Severe Tropical Cyclone Namu was considered to be one of the worst tropical cyclones to impact the Solomon Islands on record, after it caused over 100 deaths within the island nations. It was first noted as a weak tropical depression to the north of the Solomon Islands during 15 May 1986. Over the next couple of days, the storm steadily intensified while meandering. After briefly moving west, the storm attained Category 2 intensity on the Australian intensity scale on 18 May, as it moved through the island chain on the next day. Cyclone Namu attained peak intensity of . After retaining its peak intensity for a day, Namu turned south and weakened steadily. By 21 May, the winds of Cyclone Namu had been reduced to only . Continuing to weaken, Namu turned east and dissipated on 22 May, away from the island chain.
The system impacted the Solomon Islands, Vanuatu and New Caledonia and caused over 100 deaths, as well as varying amounts of damage to the island nations. As a result, the name Namu was later retired from the lists of tropical cyclone names for the South Pacific by the World Meteorological Organization.
The storm's slow motion allowed for prolonged periods of heavy rainfall, resulting in phenomenal flooding across the Solomon Islands. The islands of Malaita and Guadalcanal experienced the most significant damage from Namu. Coastal areas of the former were severely damaged by rough seas and strong winds, especially along the eastern side where entire villages were destroyed. Meanwhile, on the island of Guadalcanal, a village of 43 people had only 5 survivors. Moreover, Cyclone Namu flooded 75% of Guadalcanal's plains. In addition, 22% of homes were either damaged or destroyed on the island.
Across the Solomon Island group, schools, buildings, electricity, water supplies, roads, communication systems, forests, and agriculture sustained widespread damage. In some regions, nearly all homes were destroyed. Mudslides destroyed roads, bridges, water pipes and drainage systems. Crops such as cocoa, copra, coffee, and rice were destroyed. Villages throughout the entire island group sustained severe damage. Overall, approximately 90,000 people, one third of the country's population, were reported as homeless. In all, Cyclone Namu was responsible for at least 150 deaths, mostly from flooding and landslides. Property damage and economic losses across the Solomon Islands totaled $25 million and $100 million (1986 USD) respectively. During the aftermath of the storm, the government of the Solomon Islands declared a national state of emergency. Meanwhile, the United Kingdom, Papua New Guinea, the United States, and Japan also sent supplies and goods to the Solomon Islands.
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Meteorological history
On 15 May 1986, the Fiji Meteorological Service (FMS) started to publicly monitor a tropical depression that developed within a monsoon trough to the north of Malaita in the Solomon Islands. The system initially moved eastwards away from the archipelago and showed signs of weakening, as clouds associated with the system dissipated and there were no banding features present. As a result, the FMS was doubtful about the presence of gale-force winds and suspended issuing warnings on the system but continued to monitor it. During 17 May, the system showed signs of reintensifying as it turned and started to move south-westwards back towards the island nation. Later that day, the United States Joint Typhoon Warning Center (JTWC) initiated advisories on it and designated it as Tropical Cyclone 33P, before the FMS reinitiated advisories on the system as it started to rapidly intensify. At around 21:00 UTC (08:00 SIT, 18 May), the FMS determined that the depression had become a tropical cyclone and named it Namu. After being named, Namu intensified as it moved south-westwards towards the Solomon Islands before it passed near or over Manawai Harbour on Malaita at about 14:00 UTC (01:00 SIT, 19 May). The system subsequently changed direction and moved southwards parallel to Malaita's east coast before it crossed the island to the north of Maka.
After crossing Malaita, Namu emerged into the Indispensable Strait, where it was thought to have developed a small ring of marginal hurricane-force winds. According to eyewitness reports obtained after the event, the system made landfall on the island of Guadalcanal near the Marau Sound at about 16:00 UTC (03:00 SIT). Around two hours later, the FMS reported that Namu had peaked with 10-minute sustained winds of , which made it a Category 3 severe tropical cyclone on the modern-day Australian scale. While over Guadalcanal, the system appeared to slow down or become near-stationary for three hours as it approached Avuavu before it turned and moved southwards into the Solomon Sea on 19 May. After entering the Solomon Sea, Namu moved out of the South Pacific tropical cyclone basin and into the Australian region, where the Australian Bureau of Meteorology took over the primary warning responsibility from the FMS. The system subsequently passed about to the northwest of Bellona as it came under the influence of westerly winds that steered it southeastwards. On 20 May, a broad and ragged eye appeared on satellite imagery; however, it quickly became obscured by high clouds. Later that day, the JTWC reported that Namu had peaked with 1-minute sustained wind speeds of , which made it a Category 2 hurricane on the Saffir-Simpson hurricane wind scale. During the following day, the system moved back into the South Pacific basin, where it passed to the northeast of Noumea in New Caledonia and rapidly weakened into a depression as it interacted with cooler air. The system was subsequently lost by the FMS during 22 May as it merged with an eastwards-moving trough near southern Vanuatu, before the system was last noted by the JTWC during the following day.
