Difference in Cyclones

Tropical Cyclones

• As their name implies, tropical cyclones form in the tropics. Tropical cyclones obtain their energy from warm ocean waters above 26.5 degrees Celsius (80 degrees Fahrenheit). Unlike some other types of cyclones, tropical cyclones do not have warm or cold fronts associated with them, but they do contained thunderstorms, bands of rain, and a definitive pattern of wind circulation. Tropical cyclones may be called by different names, depending on their location and intensity. In the Atlantic and eastern Pacific, they are known as hurricanes, tropical storms and tropical depressions. In the northwestern Pacific, they are called typhoons or super-typhoons, while in the Indian Ocean and southwestern Pacific, they are known simply as cyclones. Hurricanes have sustained winds of at least 119 kilometers per hour (74 miles per hour); tropical storms possess winds between 63 kilometers to 119 kilometers per hour (39 and 74 miles per hour), while the name tropical depression is given to tropical disturbances with winds below 63 kilometers per hour (39 miles per hour).

Mid-Latitude Cyclones

• Also known as extratropical cyclones, mid-latitude cyclones are associated with cold and warm fronts. They have a clearly-defined life cycle which plays out over the course of several days. Mid-latitude cyclones play an important role in balancing heat energy throughout the Earth, by moving warm air toward the poles and cooler air toward the equator. Mid-latitude cyclones, as the name suggests, are found in the Earth̵7;s middle latitudes, between approximately 30 and 55 degrees. There is a substantial size difference between tropical cyclones and mid-latitude cyclones. Tropical cyclones range from 200 to 1,000 kilometers (124 to 621 miles) in diameter, while mid-latitude cyclones are much larger, with diameters between 1,500 and 5,000 kilometers (932 and 3,107 miles). Extratropical cyclones also differ from tropical cyclones in that their strongest winds are approximately 12 kilometers (8 miles) high in the atmosphere, while the strongest winds of tropical cyclones occur near ground level. Unlike tropical cyclones, there is no wind speed scale for extratropical cyclones ̵1; they can be of any intensity. Some, such as what are called Northeasters, can be extremely intense and hurricane-like, while others are relatively mild.

Subtropical Cyclones

• Subtropical cyclones are a hybrid of tropical and extratropical cyclones. They occur in latitudes from the equator to about 50 degrees north or south. Subtropical cyclones develop over warm water underneath a colder, high-level low pressure system. Unlike mid-latitude cyclones, subtropical cyclones cannot develop over land or cool water. Like tropical cyclones, they have sustained winds, but they don̵7;t reach hurricane force. There is, however, a wind speed scale for measuring subtropical cyclones. Subtropical cyclones with sustained winds less than 63 kilometers per hour (39 miles per hour) are known as subtropical depressions, while subtropical cyclones with winds between 63 and 119 kilometers per hour (39 and 74 miles per hour) are called subtropical storms. Unlike mid-latitude cyclones, subtropical storms are given names, such as Subtropical Storm Gustav. Subtropical cyclones can occasionally transform into tropical cyclones, or vice versa.

Mesoscale Cylones

• Mesoscale cyclones, known as mesocylones for short, exist on a much smaller scale than tropical, mid-latitude or subtropical cyclones. Mesocyclones typically consist of rotating storms about 3 to 10 kilometers (2 to 6 miles) in diameter. Mesocylones can form ahead of a cold front when a change in wind direction and speed with height creates a horizontally rotating column of air. Updrafts into the developing thunderstorm change the orientation of the rotating air column from horizontal to vertical. Meteorologists can spot this rotation on Doppler radar. Often associated with supercell thunderstorms, mesocyclones may spawn funnel clouds, tornadoes or waterspouts. Known for their ferocious winds, the wind speeds of the strongest tornadoes can reach over 322 kilometers per hour (200 miles per hour), while even the weakest tornadoes have minimum wind speeds of 105 kilometers per hour (65 miles per hour). Unlike tropical and subtropical cyclones, tornadoes most frequently form over land. Mesocylones in general don̵7;t last nearly as long as the other types of cyclones. A typical life cycle completes itself within a matter of hours.