Forecasters warn Tropical Cyclone Ian is now a category three storm as it moves towards Tonga.
Forecasters in Fiji are warning Tropical Cyclone Ian is again threatening Tonga.
Sanjay Prakash, a forecaster from the Fiji Meteorological service, told Pacific Beat the cyclone has become stronger in the last few hours.
"Ian has intensified, past six hours it's become a category three system," he said.
"It is expected to intensify further and probably reach its maximum intensity by tomorrow."
Mr Prakash says it is expected to move in a southeast ward direction and reach Tonga in the next 24 to 36 hours' time.
On its current track it may bring damaging gale force winds to Niuafo'ou in the next 12 to 24 hours and to Vava'u and Ha'apai in the next 24 to 48 hours.
"It will be at its peak during the time of the landfall, I expect it to be at maximum intensity on the category three stage, that is having a sustained wind speeds of close to 85 knots at its centre," Mr Prakash said.
He says the cyclone will be "catastrophic" and "bring a lot of damage to the kingdom".
Earlier this week, a cyclone alert was issued for the island groups of Ha'apai and Vava'u with warnings of gale force winds, heavy rain, squally thunderstorms and the risk of sea flooding.
The alert was cancelled yesterday.
However, both the Fiji Meteorological Service and the Tonga Meteorological Service have since issued new warnings on Wednesday.
Ian has been hovering in the ocean between Fiji and Tonga since Monday.
A tropical cyclone alert and wind warning has also been issued for the northernmost group of islands of Tonga, the Niuas.
The slow moving cyclone may also cause thunderstorms, rough seas and some flooding in other parts of Tonga on Friday.