Interaction With Other Atmospheric Features

Tropical cyclones thrive in warm, moist, and homogenous (uniform) environments, which are typically found in the tropics of the Earth between 23 degrees North and 23 degrees South around the Equator. Once tropical cyclones drift poleward due to their internal dynamics, they will begin to encounter mid-latitude systems, which introduce features such as cold fronts and warm fronts. These features are harmful for tropical cyclone development because they bring different air masses which may introduce colder and/or drier air to the tropical cyclone.

Vertical wind shear, or winds changing direction and speed with height, is also a limiting factor for tropical cyclone development. Wind shear values over 20 knots will prevent hurricanes from strengthening, or may even cause them to weaken, as the circulation around the tropical cyclone is disturbed by the changing winds with height. Mid-latitude systems often bring large amounts of wind shear, which can also be damaging for tropical cyclones.

The combination of fronts and wind shear from mid-latitude systems, as well as cooler sea surface temperatures closer to the poles, typically result in tropical cyclones weakening or dissipating as they leave the tropics region of the Earth.

Within the tropics are usually light surface winds from the east called trade winds. The trade winds typically steer young tropical cyclones toward the west in the early stages of their life cycle. As the tropical cyclones mature, they begin to drift towards the poles of the Earth (towards the north in the Northern Hemisphere and towards the south in the Southern Hemisphere). Within the mid-latitudes, there is usually a strong jet stream of upper-level winds moving west to east, which will begin to steer tropical cyclones back toward the east as they move into the mid-latitudes.