Cyclone Gita

Severe Tropical Cyclone Gita was the most intense tropical cyclone to impact Tonga since reliable records began. The second named storm and first major tropical cyclone of the 2017–18 South Pacific cyclone season, Gita originated from a monsoon trough that was active in the South Pacific in early February 2018. First classified as a tropical disturbance on 3 February, the nascent system meandered near Vanuatu for several days with little development. After acquiring a steady east trajectory near Fiji, it organized into a Category 1 tropical cyclone on 9 February near Samoa. Arcing south in a clockwise turn, the system rapidly intensified, and became a severe tropical cyclone on 10 February near Niue.

Throughout its path in the South Pacific, Cyclone Gita affected multiple island nations and territories. Tonga was the hardest-hit, with severe damage occurring on the islands of Tongatapu and ʻEua; two fatalities and forty-one injuries occurred in the kingdom. At least 171 homes were destroyed and more than 1,100 suffered damage. Violent winds destroyed homes and left the two islands largely without power. Torrential rains and damaging winds caused widespread disruptions in Samoa and American Samoa, prompting emergency declarations in both. Outlying islands in the Fijian Lau Islands were significantly affected, particularly Ono-i-Lau and Vatoa. Wallis and Futuna, Niue, and Vanuatu were also affected, but impacts in those areas were minor. Total damage from Gita is estimated to be in excess of US$252 million, primarily in American Samoa and Tonga.

On 3 February, the Fiji Meteorological Service (FMS) started to monitor Tropical Disturbance 07F, which had developed within a trough of low pressure, about 435 km (270 mi) to the southeast of Honiara in the Solomon Islands. The system was poorly organized and was located along an upper-level ridge of high pressure, in an area of high vertical wind shear. Over the next couple of days, the system moved erratically near northern Vanuatu and remained poorly organized, with convection located to the south of the low-level circulation center. The system subsequently started to move south-eastwards, towards the Fijian Islands and a favorable environment for further development, on 5 February. The system subsequently passed near the island nation during 8 February, where it developed into a tropical depression and started to move north-eastwards towards the Samoan Islands. During 9 February, the United States Joint Typhoon Warning Center (JTWC) initiated advisories on the system and designated it as Tropical Cyclone 09P, after an ASCAT image showed that it had winds of 65–75 km/h (40–45 mph) in its northern semicircle. The FMS subsequently named the system Tropical Cyclone Gita early, after the United States National Weather Service Weather Forecast Office in Pago Pago requested that the system be named early for warning and humanitarian reasons.

After Gita was named, a prolonged period of rapid intensification ensued as it quickly intensified into a Category 1 tropical cyclone on the Australian tropical cyclone intensity scale, before it passed within 100 km (60 mi) of Samoa and American Samoa. After moving past the Samoan Islands, Gita turned southeast, then southwards, under the influence of a near-equatorial ridge to the northeast. On 10 February, Gita rapidly intensified to a category 3 severe tropical cyclone on the Australian scale while traversing anomalously warm sea surface temperatures of between 28–29 °C (82–84 °F). The system bypassed Niue to the east during this intensification phase. On 11 February, Gita continued to intensify into a category 4 severe tropical cyclone. At the same time, Gita turned westward under the influence of a subtropical ridge to the south. Around 12:00 UTC on 12 February, the cyclone passed near or over the Tongan islands of ʻEua and Tongatapu as a high-end Category 4 severe tropical cyclone. At this time, maximum 10-minute sustained winds were estimated at 195 km/h (121 mph) making Gita the strongest cyclone to strike the nation since reliable records began. The JTWC estimated the system to have reached its overall peak intensity at this time as a Category 4-equivalent on the Saffir-Simpson scale with 1-minute sustained winds of 230 km/h (140 mph).

At 18:00 UTC on 13 February, Gita reached its peak strength approximately 205 km (127 mi) south of Kandavu, Fiji, as a Category 5 severe tropical cyclone with ten-minute sustained winds of 205 km/h (127 mph), gusts to 285 km/h (177 mph), a minimum pressure of 927 mbar (hPa; 27.37 inHg).

Gita impacted the Pacific island nations and territories of Vanuatu, Fiji, Wallis and Futuna, Samoa, American Samoa, Cook Islands, Niue, Tonga, New Caledonia, and New Zealand, with the most significant damage being reported in the Samoan Islands and Tonga. Owing to the cyclone's significant and widespread impact, the name Gita was retired following its usage and will never be used for a South Pacific tropical cyclone again.

Gita brought torrential rain to parts of Samoa on 8–9 February. Accumulations averaged 150–250 mm (5.9–9.8 in) across the country, peaking at 320 mm (13 in) along the eastern slops of Mount Le Pu'e on Upolu. Storm-force winds impacted the nation, reaching 99.7 km/h (62.0 mph) at Faleolo International Airport and 98.2 km/h (61.0 mph) in Apia. Multiple rivers in the city burst their banks and inundated homes. At least 233 people sought refuge in emergency shelters. Landslides and flooding rendered many roads impassable. Communications were briefly lost with the southern coast of Upolu. A state of disaster was declared for the nation on 10 February. Damage to the power grid reached $10 million. No casualties were reported nationwide.

On 8 February, the National Weather Service (NWS) office in Pago Pago issued a tropical storm watch, a high surf advisory, and a flash flood watch for all of American Samoa as the nascent cyclone approached the territory. With Tropical Depression 08F existing simultaneously to the south of Fiji, uncertainty existed in the exact track of Gita. However, NWS Forecasters emphasized the risk of flash floods and mudslides as the interaction of two cyclones led to persistent monsoonal flow across the region. In the two days preceding Gita's arrival, this monsoon trough produced significant rains, reaching 432 mm (17.0 in). Monsoonal rains continued for two days after Cyclone Gita, and the flash flood watch was finally discontinued on 12 February. The American Samoa Emergency Management Agency advised residents to "remain on alert and secure loose items as necessary". The tropical storm watch was soon upgraded to a warning, indicating the expected arrival of gale-force winds within 36 hours. Pago Pago International Airport suspended operations for the duration of the storm. The NWS discontinued the tropical storm warning late on 9 February as Gita moved away from the territory.