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Hurricane Debbie (1969)

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Hurricane Debbie
Satellite image of Hurricane Debbie on August 20, 1969
Meteorological history
FormedAugust 14, 1969
ExtratropicalAugust 23, 1969
DissipatedAugust 27, 1969
Category 3 major hurricane
1-minute sustained (SSHWS/NWS)
Highest winds125 mph (205 km/h)
Lowest pressure950 mbar (hPa); 28.05 inHg
Overall effects
Areas affectedBermuda, Newfoundland
IBTrACSEdit this at Wikidata
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, but it still reached winds corresponding to Category 3 status on the Saffir–Simpson scale. 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

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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][2] The system had significantly organized by August 15,[3] having intensified into a tropical storm by 00:00 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.[4] It attained Category 1 hurricane strength on August 16 as it turned toward the northwest. It continued to mature, and at around 12:00 UTC on the next day, it achieved winds corresponding to Category 2 on the Saffir–Simpson scale. After attaining an initial peak of 105 mph (165 km/h) six hours later, Debbie oscillated in strength over the succeeding two days, weakening back to Category 1 status early on August 19.[1][5]

Debbie's abrupt fluctuation in intensity may have been the result of a seeding experiment carried out on the storm in an attempt to weaken it, though posthumous assessment by the Atlantic hurricane reanalysis project determined that an eyewall replacement cycle was more likely responsible.[5][2] Upon reversion to minimal hurricane force, Debbie turned more to the west, although it maintained a general northwesterly path.[1][6] By later in the day, Debbie had begun to restrengthen, reaching major hurricane intensity, Category 3 on the Saffir–Simpson scale, by 18:00 UTC. Six hours later, early on August 20, the cyclone acquired peak winds of 125 mph (205 km/h), the highest in its lifespan; approximately 18 hours later, its lowest recorded barometric pressure fell to 950 mb (28 inHg), as measured by hurricane hunters.[1][2]

The storm's eye

The storm then weakened as it turned northward and eventually northeastward on August 21.[7][2] Gradually losing strength, Debbie 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] Debbie mostly maintained its severity through 06:00 UTC on August 23 as it continued generally toward the northeast.[1] By 12:00 UTC on August 23, Debbie weakened to below Category 2 status and turned northward, becoming extratropical six hours later, while still retaining winds of hurricane force.[1][2] The next day, the storm's remnants—no longer bearing winds of hurricane intensity, but only gale force—skirted the southeastern tip of Newfoundland.[8] The remnants of Debbie began to lose definition as they accelerated northeastward,[9] while moving over increasingly cold waters. Debbie's remnants finally dissipated west of Norway on August 27.[5][1][2]

Impact and Project Stormfury

[edit]
Radar image of Hurricane Debbie on August 20
Main article: Project Stormfury

Debbie remained predominately at sea throughout its 3,000 mi (4,800 km) path, and as a result, it caused little damage.[10] The storm had little or no impact on the island of Bermuda as it passed to the south.[11] Later, winds of 50 to 65 mph (80 to 105 km/h) were recorded over eastern Newfoundland.[9]

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.[12] 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).[13] On the second day, windspeeds fell by 18%.[5][14] Both changes were consistent with Stormfury's working hypothesis. The results were so encouraging that "a greatly expanded research program was planned."[15] Among other conclusions was the need for frequent seeding at close to hourly intervals.[10] However, later studies determined that Project Stormfury likely had little or no impact on the evolution of Debbie and other storms, positing instead that natural fluctuations induced by eyewall replacement cycles were more likely to blame.[16][2]

See also

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References

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  1. ^ a b c d e f g h i Atlantic hurricane research division (2009). "Atlantic hurricane database (HURDAT) "best track" (1851–2008)". National Oceanic and Atmospheric Administrations. Archived from the original on May 6, 2009. Retrieved January 11, 2010.
  2. ^ a b c d e f g Sandy Delgado; Christopher W. Landsea (2021). "1966 Atlantic Hurricane Database Reanalysis" (PDF). Atlantic Oceanographic and Meteorological Laboratory. Retrieved January 18, 2022.
  3. ^ Forecaster Simpson (August 15, 1969). "National Hurricane Center Bulletin 10 AM EDT Friday August 15, 1969". National Hurricane Center. Retrieved January 27, 2010.
  4. ^ Forecaster Hope (August 15, 1969). "Tropical Storm Debbie Public Advisory Number 1". National Hurricane Center. Retrieved January 27, 2010.
  5. ^ a b c d e f 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 Herbert (August 19, 1969). "Hurricane Debbie Public Advisory Number 18". National Hurricane Center. Retrieved January 27, 2010.
  7. ^ Forecaster Kraft (August 21, 1969). "Hurricane Debbie Public Advisory Number 24". National Hurricane Center. Retrieved January 27, 2010.
  8. ^ Forecaster Pelissier (August 24, 1969). "Hurricane Debbie Public Advisory Number 37". National Hurricane Center. Retrieved January 27, 2010.
  9. ^ a b Forecaster Herbert (August 24, 1969). "Hurricane Debbie Public Discussion Number 38". National Hurricane Center. Retrieved January 27, 2010.
  10. ^ 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.
  11. ^ Forecaster Sugg (August 21, 1969). "Hurricane Debbie Bulletin". National Hurricane Center. Retrieved January 27, 2010.
  12. ^ ABC Whipple (1982). Storm. Time Life Books. ISBN 0-8094-4312-0.
  13. ^ "From the Archives (December 12, 1969): Weakening a hurricane". The Hindu. December 12, 2019. ISSN 0971-751X. Retrieved December 18, 2019.
  14. ^ H.E. Willoughby; D.P. Jorgensen; R.A. Black; S.L. Rosenthal (May 1985). "Project STORMFURY: A Scientific Chronicle 1962-1983". 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.
  15. ^ Pete Davies (2000). Inside the Hurricane: Face to Face with Nature's Deadliest Storms. Henry Holt and Company. ISBN 0-8050-6574-1.
  16. ^ Chris Landsea (n.d.). "Has there ever been an attempt or experiment to reduce the strength of a hurricane ?" (FAQ). Tropical Cyclone FAQ Subject C4. Hurricane Research Division. Retrieved June 8, 2006.
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