Severe Tropical Cyclone Sina was the only named tropical cyclone to develop within the South Pacific basin during the 1990–91 season. The system was first noted as a shallow depression within the South Pacific Convergence Zone to the west of Wallis Island. Over the next three days the system moved towards the west-northwest, before it was named Sina during November 24, after it had developed into a tropical cyclone. Over the next couple of days the system intensified further and developed an eye feature as it erratically moved towards Fiji. Sina subsequently peaked in intensity during November 26, before the system passed through the Fijian Islands over the next two days as it started to gradually weaken. Sina subsequently passed just to the north of Tongatapu in Tonga during November 29,