Cyclone Isaac
Severe Tropical Cyclone Isaac was a South Pacific tropical cyclone that severely affected Tonga in 1982. On February 27, the Fiji Meteorological Service started to monitor an area of low pressure within the South Pacific Convergence Zone to the southwest of Tokelau. It continued to develop northeast of Samoa while travelling southwest and was named Isaac after becoming a tropical cyclone on March 1. Isaac moved through the Haʻapai island group and only northwest of Tongatapu.
Meteorological history
On February 27, 1982, an area of low pressure that had developed within the South Pacific Convergence Zone about to the southwest of Tokelau. That day, the system moved southeastwards and developed into a tropical depression as it passed about to the southwest of Swains Island. The system continued to develop the next day as it moved southwestwards and passed near or over American Samoa's Manu'a Islands. 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.Isaac continued to intensify on March 1, with an eye becoming visible on satellite imagery. 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. Six hours later, the system passed about to the west of Tongatapu as it peaked in intensity with 10-minute sustained winds of around. 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. The system was last noted on March 5, while it was located about to the southeast of Tongatapu.
In September 2017, a study was published by the Royal Meteorological Society in which the intensity of Isaac was reanalyzed. The authors of the study estimated that at its peak Isaac had 1-minute sustained windspeeds of, which would make it a Category 4-equivalent tropical cyclone on the Saffir-Simpson scale.
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. When the system hit, the pressure at Tongatapu fell to. Winds of 92 knots were measured at Nukuʻalofa, and rainfall of 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. The island groups of Ha'apai and Vava'u were hit worst. Six were killed, while 45,000 became homeless and 95% of the livestock was killed. The island of Tatafa was bisected by a wide channel caused by Isaac's storm surge. Tonga's only power station was "leveled", causing the entire nation to be without power. More than a tenth of the nation's schools were destroyed.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. An air lift was also set up. To replace the destroyed schools, cyclone-proof replacements were built, with prefabricated versions used instead for the outer islands.