The storm, codenamed Ernest, was out at sea some 110 kilometers (65 miles) southwest of the coastal town of Tulear, said Hubert Andriamparison of the Madagascar weather service.
He said the weather service expected to be able to lift a storm alert within the next 24 hours, as the storm was not expected to make a landfall. The cyclone was causing winds of some 155 kilometers (95 miles) an hour, with gusts of up to 215 kilometers (130 miles) an hour.
In February and March last year two tropical cyclones wreaked havoc in parts of Madagascar, causing 29 and 241 deaths respectively.