Communities around Mayon, Pinatubo, Taal face lahar threat
Tropical cyclone wind signals were raised in more areas, including Metro Manila that is now placed under Signal No. 2 ahead of typhoon Rolly’s (international name “Goni”) landfall over Catanduanes-Camarines Norte/Camarines Sur provinces on Sunday morning.
Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) weather specialist Ariel Rojas said Rolly may make landfall over Catanduanes around 4 a.m. to 6 a.m., then over Camarines Norte-Camarines Sur around 6 a.m. to 8 a.m.
Rolly is somewhat similar to Typhoon “Rosing” (international name “Angela”) which pummeled Luzon 25 years ago, PAGASA said.
Rosing was one of the strongest typhoons in the Philippines to hit land with sustained winds of 180 kph and gusts reaching up to 240 kkph as it approached the Bicol region and tore across Metro Manila late evening of All Saints’ Day in 1995.
Its strength is comparable to a super typhoon nowadays but it was only in 2015 when PAGASA included supertyphoon as one of its tropical cyclone classifications.
Rojas said Rolly will be somewhat similar to the track and strength of Rosing.
With the strength of Rolly, it is expected to dump torrential heavy rains in Luzon and threatening communities around Mayon Volcano, Mount Pinatubo, and Taal Volcano with massive lahar.
As of 4 p.m. Saturday, the eye of typhoon Rolly was estimated at 345 kilometers (km) east-northeast of Virac, Catanduanes, packing maximum sustained winds of 215 kilometers per hour (kph) and gustiness of up to 265 kph.
It could remain a typhoon with maximum sustained winds of 185 kph to 205 kph by the time it makes landfall.
After Bicol, Rolly will likely traverse mainland Quezon, other parts of Southern Luzon and Metro Manila from Sunday afternoon to Sunday evening.
While traversing Luzon, Rolly may weaken considerably but will still be possibly destructive, and emerge as a severe tropical storm or minimal typhoon over the West Philippine Sea by Monday morning.
Signal No. 3 has been hoisted over Catanduanes, eastern portion of Camarines Sur (Cabusao, Libmanan, Pasacao, Pamplona, Magarao, Bombon, Calabanga, Canaman, Camaligan, Gainza, Naga City, Milaor, San Fernando, Minalabac, Pili, Ocampo, Baao, Bula, Balatan, Nabua, Bato, Iriga City, Buhi, Sagnay, Tigaon, Goa, Tinambac, Siruma, Lagonoy, San Jose, Garchitorena, Presentacion, Caramoan), and Albay.
Signal No. 2 was also raised over Metro Manila, Bulacan, Rizal, Laguna, Cavite, Batangas, Quezon including Polillo Islands, Camarines Norte, the rest of Camarines Sur, Sorsogon, Masbate including Ticao and Burias Islands, Marinduque, Romblon, Oriental Mindoro, Occidental Mindoro including Lubang Island, Northern Samar, northern portion of Samar (Hinabangan, Paranas, Motiong, Jiabong, Catbalogan City, San Jose de Buan, San Jorge, Tarangnan, Gandara, Santa Margarita, Matuguinao, Calbayog City, Tagapul-An, Almagro, Santo Nino, Pagsanghan), and northern portion of Eastern Samar (San Julian, Sulat, Taft, Can-Avid, Dolores, Maslog, Oras, San Policarpo, Arteche, Jipapad).
Meanwhile, areas under Signal No. 1 were Pampanga, Bataan, Zambales, Tarlac, Nueva Ecija, Aurora, Pangasinan, La Union, southern portion of Ilocos Sur (Quirino, Gregorio Del Pilar, Salcedo, San Emilio, Candon City, Galimuyod, Santa Lucia, Cervantes, Sigay, Santa Cruz, Suyo, Tagudin, Alilem, Sugpon), Mountain Province, Benguet, Ifugao, Nueva Vizcaya, Quirino, central and southern portions of Isabela (Mallig, Quirino, Ilagan, Roxas, San Manuel, Burgos, Gamu, Palanan, San Mariano, Benito Soliven, Naguilian, Reina Mercedes, Luna, Aurora, Cabatuan, San Mateo, Cauayan City, Dinapigue, San Guillermo, Echague, San Agustin, Jones, Angadanan, Alicia, San Isidro, Ramon, Santiago City, Cordon), Calamian Island, the rest of Eastern Samar, the rest of Samar, northern portion of Leyte (Leyte, Tabango, San Isidro, Calubian, Capoocan, Carigara, Tunga, Barugo, San Miguel, Babatngon, Tacloban City), northwestern portion of Aklan (Numancia, Lezo, Makato, Tangalan, Ibajay, Nabas, Malay, Buruanga, Kalibo), and northwestern portion of Antique (Libertad, Pandan).
Based on the intensity forecast, the highest possible wind signal to be raised will be Signal No. 4 for very destructive typhoon-force winds.
Rojas warned of violent winds and intense rainfall associated with the inner rainband-eyewall region over Catanduanes, Camarines Norte, and Camarines Sur by early Sunday morning through afternoon and over Quezon by afternoon through evening.
The outer rainbands of Rolly will bring light to moderate with at times heavy rains over Bicol region and Eastern Visayas tonight.
