The cyclone was located at about 375km southwest of Malekula at 5am (local time).
Winds close to the centre of the system are estimated at 110km/hr.
Damaging gale force winds of 75km/hr gusting up to 105km/hr within 30 nautical miles from its centre.
Heavy rainfall and flash flooding are expected over low lying areas and areas close to river banks including flooding over the group.
TC Lucas is moving to the southwest of Vanuatu towards New Caledonia's Loyalty Islands.
Photo Fiji Met