Tropical Storm Pena has become the first tropical storm to form in the Central Pacific during November since 1982, in another sign of an exceptionally active Pacific hurricane season fuelled by a strengthening El Nino. Fox Weather reported that Pena formed south of Hawaii on Friday, with sustained winds reaching 50 mph as it moved west-northwest across the Central Pacific.

The storm was churning more than 550 miles south-southeast of Hawaii and is forecast to remain well south of the islands, according to the National Hurricane Center, which was issuing advisories on Pena on Sunday. A broad area of high pressure to the north is steering the storm generally westward, keeping its forecast track away from Hawaii.

Forecasters say Pena could strengthen into a hurricane next week, which would make it the season's 14th hurricane, although the National Hurricane Center's latest discussion notes considerable uncertainty, with some models showing it remaining a weak tropical storm or degenerating into a trough of low pressure. The last time a tropical storm formed in the Central Pacific in November, in 1982, the Pacific was experiencing one of the strongest El Nino events on record.

El Nino, the warming of waters in the equatorial Pacific, has helped fuel a hyperactive season across the basin, which has already produced 24 named storms, including 13 hurricanes and 10 major hurricanes. The US National Oceanic and Atmospheric Administration expects Super El Nino conditions to take hold later this autumn or winter.

The Eastern Pacific hurricane season officially ends on 30 November, but tropical cyclones can develop whenever oceanic and atmospheric conditions remain favourable. The Hurricane Center is also monitoring a separate area of low pressure just offshore of Nicaragua, which could bring heavy rain to parts of Central America even though its chance of developing is low.