Question

how are cyclones formed in sea

Answer 1

It is caused by a combination of strong winds driving water onshore and the lower atmospheric pressure in a tropical cyclone. In the southern hemisphere the onshore winds occur to the left of the tropical cyclone's path.

Answer 2

Only tropical cyclones that form over the Atlantic Ocean or eastern Pacific Ocean are called "hurricanes." Whatever they are called, tropical cyclones all form the same way. Tropical cyclones are like giant engines that use warm, moist air as fuel. That is why they form only over warm ocean waters near the equator.