South Pacific Ocean: Category-1 Tropical Cyclone Zazu continues to track southeastward between Niue and Tonga, Dec. 16 /update 4

Event

Category-1 Tropical Cyclone Zazu maintains strength as it tracks southeastward in the South Pacific Ocean, Dec. 16. As of 0100 TOT, the storm's center of circulation was approximately 337 km (210 miles) northeast of Nuku'alofa, Tonga. Forecast models indicate the system will strengthen slightly into a Category-2 Tropical Cyclone by 1200 Dec. 16 as it continues moving southeastward. Impacts associated with the system will likely be felt in Tonga and Niue through at least Dec. 16. The storm is forecast to weaken gradually and turn extratropical by early Dec. 17 as it begins to dissipate over the South Pacific Ocean. Some uncertainty remains in the track and intensity forecast, and changes could occur in the coming days.

Government Advisories
As of Dec. 16, the Tonga Meteorological Services has issued gale and damaging swell warnings for 'Eua, Ha'apai, Tongatapu, and Vava'u land areas and coastal waters. A heavy rainfall warning is also in effect for Ha'apai, Niuas, and Vava'u. The Fiji Meteorological Service has issued a gale warning and a tropical cyclone warning for Niue. Authorities will likely issue new warnings or update existing advisories throughout the system's progression in the coming days. Weather warnings could remain active even after the system's immediate threat has diminished, as some areas may still be highly susceptible to rain-induced hazards. The possibility of localized evacuations cannot be discounted if weather conditions prove particularly hazardous.

Hazardous Conditions
Sustained heavy rainfall could trigger flooding in low-lying communities near streams, creeks, and rivers, as well as in urban areas with easily overwhelmed stormwater drainage systems. Sites 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 Zazu could result in coastal flooding. Abnormally high tides are possible. In addition to the heavy rain, flooding, and storm surge, the storm will produce damaging wind gusts. Widespread and prolonged power outages due to uprooted trees and toppled utility lines are likely.

Transport and Infrastructure
Inclement weather associated with the storm is likely to trigger localized business, transport, and utility disruptions through at least Dec. 17. Floodwaters and debris flows may render some bridges or roadways impassable, further impacting overland travel in and around affected areas. 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, including Niue Hanan International Airport (IUE) in Niue and 'Eua Airport (EUA) in 'Eua, Tonga. Power outages are likely in areas that experience severe weather. 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.

Advice

Heed the instructions of authorities as the storm approaches. Use extreme caution in low-lying coastal areas and near streams, creeks, and other waterways due to the high 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 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. Keep any necessary medications in a waterproof container.

Plan accordingly for protracted commercial, transport, and logistics disruptions in areas in the path of the storm, 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
Fiji Meteorological Service
Tonga Meteorological Services