Australian Weather

05 Dec 2025, 5:33AM UTC

Australia’s East Coast could be impacted by periods of strong waves over the next couple of weeks as tropical cyclone activity increases in the Coral Sea and southwest Pacific Ocean. A number of these computer models are forecasting the development of tropical lows or cyclones over the Coral Sea and southwest Pacific over the next two weeks. Image: Four computer models predicting tropical lows or cyclones being active east of Australia late next week. Source: Weatherzone. This increased potential for tropical systems in the region is partly driven by an active phase of the Madden-Julian Oscillation (MJO) moving into the western Pacific region. The MJO causes an increase in cloud and thunderstorm activity when active over a region. This enhanced storminess can help create low pressure systems that can deepen into tropical cyclones. Image: Conceptual visualization of the MJO moving over the north of Australia, increasing thunderstorm, rain and tropical low activity. Source: Weatherzone. Along with this active phase of the MJO, oceans are very warm across the Coral Sea and southwest Pacific. This is partly due to the weak La Niña conditions currently in place across the Pacific. These warm sea surface temperatures greatly increase the potential for tropical cyclone development, which requires waters warmer than 26.5°C. Currently oceans across the region are 2-3°C warmer than normal, with waters even warm enough to support a tropical cyclone off southeast Queensland. Image: Sea surface temperatures around Australia on Thursday, December 4, 2025. Source: DTN. How will Australia be impacted? Fortunately for those in eastern Australian, there is only a low chance of a tropical cyclone being within the Australian region in the next 7 days. If a tropical cyclone does form, it will most likely be located a long way off Australia’s east coast and pose very little direct threat to the Australian mainland. However, tropical cyclones generate very large seas that radiate across the oceans, and these long-range swells can impact Australia’s coastline from thousands of kilometres away. Over the weekend, an area of low pressure will deepen near or just south of Fiji, potentially briefly reaching tropical cyclone intensity early next week before undergoing extra-tropical transition. While this system will remain around 2,000-2,500 kilometres east of Australia, enhanced easterly trade winds around the low, with more powerful 35-45 knots winds near the core, will generate a large area of swell generation, directed towards Australia. Image: DTN’s OneFX Significant Wave Heights reaching 5 to 6 m generated on Tuesday, December 9, 2025. Source: Weatherzone. Large seas generated by the low should reach 5 to 6 m over parts of the southwest Pacific between Fiji and New Zealand early next week. This area of large waves being over 2,000 kilometres away from Australia’s East Coast will take about 3 to 4 days to propagate and reach the Australian mainland. Across this journey, the swell height will significantly decrease, but the wave period will increase. Image: DTN’s OneFX Peak Wave Period showing easterly swell propagating across the Tasman and lower Coral seas next week. Source: Weatherzone In deep open ocean waters, longer period swell travels faster than short period swell, so coastal parts of eastern Australia could see swell “front runners” as early as Thursday afternoon (December 11). These swell propagation leaders should come in with periods of 14 to 15 seconds, and small amplitudes of less than a metre. The bulk of the swell energy is then expected to fill into Friday, December 12, with coasts from the NSW South Coast to Queensland’s K’gari experiencing 1 to 1.5 m swell at 12 second periods, and up to 2 m around the NSW Northern Rivers and southeast Queensland. Looking further ahead, another tropical low could develop just south of the Solomon Islands from mid-next week. While most models feature a low developing in the far northeast of the Coral Sea next week, different model and model runs vary on the intensity and location of the system. Image: GFS weather forecast of Mean Sea Level Pressure (MSLP) and 10 m wind speeds between Sunday, December 7, 2025, and Thursday, December 18, 2025. Source: TropicalTidbits.com This possible tropical cyclone could come within 1,000-1,500 kilometres of northeast NSW and southeast Queensland from around Saturday, December 13. The potential for significant easterly swell generation will greatly depend on the proximity, intensity and movement of the system. Why long period easterly swell can be dangerous and disruptive Easterly swells are especially hazardous for Austarlia’s east coast because they can bypass the headlands and breakwalls that protect beaches, ports and harbours from the more typical south swells that impact NSW and southeast Queensland. These easterly swells can enhance coastal erosion across beaches usually protected from south swells. Long period “groundswell” energy often goes unnoticed underneath ships at sea, but can be highly disruptive as the energy surges into ports and harbours. The “waves” of deep water energy surging into ports can cause ships to drag on their moorings and anchors. Seiching can also amplify this water movement as the energy sloshes within the port boundaries, increasing horizontal and vertical ship movements. Be sure to check the latest coastal warnings in eastern Australia over the next two weeks before heading down to the beach.