Beginning early Sunday morning, the passage of typhoon Rolly will bring heavy to intense rains over Metro Manila, Bicol region, Cavite, Laguna, Batangas, Rizal, Quezon, Aurora, Bulacan, Zambales, Bataan, Marinduque, Romblon, Occidental Mindoro, and Oriental Mindoro.
Moderate to heavy rains with at times intense rains, especially the eastern sections of Northern and Central Luzon will affect Cagayan Valley, Cordillera Administrative Region, Ilocos Region, and the rest of Central Luzon.
PAGASA warned that flooding, rain-induced landslides, and sediment-laden streamflows or lahar may occur during heavy or prolonged rainfall especially in areas that are highly susceptible to these hazards.
Destructive typhoon-force winds will be experienced in areas under Signal No. 3, damaging gale- to storm-force winds in areas under Signal No. 2, and strong breeze to near gale conditions in areas under Signal No. 1.
Elsewhere, strong breeze to near gale conditions due to the northeasterlies will be experienced over Batanes, Babuyan Islands, Ilocos Norte, Apayao, and the coastal and mountainous areas of Cagayan and Isabela that are not under Signal No. 1.
There is a high risk of storm surge of more than 3.0 meters (m) over the northern coastal areas of Quezon including Polillo Islands, Camarines Norte, Camarines Sur, and Catanduanes; up to 2.0 m to 3.0 m over the coastal areas of Manila, Cavite, Bulacan, Pampanga, Bataan, southeastern coastal area of Batangas and southwestern coastal area of Quezon; and 1.0 m to 2.0 m over the coastal areas of Aurora, Zambales, Occidental Mindoro, the rest of the coastal areas of Bicol Region, Batangas, and Quezon in the next 24 hours which may result in life-threatening and damaging coastal inundation.
PAGASA said this storm surge may be accompanied by swells and breaking waves reaching the coast.
Rough to “phenomenal” seas (2.5 to 15.0 m) will be experienced over the seaboard of areas where tropical cyclone warning signal is in effect and rough to very rough seas (2.5 to 5.0 m) over the remaining seaboards of Northern Luzon and the eastern seaboards of Eastern Visayas (that are not under tropical cyclone warning signals) and Caraga.
Sea travel is risky for all types of sea vessels over these waters, especially those under storm warning signals.
Meanwhile, moderate to rough seas (1.2 to 2.5 m) will be experienced over the remaining seaboards of the country.
Mariners of small sea vessels were advised to take precautionary measures when venturing out to sea, while inexperienced mariners should avoid navigating in these conditions.
While “Rolly” is unleashing heavy rains and intense winds over Luzon, the tropical depression with international name “Atsani” could enter the Philippine area of responsibility (PAR) on Sunday afternoon. It will be assigned its local name “Siony” once inside the PAR.
It was estimated at 1,520 km east of Southern Luzon around 4 p.m. Saturday.
“Atsani” has maximum sustained winds of 55 kph near the center and gustiness of up to 70 kph, while moving northwestward at 25 kph. It is likely to re-intensify into a tropical storm in the next 24 hours.
It remains less likely to affect any portion of the country over the next three days.
Meanwhile, the Philippine Institute of Volcanology and Seismology (Phivolcs) warned residents of communities around Mayon Volcano, Mount Pinatubo, and Taal Volcano, especially those in pre-determined zones of lahar and related hazards, to increase their vigilance and take precautionary actions against the possible phenomenon.
“Due to its trajectory, current severe intensity and potentially high-volume rainfall, Rolly can be expected to generate volcanic sediment flows or lahar, muddy streamflows, or muddy runoff in rivers and drainage areas on the monitored active volcanoes of Mayon, Pinatubo, and Taal,” Phivolcs said in an advisory.
State volcanologists said prolonged and heavy rainfall could generate post-eruption lahar from Mayon Volcano in Albay to flow to the watershed areas of the Miisi, Mabinit, Buyuan, and Basud Channels.
Mayon lahar may threaten communities downstream of the said channels, including the Miisi, Binaan, Anoling, Quirangay, Maninila, Masarawag, Muladbucad, Nasisi, Mabinit, Matan-ag, and Basud Channels in Albay.
For Pinatubo, which is in the boundary of Zambales, Tarlac, and
Pampanga, Phivolcs said non-eruption lahar are likely to be “channel-confined” and could occur in the upper to middle reaches of the Sto. Tomas-Marella and Bucao River systems.
Phivolcs said this could transition to muddy streamflows and floods on the lower reaches and affect nearby communities of San Marcelino, San Narciso, San Felipe, and Botolan in the Zambales Province.
Muddy streamflows could also be generated along the O’Donnell and Pasig-Potrero River systems draining the Pinatubo edifice to the north and southeast, respectively, and affect downstream communities in the provinces of Tarlac and Pampanga.
As Rolly moves near Luzon landmass, it could also trigger lahar around Taal Volcano in Batangas, particularly on the slopes west of Taal Lake where thin remnant ash can be remobilized in streams and roads and overland of the lakeward slopes.
With this development, Phivolcs said muddy streamflow and runoff may recur on previously affected communities of Agoncillo and Laurel in Batangas.