DOUALA, Cameroon -- As Capt. Terry Palmer's airliner neared the international airport at this commercial hub in central Africa, the routine weather report he received from the tower indicated light rain and scattered clouds on the final approach.

"Instead, in the fading light I saw this huge black mass, like a twister just to the side of the runway heading. It was a waterspout, the top of which appeared to be significantly above our level," said Palmer, who was flying a Canadian-built DHC-6 twin turboprop from Cameroon's capital of Yaounde.

"If that had been at night and if we had flown into it, I wonder if we would have survived it," the New Zealander said.