1.
Conditions for the Formation of Tropical Depressions
Tropical depressions can form and develop into typhoons when the following conditions are met in tropical regions.
2.
Sea Surface Temperature
They form overseas with a temperature of at least 26–27°C. Since the source of energy is the latent heat released as air rises, tropical depressions are more likely to form over warm seas with abundant moisture sources. Therefore, tropical depressions do not form over regions with low sea surface temperatures like the South Atlantic or the eastern South Pacific.
3.
Coriolis Effect
They form in regions where the Coriolis effect operates. The Coriolis effect is absent at the equator and increases towards the poles. Therefore, tropical depressions do not form in regions below 5 degrees latitude, where there is little rotational force.
4.
Intertropical Convergence Zone and Trade Wind Waves
They form in regions between 5 and 25 degrees latitude, in the Intertropical Convergence Zone (ITCZ), or in the regions with trade wind waves. These areas are conducive to the formation of cumulonimbus clouds, which can serve as the seeds of tropical depressions. Regions where the ITCZ and trade wind waves overlap provide even more favorable conditions for cumulonimbus development due to their interaction.
5.
Low Wind Shear
They form in regions where there is a small difference in wind speed between the upper and lower levels. This is because the latent heat released as cumulonimbus clouds develop must be allowed to rise upward without being displaced by strong upper-level winds. If strong upper-level winds are present, they can push the clouds away, weakening the upward force and inhibiting further development.