Final answer:
A mesocyclone is a rotating updraft within a supercell thunderstorm, not to be confused with tropical cyclones or hurricanes. It plays a key role in the formation of tornadoes by transitioning horizontal rotation caused by wind shear into vertical rotation. The correct answer is option b.
Step-by-step explanation:
A mesocyclone is b. a rotating updraft within a supercell thunderstorm. Supercell thunderstorms are known for their severe weather, which includes the potential for tornadoes. Tornadoes can exhibit rotational motion, originating from mesocyclones. These intense rotating updrafts are usually about four miles across. The horizontal rotation is often caused by wind shear, which is a difference in wind speeds at different altitudes. For instance, the stronger cold winds higher in the atmosphere from the jet stream and the weaker winds from the Gulf of Mexico can cause the rotation to shift from horizontal to vertical, potentially leading to tornado development.
The term 'mesocyclone' does not refer to tropical cyclones or hurricanes, which are large storm systems characterized by low pressure centers, strong winds, and heavy rains, developing over warm ocean waters and driven by the Coriolis force.