

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THE MAPS…

No change in two months – NZ and Australia remain in an “El Niño Alert”. Our expectation of it being announced hasn’t moved – and remains in late winter or early spring. Graphic by BoM.

Current sea surface temperatures (SSTs) showing it’s a few degrees above normal at the equator near South America – classic strong El Niño set up. However the SST also remain high around NZ due to a localised marine heatwave, and SST are also high in the western Pacific, which isn’t usually the case with El Niño… this is helping to complicate the atmosphere’s response to what is happening in the eastern Pacific.

Local marine heatwave around NZ continues on with some coastal regions still “severe” – like Wairarapa. Credit: Moana Project.

El Niño is only just getting started, peaking in summer 2023/24 based on international modelling.

Forecasts from global forecasters around the world (excluding NZ sadly) shows Sea Surface Temperatures (SST) continue to remain in El Niño territory this month.

El Niño continues to build right up to December. The ONLY model to show a slight reduction in December is from NOAA out of America.

What happens in a Spring El Nino? This public graphic from Niwa (a tax funded agency) shows how the east and north of the South Island lean drier than usual, while a big chunk of the North Island leans drier. Those wetter than normal will be Southland, the West Coast and potentially parts of Auckland and Northland (which get a lot of showery westerlies in spring – but they tend to fade more in summer). Image Credit: Niwa / NZ taxpayers.

TRACKING THE AIR PRESSURE TRENDS…
August is basically an extension of July’s weather pattern with more high pressure over Australia and NZ only partially being covered by highs. The highs are fairly consistent for Aussie – but more broken up in the NZ area, which will bring us varying wind directions in the weeks ahead. Westerlies look most frequent, but easterlies and northerlies are in the mix too.

NZ remains in a neutral and chaotic weather pattern as of August 2nd.

**WEEK 1** kicks off unsettled over NZ with a windy S to SW airflow and low pressure. But high pressure from Australia will return (to some degree) in the coming days bringing frosts and sunnier days – but still unsettled with showers due to NZ being on the edges of that high.

**WEEK 2** – We’re still seeing the trend of powerful highs exiting the Indian Ocean and crossing NZ. However the southern placement of this high pressure zone coupled with some weaknesses on the northern edges of that Tasman Sea high means easterlies for Queensland and a risk of rain to our north (which isn’t usual in El Niño – and again highlights we’re still very much in a NEUTRAL and CHAOTIC weather pattern, even if we do see some hints of El Niño showing up in the form of more westerlies. In our video today Phil Duncan mentions this set-up producing more “westerlies”, which it does off and on, however this particular map here does show easterlies back in the NZ area for a time.
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Another period of easterlies and northerlies at the top of NZ – westerlies more likely in the south. Still looks like El Niño is trying to form – but so too is a westerly driven spring pattern which usually starts around mid to late August for parts of NZ and Australia.

Niwa’s soil moisture map shows many regions returning to normal – but eastern areas in particular still lean wetter than average.

UPCOMING RAINFALL…

Rainfall is a bit messy for NZ but the Fiji area southwards to the upper North Island doesn’t look like El Niño yet, instead it’s perhaps even still looking a bit like La Niña … but remember we’re in a **neutral** pattern now, so that means we can get weather from all directions.

The rain in the north is not yet locked in – but could be from that low at the start of Week 3, around the middle of August. We can’t lock in that rain for the top of the North Island this far out – but shows you the tropics and sub-tropics aren’t quiet yet (which they usually are when El Niño kicks in). Most rain looks to be on the West Coast whilst driest weather looks to be in the east from the Catlins to East Cape.

IBM’s powerful global super computer looks at the trends coming up – and this shows August leaning a little drier for parts of NZ in the yellow/gold shading…but when you look at the key it shows you it’s not departing very far from “normal” – so it means rain is still coming, but perhaps 10 to 30mm below normal for the month ahead. The lower South Island, mostly Southland and coastal Otago, are still exposed to a slightly wetter than normal trend.

TEMPERATURES…

NZ continues to lean 0.5C to 1C above normal in August compared to what was recorded in this month historically. This continues a trend we’ve been seeing for a number of years now.

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Before you add a new comment, take note this story was published on 2 Aug 2023.

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Peter Thomas Langer on 3/08/2023 2:34pm

since that so called la nina gave rain to the south island a lot why wouldnt a el nino give rain to the north since things are topsy tipsy

Maria on 2/08/2023 7:09pm

Thanks Philip, learning so much more about weather and climate by listening to your videos.

WW Forecast Team on 4/08/2023 5:54am

Hi Maria – thanks very much for the feedback, it’s very much appreciated 🙂
Cheers
Phil

L J McDonald on 2/08/2023 3:16am

Last time there was a ‘Super’ El Nino, it didn’t behave for the south and west as predicted

North Island

South Island

North Island

South Island