Polar cold snap to bring subzero temperatures, snow to parts of NSW


A pair of Antarctic cold fronts will bring subzero temperatures and snow to parts of NSW this weekend.

Sydney will experience a dramatic 10 degree drop in just a few days, with Friday’s 30C weather giving way to temperatures in the low 20s by Monday.

On the NSW south coast, temperatures will drop in two stages as the cold fronts succeed each other.

Friday’s temperatures between 22 and 25 degrees will drop to around 20 degrees by Saturday, and then down to a low of 17 on Sunday.

Not far from the coast, the Canberra region will be much colder, with Saturday morning temperatures of around 5C before the mercury will be expected to hover around the zero mark by Monday.

“The really cold weather will come by Monday or Tuesday, that’s because the cold front brings cooler air, and the wind needs to settle down before it gets really chilly,” the Bureau of Meteorology’s Jiwon Park explained.

Unlike the capital, the coast will be buoyed by unseasonably warm water temperatures.

“The south coast will remain a bit warmer because of the influence of the water,” Mr Park said.

“We are seeing sea surface temperatures remaining slightly warmer than usual.”

In fact, with the ocean temperature remaining around the mid-20s around Batemans Bay, and a few degrees cooler at Merimbula, south coast residents who want to stay warm may want to hit the surf.

The places where the polar conditions will really be felt include the alpine region, Monaro, the ACT, the southern tablelands and parts of the central tablelands like the town of Oberon.

“In parts of those areas we may see temperatures dropping down to below zero degrees during the early part of next week,” Mr Park said.

“There might even be some snow in some parts.”

In the Southern Alps, the snow level could drop below 1200 metres above sea level.

Where it doesn’t snow, the next few days are expected to be drier overall then the beginning of the week, Mr Park said.

“We’ve been under the influence of a moist easterly, and with the passage of the consecutive cold fronts from Friday to Sunday, there’ll be a replacement of that moist easterly by a cooler and drier southerly wind,” he said.

“It will be very dry.”



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La Nina officially ends, but strong Madden-Julian Oscillation to bring rain


La Nina has officially left the building.

The climate driver that has been largely responsible for a cool, wet summer over much of Australia, has – or is close to – dissipating, the Bureau of Meteorology has confirmed.

Its departure is around a month earlier than had been expected.

The once in a century rain event that soaked New South Wales and parts of Queensland, and led to three deaths, was likely its final push. It also led to one of the quietest bushfire seasons for years.

However, the Bureau has warned that while La Nina may have gone, another climate driver could still crank up the rain during the coming month and could lead to an uptick in tropical cyclones.

And there is good chance the La Nina could come back for an encore appearance after winter passes.

In a climate note, the BOM confirmed its El Nino – Southern Oscillation (ENSO) outlook had moved from La Nina to inactive. That means the climate driver is effectively in neutral – neither a La Nina nor an El Nino.

Other climate agencies have slightly different definitions of a La Nina – the US meteorological service still has a La Nina in place – but it is also likely to call an end to it in the coming weeks.

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The La Nina was called in September last year. And while it wasn’t hugely powerful in itself, it nonetheless led to some of the biggest weather impacts related to the climate driver for a decade.

Although the numbers around the 2020-21 La Nina have not yet fully been crunched, it’s likely March will have been one of the wettest on record in NSW.

This rain event was beyond what we were expecting,” Dr Ailie Gallant from the Monash University Climate Change Communication Research Hub told news.com.au.

“Ten years ago, in 2011, was a very strong La Nina. But this La Nina was very middle of the road, it wasn’t super weak or super strong.”

La Nina leads to quietest fire season for a decade

Today the NSW Rural Fire Service said it had been the quietest bushfire season since the strong La Nina year of 2010/11.

There were just 11 days of total fire bans in the state compared to 60 last year, said RFS commissioner Rob Rogers.

“Firefighters have responded to just over 5500 bush and grass fires burning 30,963 hectares across NSW, considerably less than the 11,400 fires and 5.5 million hectares lost last season.”