Effects Namu's main effects were felt in the Solomon Islands, where at least 100 people were reported dead, while the cyclone also caused heavy rainfall and various road closures in New Caledonia. The system was also expected to affect southern Vanuatu, which prompted the FMS to issue special weather bulletins for the island nation on 21 May; however, these were terminated later that day as Namu rapidly weakened.
Solomon Islands
Namu caused over 100 deaths, thousands of injuries and widespread damage to electrical and water supplies, buildings, crops, roads, communication systems and forests, leaving over 90 000 people homeless.
Preps The FMS began issuing special weather bulletins for the Solomon Islands Meteorological Service (SIMS) on 15 May, advising that the system had gale-force winds associated with it and would affect Malaita and smaller islands. However, these bulletins were suspended the next day after the system weakened and it became doubtful that any gales were associated with the depression. After the depression was named Namu on 17 May, the FMS resumed issuing special weather bulletins, which advised the SIMS of the threat posed by Namu to the island nation. Over the next few days, these bulletins were revised accordingly and advised the SIMS which areas would be affected by gale-, storm- and hurricane-force winds and the threat of flooding from rain or storm surge. These bulletins were then used by the SIMS to prepare various gale and tropical cyclone warnings, which were broadcast in both English and Pidgin by the Solomon Islands Broadcasting Corporation. Initially, expectations were for a run-of-the-mill tropical cyclone of moderate intensity to impact the Solomon Islands.
As the system approached and moved over the island nation on 18 May, the National Disaster Council was convened to oversee the relief effort. Ahead of the system's impact on Guadalcanal, authorities decided to close Henderson Field to civilian aircraft, while the Honiara Central Hospital evacuated patients, as the hospital was located on a coastal strip that was vulnerable to river flooding and seawater inundation.
Weather Namu impacted the Solomon Islands between 18 and 21 May with torrential and prolonged rainfall, high seas, gale- to hurricane-force winds and gusts of over , which caused flooding, landslides, mudslides, tidal and wind surges throughout the island nation. In particular, the FMS estimated that storm- or hurricane-force winds had impacted Malaita, Guadalcanal, Bellona as well as other smaller islands that Namu's center had passed within of. They also estimated that gale-force winds had impacted the area between San Cristóbal, the Russell Islands and Santa Isabel. However, the FMS noted that most of the deaths and damage were caused by Namu's slow movement across the island nation, which brought prolonged torrential rainfall, flooding and mudslides. It was later estimated that parts of Guadalcanal had received over of rainfall, while the weather station at Henderson Field recorded a rainfall total of between 18 and 21 May. Flooding caused meandering rivers to cut straight paths, bringing tons of mud, silt and waste debris to rich farming areas and swamping rice crops under floodwaters. Many people were caught off guard by the cyclone's sudden increase in winds and the prolonged heavy rain, especially in remote areas where weather forecasts were difficult to disseminate because of communication problems.
Sikaiana On 17 May, as Namu moved southwestwards, Sikaiana became the first atoll impacted, where the storm destroyed traditional houses made of palm fronds. Additionally, the storm surge washed over the island and polluted wells, which compounded ongoing problems with access to freshwater. Reports indicated that the islanders relied on coconut milk over the following weeks until HMAS Brunei delivered relief supplies and over 200 drums of freshwater on 4 June.
Malaita After impacting Sikaiana, Namu moved south-westwards towards the southern part of Malaita, where it seemed to slow down and remain near-stationary for around five hours. High winds associated with Namu, damaged roofs and defoliated the hills over central, southern and western Malaita, while waves damaged the coastline.
Gudalcanal Within the island nation meandering rivers changed their course and cut a straight path, which brought mud, silt and debris to rich farming areas. The floods also exposed a site of an American and Japanese World War 2 ammunition dump on Guadalcanal from Henderson Field to Red Beach.
Rennell and Bellona Namu passed just to the west of the Rennell and Bellona Province, with both islands in the province feeling the effects of the cyclone. On Rennell Island, 20 houses were destroyed while both the school and the airstrip were damaged by storm surge, high winds and heavy rain. The damage to Bellona was considered more serious with 160 traditional houses destroyed by storm surge, high winds and heavy rain.
Other areas
Impact
Along the eastern coast of the island, damage was massive; entire villages were destroyed. Gardens were devastated and walking pathways were blocked. In Babanakira, 5 people died.
On the island of Guadalcanal, a single mudslide was responsible for killing 38 villagers. Of the 43 people that lived in the small town of Valebaibai, only 5 survived, all of whom narrowly escaped. Moreover, 14 dead bodies were found in the central and southern areas of Guadalcanal on 21 May when flood waters began to recede.