Cyclone Meena is moving towards the southern Cook Islands group and continuing to intensify.
Forecasters at the Regional Specialised Meteorological Centre, at Nadi Airport in Fiji, say the cyclone is moving southeast towards Rarotonga at about 10 knots.
The forecasters expect sustained winds of 150 kilometres per hour close to the eye-wall of Cyclone Meena, and phenomenal seas.
They say this will increase to a sustained 170 kilometres per hour in the next 12 to 24 hours.
The US Joint Typhoon Warning Centre based in Pearl Harbour in Hawaii says Cyclone Meena may now be producing a significant wave height of eleven metres.
Satellite pictures show a huge vortex of cloud south of Suwarrow in the northern Cook Islands group.