Tropical cyclone Kofi, a category one system, is passing Tonga's southern islands, bringing damaging gale force winds.
The Metservice in Nadi says the cyclone has winds of 75 kilometres an hour close to its centre, but they are increasing to 90 kilometres an hour.
The system has been moving in a south-easterly direction on a track to pass about 50 kilometres west of the capital, Nuku'alofa.
By this afternoon, the storm is expected to be about 180 kilometres south-southeast of Nuku'alofa.
A gale force warning remains in force for the Ha'apai and Tongatapu group.
