Cyclone Ofa

Severe Tropical Cyclone Ofa

Category 4 cyclone (Australian scale) Category 4 cyclone (SSHWS)
Cyclone Ofa on February 3, 1990
Formed	January 27, 1990 (1990-01-27T0Z)
Dissipated	February 10, 1990 (1990-02-10T0Z)
(extratropical after February 8, 1990)
Highest winds	10-minute sustained: 185 km/h (115 mph) 1-minute sustained: 215 km/h (130 mph)
Lowest pressure	925 mbar (hPa); 27.32 inHg
Fatalities	8 total
Damage	$187 million (1990 USD)
Areas affected	Tuvalu, Western Samoa, American Samoa, Tokelau, Niue, Tonga
Part of the 1989-90 South Pacific cyclone season

Severe Tropical Cyclone Ofa (JTWC designation: 13P, also known as Hurricane Ofa) was considered to be the worst cyclone to affect the Samoan islands since the 1889 Apia cyclone.^[1] The system was first noted on January 27 near Tuvalu, as a shallow tropical depression that had developed within the South Pacific Convergence Zone. The cloud pattern slowly organized, and on January 31, while located east of Tuvalu,Ofa attained cyclone intensity. Moving slowly southeast, Ofa developed storm-force winds. It attained hurricane-force winds on February 2. Cyclone Ofa reached peak intensity on February 4. Shortly after, its peak Ofa began to weaken over a less favourable environment. Ofa was declared an extratropical cyclone on February 8, though the system was still tracked by meteorologists until February 10.

Ofa produced gales or high winds or gales on many islands, resulting in widespread damage due to a combination of storm surge and high seas. In all, eight people were killed and damage totaled to 7008187000000000000US$187 million. The worst effects were recorded in Samoa, where seven people were killed. Roughly 200 people were evacuated, and 10 to 20 others were injured though the islands. Extreme damage to crops and trees was also recorded. Elsewhere, Ofa was blamed for the lowest ever recorded pressure on the island of Niue, along with considerable damage.

Meteorological history

On January 27, the Fiji Meteorological Service's Nadi Tropical Cyclone Warning Center started to monitor a shallow tropical depression that had developed within the South Pacific Convergence Zone over the islands of Tuvalu.^[2][3] Over the next few days the depression remained slow moving near Tuvalu, as it slowly developed the characteristics of a tropical cyclone.^[2] During January 31, the Naval Western Oceanography Center (NWOC) reported that Ofa had become equivalent to a tropical storm and designated it as Tropical Cyclone 13P.^[4][5] Later that day, TCWC Nadi named the depression Ofa after it had developed into a category 1 tropical cyclone on the Australian tropical cyclone intensity scale, while it was located about 290 km (180 mi) to the east of Funafuti, Tuvalu.^[2][6]

From the time the system was named it developed steadily reaching storm intensity in less than 12 hours and hurricane intensity within 36 hours.^[2] Soon after 0000 UTC on the 2nd of February, Ofa curved towards the southsoutheast and moved on this new path for the next 48 hours.^[2] It passed about 60 miles west of Savaiti island in Western Samoa between 1000 UTC and 1800 UTC on the 3rd.^[2] Thereafter it took a more southeastward track and accelerated to about 15 knots.^[2] The system reached peak intensity around 1200 UTC on the 4th with maximum average winds estimated at 185 km/h (115 mph) close to the centre. Storm force winds extended to about 90 miles and gales to about 250 miles from the cyclone centre.^[2] It maintained this intensity for about 24 hours as it continued moving toward east southeast. By now Ofa was fast approaching Niue. It passed within 30 miles west of Niue around 0300 UTC on the 5th of February.^[2] As Ofa passed Niue it began to show a slight weakening trend.^[2] Subsequently, it curved slowly towards the south and slowed down to about 10 knots. It crossed the 25 degree south latitude and into TCWC Wellington's area of responsibility for issuing maritime warnings, just before 1800 UTC on the 6th of February.^[2] At this time Ofa was still very intense with maximum average winds estimated at 75 to 80 knots close to its centre.^[2] Thereafter, the system weakened rather fast as a result of encountering shear from strong upper-level winds and also due to its entrance into cooler waters.^[2]

Preparations, impact and aftermath

Cyclone Ofa affected seven different island nations and caused gales or much stronger winds in six of those countries which resulted in damage ranging from moderate to very severe. Storm tide from the cyclone which is the combined effect of storm surge and high tide caused havoc in several countries and was the major cause of destruction.^[2] Overall the system killed at least eight people while it was estimated that the overall damage would amount to over 7008180000000000000US$180 million with damage totals of at least 7008150000000000000US$150 million and 7007300000000000000US$30 million in Western and American Samoa.^[2]

Tuvalu

Early on January 30, TCWC Nadi issued a tropical cyclone alert for the Tuvaluan Islands, as it was possible that the system could produce gale force winds over the islands within 24 - 36 hours.^[2] Over the next day, this alert was maintained this alert as Ofa gradually developed further, before late on January 31, it was replaced with a gale warning for the islands of Funafuti, Nukulaelae and Niulakita and a strong wind warning for the rest of the archipelago.^[2] Along with the Samoa depression that occurred a few days after the cyclone had moved away from the islands, Ofa had a major impact on Tuvalu with residential houses, trees and food crops destroyed on Vaitupu, Niutao, Nui and Nukulaelae Islands.^[2][10][11]

