Showing all posts tagged: climate
Weird winter weather points to yet more unstable weather
5 September 2024
Mick Tsikas, writing for The Conversation:
The severe weather rounds out a weird winter across Australia. The nation’s hottest ever winter temperature was recorded when Yampi Sound in Western Australia reached 41.6C on Tuesday. Elsewhere across Australia, winter temperatures have been way above average.
41.6°C? It doesn’t even get that hot in summer, at least where we are on the east coast of Australia. Well, hardly ever. There have been one or two days when highs have pushed into the forties, but that’s usually at the height of summer, and still, is rare.
There’s been some strong winds recently. But the trade winds are common around this time of year, particularly August. The warm weather experienced in parts of Australia last week — in what was still winter — is definitely unusual though. I looked up the Southern Annular Mode (SAM), and found the value had been neutral in second half of August. The SAM is a metric of how close cold weather fronts come to the southern part of the Australian landmass.
A negative SAM value means they reach quite some way inland. Cold fronts bring rain and cooler weather. With SAM values being neutral or positive though, these fronts have not been coming through, which may partly explain why it was so warm. But I think climate change, of course, is the remainder, or most, of the reason.
On one day, temperatures almost reached 30°C during this late winter heatwave, in our part of the world. I truly dread to think what summer will bring…
RELATED CONTENT
climate, climate change, environment, weather
Is the Australian winter 2024 colder than normal?
5 August 2024
It depends how you define normal. Winter this year, or certainly in July, and absolutely since the recent Sudden Stratospheric Warming event, has felt distinctly chillier. But the bad news is, no this winter, when compared to the long term average, isn’t all that much cooler than “normal”.
Despite the relatively cool conditions, most capitals have still recorded temperatures comfortably above the long-term average, and all except for Melbourne and Adelaide were colder in 2022.
2022 seems a long time ago, as I don’t recall the winter of 2022 feeling cooler than this year. The thing is though, we’ve become accustomed to warmer winters, because you know why, so when a normal winter comes along, or one that is closer to statistically normal, it feels colder.
RELATED CONTENT
Sudden Stratospheric Warming is bringing weird weather to parts of Australia
29 July 2024
El Niño and La Niña are global metrological events most people are probably familiar with. In Australia, the influence of one or other seems more pronounced over the summer months. El Niño marks periods when ocean temperatures in parts of the Pacific Ocean rise by a certain amount, while La Niña events refer to occasions when these temperatures fall by a certain amount.
While ocean temperatures may affect how many people decide to go for a swim, depending how warm or cool the water is, these variations in ocean temperatures can have a significant, and far reaching, impact on the weather. For instance, parts of Australia may experience higher than normal temperatures during an El Niño event. La Niña’s on the other hand, may instead result in below average temperatures in the same regions.
But El Niño and La Niña are not the only metrological phenomena that influence weather and climate in Australia. The Southern Annular Mode (SAM) is another. The SAM is an indicator of westerly wind belts, and their proximity to the southern coast of Australia. A negative SAM for instance, sees these westerly wind belts, and their associated rain fronts, come much closer to southern Australia, bringing higher rainfall with them.
Then there’s the Indian Ocean Dipole (IOD), sometimes known as the Indian Niño, an indicator of temperature differences between the eastern and western regions of the Indian Ocean. A positive IOD reading can result in periods of low rain fall and drought, particularly in southeast Australia, while negative readings bring higher rainfall to effected regions.
But in trying to determine how the weather may play out over the coming months, an eye should also be kept on Sudden Stratospheric Warming (SSW) events, of which one occurred a few weeks ago, albeit thousands of kilometres from Australia. SSW, as the name suggests, refers to temperature increases in the stratosphere, a layer of the Earth’s atmosphere. The stratosphere is situated anywhere from ten to twenty kilometre’s above the planet’s surface. Higher in equatorial regions; lower near the poles.
But SSW events, which usually occur in the northern hemisphere, can see temperatures rise markedly, generally in the order of about twenty-five degrees Celsius. However, the recent SSW event, over Antarctica — which, in July especially, is unusual to begin with — saw temperature rise by about fifty-degrees Celsius. Fifty-degrees. Remember though, this happened some twenty kilometres above Antarctica, and not on the ground.
One can only imagine the impact of a snap surface temperature increase of fifty degrees in Antarctica, or anywhere for that matter, were that ever to happen. That’s not to say nothing at all, weather wise, will happen though. The previous time a SSW event occurred over Antarctica was in September 2019, resulting in warm, dry weather, across much of Australia in the months that followed. Coupled with an extended period of drought, the event precipitated the tragic Black Summer bush fires of 2019 and 2020.
At this stage meteorologists anticipate more westerly winds for southern parts of Australia over the coming weeks. A negative SAM index reading, then? This has already resulted in heavy snow in some places, but temperatures nudging past twenty-degrees Celsius on parts of the southeast coast, unusual for the middle of winter. As the SSW event occurred in July, and large parts of Australia have been drought-free for some time, it is expected, hopefully, there will not be a repeat of the widespread bush fires of four or five years ago.
RELATED CONTENT
Five-thousand kilometre long cloud-band across Australia
3 June 2024
The Daily Aus (TDA), Friday, 31 May 2024:
Rain is forecast across 90% of the country over the coming days as a 5,000km ‘cloudband’ makes its way from WA‘s north to south-east Australia.
According to the Bureau of Meteorology (BOM), a ‘northwest cloudband’ is an extensive layer of air and moisture from over the Indian Ocean that can bring widespread rain to much of the country.
The cloud-band was not only extremely long, and also full to brimming with moisture. While rainfall remained constant throughout Saturday, there were some decidedly heavy downpours at times. These invariably came along just as we’d parked the car, and needed to cross a street to shelter, or while outside at some exposed mid-point between buildings.
