Cyclone Isaac

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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
Disc Plain black.svg Tropical cyclone
Solid black.svg Subtropical cyclone
ArrowUp.svg Extratropical cyclone, remnant low, tropical disturbance, or monsoon depression

On February 27, 1982, an area of low pressure that had developed within the South Pacific Convergence Zone about 300 km (185 mi) to the southwest of Tokelau. [1] That day, the system moved southeastwards and developed into a tropical depression as it passed about 100 km (60 mi) to the southwest of Swains Island. [2] [3] The system continued to develop the next day as it moved southwestwards and passed near or over American Samoa's Manu'a Islands. [3] [2] During this time, the system had been gradually developing, before it was declared to be a tropical cyclone and named Isaac by the FMS early on March 1. [2]

Isaac continued to intensify on March 1, with an eye becoming visible on satellite imagery. [3] [2] Isaac subsequently continued to move southwestwards and started to impact Tonga during March 2 before it directly passed over the island group of Ha'apai at around 1800 UTC (0700 TOT, March 3). [1] [2] Six hours later, the system passed about 25 km (15 mi) to the west of Tongatapu as it peaked in intensity with 10-minute sustained winds of around 175 km/h (110 mph). [2] [1] [3] This made Isaac equivalent to a modern-day Category 4 severe tropical cyclone on the Australian tropical cyclone intensity scale. On March 3, after the system had peaked in intensity, it recurved southeastwards and rapidly weakened as vertical wind shear over the system increased. [2] The system was last noted on March 5, while it was located about 2,000 km (1,245 mi) to the southeast of Tongatapu. [3]

In September 2017, a study was published by the Royal Meteorological Society in which the intensity of Isaac was reanalyzed. [4] The authors of the study estimated that at its peak Isaac had 1-minute sustained windspeeds of 240 km/h (150 mph), which would make it a Category 4-equivalent tropical cyclone on the Saffir-Simpson scale. [4]

Preparations, impact, and aftermath

Severe Tropical Cyclone Isaac impacted Tonga on March 2 and 3. Ahead of the system affecting Tonga, a tropical cyclone alert was issued for the nation by the FMS on March 1, and cyclone warnings were issued for the Ha'apai and Tongatapu island groups the next day. [5] When the system hit, the pressure at Tongatapu fell to 976.4 mbar (28.83 inHg). Winds of 92 knots were measured at Nukuʻalofa, [6] and rainfall of 120 millimetres (4.7 in) was measured there. Isaac reached maximum intensity on March 2. The tropical cyclone was considered the worst storm in Tonga's history, devastating the island group. [7] The island groups of Ha'apai and Vava'u were hit worst. Six were killed, [6] while 45,000 became homeless and 95% of the livestock was killed. [8] The island of Tatafa was bisected by a 16 metres (52 ft) wide channel caused by Isaac's storm surge. [9] [10] [11] Tonga's only power station was "leveled", causing the entire nation to be without power. [12] More than a tenth of the nation's schools were destroyed. [13]

Following the cyclone, the Australian government sent six Lockheed C-130 Hercules planes, filled with food, medical supplies, and 50 army engineers and communications personnel. [14] An air lift was also set up. [15] To replace the destroyed schools, cyclone-proof replacements were built, with prefabricated versions used instead for the outer islands. [13]

See also

References

  1. 1 2 3 Thompson, C.S (1986). The Climate and Weather of Tonga (PDF) (Report). pp. 10–15. ISSN   0110-6937.
  2. 1 2 3 4 5 6 7 Browne M L (1983). "Tropical Cyclone 'Isaac', 28 February - 3 March 1982" (PDF). Weather and Climate. 3 (1): 32–35.
  3. 1 2 3 4 5 "1982 Tropical Cyclone Isaac (1982058S10185)". International Best Track Archive for Climate Stewardship. Retrieved 5 September 2023.
  4. 1 2 Hoarau, Karl; Chalonge, Ludovic; Pirard, Florence; Peyrusaubes, Daniel. "Extreme tropical cyclone activities in the southern Pacific Ocean". International Journal of Climatology. doi:10.1002/joc.5254. ISSN   1097-0088.
  5. ↑ Carter, W Nick (April 1982). A report on Cyclone Isaac (PDF) (Report). United Nations Office of the Disaster Relief Co-Ordinator. Retrieved 3 December 2016.
  6. 1 2 Dirk H.R. Spennemann, Conservation management and mitigation of the impact of tropical cyclones
  7. ↑ Tonga – History
  8. ↑ Tonga in the News
  9. ↑ James P. Terry (2007). Tropical cyclones: climatology and impacts in the South Pacific. Springer. p. 111. ISBN   978-0-387-71542-1 . Retrieved 24 February 2011.
  10. ↑ Terry, James P (2007). "5 – Meteorological Conditions". Tropical cyclones: Climatology and impacts in the South Pacific. pp. 52, 63–64. ISBN   9780387715421.
  11. ↑ Woodroffe, Colin D. (1983). "The Impact of Cyclone Isaac on the Coast of Tonga". Pacific Science. 37 (3). University of Hawaii: 181–210. hdl:10125/675. ISSN   0030-8870.
  12. ↑ "Cyclone devastates island kingdom of Tonga". St. Joseph News-Press. Associated Press. 5 March 1982. p. 3A. Retrieved 8 January 2026.
  13. 1 2 Gray, Denis D. "'Disaster architect' seeks to save lives". The Press-Courier. Associated Press. p. 13. Retrieved 8 January 2026.
  14. ↑ "Tonga Cyclone Leaves Islanders Homeless". Schenectady Gazette. Vol. LXXXVIII, no. 134. United Press International. 5 March 1982. p. 4. Retrieved 8 January 2026.
  15. ↑ "Cyclone devastates island kingdom". The Calgary Herald. Reuters. 5 March 1982. p. A4. Retrieved 8 January 2026.
Severe Tropical Cyclone Isaac
Isaac 1982-03-02 1815Z.png
Cyclone Isaac moving over Tonga near peak intensity on March 2
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