Wallis and Futuna

During February 1, TCWC Nadi issued a tropical cyclone alert for the both Wallis and Futuna islands as Cyclone Ofa was located about 445 km (275 mi) to the north of Wallis Island and rapidly intensifying.^[2] During the next day as Ofa was expected to pass close enough to Wallis Island to cause gale force winds on the island, TCWC Nadi issued a gale warning for Wallis while the alert for Futuna was maintained.^[2] Later that day Ofa passed about 240 km (150 mi) to the east of Wallis, before the alert and warnings were cancelled during the next day.^[2]

Samoa

Ahead of and as Cyclone Ofa affecting Western Samoa, between February 2 – 4, TCWC Nadi issued various gale and storm force wind warnings for Samoa, however due to communication and various other problems some of these warnings did not reach the Apia Observatory.^[2] Some of the warnings that did get through were distorted and contained strong wind warnings rather than storm force wind warnings.^[2] As a result it was not known what was broadcast to the public who were warned to expect strong winds rather than storm force winds and thus there was no doubt that the correct precautionary measures may not have been taken.^[2]

Cyclone Ofa affected Samoa between February 2 – 4, with widespread heavy rain and north-westerly winds of up to 110 km/h (70 mph).

As the winds increased further during the next day, communication between Western Samoa and the outside world was lost almost completely. The Apia meteorological office was hit by high sea waves at 10.45 am on 2 February (Samoa time) and had to be abandoned due to rising floods. A few hours later, the office was destroyed completely. The station at Faleolo also suffered damage and lost communication with Nadi for about 24 hours from 0500 UTC on the 3rd. During the height of the cyclone the only means of communication left with Western Samoa was through a Polynesian Airline Boeing 727 aircraft standing on the tarmac at Faleolo Airport. Due to communication problems quite a number of yital meteorological observations could not reach Nadi.

Winds over Western Samoa became very destructive, with average speeds reaching 60 knots with gusts over 80 knots from the evening of the 2nd (Samoan time). Rain became continuous and very heavy. Huge waves and sea spray resulting from storm tide (combined effect of storm surge and high tides) flooded low lying coastal areas, reaching 10 to 15 km inland in places and adding to the already extensive flooding caused by the heavy rain. Destructive winds lasted for almost 24 hours and the heavy rain for several hours longer.

The combined effect of very high winds, heavy rainfall and storm tide created an impact never encountered before in Western Samoa in more than 100 years, and left the whole population in a state of terrible shock and distress. Reports reaching Nadi indicate that all of some 330 villages in the islands-received at least some damage with the northern coasts of Upolu and Savaii being the worst hit. Roofs of houses were peeled away, walls knocked down, trees felled, and roads, bridges and power lines were badly damaged. Storm tide caused even more damage, washing off about 80 percent of the northwestern coastlines of the two main islands, reshaping them and creating several islands of coral debris near the reef line. Meteorological records and equipment at the Apia Observatory were ruined when huge sea waves struck the beachfront facility.

Altogether seven lives were lost, most of them washed away by waves or killed by flying debris. According to a preliminary estimate of the damage, the cyclone cost the country about US$306 million (roughly US$130 million).

The worst effects were recorded on Samoa, where seven people were killed in a number of ways^[12] and it became the worst cyclone to affect the area in nearly 100 years. Damage on Western Samoa totaled to 7008130000000000000US$130 million.^[6] The storm brought waves of up to 18 m (59 ft)^[13] resulting in coastal erosion in northern Upolo and Savaii, washing out roads.^[14] Wind gusts up to 100 mph (160 km/h) were recorded on some locations.^[7]

Thousands of people were left homeless and entire villages were destroyed.^[13] Roughly 200 people were evacuated, and 10 to 20 people were injured due to flying derbis. Roughly two thirds of the territories population was without water.^[15] Roughly 85% of schools on American Samoa were destroyed.^[16] Some villagers held them to trees in order to prevent them from being swept away.^[1] Around 31% of the island's tress were uprooted;^[17] tree crops suffered from salt burns.^[18] Tree plantations were also badly damaged.^[19] The sociological affect on Western Samoa was considered severe.^[12] The storm affected shipping in many ways, the worst came from the ship Queen Salamasina in Apia.^[12]

American Samoa

Despite passing about 160 km (100 mi) to the west of Pago Pago, Cyclone Ofa affected American Samoa between February 3–5 with wind gusts of up to 160 km/h (100 mph), which caused widespread and extensive damage to the territory.^[2][7][20] Ahead of the cyclone affecting the island nation, a gale warning was issued by TCWC Nadi for the American territory, while forecasting that very heavy rain, high seas and damaging sea swells would impact the area.^[2]

