Warning and errors in the simulations

[Andel]

Hi PVsyst,

I made simulation for one Grid-connected PV system that we are planning to install it. In the report there is warning and error message as follow: 

*** Warnings during the initialization:
Initialization;The clearness index of the best clear days seems high with respect to the clear day model.
You can check the values using the "Best clear days Ktcs" graph.
The clearness index of the best clear days seems high with respect to the clear day model.
You can check the values using the "Best clear days Ktcs" graph.

Can you give me an brief explanation what does it this message mean?

Is related to PVsyst itself or Should I modify something to avoid this message?