These dates conventionally delimit the period of each year when most tropical and subtropical cyclones form in the basin, which is west of 90°E and south of the Equator.

Tropical and subtropical cyclones in this basin were monitored by the Regional Specialised Meteorological Centre in Réunion, though the Joint Typhoon Warning Center issued unofficial advisories.

On the evening of July 17, RSMC La Réunion initiated warnings on the storm after a scatterometer pass revealed 75 km/h (45 mph) winds.

[5] The small system briefly attained severe tropical storm strength the next day as a low-level eye developed.

[2][6] Abela began to weaken quickly in the subsequent hours as it moved into a region with cool sea surface temperatures and low oceanic potential.

[24][19] The origins of Dineo can be tracked back to a cluster of thunderstorms that organized into an area of low pressure in the Mozambique Channel on February 11.

Over the next two days, the system gradually drifted in a generally southern track as it gained intensity and prompted the JTWC to issue a TCFA.

[38] A monsoon trough started to persist west of Diego Garcia in late February 2017 as the Madden–Julian oscillation (MJO) over the Indian Ocean grew more noticeable.

[39] On 2 March, a zone of disturbed weather formed within the area, although it was initially difficult to define a clear centre;[40] later, the Joint Typhoon Warning Center (JTWC) issued a Tropical Cyclone Formation Alert for the improving low-level structure and favourable environmental conditions.

[44] Enawo developed into a severe tropical storm at around 18:00 UTC on 4 March, for showing an impressive embedded centre pattern associated with extremely cold cloud tops.

[45] Enawo formed a ragged eye soon thanks to favourable conditions of excellent outflow, weaker vertical wind shear, and warm sea surface temperatures;[46] however, the strengthening phase was halted for a half of day owing to a possible eyewall replacement cycle.

[47] Enawo started to intensify again and developed a well-defined eye indicated by both of satellite and microwave imageries, prompting Météo-France upgrading the system to an intense tropical cyclone at 12:00 UTC based on the structural improvements.

[48] Enawo reached its peak intensity at 06:00 UTC on 7 March, with ten-minute maximum sustained winds at 205 km/h (125 mph) and the central pressure at 925 hPa (27.32 inHg).

[50] The cyclone started to rapidly weaken due to land interaction with a cloud-filled eye and the warming cloud tops;[51] the JTWC also issued a final warning later for the inland movement.

[54] As the low-level circulation center (LLCC) became more consolidated and bands of convection improved, the JTWC issued a TCFA for the system;[55] and less than three hours later, RSMC La Réunion began tracking it as a tropical depression.

[61] RSMC La Réunion first reported the post-tropical nature of Fernando on March 15 at 00:00 UTC while the central pressure continued to drop.

[63] During May 30, the Australian Bureau of Meteorology started to monitor Tropical Low 31U, which had developed about 2,000 km (1,245 mi) west of Jakarta, Indonesia.

[64] Over the next few days, the system moved southwestwards and was classified as an area of low pressure by RSMC La Réunion, before it started to fill up and dissipated on June 2.