On February 4, within the immediate aftermath of the cyclone, the Lieutenant Governor Galea'i Peni Poumele placed the whole of American Samoa under a state of emergency.^[21] Upon his return from an international conference the Governor Peter Tali Coleman subsequently wrote to the United States President George H. W. Bush on February 7, asking him to declare the islands a federal disaster area and asked for money to help the American territory rebuild and recover from the Cyclone.^[22] The President subsequently declared the islands a major disaster area on December 9, which enabled Samoans to claim federal aid.^[23][24]

Tokelau

Early on February 2, TCWC Nadi issued a gale warning for Tokelau and Swains Island, with the islands forecast to experience damaging gale force wind gusts of up to 130 km/h (80 mph) during that day as it moved to the south of Swains Island.^[2] Heavy rain, high seas, damaging swell and some flooding of low-lying coastal areas were also forecasted to occur.^[2] The warnings continued throughout that day before all warnings were cancelled at 1800 UTC and replaced with a strong wind warning, with rain squalls continuing to affect the islands.^[2] Within Tokelau, the system caused extensive damage to several public buildings and 91 houses, while destroying gardens, tree crops and 22 houses.^[25][26] High seas associated with the cyclone washed away sea walls surrounding the atolls off Nukunonu, Atafu and Fakaofo.^[8][26] Overall about 80 percent of the breadfruit and coconut trees were destroyed or damaged by the winds, while an inundation of water associated with Ofa was responsible for washing away or contaminating topsoil.^[8][25][26] There were no deaths or serious injuries within Tokelau or on Swains island, while in monetary terms the damage was estimated at about 7006240000000000000US$2.4 million after Ofa's wind, rain and waves caused a major impact on the islands.^[7][9] About a week after the system had affected Tokelau, the Royal New Zealand Air Force delivered urgently needed supplies via airdrop, before further assistance from New Zealand arrived by sea.^[26]

Niue

Early on February 4, TCWC Nadi issued a gale warning for Niue while Ofa was located to the northwest of the island, with gale force winds forecast to occur over the island nation during the next day.^[2] During that day after the system had accelerated and moved further towards the south-southeast than had been expected, TCWC Nadi issued a hurricane warning at 1800 UTC and reported that Ofa appeared to be heading directly for Niue.^[2] At around 1800 UTC that day Niue started to experience strong and gusty winds, before it was affected by destructive hurricane force winds for several hours during February 5.^[8] At around 0300 UTC, as Ofa's eye passed about 30 km (20 mi) to west of the island, Niue recorded its lowest ever recorded pressure of 962.4 hPa (28.42 inHg).^[6] During that day the system continued to move towards the south-southeast and lost its intensity, the hurricane warning, was gradually replaced with a damaging swell and a strong wind warning.^[2]

Cyclone Ofa caused very severe damage on Niue with gigantic seas resulting from storm surge swept over the northern and western coastal areas.^[8] Virtually all landings to the sea were washed away or damaged badly by huge seas.^[8] There was considerable damage to hospital buildings, the islands hotel, roads, houses, churches and other facilities for the public.^[8] Due to the damage to the power lines, electricity was out for about 24 hours.^[8] Most of the islands private water supply tanks were contaminated by salt water and declared unsuitable for drinking.^[8] Within the aftermath of the cyclone the Royal New Zealand Air Force flights brought in emergency medical supplies, generators, water and fuel pumps, and food to Niue while a New Zealand navy vessel, the Endeavour, delivered additional foodstuffs, as well as building and plumbing materials, two weeks after the storm.^[27]

Tonga and Fiji

During February 2, as Ofa moved southwards TCWC Nadi issued a gale warning for Niuafo'ou and Niuatoputapu islands, while issuing the rest of Tonga with a tropical cyclone alert and a strong wind warning.^[2] During the next day a hurricane warning was issued for Niuatoputapu, after the system had rapidly intensified and it had became apparent that the cyclone centre would pass quite close to the island.^[2] As it issued the hurricane warning, TCWC Nadi issued a gale warning for the rest of Tonga, while Ofa was located about 160 km (100 mi) to the north of Niuatoputapu.^[2] As the cyclone headed south-eastwards on its current path, TCWC Nadi predicted that it would pass about 55 km (35 mi) to the east of Niuatoputapu, at about 1100 UTC, December 4, (0000 UTC+13, December 5).^[2] However over the next 12 hours, Ofa curved more towards the southeast, with the cyclone subsequently passing about 110 km (70 mi) to the east of Niuatoputapu.^[2] This meant that the island only received storm force winds from the system and that Haapai and Tongatapu Groups were spared from damaging gale force winds.^[2] As Ofa moved away from Niuatoputapu and the rest of Tonga, the hurricane warning was replaced with a gale warning, before all gale warnings for Tonga were cancelled early on December 5.^[2]

Within Tonga the worst affected islands were Tafahi and Niuatoputapu, which both suffered severe damage to houses, church buildings, coconut plantations, food crops and other vegetation while one person was killed.^[8] A preliminary estimate of the damage stood at about 7006320000000000000US$3.2 million.^[8]

Within Fiji, high seas associated with Ofa, caused serious damage to the eastern Lau Islands.^[28]

See also

• Cyclone Val
• Cyclone Heta

References

External links

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

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