PROJECT STORMFURY READY TO SEED HURRICANES: WILL TEST NEW MODIFICATION THEORY THIS YEAR

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This is a digitised version of an article from The Cayman Compass's print archive. Occasionally, the digitisation process introduces transcription errors, or other problems.

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Project Stormfury hurricane research and modification plans for 1971 were announced today by Dr. Robert M. White, Administrator of the Commerce Department's National Oceanic and Atmospheric Administration, and Rear Admiral William J. Kotsch, U.S. Navy, Commander of the Naval Weather Service Command. The project will be on the alert from August 4 through October 31, awaiting the opportunity to seed hurricanes and perhaps diminish their force. Project Stormfury is a joint Department of Commerce/Department of Defense program of scientific experiments to explore the nature of tropical storms and hurricanes, and to investigate the possibility of modifying them. Seeding experiments will be conducted on storms in the southwestern Atlantic, the Caribbean, and the Gulf of Mexico, when the probability is small-19 percent or less that the hurricane centre will come within 50 miles of a population area within 18 hours after seeding. This will allow ample time to measure seeding effects before they are obscured by proximity to land.

In 1970, there were no hurricanes that met these criteria. The project's major goal for 1971 is to confirm the promising results of the experiments conducted in 1969. On each of two days August 18 and 20, 1969,--Hurricane Debbie was seeded five times during an eight-hour period. After seeding on August 18, the hurricane's maximum winds at 12,000 feet decreased 31 percent, dropping from 98 knots before the experiment to 68 knots after seeding. Seeding on August 20 was followed by a decrease of 15 percent, from 99 knots to 84 knots. This year, the principal Stormfury seeding experiment will be testing a new hypothesis for the seeding. In the successful 1969 experiments on Hurricane Debbie, silver iodide generators were dropped along a line beginning at the radius of maximum winds, or near the middle of the eyewall, and continuing away from the centre for 15 to 25 miles. The hypothesis then, and for the earlier seedings of Esther (1961) and Beulah (1963) was that seeding caused sudden freezing of supercooled water existing at 5 to 20 degrees Centigrade in the massive cloud wall around the hurricane centre; the freezing released enough latent heat of fusion to raise cloud temperatures; and the heating reduced the great difference in pressure across the eyewall-thus diminishing the maximum winds. However, recent computer simulations of the hurricane experiment using mathematical models developed by NOAA's National Hurricane Research Laboratory and the analyzed data collected in Hurricane Debbie have indicated that best results should be realized by seeding essentially the same annular band as in Debbie, but by concentrating on the clouds beyond the ring of maximum winds which can be made to grow taller and larger by seeding. The computer experiments and the data collected in Debbie and in unmodified storms of recent years have led to a revised Stormfury hypothesis as to how hurricane seeding reduced a storm's intensity. In the new theory freezing of supercooled water is only the beginning, the trigger that sets off a chain re-action. The heat thus released causes explosive cloud growth and, as the clouds grow, condensation of water vapor releases many times more heat than the freezing alone. Inducing cloud growth outside the storm's original eyewall creates a new wall cloud surrounding the original one at a larger radius, which draws off inflowing air before it can reach the original eyewall. The energy formerly concentrated in a tight ring around the centre is thus dispersed over a greater area, causing a decrease in maximum winds. In accordance with the computer simulations and the new theory, seeding runs this year will begin about two miles further out from the inner edge of the storm's eyewall than in previous experiments. Seeding will be repeated five times, at two-hour intervals, with 208 silver iodide generators being dropped on each run. Other experiments planned for 1971 include seeding of hurricane rainsectors and rainbands, and continuation of experiments on lines of tropical cumulus clouds not associated with hurricanes.

In 1969 and 1970, the Project seeded lines of clouds over the ocean south of Puerto Rico. Since these cumulus cloud lines resemble hurricane rainbands in many ways, the results of such tests can contribute to research in hurricane modification. Dr. R. Cecil Gentry, Director of NOAA's National Hurricane Research Laboratory, Miami, Fla., is Director of Project Stormfury. Captain L.J. Underwood, U.S. Navy, commanding Officer of the Fleet Weather Facility at Jacksonville, Fla., is Assistant Director of the project and Navy project Coordinator. Dr. Pierre St. Amand is the Project Manager at the Naval Weapons Centre at China Lake, Calif., where the silver iodide pyrotechnicdevices! used by Project Stormfury for seeding were designed and developed. Aircraft and flight crews for the 1971 experiments are being provided by the NOAA Research Flight Facility, Miami, Fla; Navy Hurricane Hunter Squadron VW-4 Naval Air Station, Jacksonville, Fla.; and Navy Attack Squadron 85, Naval Air Station, Oceana, Va.