Vaianu ultimately peaked with winds corresponding to Category 1 status on the Saffir-Simpson Hurricane Scale, and passed between Fiji and Tonga.

Late on February 9, the Regional Specialized Meteorological Centre (RSMC) in Nadi, Fiji reported that Tropical Depression 12F had developed within a convergence zone which was located about 140 km (87 mi) to the northeast of Vanua Levu.

[4] At the time of being upgraded to a cyclone, Vaianu was situated about 190 km (120 mi) to the northwest of Vavaʻu, a Tonga island chain.

[3] RSMC Nadi assessed the storm as having peaked slightly later, with 10-minute winds of 130 km/h (80 mph), which made it a Category 3 severe tropical cyclone.

Beginning to accelerate, Vaianu entered the area of responsibility of the Tropical Cyclone Warning Centre in Wellington, New Zealand.

[4] It curved southeastward and slowly deteriorated due to increasing wind shear and colder sea surface temperatures.

[1] At 0600 UTC, the JTWC classified it as extratropical,[3] but it remained a powerful storm system for several days as it tracked over the open ocean.