Weatheria

Weatheria is an island in the White Sea in the sky. A scientific island floating in the sky, it is notable for the study of weather conditions as well as tools that can create various conditions, such as the Wind Knot. Nami was sent to this island by Bartholomew Kuma in the events in the Sabaody Archipielago.

Wind Knot
The Wind Knot is a magical rope that is tied three times. Untie one knot results in a light breeze. Untie a second knot brings a strong wind. Untie the last knot summons a squall.