Floating sensors that have predicted extreme weather events for decades and saved lives in the process have been left to "collapse" amid vandalism and US budget cuts.

The United States and Japan set up the Tropical Pacific Observing System - made up of about 70 buoys - after a large El Nino event in 1982-83 caught forecasters unaware. Fourteen years later, the moored devices helped provide warnings of the “super” 1997-98 El Nino almost a year before it hit, probably saving lives and preventing billions of dollars in damage.

Sensitive equipment: maintaining the TAO array.

But the performance of the moored devices, which take atmospheric readings and monitor conditions down to 500 metres below the sea's surface, has fallen to about 40 per cent since 2012, according to the the climate observation director of the US National Oceanic and Atmospheric Administration, David Legler.

That is affecting the ability of forecasters and climate modellers, including those in Australia, to predict extreme weather patterns.