Bring an umbrella next month: Chinese scientists claim they can forecast rain weeks in advance

A new weather forecasting model developed by Chinese researchers purports to detect heavy rainstorms weeks before they take place, challenging the "butterfly effect" thought to make such prediction impossible.

The scientists' algorithm can predict heavy rain up to 30 days in advance "without false alarm or omission", according to a paper published in the journal Advances in Atmospheric Sciences.

This should be impossible however, due to the "butterfly effect".

American meteorologist Edward Lorenz coined the term in 1961 in a key work on chaos theory. Lorenz showed how in an unpredictable and chaotic system such as weather, tiny events – like the flapping of a butterfly's wings – can have dramatic effects, such as a hurricane.

Under Lorenz's theory, no accurate weather forecast can be made more than two weeks in advance, because tiny disturbances can quickly lead to major fluctuations in weather patterns, throwing the predictions off.

With the rapid increase in computing power and data gathering capability – helped in part by global research on climate changes – scientists have hoped to overcome Lorenz's problem and extend weather forecasting to weeks and even months.

Bigger and bigger super computers have been employed to run larger and larger models, but so far efforts have largely been in vain.