The first four disturbances in the season developed in the northeastern portion of the basin in association with a near-equatorial trough, but failed to develop due to wind shear.

At the beginning of September 2005, the ITCZ was active in the northeastern portion of the basin, accompanied by a small circulation and scattered convection.
Located in the presence of strong wind shear, the circulation was exposed from the convection, a sign of unfavorable conditions.
However, warm waters fueled an increase in convection, and the MFR classified the system as Tropical Disturbance 1 on September 5.
That day, the JTWC issued a TCFA, but continued shear caused weakening as the disturbance tracked southeastward.
By September 8, the MFR had discontinued advisories on the system, after the circulation had become exposed.
After turning to the west-northwest, the circulation began dissipating on September 12.

The second disturbance was first classified by the MFR on October 12 about 1,575 km (980 mi) east of Diego Garcia.
The system had enough of a circulation and associated convection, and proceeded southwestward for its duration.
After the convection consolidated more and developed curved rainbands, the MFR upgraded the system to a 55 km/h (35 mph) tropical depression on October 14.
This period of organization occurred during a brief decrease in wind shear.
At 12:00 UTC on October 14, the JTWC classified the system as Tropical Cyclone 01S, estimating peak 1 minute winds of 75 km/h (45 mph).
Increasingly unfavorable conditions caused the convection to diminish.
Late on October 15, both the JTWC and MFR discontinued advisories due to the increasing disorganization of the disturbance.
The circulation remained well-organized but devoid of convection, and the MFR last monitored the center on October 21.

Tropical Depression Three formed on November 6 while east-southeast of Diego Garcia; it moved generally southward, reaching peak winds of 55 km/h (35 mph) before dissipating on November 8.
Simultaneous to the depression was Tropical Depression Four, which entered the basin on November 7 from the Australian region, and was also classified by the JTWC as Tropical Cyclone 02S with winds of 65 km/h (40 mph).
The depression was weakening at the time, and both the JTWC and MFR discontinued advisories on November 8.

On December 21, the BoM began monitoring a tropical low in the western portion of the Australian basin, which had moved eastward from the south-west Indian Ocean basin.
The system moved southwestward and later to the southwest, once again crossing 90º E and causing the MFR to designate it Tropical Depression 6.
At the time, the circulation was partially exposed from the convection, although it organized over the next day.
This spurred the JTWC to designate it as Tropical Cyclone 04S on December 24 with winds of 65 km/h (40 mph).
As with other systems in the season, strong shear caused the system to weaken; the JTWC discontinued advisories on December 25, and the MFR followed suit the next day.
However, the system continued to the southwest, reorganizing enough on December 27 for the MFR to reissue advisories.
Shear again weakened the convection, and the MFR discontinued advisories again on December 29 while the system was a short distance west-northwest of Rodrigues.

Tropical Disturbance 12 briefly was classified by the MFR on March 4, located 620 km (385 mi) north of the developing Tropical Storm Diwa.
The disturbance moved quickly to the southeast around Diwa's circulation, and was ultimately absorbed by the larger storm.
The first four disturbances in the season developed in the northeastern portion of the basin in association with a near-equatorial trough, but failed to develop due to wind shear.
At the beginning of September 2005, the ITCZ was active in the northeastern portion of the basin, accompanied by a small circulation and scattered convection. Located in the presence of strong wind shear, the circulation was exposed from the convection, a sign of unfavorable conditions. However, warm waters fueled an increase in convection, and the MFR classified the system as Tropical Disturbance 1 on September 5. That day, the JTWC issued a TCFA, but continued shear caused weakening as the disturbance tracked southeastward. By September 8, the MFR had discontinued advisories on the system, after the circulation had become exposed. After turning to the west-northwest, the circulation began dissipating on September 12. 
The second disturbance was first classified by the MFR on October 12 about 1,575 km (980 mi) east of Diego Garcia. The system had enough of a circulation and associated convection, and proceeded southwestward for its duration. After the convection consolidated more and developed curved rainbands, the MFR upgraded the system to a 55 km/h (35 mph) tropical depression on October 14. This period of organization occurred during a brief decrease in wind shear. At 12:00 UTC on October 14, the JTWC classified the system as Tropical Cyclone 01S, estimating peak 1 minute winds of 75 km/h (45 mph). Increasingly unfavorable conditions caused the convection to diminish. Late on October 15, both the JTWC and MFR discontinued advisories due to the increasing disorganization of the disturbance. The circulation remained well-organized but devoid of convection, and the MFR last monitored the center on October 21.
Tropical Depression Three formed on November 6 while east-southeast of Diego Garcia; it moved generally southward, reaching peak winds of 55 km/h (35 mph) before dissipating on November 8. Simultaneous to the depression was Tropical Depression Four, which entered the basin on November 7 from the Australian region, and was also classified by the JTWC as Tropical Cyclone 02S with winds of 65 km/h (40 mph). The depression was weakening at the time, and both the JTWC and MFR discontinued advisories on November 8.
On December 21, the BoM began monitoring a tropical low in the western portion of the Australian basin, which had moved eastward from the south-west Indian Ocean basin. The system moved southwestward and later to the southwest, once again crossing 90º E and causing the MFR to designate it Tropical Depression 6. At the time, the circulation was partially exposed from the convection, although it organized over the next day. This spurred the JTWC to designate it as Tropical Cyclone 04S on December 24 with winds of 65 km/h (40 mph). As with other systems in the season, strong shear caused the system to weaken; the JTWC discontinued advisories on December 25, and the MFR followed suit the next day. However, the system continued to the southwest, reorganizing enough on December 27 for the MFR to reissue advisories. Shear again weakened the convection, and the MFR discontinued advisories again on December 29 while the system was a short distance west-northwest of Rodrigues.
Tropical Disturbance 12 briefly was classified by the MFR on March 4, located 620 km (385 mi) north of the developing Tropical Storm Diwa. The disturbance moved quickly to the southeast around Diwa's circulation, and was ultimately absorbed by the larger storm.
2005–06 South-West Indian Ocean cyclone season