Beta drift
In addition to environmental steering, a tropical cyclone will tend to drift poleward and westward, a motion known as "beta drift". This motion is due to the superposition of a vortex, such as a tropical cyclone, onto an environment in which the Coriolis force varies with latitude, such as on a sphere or beta plane. The magnitude of the component of tropical cyclone motion associated with the beta drift ranges between 1–3 m/s (3.6–10.8 km/h; 2.2–6.7 mph) and tends to be larger for more intense tropical cyclones and at higher latitudes. It is induced indirectly by the storm itself as a result of feedback between the cyclonic flow of the storm and its environment.Physically, the cyclonic circulation of the storm advects environmental air poleward east of center and equatorial west of center. Because air must conserve its angular momentum, this flow configuration induces a cyclonic gyre equatorward and westward of the storm center and an anticyclonic gyre poleward and eastward of the storm center. The combined flow of these gyres acts to advect the storm slowly poleward and westward. This effect occurs even if there is zero environmental flow. Due to a direct dependence of the beta drift on angular momentum, the size of a tropical cyclone can impact the influence of beta drift on its motion; beta drift imparts a greater influence on the movement of larger tropical cyclones than that of smaller ones. Multiple storm interaction
A third component of motion that occurs relatively infrequently involves the interaction of multiple tropical cyclones.
In 2003, the Atlantic hurricane reanalysis project examined and analyzed the historical record of tropical cyclones in the Atlantic back to 1851, extending the existing database from 1886.Before satellite imagery became available during the 20th century, many of these systems went undetected unless it impacted land or a ship encountered it by chance. Often in part because of the threat of hurricanes, many coastal regions had sparse population between major ports until the advent of automobile tourism; therefore, the most severe portions of hurricanes striking the coast may have gone unmeasured in some instances. The combined effects of ship destruction and remote landfall severely limit the number of intense hurricanes in the official record before the era of hurricane reconnaissance aircraft and satellite meteorology. Although the record shows a distinct increase in the number and strength of intense hurricanes, therefore, experts regard the early data as suspect. The ability of climatologists to make a long-term analysis of tropical cyclones is limited by the amount of reliable historical data. During the 1940s, routine aircraft reconnaissance started in both the Atlantic and Western Pacific basin during the mid-1940s, which provided ground truth data, however, early flights were only made once or twice a day. Polar-orbiting weather satellites were first launched by the United States National Aeronautics and Space Administration in 1960 but were not declared operational until 1965.