The probability of occurrence of rogue waves in wind-generated fields is investigated experimentally in an annular wind-wave flume. Unlike many experiments on rogue waves, where waves are mechanically generated, here the wave field is forced naturally by wind as it is in the ocean. The peculiar geometry of the flume makes waves propagating circularly in an unlimited-fetch condition. Water surface elevation was measured at specific cross-sections under the effect of different wind speeds to monitor the temporal evolution of the wave field. Results show that the kurtosis of the surface elevation, the fourth order moment of the probability density function and a measure of the percentage of extremes in a wave record, gradually increases in time with the evolution of the wave field. Deviations from Normal statistics are observed to be a function of wind speed. The maximum departure from Normality resembled the one induced by quasi-resonant wave-wave interactions and it is observed at the final stage of wave growth and immediately before reaching the fully development regime.

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