What are the favorable environmental conditions that must be in place before a tropical cyclone can form?
There are several favorable environmental conditions that must be in place before a tropical cyclone can form. They are:
1 . Warm ocean waters (at least 80°F / 27°C) throughout a depth of about 46 m.
2 . An atmosphere which cools fast enough with height such that it is potentially unstable to moist convection.
3 . Relatively moist air near the mid-level of the troposphere (4,900 m).
4 . Generally, a minimum distance of at least 480 km from the equator.
5 . A pre-existing near-surface disturbance.
6 . Low values (less than about 23 mph / 37 km/h) of vertical wind shear between the surface and the upper troposphere. Vertical wind shear is the change in wind speed with height.
Why tropical cyclones in the South Atlantic and South Eastern Pacific regions are extremely rare?
Tropical cyclones in the South Atlantic and South Eastern Pacific regions are extremely rare . Reasons behind non formation of tropical cyclones in the South Atlantic and South Eastern Pacific regions are:
1 . Very strong vertical wind shear in the troposphere is considered a deterrent.
2 . The Intertropical Convergence Zone moves one to two degrees south of the equator, not far enough from the equator for the Coriolis force to significantly aid development.
3 . Water temperatures in the tropics of the southern Atlantic are cooler than those in the tropical north Atlantic.
Thus, strong wind shear as well as a lack of weather disturbances favorable for development of cyclones in the South Atlantic Ocean, make any strong tropical system extremely rare.
Hurricane Catarina in 2004 is the only recorded South Atlantic hurricane in history.
Tropical Cyclone Formation Basins
Why warm water is regarded as one of the most important factor for the formation of tropical cyclone?
The warm water is one of the most important keys as it is water that powers the tropical cyclone. As water vapor (water in the gaseous state) rises, it cools.
This cooling causes the water vapor to condense into a liquid we see as clouds. In the process of condensation, heat is released.
This heat warms the atmosphere making the air lighter still which then continues to rise into the atmosphere. As it does, more air moves in near the surface to take its place which is the strong wind we feel from these storms.
Therefore, once the eye of the storm moves over land it will begin to weaken rapidly, not because of friction, but because the storm lacks the moisture and heat sources that the ocean provided.
This depletion of moisture and heat hurts the tropical cyclone’s ability to produce thunderstorms near the storm center. Without this convection, the storm rapidly diminishes.
Must read: Why cyclones hit the east coast of India often in October?
External link: https://www.britannica.com/science/tropical-cyclone/Location-and-patterns-of-tropical-cyclones
PRACTICE QUESTIONS
QUES 1 . In the South Atlantic and South Eastern Pacific regions in tropical latitudes, cyclone does not originate. What is the reason? UPSC PRELIMS 2015
(a) Sea Surface temperature are low
(b) Inter Tropical Convergence Zone seldom occurs
(c) Coriolis force is too weak
(d) Absence of land in those regions
Ans: (a) Sea Surface temperature are low
