Tropical cyclones usually require very warm water to depth , generally above NUMBER@1 ° C -LRB- NUMBER@2 ° F -RRB- extending to a depth of NUMBER@3 metres -LRB- NUMBER@4 ft -RRB- .

Tropical cyclones usually need sea surface temperatures above NUMBER@1 ° C -LRB- NUMBER@2 ° F -RRB- with a depth of NUMBER@3 metres -LRB- NUMBER@4 feet -RRB- to survive .
