PART V — SEVERE STORMS 



Figure V-1 — A HISTORY OF HURRICANE SEEDLINGS 



The diagram shows areas of formation and decay of hurricane seedlings during 

 1968. Although the African continent appears to be important in the development 

 of seedlings, some form in other parts of the Atlantic and the Caribbean. A hurri- 

 cane may develop from any of the seedlings. Surveillance and tracking is much 

 easier with satellites, but the question of why one seedling develops into a hurri- 

 cane and another does not remains unanswered. 



TROPICAL 

 STORMS 



Figure V-2 — HURRICANE BEULAH, 1967 

 BEULAH 



SEEDLINGS 



This cloud mosaic from September 18, 1967, shows Hurricane Beulah before it 

 struck the Texas coast. The mosaic was compiled from pictures taken on eleven 

 successive passes by the polar orbiting satellite, ESSA-3. Polar orbiting satellites 

 pass over a given area twice per day, once during daylight hours and once at night. 



logical satellites alone. Judicious de- 

 ployment of aircraft reconnaissance 

 is also required to probe the storm 

 center directly. The delicate balance 

 of forces that usually exists within 

 a hurricane and determines its destiny 

 can be measured only by direct sens- 

 ing, and the only practicable tool in 

 sight for this purpose is the recon- 

 naissance aircraft. 



Numerical Modeling — The prob- 

 lem of modeling numerically the 

 movement and development of hur- 

 ricane seedlings, and especially the 

 movement of full-blown hurricanes, 

 is more complicated than that of 

 modeling temperate-latitude frontal 

 storms. The large-scale temperate- 

 latitude storm derives its energy 

 mainly from the sinking of large 

 amounts of cold air, a process that 

 can be described in terms of tem- 

 perature contrasts on a scale of many 

 hundreds of miles. The tropical 

 storm, in contrast, develops in an 

 environment where lateral tempera- 

 ture constrasts are absent. 



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