45th Anniversary of the seeding of Hurricane Ginger

Track of Hurricane Ginger 1971 (UNisys)
Track of Hurricane Ginger 1971

Beginning on September 16, 1971, Hurricane Ginger was seeded with silver iodide by Project STORMFURY.  This was the fourth and last storm experimented on by the Project.  The seeding experiments were carried out on three separate days in Ginger with inconclusive results.

Ginger was the second-longest lasting Atlantic hurricane on record at 27 days.  It formed from a persistent upper-level cold low east of the Bahamas.  By Sept. 6th, enough convection had generated near the circulation center for it to be classified a tropical depression.  Over the next three days it drifted slowly northeastward.  When it turned eastward, it had become organized enough to be designated a tropical storm and was named Ginger.  It intensified into a hurricane a day later, and three days later reached its peak intensity with maximum sustained winds of 110 mph (175 km/hr).  Ginger slowed and then began to backtrack westward.  It slowed to a crawl and spent four days making a cyclonic loop at mid-ocean, barely maintaining hurricane-force winds.  Eventually, it resumed its westward motion and began to intensify again.  There was a slight weakening as Ginger interacted with Tropical Storm Janice to its southeast, and absorbed much of the moisture and energy from Janice when it collapsed.

Hurricane Ginger on Sept. 27. 1971 between seeding days (NOAA)
Hurricane Ginger on Sept. 27. 1971 between seeding days

By Sept. 26th, Ginger had entered the STORMFURY target zone and was within flight range of Miami.  The NOAA aircraft had just returned from research flights into Janice but were able to carry out their seeding patterns along with Navy and Air Force planes with little crew rest.  Instead of seeding the area outside the eyewall as had been done in other experiments, this time the scientists concentrated on dropping the silver iodide canisters in an outer rainband.  Ginger had again slowed down and the Project was able to carry out further rainband experiments on Sept. 28th and 29th.

Ginger was now moving northwestward toward the Carolinas and intensifying, so no more seeding experiments were allowed.  By the evening of Sept. 30th, Ginger made landfall near Morehead City, NC with wind of 75 mph (120 km/hr).  It caused one direct death and US$10 million in damages.

The Ginger experiments were controversial for Project scientists.  By the time it was within range of the aircraft, Ginger no longer had a classic hurricane wind profile.  The eye was large and the the wind field very spread out.  The decision to carry out rainband seeding further muddied the results, since it was uncertain what impact on storm strength or structure would result from this type of experiment.  In retrospect, as this was the last series of tests that the Project would fly, it seemed a wasted opportunity.

Research papers from HRD scientists about Hurricane Ginger

Francis J. Merceret, 1974: On the Size Distribution of Raindrops in Hurricane Ginger. Mon. Wea. Rev., 102, 714–716.

Kenneth H. Bergman and Toby N. Carlson, 1975: Objective Analysis of Aircraft Data in Tropical Cyclones. Mon. Wea. Rev., 103, 431–444.

H. E. Willoughby, D. P. Jorgensen, R. A. Black, and S. L. Rosenthal, 1985: Project STORMFURY: A Scientific Chronicle 1962–1983. Bull. Amer. Meteor. Soc., 66, 505–514.

Neal M. Dorst, 2007: The National Hurricane Research Project: 50 Years of Research, Rough Rides, and Name Changes. Bull. Amer. Meteor. Soc., 88, 1566–1588.