Once a new supervisor is added, the next obvious step would be to rebalance the topologies, which are executed on the cluster so that the load could be shared across to the newly added supervisor.
Rebalance option is available on the Nimbus UI where you can choose the topology that is to be rebalanced, and then use the option from the GUI. The topology drains as per the specified time-out. During that duration, it stops accepting any messages from the spout and the ones in the internal queues are processed and once completely clear, the workers and tasks are redistributed. The user also has option to increase or decrease the parallelism for various bolts and spouts using the rebalance options. The following screenshot describes how to rebalance a topology using the Storm UI options:
