Determine the valence intensity of the following tweet, considering the mental state of the author. Assign a real number between 0 and 1, where 0 denotes extremely negative and 1 denotes extremely positive.
Tweet: Completely blown away by @EvaNoblezada @alistairbrammer @JonJonBriones and the cast of @MissSaigonUK tonight. #fathomevents #speechless
0.677