[4] Warmer than average sea surface temperatures in the central and western tropical Indian Ocean and cooler waters near Indonesia and northern Australia, indicating a positive IOD phase, had also persisted since May.

[4] The record-strength positive IOD contributed to the development of a region of higher than normal atmospheric pressure across northern Australia during September, after having remained near neutral throughout winter.

[7] Citing considerable rotation extending into the mid troposphere, well-established dual-channel outflow and warm sea surface temperatures, the JTWC assessed the system as having a moderate chance of attaining tropical cyclone intensity within the following 24 hours.

[8] The system gradually gathered strength in the favourable environment as it tracked slowly towards the south-southwest,[9] leading the JTWC to issue a Tropical Cyclone Formation Alert at 03:30 UTC the following day.

[17][18] As the weakened cyclone continued over water towards the southwest, paralleling the coastline, low vertical wind shear allowed an area of deep convection to gradually redevelop over the system on 7 January.

[19] Blake made its final landfall just to the west of the Wallal Downs cattle station on Eighty Mile Beach at approximately 17:00 UTC at minimal Category 1 intensity.

[34] On 29 January, the tropical low began to track rapidly southwestwards towards central Australia,[35] causing the system's convection to degrade due to interaction with the dry Australian outback.

[56][57] The BOM issued a tropical cyclone warning for Australian Tasman Sea territory of Lord Howe Island at 06:00 UTC on 12 February in anticipation of Uesi generating destructive winds while passing nearby.

[81] In the diurnally favourable overnight period, however, increased deep convection began to wrap around the centre, and an intermittent eye feature emerged on enhanced infrared satellite imagery.

The small size of Ferdinand's wind field allowed the system to strengthen rapidly into a Category 3 severe tropical cyclone on the Australian scale at 00:00 UTC on 25 February.

[84] The BOM reported that Ferdinand peaked in intensity at around 18:00 UTC as a high-end Category 3 severe tropical cyclone on the Australian scale, with estimated maximum 10-minute sustained winds of 155 km/h (95 mph) and a central barometric pressure of 960 hPa (28.35 inHg).

[92][93] After being downgraded to a tropical storm on the SSHWS at 12:00 UTC,[94] Ferdinand's rate of weakening slowed considerably, with the system maintaining a relatively constant intensity throughout the overnight period despite dry air wrapping entirely around the cyclone.

[97] During early March, a monsoon trough began to develop over the eastern Indian Ocean as a pulse of the Madden–Julian Oscillation moved into the Maritime Continent, bringing increased cloudiness and convective activity to Australian longitudes.

[101] The tropical low steadily organised as it tracked southwards, with deep convection developing over the low-level circulation centre and the minimum atmospheric pressure falling to 999 hPa (29.50 inHg) by 18:00 UTC on 10 March.

[103] Around the same time, the JTWC issued a Tropical Cyclone Formation Alert, citing the system's improving structure, sustained winds near gale force detected by a satellite's scatterometer instrument, and environmental conditions they assessed as being favourable for intensification.

[104] At 06:00 UTC on 11 March, the JTWC determined that a small area of sustained gale-force winds had developed under the deep convection in the southern semicircle of the circulation, and hence classified the system as Tropical Storm 21S.

Low vertical wind shear, warm sea surface temperatures and a good poleward outflow channel were forecast to remain sufficient to support the system's intensity in the short term.

[117] On 8 March, the BOM noted that a strong pulse of the Madden–Julian Oscillation was located in the Maritime Continent, generating increased rainfall and cloudiness, and elevating the risk of tropical cyclone formation in the waters to the north of Australia.

[119] Originally located approximately 250 km (160 mi) west-northwest of Weipa,[119] the tropical low began tracking southeastwards over the following days, making landfall at Aurukun on the western coast of Cape York Peninsula as a very weak system on the morning of 11 March.

[121] Initially forecast to develop steadily and reach tropical cyclone strength near Willis Island by the evening of 13 March,[121] the system instead struggled to form a defined centre of circulation within a broad and complex area of low pressure.

[122] As a result, exposed sections of North Queensland's east coast and the nearby reefs and islands experienced strong winds, despite being located a considerable distance from the tropical low itself.

[133] The tropical low organised rapidly as it tracked towards the east-southeast over the Solomon Sea, developing tightly curved convective banding and exceeding intensity estimates from several sources, including numerical weather prediction products, the Dvorak technique and some satellite-based analyses.

[137] On 9 April, satellite scatterometer data indicated the presence of a broad low pressure circulation in the central Indian Ocean, near the western edge of the Australian region.

[152] Situated approximately 305 km (190 mi) southwest of the Sumatran coastal city of Bengkulu, the system was located within the area of responsibility of TCWC Jakarta, who classified it as a tropical depression.

[154] Citing a favourable environment for intensification, including very low vertical wind shear, anomalously warm sea surface temperatures and a good poleward outflow channel, the JTWC issued a Tropical Cyclone Formation Alert for the system on 5 May.

[153] The areas were warned to expect moderate to heavy rainfall and strong winds, as well as wave heights reaching 4 m (13 ft) in Indian Ocean waters off the south coast and in the Sunda Strait.

[161] Environmental conditions were assessed as favourable for tropical cyclogenesis by Météo-France and the JTWC, with warm sea surface temperatures, low vertical wind shear, sufficient moisture in the mid troposphere, and a good poleward outflow channel.

[168] Due to the potential of the tropical low to generate for moderate to heavy rainfall, TCWC Jakarta issued an extreme weather warning for the southwestern coast of Sumatra and the westernmost part of Java on 21 May.

[177] Late on 6 February, the BOM noted that a tropical low had developed within a low-pressure trough near the Australian region's western border, approximately 200 km (120 mi) west of the Cocos Islands.

Later in 2020, the Bureau of Meteorology retired the names Damien and Harold, replacing them and Declan and Heath respectively due to the damage caused by both systems in Western Australia and the South Pacific respectively.