South China Sea: Tropical Storm Conson tracking northwestward over eastern South China Sea late Sept. 8 /update 4

Event

Tropical Storm Conson (known in the Philippines as Jolina) is tracking northwestward over the far eastern reaches of the South China Sea late Sept. 8 after transiting over the northern Philippines. As of 20:00 PHT, the storm's center of circulation was approximately 95 km (60 miles) south-southeast of Manila.

The system is forecast to shift to a westward course and intensify into a typhoon before weakening slightly into a tropical storm as it passes south of Hainan Province, China, and approaches central Vietnam Sept. 13. The storm's track and intensity forecast remain somewhat uncertain, and the system may change accordingly over the coming days.

Conson has caused significant power outages in parts of Samar and southern Luzon. Philippines officials say Conson has affected Mimaropa, Bicol, Western Visayas, and Eastern Visayas, with around 8,600 people in 55 evacuation centers across the impacted area and up to 2,376 people sheltering elsewhere.

Government Advisories
The Philippine Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA) has issued the following advisories associated with Conson:

• Tropical Cyclone Wind Signal (TCWS) 2*: The western portion of Tarlac (Bamban, Capas, San Jose, Mayantoc); the western portion of Pampanga (Mabalacat City, Angeles City, Porac, Floridablanca, Lubao, Guagua, Santa Rita, Bacolor, City of San Fernando, Minalin, Sasmuan, Macabebe, Masantol, Santo Tomas); Zambales; the northern portion of Bataan (Samal, Bagac, Pilar, Morong, Dinalupihan, Abucay, City of Balanga, Orion, Orani, Hermosa)

• TCWS 1**: Pangasinan; the rest of Tarlac; Nueva Ecija; the southern portion of Aurora (Dingalan); the rest of Pampanga; the rest of Bataan; Bulacan, Metro Manila, Rizal, and the northern portion of Quezon (General Nakar); Cavite; the western portion of Laguna (Santa Maria, Los Baños, Bay, City of Calamba, Cabuyao City, City of Santa Rosa, City of Biñan, City of San Pedro); the western portion of Batangas (Santo Tomas, Malvar, Balete, Mataasnakahoy, Cuenca, Lipa City, San Jose, Mabini, San Pascual, Alitagtag, Bauan, Santa Teresita, San Luis, Taal, San Nicolas, City of Tanauan, Talisay, Laurel, Agoncillo, Lemery, Balayan, Calaca, Tuy, Nasugbu, Lian, Calatagan); and Lubang Islands

*TCWS 2 means that damaging gale-force winds are prevailing or expected within 24 hours.
**TCWS 1 means that strong winds are prevailing or expected within 36 hours.

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
Officials in the Philippines forecast that heavy rains associated with Tropical Storm Conson will affect Bataan, Batangas, Camarines Norte, Cavite, Laguna, Marinduque, Metro Manila, Occidental Mindoro, Oriental Mindoro, Quezon, Rizal, and Romblon provinces through early Sept. 9. Moderate-to-heavy rainfall is likely over the same period in Aklan, Antique, Aurora, Bulacan, Camarines Sur, Capiz, Guimaras, Iloilo, Negros Occidental, Nueva Ecija, northern Palawan including Calamian and Cuyo Islands, Pampanga, Tarlac, and Zambales provinces.

PAGASA has also warned of potential flooding in parts of Bulacan after officials released excess water from the Ipo Dam. Residents in low-lying areas and those near Angat River from Angat, Baliuag, Bustos, Hagonoy, Norzagaray, Plaridel, Pulilan, and San Rafael municipalities should remain vigilant for the possibility of flash floods.

The storm will likely bring heavy rainfall, strong winds, and rough seas to parts of far southern China and central Vietnam starting Sept. 10. Sustained heavy rainfall could trigger flooding in low-lying communities near streams, creeks, rivers, and urban areas with easily overwhelmed or a lack of 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. Persistent onshore flow could make it difficult for the surge to recede and for water levels to decrease in coastal river catchments.

Transport
In addition to the immediate threat to personal safety, 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. Areal flooding in urban locations could also result in severe traffic congestion, while strong winds will pose a hazard to high-profile vehicles.

Conson has caused significant flight disruptions in parts of the Philippines. Heavy rain and low visibility may trigger further flight disruptions at regional airports. Officials may also suspend ferry and cargo services in affected areas.

Disruptions triggered by inclement weather and resultant hazards, such as flooding, could persist well after weather 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 the 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 or typhoon 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 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
Philippine Atmospheric, Geophysical and Astronomical Services Administration