Cyclone Bola

Severe Tropical Cyclone Bola

Category 4 cyclone (Australian scale) Category 3 tropical cyclone (SSHWS)
Satellite image of Cyclone Bola near peak intensity
Formed	February 24, 1988 (1988-02-24)
Dissipated	March 4, 1988 (1988-03-05)
Highest winds	10-minute sustained: 165 km/h (105 mph) 1-minute sustained: 195 km/h (120 mph)
Lowest pressure	940 mbar (hPa); 27.76 inHg
Fatalities	3 direct
Damage	$82 million (1988 USD)
Areas affected	Fiji, Vanuatu, New Zealand
Part of the 1987–88 South Pacific cyclone season

Cyclone Bola was one of the costliest cyclones in the history of New Zealand,^[1] causing severe damage as an extratropical cyclone when it passed near the country in March 1988. It formed on February 24 to the north of Fiji, and tracking generally southwestward it reached hurricane-force winds near Vanuatu on February 28. The next day it generated peak wind velocities of 195 km/h (120 mph), though it quickly weakened as it accelerated southward. On March 4 Bola transitioned into an extratropical storm, passing to the north of the North Island of New Zealand on March 8. It weakened further and was absorbed by a stationary trough near the South Island on March 12.

The cyclone first affected Fiji, where it produced gale force winds and strong waves. In Vanuatu, Bola dropped heavy rainfall, which destroyed two bridges and caused severe damage to islands in the group. Bola caused severe damage to the North Island of New Zealand, where heavy rainfall peaked at 917 mm (36.1 in) in Gisborne Region. Damage totaled over $82 million (1988 USD).^[2] Three people were killed due to flooding, and hundreds were evacuated when a swollen river threatened Wairoa. The name Bola was later retired, meaning it will not be used again within the same basin.^[3]

Meteorological history

On February 24, 1988, the Fiji Meteorological Service's Nadi Tropical Cyclone Warning Center (TCWC Nadi) started to monitor a tropical depression that had developed within the South Pacific Convergence Zone to the north-northeast of Suva, Fiji.^[4][5][6] During that day the system moved towards the southwest, before the Joint Typhoon Warning Center (JTWC) initiated warnings on the system and designated it as Tropical Cyclone 13P after it had become equivalent to a tropical storm.^[7] Over the next 2 days the system gradually developed tropical cyclone characteristics as it moved south-westwards and passed to the northwest of Fiji.^[5] TCWC Nadi subsequently named the system Bola during February 26, after it had become equivalent to a modern day category 1 tropical cyclone on the Australian tropical cyclone intensity scale.^[4][5][8]

Bola gradually intensified as its movement slowed and stalled, and on February 28 the Joint Typhoon Warning Center (JTWC) assessed the cyclone as reaching hurricane-force winds near Vanuatu. It turned to a southeast drift before executing a small cyclonic loop on March 1, during which the JTWC estimated Bola attained peak winds of 195 km/h (120 mph). At the same time, its minimum central pressure was estimated at 940 mbar.^[9][10]

After reaching peak intensity, Cyclone Bola quickly weakened as it accelerated southeastward toward a frontal trough.^[9][11] On March 3, its winds dropped below hurricane-force,^[9] and it gradually lost its tropical characteristics. The structure became asymmetric, with a large band of clouds extending well south of the circulation.^[11] By March 4, Bola had completed the transition into an extratropical cyclone.^[9] Which turned south and began to affect the North Island of New Zealand on March 6. A building ridge of high pressure to its south caused the extratropical remnants of Bola to slow and turn to the west on March 7. The next day, the storm passed about 110 km (70 mi) north of the North Island. Around the same time, the storm began slowly filling, meaning the low pressure area associated with Bola was losing its identity. It turned southward on March 9, and on March 12 was absorbed by a stationary trough in the Westerlies near the western coast of the South Island.^[11]

Impact

Fence posts buried alongside Lake Tutira due to erosion caused by Cyclone Bola

Fiji and Vanuatu

As a tropical cyclone, Bola first impacted Fiji shortly after forming while passing to the northwest, and again as it was weakening after peak intensity to the southwest of the island. It brushed the country with gale force winds and waves of up to 5 m (16.4 ft). Severe damage was reported throughout the archipelago, however the Fijian Government did not assess how much damage was done.^[12][13]

