Elayne, Nynaeve & crew must first locate a second "bowl of winds" in the white tower before being able to fix the weather. evidence: when searching for the bowl in tel. by need, they first jump to a storeroom in the tower. Also, in COS, (not sure of page #, but I remember the passage) a Sea Folk coin is described as bearing a picture of 2 bowls with a rainbow connecting them or something like that.