| Category 3 hurricane (SSHS) | |
|---|---|
| Hurricane Debbie on August 18, 1969 | |
| Formed | August 14, 1969 |
| Dissipated | August 25, 1969 |
| Highest winds | 1-minute sustained: 120 mph (195 km/h) |
| Lowest pressure | 951 mbar (hPa; 28.08 inHg) |
| Areas affected | Newfoundland |
| Part of the 1969 Atlantic hurricane season | |
Hurricane Debbie was an intense and long-lived hurricane that formed during August 1969. The fifth tropical cyclone, fourth named storm, third hurricane and second major hurricane of the 1969 Atlantic hurricane season, Debbie formed on August 14 in the southern Atlantic Ocean and took a general northwesterly path until turning northward into the central Atlantic. The storm was characterized by numerous fluctuations in intensity, and it reached winds corresponding to Category 3 status on the Saffir–Simpson Hurricane Scale on four separate occasions. The hurricane bypassed the island of Bermuda to the southeast on August 22, before ultimately brushing southeastern Newfoundland with strong winds. It dissipated over the cold waters east of Greenland. Although Debbie had little effect on land, it was extensively researched and was subject to a weather modification experiment by Project Stormfury, in which it was seeded with silver iodide.
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A disturbance associated with a tropical wave strengthened into a tropical depression on August 14.[1] The system had significantly organized by August 15,[2] and it intensified into a tropical storm at 1200 UTC that day.[1] Upon its designation, Debbie was moving west-northwestward at approximately 15 mph (24 km/h) and it was predicted to gradually gain power.[3] It attained Category 1 hurricane strength on August 16 as it turned toward the northwest. It continued to mature, and at around 1200 UTC the next day, it achieved winds corresponding to Category 2 on the Saffir-Simpson Hurricane Scale. On August 18, Debbie further intensified to Category 3 status, making it a major hurricane.[1]
However, the storm quickly downgraded, and by August 19 it was once again at minimal hurricane force. At roughly the same time, it turned more to the west, although it maintained a general northwesterly path.[1][4] The abrupt weakening may have been the result of a seeding experiment carried out on the storm in an attempt to deteriorate it.[5] By later in the day, Debbie had begun to restrengthen. It resumed Category 3 intensity on August 20, despite a minor oscillation in magnitude during the day. At this point, the cyclone acquired peak winds of 120 mph (195 km/h); shortly thereafter, its lowest recorded barometric pressure fell to 951 millibars.[1]
The storm turned northward on August 21,[6] and eventually curved northeastward. Debbie weakened to Category 2 strength but, for the fourth time, restrengthened to major hurricane intensity.[1] The hurricane then passed well to the southeast of Bermuda,[1] although it is believed that if not for the presence of nearby Hurricane Camille which emerged into the Atlantic from the United States on August 20, Debbie would have likely ended up further west, closer to the island.[5] It maintained its severity through August 22 as it continued generally toward the northeast.[1]
On August 23, the storm began a weakening trend and it turned towards the north.[1] The next day, the storm—having weakened to Category 1 status—skirted the southeastern tip of Newfoundland.[7] Debbie began to lose its tropical characteristics as it accelerated towards the northeast,[8] and it weakened into a tropical storm early on August 25.[1] As it moved over increasingly cold waters, it dissipated east of Greenland.[5]
Debbie was subject to an experiment called Project Stormfury, which attempted to weaken tropical cyclones by seeding them with silver iodide.[5] The storm provided an excellent opportunity to test the underpinnings of Project Stormfury. In many ways it was the perfect storm for seeding: it did not threaten any land; it passed within range of seeding aircraft; and was intense with a distinct eye.[9] On August 18 and again on August 20, thirteen planes flew out to the storm to monitor and seed it. On the first day, windspeeds fell by 31%. On the second day, windspeeds fell by 18%.[5][10] Both changes were consistent with Stormfury's working hypothesis. The results were so encouraging that "a greatly expanded research program was planned."[11] Among other conclusions was the need for frequent seeding at close to hourly intervals.[5]
Debbie remained predominately at sea throughout its 3,000 mi (4,800 km) path, and as a result, it caused little damage.[5] The storm had little or no impact on the island of Bermuda as it passed to the south.[12] Later, winds of 50 to 65 mph (80 to 105 km/h) were recorded over eastern Newfoundland.[8]