One of the factors that may have turbocharged this year’s relatively moderate La Nina was rising sea surface temperatures, often cited as a symptom of climate change.

Warmer water evaporates and heads into the atmosphere.

“A warmer atmosphere can hold more water vapour and scientists calculate that this can increase moisture in the atmosphere by approximately 7 per cent per degree of global warming,” said Dr Gallant.

What has changed for La Nina to be declared finished?

The cooling phase of the ENSO, a La Nina bubbles up when strong winds blow from east to west across the Pacific which drags cooler water up from the depths in the central and eastern equatorial ocean.

These winds then push warmer water off the coast of Australia closer to the continent which can bring more moisture.

But that’s all changed now, said the BOM

“Tropical Pacific Ocean sea surface temperatures have persisted at ENSO-neutral values for several weeks. Below the surface, much of the tropical Pacific is now at near average temperatures.”

La Ninas often decay during autumn but the expectation was it would likely linger, in a weakened form, until May.

Another climate driver now comes to fore

The BOM said the ENSO was now likely to remain in neutral until at least the end of winter. Neutral often means fairly average conditions across eastern Australia.

However, with La Nina departing, the influence of another climate driver has been beefed up.

That is the Madden-Julian Oscillation (MJO).

The MJO is a patch of cloud that circles the globe around the equator, including above northern Australia.

When it passes through, it can increase rainfall. Its effect is particularly strong from October to April when the Top End wet season is in full swing. When its visit to Australia combines with a monsoon trough – which is happening now – it can lead to even heavier rains and more cyclones.

Indeed, a tropical cyclone is a possibility over the coming days in the Indian Ocean close to north western Western Australia.

“The MJO has moved into the Australian region at moderate strength and is expected to bring increased cloudiness and rainfall to far northern Australia and the broader continent over the next week or two,” said the BOM.

Even though La Nina is fading away, the rain may not be. Some of those heavy downpours could feed their way further south during April.

La Nina could return

Like Hollywood hit movies, this La Nina could see a sequel. And, like most sequels, it probably won’t be a great as the original.

“There is a higher likelihood of having back-to-back La Ninas than a transition from a La Nina to an El Nino,” Monash University climate scientist Dr Shayne McGregor told news.com.au.

“On average, sea surface temperatures display a second cooling 12 months after a La Nina event. So it’s a double dipping but typically the second La Nina is smaller than the first.”

However, we’re now entering what’s known in climate circles as the “predictability barrier”, meaning it’s tricky to forecast what these drivers might do in the months ahead.

The fog lifts around June or July when we’ll know if La Nina is headed back, we’ll be stuck in neutral or if an El Nino is in the cards.



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La Nina related marine heatwave heating up WA waters


A rare and potentially damaging climate phenomenon has caused temperatures to soar in the waters off the Western Australia coast.

It’s partly down to the La Nina climate driver – but it’s having a different effect in Australia’s west to its east.

Climate scientists have said there is a “growing risk” from these so-called Ningaloo Ninos in years to come as they can damage coral and marine species and drive hot air onto land.

The La Nina climate driver has generally brought more moisture and cooler temperatures to Australia’s east this summer.

But its effects usually don’t bother much of Western Australia. Indeed, scorching heat has been the hallmark summer weather of the west this year.

Perth has seen a series of blistering heatwaves. Over the New Year period, the city saw 13 days straight of temperatures higher than 30C. In December there were three days where the maximum didn’t dip below 40C.

The seas off Western Australia have also been experiencing a heatwave of their own. The Bureau of Meteorology (BOM) has reported that sea surface temperatures off the WA northwest coast were 2.5C warmer than average and 3C higher in the ocean off central parts of the state.

The blame lies, in part, with La Nina. But what’s remarkable is that effect is being felt so far away from the Pacific which is the climate driver’s usual stomping ground.

The La Nina is one of the three phases of the El Nino Southern Oscillation (ENSO), the other phases being El Nino and neutral.

