User:Jason Rees/Isaac

Severe Tropical Cyclone Isaac in February and March 1982 was thought to be the worst tropical cyclone, to affect the South Pacific island nation of Tonga since an unnamed tropical cyclone in 1961. The system was first noted during February 27, as an area of low pressure within the South Pacific Convergence Zone to the southwest of Tokelau. Over the next couple of days the system gradually developed further and was named Isaac during March 1, after it had become a tropical cyclone.

The tropical cyclone developed 160 km/100 mi northeast of western Samoa and travelled southwest at 12 knots, moving through the Ha'apai island group and only 50 km/30 mi northwest of Tongatapu. The pressure at Tongatapu fell to 976.4 mbar. Winds of 92 knots were measured at Nuku'alofa, and rainfall of 120 mm was measured there. Isaac reached maximum intensity on March 2. The tropical cyclone was 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 in half by a 16 m wide channel caused by Isaac's storm surge.

Meteorological history
On February 27, 1982, the Fiji Meteorological Service started to monitor an area of low pressure, that had developed within the South Pacific Convergence Zone about 300 km to the southwest of Tokelau. During that day the system moved south-eastwards and developed into a tropical depression, as it passed about 100 km to the south-west of Tokelau's Swains Island. The system continued to develop during the next day, as it moved south-westwards and passed near or over American Samoa's Manu'a Islands. Throughout this time the system had been gradually developing, before it was declared to be a tropical cyclone and named Issac by the FMS early on March 1.

During March 1, Isaac continued to intensify during that day, with an eye becoming visible on satellite imagery before the system was classified as a hurricane. Isaac subsequently continued to move south-westwards 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). Six hours later, the system passed about 25 km to the west of Tongatapu, as it peaked in intensity with 10-minute sustained winds of around 175 km/h (110 mph). 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 south-eastwards and rapidly weakened, as vertical wind shear over the system increased. The system was subsequently last noted on March 5, while it was located about 2000 km to the southeast of Tongatapu.

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

Preparations and impact
Severe Tropical Cyclone Isaac impacted Tonga between March 2-3 took less than 24 hours to affect Tonga moved through Tonga

Ahead of the system affecting Tonga, a tropical cyclone alert was issued for the island nation by the FMS during March 1, before hurricane warnings were issued for the Happai and Tongatapu island groups during the next day.