. Compendium of meteorology. Meteorology. Fig. 8.—Continued The height of the hurricane season is reached in the first half of September. During this period many still develop in the Cape Verde region. During the last half of the month the area of most frequent origin shifts back to the southwestern Atlantic and storms again develop strong northerly components as the polar westerlies move southward. October continues to have a large number of tropical storms but the frequency and average intensity decline rapidly after mid-October. All have strong northerly components and recurve quickly. Many
. Compendium of meteorology. Meteorology. Fig. 8.—Continued The height of the hurricane season is reached in the first half of September. During this period many still develop in the Cape Verde region. During the last half of the month the area of most frequent origin shifts back to the southwestern Atlantic and storms again develop strong northerly components as the polar westerlies move southward. October continues to have a large number of tropical storms but the frequency and average intensity decline rapidly after mid-October. All have strong northerly components and recurve quickly. Many develop in the western Caribbean north of Panama and move northward across Cuba. Rarely do they reach as far west as Texas. November is an unimportant hurricane month. The few storms mostly develop in the Carribbean and move northward immediately. The stronger northerly components in the early and late portions of the tropical cyclone season and the more westerly component during the middle of the season are characteristic of all areas with the possible exception of the Bay of Bengal and the Arabian Sea. Of course, many exceptions to the mean tracks occur, depending upon the mean position of polar troughs which influence recurvature. Steering Currents. The direction and rate of move- ment of a tropical cyclone are dependent upon the direction and speed of the air in which the storm is imbedded. There is no physical basis for believing the current at any single level is responsible for steering a storm, but Norton, Riehl, and others have found that the winds at or just above the top of the warm lower cell of the storm, where the vortical circulation vir- tually disappears, best approximate the direction of movement of the storm. This level will vary in indi- vidual storms from 20,000 ft to 30,000 ft or higher. It has been noted that most storms appear to have some deflection to the right of the steering current. The angle varies with the speed of movement of the storm, being
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