We stopped at a cafe, a nice place, located in what was once a small warehouse, with an open ceiling with a corrugated iron roof. But we could barely hear ourselves speak at times, though during some of the showers, so heavy were they.
RELATED CONTENT
Weather forecasting has improved, sadly weather apps remain oddly deficient
20 March 2024
Four day weather forecasts are now as accurate as one day forecasts from thirty years ago. That’s good news. Access to accurate weather information is perhaps more vital than many of us can appreciate.
Weather forecasting has come a long way. In 650 B.C. the Babylonians would try to predict weather patterns based on cloud patterns and movements. Three centuries later, Aristotle wrote Meteorologica, discussing how phenomena such as rain, hail, hurricanes, and lightning formed. Much of it turned out to be wrong, but it represents one of the first attempts to explain how the weather works in detail.
But more of this data needs to be ported through to the weather apps on our smartphones. I don’t know if it’s me, but the number of times I’m caught outside somewhere, in what I call “off-app” rain — that is, where no rain whatsoever is predicted for hours, if not days — seems to be increasing.
RELATED CONTENT
El Nino weather event formally declared for Australia
21 September 2023
Australia is officially in the grip of an El Niño weather event. This means affected areas can expect higher than normal temperatures, and reduced rainfall. The Australian Bureau of Meteorology announcement on Tuesday confirmed what many people had suspected for some time.
The Bureau of Meteorology has formally declared an El Niño weather event, meaning one is underway for the first time in eight years. The major climate event impacts the weather patterns of 60 per cent of the globe, with Australia particularly vulnerable to its impacts.
That the declaration was made during the midst of a spring/pre spring equinox heatwave is all the more concerning. After parts of the northern hemisphere experienced a horror summer this year, with record high temperatures, and massive bushfires, some people will be dreading summer in the southern hemisphere.
RELATED CONTENT
Australia, climate, environment, weather
Parts of Australia may see heatwaves before the spring equinox
11 September 2023
The ten-day weather forecast for some parts of NSW are currently predicting several days with maximum temperatures in the vicinity of thirty degrees centigrade. This, at the moment, for Saturday and Sunday, 16 and 17 September, and Tuesday 19 September. These temperature ranges come close to the official definition of a heatwave:
A heatwave occurs when the maximum and the minimum temperatures are unusually hot over a three-day period in a specific location. This is considered in relation to the local climate and past weather at that place.
Such a forecast may not be entirely surprising if not for the fact Australia is only into the first few weeks of spring. Technically though, were the spring equinox — which falls on Saturday 23 September this year — to be observed as the beginning of spring (as is the case in parts of the world), then it would still be winter in Australia. A heatwave in winter, fancy that.
Long range forecasts are not always accurate though, and conditions may change between now and the weekend. Still, such warm temperatures in the middle of September are alarming to say the least.
And for anyone wondering, each season in Australia commence on the first days of March, June, September, and December, because Australia adheres to the meteorological seasonal system. Many northern hemisphere nations however observe the astronomical season convention, meaning seasons change on about the beginning of the third week in March, June, September, and December.
RELATED CONTENT
Australia, climate, environment, weather
Tropical cyclones may return to Sydney coastal region
24 November 2022
For about thirty years, until the mid-seventies, tropical cyclones were relatively regular weather events in the Sydney region, but now meteorologists are concerned they may return. But climate change is not behind their possible re-emergence, rather changes in the Interdecadal Pacific Oscillation (IPO):
The inordinate frequency of cyclones from the 40s to the 70s and the disappearance in recent decades is not random variability. A 2020 report in the Journal of Southern Hemisphere Earth Systems links NSW cyclone activity with changes in the Interdecadal Pacific Oscillation (IPO). The current state of the IPO and other cyclone influences has rapidly shifted in the past three years to resemble the 1950s. Meaning, the current phase of the Pacific is conducive to tropical cyclones impacting NSW.
While more often see in northern regions of Australia, tropical cyclones haven’t reached Sydney in decades, but they have impacted some parts of NSW, bringing flooding and storm damage with them.
RELATED CONTENT
A spring of Sam (Southern Annular Mode) and La Nina summer?
5 September 2022
Image courtesy of disassociated.
While there’s a slim chance regions of Australia may yet be spared a third consecutive wet, rainy, La Niña weather event this summer, the outlook for spring is not so promising.
The Bureau of Meteorology advised last week parts of eastern Australian can expect higher than usual rainfalls, thanks to another meteorological phenomenon, a positive Southern Annular Mode, or SAM, for short:
Further, Dr Bettio said a positive Southern Annular Mode (SAM) is also likely, which pushes weather systems south, bringing wetter easterly winds to NSW and fewer cold fronts to western Tasmania. Dr Bettio said parts of Western Australia and western Tasmania are likely to experience below average rainfall this spring. Almost all of Australia is likely to experience warmer than average nights, while cooler days are likely for large parts of the mainland except the tropical north.
RELATED CONTENT
Australia on alert for a third La Nina event this summer
18 August 2022
Another wet summer may be on the cards for parts of Australia, after the Bureau of Meteorology moved the ENSO Outlook to a La Niña alert status.
This status change follows a renewal of cooling in the tropical Pacific Ocean towards La Niña thresholds over recent weeks, as well as the persistence of the Southern Oscillation Index (SOI) at La Niña levels and strengthened trade winds at La Niña levels. Climate models indicate further cooling is likely, with four of seven models suggesting La Ni Niña a could return by early-to-mid southern hemisphere spring.
If another La Niña eventuates this summer, it will be the third in a row.
RELATED CONTENT