04 Dec 2025, 12:03AM UTC

Hot, dry and windy weather will sweep across southeastern Australia over the next three days, causing Extreme fire danger in parts of SA, Vic and NSW. Clear skies associated a large and slow-moving high pressure system have allowed hot air to build up over parts of northern, western and central Australia this week. This hot air will spread across southern and southeastern Australia between now and the weekend under the influence of a broad low pressure trough, which will also cause wind to strengthen over several states. While temperatures will rise over all of southeastern Australia in the next few days. the burst of heat, wind and elevated fire danger ratings will be most notable in SA, Vic and NSW. South Australia North to northwesterly winds will strengthen over SA on Thursday as the low pressure trough deepens over the state. These blustery winds will drive hot inland air towards the south, causing temperatures to reach about 34°C in Adelaide and 36°C around Keith. Further north, temperatures are likely to exceed 40°C in the state’s Pastoral districts on Thursday. Image: Forecast maximum temperatures on Thursday, December 4, 2025. Source: Weatherzone. The combination of heat, blustery winds and low relative humidity will cause Extreme fire danger ratings over central and eastern part of SA on Thursday. Total fire bans have been declared in eight of the state’s 15 districts: Eastern Eyre Peninsula Flinders Mid North Yorke Peninsula Mount Lofty Ranges Riverland Murraylands Upper South East Milder southerly winds will drop temperatures and fire danger ratings in the state’s south from Thursday afternoon into Friday, although intense heat will linger in the north of SA until Saturday. While Adelaide is only forecast to reach 22°C on Saturday, some northern pastoral areas could reach the high-40s on Saturday afternoon. Victoria All of Victoria will be affected by a surge of hot northwesterly winds on Thursday, with temperatures forecast to reach 34°C in Melbourne, 36°C in Mallacoota and 38°C in Mildura. Extreme fire danger ratings are likely to develop in parts of the Mallee, Wimmera and Northern Country districts amid this heat on Thursday, with total fire bans declared for all three districts. Image: Forecast fire danger ratings and total fire bans on Thursday, December 4, 2025. Source: Weatherzone. Milder southwesterly winds will spread through southern Vic from Thursday afternoon into Friday, although northern Vic will remain hot on Friday before cooling over the weekend. Extreme fire danger is expected to linger in parts of the Mallee and Northern Country districts on Friday. New South Wales Hot air will spread over NSW from Friday into the weekend, causing a spike in temperatures and fire danger ratings. Sydney’s daily maximum temperatures are forecast to reach 30°C on Thursday, 35°C on Friday and 36°C on Saturday. The city’s western suburbs will be several degrees warmer, likely reaching around 40-41°C on Friday and Saturday. Temperatures will also reach the low to mid-40s in western NSW on Friday and Saturday. Image: Forecast maximum temperatures on Saturday, December 6, 2025. Source: Weatherzone. Extreme fire danger ratings are likely to develop in parts of southern NSW on Friday and central, eastern and northern NSW on Saturday. Saturday’s Extreme fire danger is likely to affect parts of the Greater Sydney, Greater Hunter and Illawarra/Shoalhaven districts. Thunderstorms possible While much of southeastern Australia will experience hot and windy weather over the next few days, some places could also see thunderstorms. The atmosphere is too dry for widespread storms and heavy rain, so storms are likely to be scattered and fast-moving. The biggest threats from these storms will be damaging and possibly destructive winds, and dry lightning, which could ignite bush or grass fires. Heat and thunderstorm activity will also spread further north into northern NSW and Queensland on Sunday and Monday. Be sure to check the latest fire and thunderstorm warnings in your area over the next few days.