Tropical Climate Update

Hot conditions across northern Australia

Since 27 September, hot days and warm nights with temperatures 2 to 8 °C above average occured regularly through much of northern Australia. Daily maximum temperatures were between the high 30s and low 40s and minimum temperatures in the low to mid 20s. Between 28 and 30 September, some stations across northern parts of Western Australia, the Northern Territory and Queensland recorded their highest daily maximum temperature for September. A severe heatwave developed from 28 September in parts of western Top End including the Tiwi Islands in the Northern Territory and the western Kimberley in Western Australia and has continued into early October. Severe heatwave conditions are also forecast for parts of Cape York Peninsula in Queensland this week.

For the comming fortnight, the long-range forecast (issued 7 October) indicates an increased chance of unusually warm days and nights (in the warmest 20% of October days and nights observed between 1981 and 2018) for large parts of northern Australia, with highest chances across the Top End.

Close to average tropical cyclone activity in 2024–25

On 8 October, the Bureau of Meteorology released its Australian tropical cyclone season long-range forecast, to help the community prepare for the coming tropical cyclone season which occurs between 1 November and 30 April.

With the El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) in a neutral state, there is no strong shift expected in the average number or location of tropical cyclones. During ENSO-neutral seasons, the first tropical cyclone to cross the Australia coast typically occurs in late December.

Since 1970, the Australian region has observed an average of 11 tropical cyclones each season with an average of 4 crossing the coast. In recent decades, since 2000–01, the number of tropical cyclones that form in the Australian region decreased to an average of 9 per year. However, as the ocean temperatures in the Australian region are forecast to be warmer than average in coming months, there is an increased chance that a higher proportion of tropical cyclones that form this season will be severe.

On average, 3 cyclones occur in the Northern Region of Australia, with 7 on average in the Western Region, 5 in the North-western Region and 4 in the Eastern Region.

Tropical cyclones are not the only weather hazard in the Australian tropics. Tropical lows can also cause damaging winds, widespread rainfall and dangerous flooding, while storm surges, including from cyclones that don't make landfall, are a major hazard to coastal communities. These impacts can extend beyond the tropics into southern parts of Australia.

Hurricanes Helene and Milton

Hurricane Helene developed from a tropical storm in the western Caribbean Sea and became a hurricane early on 25 September. It intensified into a Category 4 on the 26th while traversing the Gulf of Mexico. Hurricane Helene made landfall late on 26 September in the Big Bend region of Florida, near the city of Perry, with maximum sustained winds of 220 km/h and minimum barometric pressure of 938hPa. While Hurricane Helene was downgraded to a tropical depression on the 27th and dissipated on the 29th, it brought catastrophic flooding across the inland states of North Carolina, eastern Tennessee and south-western Virginia. It was the second major hurricane of the 2024 Atlantic hurricane season and the deadliest since Katrina in 2005.

A tropical storm that developed on 5 October in the western Gulf of Mexico intensified into a hurricane named Milton on the 6th and reached the Category 3 intensity on the 7th while moving north-eastwards. It rapidly intensified further and reached the Category 5 intensity with sustained winds of nearly 280 km/h. It is expected to make landfall on Florida's western Gulf Coast later on the 9th as a Category 3 system and remain at hurricane strength as it moves across the Florida Peninsula and into the Atlantic Ocean, potentially impacting areas still in recovery from Helene.

Madden–Jullian Oscillation weakens in the Indian Ocean

In the past fortnight, the Madden–Jullian Oscillation (MJO) progressed eastwards across the Western Pacific and as of 6 October, the pulse of the MJO has weakened over the Indian Ocean. Climate models surveyed by the Bureau indicate it will remain weak for the next 7 days, before a pulse of MJO could emerge over the Maritime Continent or Western Pacific region.

It is expected that the MJO will have little impact on northern Australian rainfall over the next week, but potentially could influence tropical rainfall in the second part of the fortnight.