The ENSO is a measure of sea surface temperatures and winds in the Pacific Ocean. A La Nina is caused by cooler waters in the central and eastern equatorial Pacific being hauled up to the surface while strong winds push warmer seas towards Australia.

That aids in the creation of clouds and so more moisture and windier conditions for the east of the continent.

But raised sea levels, due to La Nina, has seen some of that warm water escape the east and, during the summer, make a beeline for the west of the continent.

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JOURNEY TO BECOMING NINGALOO NINO

First it flowed through the gaps in the Indonesia archipelago and then it headed down the WA coast.

In the vicinity of the UNESCO world heritage listed Ningaloo Coast, near the town of Exmouth, this water met the Leeuwin Current. Together, the pair have being causing maritime mayhem.

The Leeuwin Current is named after Cape Leeuwin, the most south westerly point of mainland Australia, located about 50 kilometres south of Margaret River.

This current funnels Indian Ocean water down the WA coast and then swing shots it around the cape where it can affect sea surface temperatures as far east as Tasmania.

Many marine species hitch rides on the Leeuwin Current across the Great Australian Bight.

This year, the warm La Nina waters have helped to turbocharge the current over summer, raising ocean temperatures and creating a marine heatwave.

Marine heatwaves are generally defined as sea surface temperatures being warmer than the long term average over a five day period.

These particular heatwaves are often called “Ningaloo Ninos”. The nickname recognises where the heatwaves often form and that they have a heating effect similar to an El Nino rather than a La Nina.

This heating can be exacerbated by other factors in WA including the collapse of sea breezes.

GROWING CONCERN

According to the BOM, the last time marine heatwaves occurred off the coast of WA was in 2012-2013 and before that in 2011-2012. Indeed, 2011 was a horror of a Ningaloo Nino which saw see temperatures skyrocket 5C above average.

That wasn’t great for the Ningaloo Reef which experienced significant coral bleaching in the warm water, the first major bleaching it had seen.

Some fisheries can wane during maritime heatwaves and seagrasses often die.

All of these Ningaloo Ninos have one thing in common – they coincided with a La Nina.

This maritime heatwaves can also lead to increased temperatures in land as wind blows in from the clean.

A report by the Monash University Climate Change Communications Research Hub stated there was a “growing risk” of more marine heatwaves due to the rising overall temperature trend.

While belching had not been as bad as in 2011 this year, the increase in temperatures means its becoming more of a common event.

“The observations show us that, over the past 40 years, waters around the Ningaloo Reef have warmed much faster than most other surrounding Australian waters in summer”, said Monash Associate Professor David Holmes.

“Climate projections suggest that more frequent and intense marine heatwaves can be expected in the future.”

The La Nina climate driver has now passed its peak, meteorologists have said, and the ENSO could well swing back into neutral conditions around May.

However, its effects will continue to be felt for the next couple of months.

That will mean continued rain for the east coast while the west can expect its rare Ningaloo Nino to linger for a little longer.



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Australian jobs that could become too dangerous to perform


Scores of jobs could soon become too dangerous to undertake in Australia.

No, it’s not the increasing rise of robots and automation this time. It’s something all around us that might seem mundane but is increasingly deadly.

Rising humidity levels across the continent are leading to an increased risk of heat stress, a condition that can injure or kill those outdoors for long periods of time.

Yet hot weather can be overlooked as a factor in someone’s death.

“Often its role is very quiet. People who pass away from heat stress don’t necessary have it on their death certificate,” Dr James Goldie from Monash University’s Climate Change Communications Research Hub told news.com.au.

“It might be marked down as a heart attack, lung or acute kidney failure, but it’s only when we step back that we can see on hot days more people are passing away from these conditions and that’s when we join the dots and say, yes, this can kill.”

However, there is an easy and perhaps surprising method to beat, or at least, minimise the heat – slushies.

