Showing all posts tagged: climate
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.
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.
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.
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.
18 August 2022
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.