Cyclone Sina

Severe Tropical Cyclone Sina

Category 3 cyclone (Australian scale) Category 4 Tropical Cyclone (SSHWS)
Cyclone Sina near its peak intensity
Formed	November 20, 1990
Dissipated	December 4, 1990
(extratropical after December 1, 1990)
Highest winds	10-minute sustained: 140 km/h (85 mph) 1-minute sustained: 230 km/h (145 mph)
Lowest pressure	960 mbar (hPa); 28.35 inHg
Fatalities	None reported
Damage	$18.5 million (1990 USD)
Areas affected	Fiji, Tonga, Niue, Southern Cook Islands
Part of the 1990–91 South Pacific cyclone season

Cyclone Sina was the only named tropical cyclone within the South Pacific basin during the 1990-91 season and affected Fiji, Tonga, Niue and the Southern Cook Islands during November 1990. The system was first noted within the South Pacific Convergence Zone on November 20, as a shallow depression within the South Pacific Convergence Zone to the west of Wallis Island. Over the next two days the system moved towards the west-northwest and the Fijian dependency of Rotuma, before the depressions chances of developing further became good during November 23, as upper outflow over the system became established. During the next day the system was named Sina, after the system had developed into a tropical cyclone while it was located about 425 km (265 mi) to the northwest of the Fijian dependency Rotuma. Over the next two days the system continued to intensify and developed an eye feature as it moved erratically towards Fiji. During November 26, Sina's eye feature became very distinct on satellite imagery, before it peaked in intensity while it was equivalent to a category 4 hurricane on the Saffir-Simpson hurricane wind scale, and a category 3 severe tropical cyclone on the Australian tropical cyclone intensity scale. Over the next 2 days the system, gradually weakened as it moved towards the east-southeast and through the Fijian Archipelago towards the southern islands of Tonga. Early on November 29, Sina passed just to the north of Tongatapu in Tonga, before as it continued its east-southeast movement the system passed about 160 km (100 mi) to the south of Niue, before it recurved sharply towards the south-southeast early the next day as it approached the Southern Cook Islands. The system subsequently rapidly weakened under the influence of strong vertical wind shear and cooler sea surface temperatures, before it degenerating into an extratropical depression during November 30. Over the next couple of days Sina's remnants maintained a south-eastward track, before it was absorbed by a trough of low pressure on December 4.

While it was active, Sina was responsible for 7007630000000000000US$63 million in losses to Fiji along with severe beach erosion and some flooding. However, only one person was left missing, no deaths were recorded, and minor damage was reported in Tonga and Niue.

Meteorological history

On November 20, the Fiji Meteorological Service's Nadi tropical cyclone warning center (TCWC Nadi) started to monitor a shallow tropical depression, that had developed within the South Pacific Convergence Zone to the west of Wallis Island.^[1][2] Over the next two days the system moved towards the west-northwest and the Fijian dependency of Rotuma, before the depressions chances of developing further became good during November 23, as upper outflow over the system became established.^[1][2] The United States Joint Typhoon Warning Center (JTWC) subsequently initiated advisories and classified the depression as Tropical Cyclone 03P at 1200 UTC the next day, after atmospheric convection surrounding the system organized further.^[1][3] Later that day at 19:10 UTC, TCWC Nadi named the system Sina after the depression had developed into a category 1 tropical cyclone on the Australian tropical cyclone intensity scale, while it was located about 425 km (265 mi) to the northwest of Rotuma.^[1][4] During the next day the cyclone continued to intensify and developed an eye as it moved erratically towards the south, before early on November 26, TCWC Nadi reported that Sina had become a category 3 severe tropical cyclone.^[1][4] At around this time the JTWC reported that Sina had become equivalent to a category one hurricane on the Saffir-Simpson hurricane wind scale (SSHWS).^[5]

During November 26, Sina's eye became very distinct on satellite imagery, as it intensified and moved erratically towards the southeast and Fiji, as the upper level steering flow changed.^[1] Later that day TCWC Nadi reported that the system had peaked as a category 3 severe tropical cyclone, with 10-minute sustained windspeeds of 140 km/h (85 mph).^[4][6] The JTWC subsequently reported early the next day that Sina had peaked with 1-minute sustained windspeeds of 140 km/h (85 mph), which made it equivalent to a category 4 hurricane on the SSHWS.^[5] During that day, Sina remained at its peak intensity as it moved towards the east-southeast and started to be observed on the Nadi Radar.^[1][4][5] Later that day as the system started to gradually weaken, it passed about 40 km (25 mi) to the south of Viti Levu before it passed over the island groups of Vatulele and Moala and the Southern Lau Islands during November 28.^[1] During that day the system moved across the 180th meridian, which prompted the JTWC issue their final warning on Sina and pass the responsibility for warning the United States Government to the Naval Western Oceanography Center.^[3][5]

Early on November 29, Sina weakened into a category two tropical cyclone on the Australian scale just before it passed to the north of the island Tongatapu in Tonga.^[1][4] During that day as the system moved eastwards towards the Southern Cook Islands and gradually weakened further, the NWOC issued their final advisory on Sina while estimating that it was equivalent to a category one hurricane on the SSHWS.^[3][5] Early on November 30, the system passed about 160 km (100 mi) to the south of Niue, before it recurved sharply towards the south-southeast later that day as it approached the Southern Cook Islands. The system subsequently started to rapidly weaken under the influence of strong vertical wind shear and cooler sea surface temperatures.^[1] TCWC Nadi subsequently passed the primary warning responsibility for Sina to TCWC Wellington as it crossed 25°S, who quickly reported that the system had lost its tropical characteristics and had become an extratropical depression.^[1][7] Over the next couple of days Sina's extratropical remnants maintained a south-eastward track, before it was absorbed by an advancing trough of low pressure near 50°S on December 4.^[7]

