Most hurricanes originate within the doldrums, a narrow equatorial belt characterized by intermittent calms, light variable breezes, and frequent squalls, and lying between the northeast and southeast trade winds. As the doldrums of the Atlantic are situated largely to the north of the equator, hurricanes do not occur in the South Atlantic Ocean. The low-pressure center develops when the warm, saturated air prevalent in the doldrums is underrun and forced upward by denser, cooler air. From the edge of the storm toward its center, the atmospheric pressure drops sharply and the wind velocity rises. The strength of a hurricane is rated from 1 to 5.
Hurricanes generally move in a path resembling the curve of a parabola.
In the northern hemisphere the storms usually travel first in a northwesterly direction and in the higher latitudes turn toward the northeast. In the southern hemisphere the usual path of the hurricane is initially to the southwest and subsequently to the southeast. Hurricanes travel at varying rates. Those areas in which the hurricane winds blow in the same direction as the general movement of the storm are subjected to the maximum destructive violence of the hurricane. Since 1943 U.S. military aircraft have been flying into hurricanes to measure wind velocities and directions, the location and size of the eye, the pressures within the storms, and their thermal structure.