Cyclone Bola remained near Vanuatu for about a week,^[14] during which it reached its peak intensity while executing a cyclonic loop.^[9] The most affected locations were Epi island, the Shepherd Islands, and the islands in Malampa Province, and throughout the country the cyclone affected more than 15,000 people and 3,000 houses.^[14] In a five-day period the cyclone dropped about 450 mm (17.7 in) of rainfall. Two bridges on Malakula were destroyed, and several other bridges were flooded or damaged. The passage of the cyclone also left several buildings, roads, and crop fields damaged.^[15]

New Zealand

Cyclone Bola created some of the heaviest rainfall totals for a single storm in the history of New Zealand, with some locations receiving more than half of their annual rainfall totals from the storm. While the cyclone passed north of the island, a strong easterly flow over the North Island contained the interaction between moist air from Bola and drier air from the ridge to its southeast. In the Gisborne region, the flow resulted in the heaviest rainfall totals, when the moisture ascended over the region's western mountainous areas and condensed into precipitation. One station recorded 419 mm (16.5 in) in a 24 hour period.^[11] The maximum rainfall total attributed to the storm was 917 mm (36.1 in), reported at a station near Tolaga Bay.^[1] Heavy rainfall totals of up to and over 300 mm (12 in) were observed in the regions of Auckland and Northland.^[11] The cyclone is the largest to be recorded in 93 years of rainfall records. As such, it had a large and lasting effect on the rivers of the area when it deposited a large amount of sediment, as recorded in the sedimentary record of Lake Tutira.^[16] Shortly prior to losing its identity, the remnants of Bola also dropped 100–200 mm (4–8 in) of precipitation on the South Island of New Zealand.^[11]

Storm damage was heaviest in Gisborne, where rain destroyed or damaged several roads and bridges.^[11] Three days of continuous rainfall led to mudslides, flooding,^[1] and erosion.^[2] Flooding killed three people when a car was swept away. In Te Karaka in Gisborne, a flooded river forced 500 residents to evacuate. A total of 1,765 farmers were affected by the flooding, accounting for about 3,600 hectares (8,900 acres) of damaged crop fields and about $90 million in crop damage (1988 NZD, $82 million 1988 USD. Water supplies were disrupted in two cities due to flooding. Rainfall in Northland Region caused flooding and outages to telephone and power.^[1] Additionally, beginning on about 6 March, the cyclone began affecting the North Island with strong easterly winds of over hurricane force, caused by the interaction between the extratropical remnants of Bola and a ridge of high pressure to its south. The winds damaged a few homes, including some in which the roofs were damaged or destroyed.^[1][11] In addition, the strong winds downed several trees, and at the same time, erosion and landslides left hillsides bare without grass or trees.^[2][11]

Aftermath

In Vanuatu, cyclone victims received food and emergency aid following the storm.^[14] Australian patrol boat HMAS Cessnock provided manpower assistance to 11 islands in the country.^[17] Reconstruction costs in Vanuatu totalled about $5 million (1988 USD), which was about 10 percent of the country's national budget.^[14]

After the passage of the storm, four towns in New Zealand declared states of emergency.^[1] The New Zealand government provided about $80 million (1988 NZD) to the east coast region of the North Island for assisting in cyclone damage. $8 million was used to create an East Coast Forestry Conservation Scheme, which was set to protect forests and prevent erosion.^[2] A study was taken five years after the storm, consisting of a group of 112 people who were evacuated or received monetary assistance in response to the cyclone; the study showed 12% of the respondents as experiencing Posttraumatic stress disorder, of which they reported a general lack of assistance and public support.^[18]

See also

• List of tropical cyclones
• Geography of New Zealand

References

External links

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

v t e Tropical cyclones of the 1987–88 South Pacific cyclone season TS 04P 1 Agi 4 Anne 4 Bola 3 Cilla 2 Dovi Book · Category · Portal · WikiProject · Commons

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