Earlier this month, the Bureau of Meteorology (BOM) and the CSIRO, the Government’s science research agency, released the State of the Climate report that stated Australia had warmed on an average by 1.44C since records began in 1910.

Heatwaves have become more frequent and are lasting longer.

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DANGERS OF HEAT STRESS

Jason Kai Wei Lee, an associate professor of human physiology at the National University of Singapore, told news.com.au the level of heat stress depends not only on the outside temperature but also how much clothing someone had on and if they are exerting themselves.

“At 25C with 80 per cent humidity it would be thermally very uncomfortable for an unfit elderly person, while younger individuals can still carry on with their outdoor activities,” he said.

“But if move closer to 35C and 100 per cent humidity then we can say all humans would feel very uncomfortable,” said Prof Lee, who spoke this week at the BOM’s annual research workshop.

Heat stress can be mild; nothing that a bit of sweating and heading indoors can’t solve. But left unchecked it can get out of control. Once the body’s core temperature, which is usually 37-38C, reaches 40C it can begin to malfunction and shut down.

RELATED: Lack of trees exacerbates extreme heat effects

ROLES AT RISK

Prof Lee said people particularly at risk of heat stress were those who remained in the hot conditions despite the suffering imposed on their bodies.

“People who are paid (per task) or have to produce a certain output may disregard thermal discomfort and maintain, or even increase, their work pace to earn as much as possible,” he said.

“Competitive athletes or soldiers who are highly fit are capable of producing high amounts of heat (in addition to the external heat) and are motivated – because they don’t like to stop – are prone to heat stress.”

Prof Lee said these types of jobs might not be possible in the future if we continued working as normal while the country gradually got hotter.

“In many instances, work productivity and health will be compromised and heat-induced incidents will increase if we do nothing about it.”

Healthcare workers with heavy PPE, gardeners and food delivery drivers with pizzas and burgers weighing them down were all prone to heat stress.

Monash’s Dr Goldie added tradies, particularly those on open building sites, as being at risk.

The manual roles, backbreaking and accompanied by long hours, are often those with low pay and little job security.

RELATED: Australian cities that could become ‘uninhabitable’

DIED THROUGH HEAT STRESS ON FIRST DAY

A 2019 report by Dr Richard Gunn at the University of Adelaide examined 13 deaths attributed to heat in Australia between 2000 and 2015.

These included a charity collector going door-to-door, two people working in construction and a farm worker.

Showing how deadly heat can be to those unaccustomed to it, a teenage Woolworths supermarket trolley collector, an insulation installer and a furniture removalist all died within days – or even on the day – of starting on the job.

A report from ANU’s Thomas Longden, published in January, estimated 2 per cent of Australia deaths between 2006 and 2017 were due to heat; that rose to 9.1 per cent in humid areas of Northern Australia.

Dr Goldie said Darwin – and other parts of the humid tropics – were often held up as places where heat stress is a real danger.

“But people in Darwin are more aware of the heat, especially those that have been there for some time.

“A humid heatwave down south, however, can catch people off guard and people might not take the danger seriously,” he said.

“Melbourne isn’t about to become Darwin,” he added, “but heatwaves may be longer and more humid and that’s an important change further south for people who are used to a drier heat.”

SLUSHIES

One strategy people can take on hotter and more humid days to keep working, Prof Lee said, was really simple – drink slushies.

He was part of a Singaporean study that gave healthcare workers slushies to combat the city-state’s equatorial humid conditions

“Ice slushies combine the goodness of both cooling and hydration in one. You induce heat sink by drinking a ball of ice and that allows you to last longer and perform better before you hit your thermal limit,” he said.

Slushies aren’t a magic bullet against all aspects of heat stress though. In hot weather, workers also needed to acclimatise to the heat and take regular rest periods where they cooled down and hydrated.

Dr Goldie said there was a clear sign of humidity-related heat stress – sweat, and lots of it.

“When you’re sweaty and gross, and you get to the point the sweat is dripping off you and not evaporating, it’s not doing its job and that’s when humid days are really dangerous.”



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