Defining the limit Wei Zhang (left) on a visit to the NOAA Global Systems Division, where Zoltan Toth (right) worked at the time this study began. (Courtesy: Z Toth)"> Defining the limit Wei Zhang (left) on a visit to the NOAA Global Systems Division, where Zoltan Toth (right) worked at the time this study began. (Courtesy: Z Toth)

What will the weather be like tomorrow, or next week or, indeed, in a month’s time? Today’s numerical weather predictions can easily answer the first two parts of this question, but they fall short beyond about 14 days. New work on predictability limits by scientists at the University of Miami and the NOAA Cooperative Institute for Marine and Atmospheric Studies (CIMAS) say that this maximum could be extended to around 129 days – but probably no further. Whether this limit can be reached in practice, however, will depend on future improvements in forecasting technologies, they say.

Numerical weather prediction was developed in the late 1940s.…