Preparations, impact and aftermath

While it was active Sina affected Fiji, Tonga, Niue and the Southern Cook Islands after initially appearing to threaten the Solomon Islands and Vanautu.^[1] After this usage of the name, Sina was retired.^[8]

Fiji

Late on November 25, TCWC Nadi issued a tropical cyclone alert for Fiji while Sina was located about 665 km (415 mi) to the northwest of the country.^[1] During the next day, a gale force wind warning was issued for the western half of Viti Levu, the Yasawa and Mamanuca island groups, which was later upgraded to a storm warning while a gale warning was also issued for the rest of Viti Levu.^[1] These storm warnings were briefly dropped early on November 27, when the storm appeared to be moving away from the country, but as Sina came within range of the Nadi radar, it became apparent that southern Fiji would be directly hit by the system.^[1] As a result, hurricane warnings were issued for Vatulele, Kadavu and smaller nearby islands, while storm warnings were re-issued for the western half of Viti Levu, and the Mamanuca island group.^[1] Over the next day as the cyclone approached, hurricane, storm and gale warnings were revised to cover various islands within the Koro and Southern Lau island groups, before all warnings were cancelled on November 28, as Sina moved away from Fiji.^[1]

Ahead of Sina affecting the Fijian islands, from November 27, until November 29, with wind gusts of up to 175 km/h (110 mph) hundreds of holiday makers were evacuated from Fiji's outer island resorts to hotels on the mainland including resorts located within Fiji's northern and eastern divisions.^{[6][9][10][11]} As the cyclone affected Fiji high winds and heavy rain forced the closure of several local airports and the Nadi International Airport for around 20 hours.^{[10][12][13][14]} As the cyclone moved towards the east-southeast between November 27–28, it passed near to or over the south-western coast of Viti Levu, Vatulele, Bequa, Northern Kadavu and various islands within the Moala and Southern Lau island groups and caused some coastal erosion.^[1][15] As it moved through Fiji, Sina caused destroyed or damaged houses and other building structures while bringing down electric and telephone lines and uprooting trees.^[1][6] The system also severely affected crops and vegetation including sugar cane and pine forests, however the extent of the damage was limited by the fact that many of the crops had already been harvested.^[1][16]

On December 7, the Australian Government via the international development bureau and Air Pacific provided emergency shelter materials, including tarpaulins, plastic sheeting and rope, after an appeal for international assistance was made by the Fijian Government.^[17][18] After the Cyclone damaged resorts were quickly repaired, while the Fijian Government launched an international advertisement campaign for the islands with discounted airfares.^[16] Overall Sina caused over 7007260000000000000$F26 million (7007185000000000000$US18.5 million) worth of damage to the Fijian islands, with most of the damage accounted for by losses to agriculture, sugar cane, and pine forests.^[1][7] After Cyclone Sina had washed away a railway bridge on Vanua Levu that was used to take sugar cane to Labasa's mills, growers had no choice but to go through the village of Korowiri.^[19] However, the workers refused to go into their fields unless they had police protection to go through the village, after Methodists from the local church attacked a group of growers for working on Sundays in defiance of Fiji's Sunday Observance Decree.^[19] As a result sugar cane that had been damaged by Sina was left rotting in Fiji's fields until the Fiji Sugar Corporation ordered that a temporary bridge be built to bypass the village.^[19]

Tonga

Late on November 27, as Sina affected the Fijian island of Viti Levu, TCWC Nadi issued a tropical cyclone alert for Tongatapu, Haʻapai and Vavaʻu group of islands.^[1] During the next day the tropical cyclone alert for Vavaʻu was cancelled, while a gale force wind warning was issued for Haʻapai and a storm force wind warning was issued for the Tongatapu islands.^[1] The system subsequently moved in between the Tongatapu and Haʻapai group of islands, before TCWC Nadi cancelled the warnings during the next day.^[1] Within Tonga sustained windspeeds of up to 96 km/h (60 mph) and wind gusts of up to 139 km/h (86 mph) were recorded at the Nukuʻalofa weather station.^[1] Parts of the Tongan capital city Nuku'alofa was left without power, after electric lines were brought down, while several homes were partially damaged after the roofs lost their iron.^[20] Overall only minor damage to weak structures, trees, banana plantations, electric and telephone lines was recorded within the island nation.^[1]

Other island nations

During November 29, TCWC Nadi issued strong wind warnings for Niue as the island experienced marginal gale force winds from the system, as it passed about 185 km (115 mi) to the south of the island.^[1][21] High seas salt spray and waves caused some damage to crops on Niue, the islands wharf, and washed away two temporary roads that were installed after Cyclone Ofa had affected the island earlier in the year.^[1][22]

Early on November 30, as the system moved towards the east-southeast TCWC Nadi issued a gale warning, for the Cook Islands of Rarotonga and Mangaia, while issuing strong wind warnings and tropical cyclone alerts for the rest of the Southern Islands.^[1][21] Warnings were subsequently maintained until the final warning was issued later that day, as Sina spared the Cook Islands its major effects and recurved sharply towards the south-southeast.^[1] Only minor damage to shallow rooted crops and weak structures was reported, after high seas and gale force winds buffeted the northern side of Rarotonga.^[1][23]

See also

• Cyclone Evan

References

External links

• World Meteorological Organization
• Fiji Meteorological Service
• Meteorological Service of New Zealand
• Joint Typhoon Warning Center

• Coastal Damage Inspection: South-West Viti Levu, Fiji after Cyclone Sina - Contains several images of the coastline before and after Cyclone Sina

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