Changes in cyclone tracks and intensities

Because cyclones are influenced by large-scale air masses, they sometimes move along rather erratic paths. Cyclones are especially influenced by the strength and direction of upper level winds. As noted above, strong upper level winds create a vertical wind shear that cause the top of the cyclone to be sheared of and result in the loss of strength of the storm. The erratic nature of a hurricanes path often make it difficult to predict where and when it will make landfall prior to several hours before it actually does make landfall. In the lower latitudes, near the equator, cyclones generally are pushed by the westerly (easterly in Northern Hemisphere) trade winds and have storm center velocities that are relatively low (8 to 32 km/hr). As they move southward (northward in the Northern Hemisphere), storm center velocities generally increase to greater than 50 km/hr. If the cyclone encounters a low pressure trough between two high pressure centers, it is steered into the trough and follows it along a southwestward trend (northeastward in the Northen Hemisphere), increasing its velocity as it does so.

The amount of damage that occurs when a hurricane approaches a coast depends on the angle of approach.

Two extreme examples of Hurricanes illustrate this point.

A hurricane that moves along the coast has a coast-parallel hurricane track. From such a track extensive damage would occur along the coastline closest to the storm, with bands of lesser damage extending inland. Since this track (upper diagram) has the most intense winds offshore (on the right side of the hurricane), the coast would not feel the highest wind velocities. Thunderstorm activity associated with this track would be most severe on the northern side of the storm, since the spiral rain bands would be feeding off the moist air above the ocean.

A hurricane that approaches perpendicular to the coast has a coast-normal track. Such a storm would produce extreme damage all along the right-hand side of its track, with bands of decreasing damage occurring both to the left and right of the track. Furthermore, as the storm approached the coast areas to right hand side of the storm would receive the heaviest thunderstorm activity, since the rain bands would be feeding off the moist oceanic air.

Cyclones cross the Queensland coast most often in January, Februrary and March - a time that corresponds to the highest tides of the year. The combination of Storm Surges caused by the wind and pressure differences and high tides results in exceptionally hig water