Australian Weather

Today, 1:15AM UTC

Sea surface temperatures in the Indian Ocean suggest that a negative phase of the Indian Ocean Dipole (IOD) may be emerging, which could influence Australian weather patterns in the coming months. What is the Indian Ocean Dipole? The IOD is an index that measures the difference in sea surface temperatures across the tropical Indian Ocean. A negative IOD occurs when cooler-than-average water sits on the western side of the Indian Ocean, near the Horn of Africa, and warmer-than-average water lies on the eastern side of the Indian Ocean, near Indonesia. A positive IOD is the opposite of this pattern (cooler water in the east, warmer in the west). Each phase of the IOD also influences atmospheric conditions above the Indian Ocean and surrounding countries. For Australia, a negative IOD typically increases the likelihood of above average rain over large areas of the country, while also promoting cooler days in the country’s south and east. IOD events typically occur between May and November and break down when the monsoon arrives in late winter or early summer. While October is late in the year for an IOD event to become established, there is still time for a negative IOD this spring. The maps below show how a negative IOD would typically impact Australian weather between October and December. Image: Typical changes to rainfall when a negative IOD occurs between October and December. Source: Bureau of Meteorology Image: Typical changes to maximum temperature when a negative IOD occurs between October and December. Source: Bureau of Meteorology Negative IOD pattern emerging The IOD is currently in a neutral phase, meaning neither a positive nor negative IOD is occurring. However, the map below shows sea surface temperature anomalies in the two IOD monitoring regions are beginning to reflect a negative IOD, with abnormally cool water in the west and warmer-than-average water in the east. Image: Sea surface temperature anomalies in the IOD monitoring regions on October 13, 2024. Source: NOAA In Australia, a negative IOD occurs when we see sustained IOD values below -0.4°C. The latest weekly IOD value was -0.58°C, which is the first reading below the -0.4°C threshold since 2022. Most forecast models suggest that the IOD index will remain below -0.4°C through the second half of spring before returning to neutral values in December. Image: IOD outlook for November 2024 from five international forecast models, all showing a weak negative IOD signal lingering through late spring. Source: Bureau of Meteorology. While it’s currently not clear whether a negative IOD will be declared in 2024, current conditions and forecast models are leaning towards Australia experiencing negative IOD-like weather in the second half of spring. The maps below show predicted rainfall anomalies from the ECMWF-SEAS5 model for November 2024. The first map shows a signal of above average rain over the central and eastern Indian Ocean and below average in the western Indian Ocean. The second map highlights an increased likelihood for rain in northern and eastern Australia during November. Image: Global rainfall anomaly forecast for November 2024. Image: Australian rainfall anomaly forecast for November 2024.

14 Oct 2024, 4:48AM UTC

A cluster of severe thunderstorms has converged on the Sydney region on Monday afternoon, delivering heavy rain, hail, and hazardous driving conditions. Fortunately, no reports of damaging hail have yet emerged, with the largest hailstones being not much bigger than pea-sized. As the storms rolled in just after 3pm, the BoM issued a Severe Thunderstorm Warning for heavy rainfall for the Sydney area as well as parts of the Hunter, Illawarra, Central Tablelands, Southern Tablelands and South West Slopes forecast districts. Storms are firing up across parts of NSW. Just a reminder that if you require storm assistance call the NSW SES on 132 500 and Triple Zero for life threatening emergency. ???? storm moves across Picton in the Southern Highlands a short time ago. pic.twitter.com/V15ESYFVrU — NSW RFS (@NSWRFS) October 14, 2024 The wild weather was caused by a trough moving over NSW which combined with an unstable airmass. The trough will deepen overnight enhancing showers and thunderstorms across the central ranges and coast of NSW, before impacting the northern ranges and coast on Tuesday. The storms were relatively fast-moving, however moderate rainfall totals were recorded in a short time-frame, including: 18.4mm at Sydney Observatory Hill in just over half an hour up till 3:30pm. 23.6mm at Canterbury (about 12km southwest of the Sydney CBD), again in little more than half an hour. 10mm in few very brief stormy minutes at Mt Ginini in the Brindabella Range overlooking Canberra. Image: Two-hour radar loop of storms to 3:10pm, Monday October 14, 2024. The storms were relatively fast-moving, with pink areas representing heat generated by lightning, The radar loop above also shows that further storms lie to the west and southwest of the Sydney region, with storms also starting to build up around Canberra. READ MORE: Destructive storms and record-challenging heat in Australia this week  Image: Skies turned greenish-grey like the traffic lights over southern Sydney as the storms arrived, with loud rumbles of thunder. This is a dangerous weather situation which is ongoing, with further storms possible in many of the areas mentioned into Monday evening, so please check the Weatherzone warnings page for the latest advice. You can also check the latest advice from the NSW SES here.