Weekly Tropical Climate Note
Tropical cyclone activity continues
Tropical cyclone activity continued in the southern hemisphere, even though the tropical cyclone season traditionally runs from November to April. Severe tropical cyclone Donna developed on 3 May, north of Vanuatu. While a direct impact of Vanuatu did not occur, heavy rainfall and minor damage was reported across the northern provinces of Vanuatu. Severe tropical cyclone Donna reached category 5 strength—estimated 10-minute mean winds of greater than 200 km/h—making it the most intense southern hemisphere system recorded in May.
The current track of Donna takes the system close to Noumea, in New Caledonia, in the coming days. Tropical cyclone Ella, which developed south of Samoa on 9 May, is expected to move to the west and potentially impact Fiji in the next few days.
Further information and warnings related to tropical cyclones in the southwest Pacific region can be found on the warnings page of the Fiji Meteorological Service.
Australian tropical cyclone and wet-season review for 2016-17
Late-season tropical cyclone activity, as observed in the southwest Pacific region, was also a feature in the Australian region. Only two tropical cyclones were observed to the end of February 2017, during the Australian tropical cyclone season which runs from November to the end of April. In the final two months of the 2016-17 season, seven tropical cyclones formed in the Australian region, for a season total of nine tropical cyclones. Across the entire southern hemisphere, tropical cyclone activity was significantly lower than usual, most notably in the southwest Pacific region, and including the Coral Sea.
The Australian region long-term average is eleven cyclones per season. Further analysis of why tropical cyclone numbers were less than early season forecasts will be done by the Bureau in coming months. However, a decreasing trend in tropical cyclone frequency has been observed in recent decades. Using 21st century data only, the seasonal average number of tropical cyclones in the Australian region is nine.
Blanche was the first system to make landfall, crossing the northern Kimberly coast as a category 2 storm on 6 March 2017. This was the latest date that a first tropical cyclone landfall has been recorded in the Australian region. Two other cyclones made landfall during the season, most notably severe tropical cyclone Debbie which crossed the mainland coast near Airlie Beach in Queensland on 28 March as a category 4 system. The strongest cyclone of the season was Ernie, reaching category 5 intensity, with estimated mean winds of 220 km/h and peak gusts of 315 km/h.
Overall, wet-season rainfall for northern Australia between October and April was the eighth-highest since 1900. Large discrepancies were observed between rainfall in Queensland and areas further west. The Northern Territory and northern Western Australia both had well above-average rainfall for the season, whereas Queensland fell significantly below its average wet-season rainfall.
Madden-Julian Oscillation in western hemisphere
A moderate Madden-Julian Oscillation (MJO) signal is currently located in the western hemisphere, near the Americas, and is predicted by most international models to move towards tropical Africa at similar strength in the coming week.
When the MJO is in these regions at this time of the year, rainfall is typically suppressed in the Maritime Continent, but has no significant effect on northern Australia’s rainfall patterns. While the MJO signal is observed near the Americas, the most significant effect for northern Australia is the increased likelihood of reduced minimum temperatures.
For more information on the MJO, see the Bureau's current MJO monitoring information.
El Niño WATCH continues
The El Niño-Southern Oscillation (ENSO) currently remains neutral. The Bureau's ENSO Outlook status remains at El Niño WATCH. This means the likelihood of El Niño forming in 2017 is approximately 50% (twice the climatological average).
See the Bureau’s ENSO Wrap-Up for official El Niño, La Niña and Indian Ocean Dipole information.
Product code: IDCKGEW000