Online Weather Generator report 5
Limitations of the Weather Generator include that it does not simulate some extremes well; and does not give spatial consistency across grid squares. It also assumes that the observed relationships between weather variables will remain the same in the future.
The Weather Generator outputs are subject to a number of limitations which must be borne in mind when using them. The most important of these are outlined here, and expanded upon further in the Annex and in the UKCP09 User Guidance.