The proper characterisation of the turbulence structure in an astronomical site requires an statistical study of the refractive-index structure constant Cn2(h). Our team is monitoring the Cn2(h) profiles since 2002 at the Teide and Roque de los Muchachos observatories (Canary Islands, Spain) with the g-SCIDAR technique. We have compared the turbulence profiles obtained with the radiosonde simultaneous profiles and with the NCEP I reanalysis maps at different levels. We show that turbulence measured at both observatories (being at 160km distant) correlate with the radiosonde data and may be explained through the atmospheric conditions in a synoptical scale. Hence, the statistical predominance of synoptical scaled phenomena may explain the similarity found in the monthly average profiles obtained at both observatories.