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Hurricane Debbie (1969)

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Hurricane Debbie
Category 3 major hurricane (SSHWS/NWS)
Hurricane Debbie on August 20, 1969
FormedAugust 14, 1969
DissipatedAugust 25, 1969
Highest winds1-minute sustained: 120 mph (195 km/h)
Lowest pressure951 mbar (hPa); 28.08 inHg
Areas affectedNewfoundland, Bermuda
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 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.

Meteorological history

Map plotting the storm's track and intensity, according to the Saffir–Simpson scale
Map key
Saffir–Simpson scale
  Tropical depression (≤38 mph, ≤62 km/h)
  Tropical storm (39–73 mph, 63–118 km/h)
  Category 1 (74–95 mph, 119–153 km/h)
  Category 2 (96–110 mph, 154–177 km/h)
  Category 3 (111–129 mph, 178–208 km/h)
  Category 4 (130–156 mph, 209–251 km/h)
  Category 5 (≥157 mph, ≥252 km/h)
  Unknown
Storm type
triangle Extratropical cyclone, remnant low, tropical disturbance, or monsoon depression

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]

The storm's eye

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]

Impact and Project Stormfury

This radar image from a Navy reconnaissance aircraft of Hurricane Debbie was taken on August 20, 1969 around 1519 UTC.
Main article: Project Stormfury

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%, from 98 to 68 knots (180 to 125 km/h; 115 to 80 mph). [10] On the second day, windspeeds fell by 18%.[5][11] Both changes were consistent with Stormfury's working hypothesis. The results were so encouraging that "a greatly expanded research program was planned."[12] Among other conclusions was the need for frequent seeding at close to hourly intervals.[13]

Debbie remained predominately at sea throughout its 3,000 mi (4,800 km) path, and as a result, it caused little damage.[13] The storm had little or no impact on the island of Bermuda as it passed to the south.[14] Later, winds of 50 to 65 mph (80 to 105 km/h) were recorded over eastern Newfoundland.[8]

See also

References

  1. ^ a b c d e f g h i j Atlantic hurricane research division (2009). "Atlantic hurricane database (HURDAT) "best track" (1851–2008)". National Oceanic and Atmospheric Administrations. Archived from the original on May 4, 2009. Retrieved January 11, 2010.
  2. ^ Forecaster Simpson (August 15, 1969). "National Hurricane Center Bulletin 10 AM EDT Friday August 15, 1969". National Hurricane Center. Retrieved January 27, 2010.
  3. ^ Forecaster Hope (August 15, 1969). "Tropical Storm Debbie Public Advisory Number 1". National Hurricane Center. Retrieved January 27, 2010.
  4. ^ Forecaster Herbert (August 19, 1969). "Hurricane Debbie Public Advisory Number 18". National Hurricane Center. Retrieved January 27, 2010.
  5. ^ a b c d e R.H. Simpson; et al. (April 1970). "The Atlantic Hurricane Season of 1969" (PDF). Weather Bureau. Archived from the original (PDF) on January 4, 2011. Retrieved January 27, 2010.
  6. ^ Forecaster Kraft (August 21, 1969). "Hurricane Debbie Public Advisory Number 24". National Hurricane Center. Retrieved January 27, 2010.
  7. ^ Forecaster Pelissier (August 24, 1969). "Hurricane Debbie Public Advisory Number 37". National Hurricane Center. Retrieved January 27, 2010.
  8. ^ a b Forecaster Herbert (August 24, 1969). "Hurricane Debbie Public Discussion Number 38". National Hurricane Center. Retrieved January 27, 2010.
  9. ^ ABC Whipple (1982). Storm. Time Life Books. ISBN 0-8094-4312-0.
  10. ^ "From the Archives (December 12, 1969): Weakening a hurricane". The Hindu. December 12, 2019. ISSN 0971-751X. Retrieved December 18, 2019.
  11. ^ H.E. Willoughby; D.P. Jorgensen; R.A. Black; S.L. Rosenthal (May 1985). "Project STORMFURY: A Scientific Chronicle 1962-1983" (Periodical). Bulletin of the American Meteorological Society. 66 (5). American Meteorological Society: 505. Bibcode:1985BAMS...66..505W. doi:10.1175/1520-0477(1985)066<0505:PSASC>2.0.CO;2. Retrieved July 2, 2014.
  12. ^ Pete Davies (2000). Inside the Hurricane: Face to Face with Nature's Deadliest Storms. Henry Holt and Company. ISBN 0-8050-6574-1.
  13. ^ a b R.H. Simpson and Paul Herbert (April 1970). "The Atlantic Hurricane Season of 1972" (PDF). Weather Bureau. Archived from the original (PDF) on May 25, 2011. Retrieved January 27, 2010.
  14. ^ Forecaster Sugg (August 21, 1969). "Hurricane Debbie Bulletin". National Hurricane Center. Retrieved January 27, 2010.
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