The fact that wind patterns are coherent over large regions means wind power intensity is similar in whole countries. In particular wind generation falls to near zero frequently over whole countries and whole regions of Europe.
Although everybody knows wind fluctuates dramatically in one location, it seems to be a common belief that local lulls are compensated by generation somewhere else in the country so that overall wind generation stays high. This is not in reality the case and this page gives extensive plots as evidence for this.
(Generation data averaged over 1 day)
it can be seen that the correlations between onshore and offshore wind are very high for small countries (Denmark and Belgium) and lower but still very significant for larger countries (United Kingdom and Germany).
The correlation increases for averages over longer periods so the short distance plots above have averages over 1 day while those below have averages over 3 days. While the longer term averages increase the overall correlation the fraction of points wth nearly zero wind generation is reduced.
(Generation data averaged over 3 days)
Table of Pearson Correlation Coefficients for wind generation between countriesThe table shows the correlation between wind generation is high between neighbouring countries and decreases with increasing geographic separation.
These strong correlations mean that exchanges between adjacent countries cannot use wind electricity because the peaks and valleys are the same.