Weatheria

Weatheria (ウェザリア, Wezaria) 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. The island itself appears to be floating on top of a large bubble. Nami was sent to this island by Bartholomew Kuma in the events in the Sabaody Archipelago.

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