Refer to figures.

TROPICAL REVOLVING STORMS (TRS). Are thermal depressions that develop over warm tropical oceans (wind speeds in excess of 33 kts). When they sustain wind speeds greater than 63 kt, they are designated tropical cyclones. TRS generate their power and energy from the release of large amounts of latent heat from moisture they have gained over the warm seas.

In the northern hemisphere (NH), conditions on the right-hand side of storms are more severe than those on their left-hand sides. For that reason, in the NH, Right-hand semicircle (RHSC) is called the “dangerous semicircle” and Left-hand semicircle (LHSC) is called the “navigable semicircle”.

1. Dangerous semicircle— It is the side of a tropical cyclone, which lies to the right of the direction of movement of the storm in the Northern Hemisphere (to the left in the Southern Hemisphere), where the storm has the strongest winds (The wind speed in the RHSC will be the sum of the cyclonic wind and the speed of the storm travel).
2. Navigable semicircle — It is the side of a tropical cyclone, which lies to the left of the direction of movement of the storm in the Northern hemisphere (to the right in the Southern Hemisphere), where the winds are weaker and better for the navigation purpose, although all parts of TRS are more or less dangerous to mariners.