PART V — SEVERE STORMS 



the data. No single radar monitored 

 the storm during the entire seeding 

 operation, and it was necessary to 

 use various radars to obtain a con- 

 tinuous time record of the eye area. 

 After considering the many prob- 

 lems of interrelating various radars, 

 calibrating ranges, distortions, etc., 

 one can only conclude that there is 

 some evidence that the seeding did 

 indeed affect the hurricane clouds 

 around the eye in the manner hy- 

 pothesized, but that the data are 

 of such a heterogeneous nature as to 

 be inconclusive in themselves. 



Pictures of Hurricane Debbie were 

 taken by ATS-3 each day of the 

 period, 17-21 August. Normally, 

 processed pictures do not reveal 

 much detail of the seeded areas. 

 Although enhanced pictures were 

 made along lines suggested by Fujita, 

 they have not yet been developed. 

 Work with a small sample of these 

 pictures suggests that we will obtain 

 some interesting information about 

 changes in the cloud structure of 

 the storm, though it is unlikely that 

 these pictures will be adequate for 

 determining with confidence whether 

 the seeding had a major effect on the 

 changes. 



Wind-field measurements did show 

 that the radius of maximum winds 

 increased following the seeding. 



Requirements for Future Activity 



The use of theoretical models to 

 study the modification hypotheses 

 was discussed in the previous section. 

 Some deficiencies of the present mod- 



els were also mentioned. We should 

 use the present models to learn as 

 much as possible about the interac- 

 tions and potential instabilities of 

 hurricanes, but we should also con- 

 tinue experiments to develop further 

 information as to how well the mod- 

 els simulate actual hurricanes. At 

 best, they can do this only in a mean 

 sense. We should also continue work 

 to remove the restrictive assumptions; 

 these relate to circular symmetry, 

 interaction between the hurricane 

 and synoptic-scale features in the 

 environment, dynamics of cumulus 

 clouds, and interactions between the 

 hurricane scale of motion and circu- 

 lations of smaller scale. The matter 

 of parameterizing cumulus processes 

 in the model must be re-examined 

 and carefully compared with cumulus 

 models and observations. A more 

 closely spaced grid should be used 

 in the eye-wall region. And, finally, 

 the outer radial boundary (now at 

 440 km) should be moved outward 

 and other outer boundary conditions 

 investigated to make sure they are 

 not determining or markedly affect- 

 ing the solutions following the "seed- 

 ing." 



When the field experiments are 

 repeated, every effort should be made 

 to obtain data that will permit veri- 

 fying various steps related to the 

 seeding hypotheses. These were dis- 

 cussed in the preceding section. Fa- 

 cilities and manpower are not avail- 

 able at the present time to obtain all 

 of these data. 



In summary, the present status of 

 our scientific knowledge suggests 



quite strongly that techniques pres- 

 ently available are adequate to 

 achieve beneficial modification of 

 mature hurricanes. Data from experi- 

 ments and theoretical studies support 

 each other, but in each case there 

 are gaps in our knowledge which 

 suggest we should be cautious in 

 making extreme claims. What is clear 

 is that we should repeat the Debbie- 

 type experiments on other hurricanes 

 as soon as possible to see if we can 

 duplicate the Debbie decrease in wind 

 speeds and to document details of 

 the effects. We should continue our 

 theoretical investigations to remove 

 some of the limiting assumptions. 



With losses from hurricanes in the 

 United States currently averaging 

 over $400 million per year and loss 

 of life still a threat, action should 

 be taken as soon as possible. Since 

 the prospects seem good that we can 

 reduce the destructive power of hur- 

 ricanes, the need for additional ex- 

 periments becomes much more ur- 

 gent. 



If present techniques are adequate 

 for modifying a hurricane, it is quite 

 likely that we can collect enough 

 information during the next one or 

 two years to justify application of 

 the experiments to storms expected 

 to affect the coastline. If present 

 techniques are inadequate, we have 

 several other approaches which should 

 be explored. The time needed to 

 develop and test better hypotheses 

 or to improve and exploit the present 

 hypotheses suggests that we should 

 plan five to ten years ahead. 



The Scientific Basis of Project STORMFURY 



Project STORMFURY is concerned 

 with the problem of devising ex- 

 periments to modify hurricanes and 

 tropical cyclones. Because the design 

 and evaluation of such experiments 

 depends essentially on understanding 

 the structure and behavior of "nat- 

 ural" hurricanes, the close associa- 



tion of the project with the National 

 Hurricane Research Laboratory of the 

 National Oceanic and Atmospheric 

 Administration is appropriate. The 

 impetus for such experiments arises 

 primarily from the large potential 

 benefits, in the form of reduced prop- 

 erty damage and loss of life, which 



could be realized from relatively small 

 modifications of the intensity or mo- 

 tion of these storms. 



During the past decade, increased 

 understanding of hurricanes, based 

 on both descriptive and theoretical 

 studies, has suggested at least two 



130 



