South Pacific: Tropical Cyclone Ruby tracking southeast in the South Pacific Ocean late Dec. 14 /update 4

Event

Tropical Cyclone Ruby is tracking southeastward in the South Pacific Ocean late Dec. 14 after passing over New Caledonia throughout the day. As of 23:00 NCT, the storm's center of circulation was approximately 326 km (202 miles) east-southeast of Noumea. Forecast models indicate the system will maintain its strength as it continues tracking southeast toward northern New Zealand, passing well north of the country early Dec. 16. Some uncertainty remains in the track and intensity forecast, and changes could occur in the coming days.

Reports indicate flooding has occurred in Kouaoua and Hienghene townships in New Caledonia; as of late Dec. 14, energy providers reported that over 17,000 customers were still without power across the territory.

Government Advisories
Officials in New Caledonia have warned that heavy rains, strong winds, and rough seas will continue to affect parts of the territory through Dec. 15, especially the southernmost islands. Level 2 cyclone warnings remain in place across southern provinces as of early Dec. 15; authorities advise residents to confine themselves indoors, stay away from windows, and wait for further instructions. Other provinces have moved to a safeguard phase, with the public being advised to continue to monitor the situation and limit nonessential travel. Weather warnings could continue to remain active even after the system's immediate threat has diminished, as some areas may still be highly susceptible to rain-induced hazards. Localized evacuations are possible if weather conditions prove particularly hazardous.

Hazardous Conditions
The tail of the storm system may continue to bring heavy rainfall, strong winds, and rough seas to parts of New Caledonia and Vanuatu over the coming days. Sustained heavy rainfall could trigger flooding in low-lying communities near streams, creeks, rivers, and urban areas with inadequate stormwater drainage systems.

Sites located downstream of large reservoirs could experience flash flooding after relatively short periods of intense rainfall. Rain-induced landslides are possible in steeply sloped terrains. Flooding could isolate some communities for several days. Prolonged swells and storm surge generated by the system will likely result in coastal flooding as the system approaches land. Persistent onshore flow could make it difficult for the surge to recede and for water levels to decrease in coastal river catchments.

Transport
Inclement weather associated with the storm could trigger localized business, transport, and utility disruptions. Floodwaters and debris flows could render some bridges or roadways impassable, impacting overland travel in and around affected areas. A landslide has blocked off a road at Moneo Sud in Ponerihouen, New Caledonia, while flooding has impacted multiple routes across the territory. As of late Dec. 14, Golone, Malabou, Nendjane, and Nehoue raft crossings are suspended and sections and crossings on the RPB7, RPN10, RT3, RPN3, and RT1 roads are closed. Areal flooding in urban locations could also result in severe traffic congestion, while strong winds will pose a hazard to high-profile vehicles. Heavy rain and low visibility may trigger flight disruptions at regional airports. Noumea-La Tontouta International Airport (NOU) remains closed as of early Dec. 15.

Disruptions triggered by inclement weather and resultant hazards, such as flooding, could persist well after conditions have improved. If there is severe damage to infrastructure, repair or reconstruction efforts may exacerbate residual disruptions.

Health
Stagnant pools of water during and after flooding increase the incidence of insect- and waterborne diseases, such as dengue fever, cholera, and malaria. The threat of these disease outbreaks is usually elevated in low-income or underdeveloped areas of major urban centers due to the presence of incomplete or open sewer lines. The latent threat of waterborne contaminants from inundated industrial sites cannot be discounted; exposure to raw sewage and other hazardous materials mixed with floodwaters poses a serious health threat.

Advice

Activate contingency plans in areas where officials forecast tropical storm conditions. Heed any evacuation orders that may be issued. Use extreme caution in low-lying coastal areas and near streams, creeks, and other waterways due to the potential for severe flooding and storm surge. Stockpile water, batteries, and other essentials in advance. Charge battery-powered devices when electricity is available; restrict the use of cellular phones to emergencies only. Power down mobile devices when not in use. Keep important documents and necessary medications in waterproof containers. Observe strict food and water precautions, as municipalities could issue boil-water advisories following flooding events. Take precautions against insect- and waterborne diseases in the coming weeks.

Plan accordingly for commercial, transport, and logistics disruptions in storm-affected areas, especially if vital infrastructure is damaged. Seek updated information on road conditions before driving or routing shipments through areas where flooding has occurred. Confirm flights before checking out of hotels or driving to the airport; clearing passenger backlogs may take several days in some locations.

Resources

Joint Typhoon Warning Center
Meteo-France Nouvelle Caledonie (French)
Department of Civil Security and Risk Management of New Caledonia
Vanuatu Meteorology and Geohazard Department