What is the fine-grained topic of the following text: The strong southward flow due to the cyclone resulted in a complete nullification of a flood current and continued the net flow towards south for approximately 18 h. This enhanced the ebb flow by about 0.12 m/s off Worli and 0.16 m/s off Satpati. Only return the topic.
Impact of cyclone on current flow and net flow pattern.