Why do Cyclones form?

What causes cyclone to form

Cyclone itself it's a natural phenomenon. The key sources to form a  cyclone are warm water and moist air.

Initially the sunlight heat the water like as when we dip the electric heating coil to heat a bucket of water. Then the upper water surface of oceans get heated. The heated water will become less denser when compared to the beneath layer. so it will start to evaporate as Steam. Evaporating means it leaves it's original place.  When it leaves it's original place there will be a vacant place, so the remained water layers tries to occupy the vacant place. Like this the escaped water vapour creates a low pressure. By the virtue of diffusion the water and air transfer from higher pressure region to lower pressure region. When evaporated water has risen to upwards it cools down by surrounded air. And it will reach the maximum holding capacity of moisture in it, we can call it is as saturated water vapour thermodynamically. Saturated water vapour means when it reach the maximum holding capacity of moisture, if it exceeds is maximum holding capacity it will condensed into water again and precipitate water in the form of rain. This process only we are calling formation of clouds.

What causes cyclone to spin?

Usually the Cyclones form at equator and tropics which are near to the equator. Because the temperatures at equator are very high. 

Fig.1 Cyclone formation

When the low pressured water vapour rises upward the surrounded air started to the travel towards the low pressured region in the straight lines. But these straight air stream lines deflected towards left  to the straight paths due to CORIOLIS EFFECT.

What is CORIOLIS EFFECT

It's a hypothetical, imaginary and fictious effect. It's due to spin or rotation of the earth. Due to spin of the earth the currents or flow lines air around the globe deflected right in the northern hemisphere and left in the southern hemisphere.

 

Fig.2 Deflection of currents

Fig.3 Deflection of currents to the left and right corresponding to their hemispheres by coriolis effect

Due to this effect only wind blow too far distances during the cyclone hit the nearby coast

References

Wikipedia

https://oceanservice.noaa.gov/education/tutorial_currents/media/supp_cur04a.html

Eenadu Epaper

Engineering thermodynamics by cengel boles