Later that day,the system was upgraded to a tropical storm and was given the name Co-may by the Japan Meteorological Agency (JMA),which refers to a Vietnamese grass (Chrysopogon aciculatus). Co-may then moved southwestwards,as it was situated in the eastern semicircle of a monsoon gyre. The storm would later rapidly intensify into a minimal,Category 1-equivalent typhoon on the Saffir–Simpson scale,with one-minute sustained winds of 120 km/h (75 mph). As it approached the southwestern edge of the gyre,Co-may altered its course and began tracking more southeastwards after passing the inflection point. The system slightly weakened before it made landfall over Agno,Pangasinan during the night of July 24. Early on the following day,Co-may gradually weakened further as its outer bands crossed the rugged terrain of the Cordillera Range,and was downgraded to a severe tropical storm by the time of its second landfall over Candon City,Ilocos Sur.
The storm weakened into a tropical depression after passing through the mountains of the Cordillera. However,it regained tropical storm status over the Ryukyu Islands despite the marginal environment. Co-may made two additional landfalls in China:one on Zhujiajian Island,Zhejiang on July 29,and another in Fengxian District,Shanghai on July 30. Co-may then weakened into a remnant low before dissipating on August 3.
Meteorological history
Map plotting the storm's track and intensity,according to the Saffir–Simpson scale
During mid-July, an area of low pressure was detected northeast of Ilocos Norte by the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA). Initially, it was not expected to develop into a tropical cyclone. However, by July 22, the system began to show signs of organisation as it moved westwards between the Calayan Group of Islands and the northern coast of Ilocos Norte. Around this time, the Joint Typhoon Warning Center (JTWC) also began monitoring the system, designating it as Invest 99W.
Later that day, the PAGASA raised the probability of cyclone formation to “high”, and within a few hours, the disturbance intensified into a tropical depression, receiving the local name Emong.[1] The JTWC also issued a Tropical Cyclone Formation Alert (TCFA), citing a high likelihood of tropical cyclogenesis in the coming days. Soon after, the JTWC upgraded the system to a tropical depression, assigning it the designation Tropical Depression 11W.[2]
Meanwhile, the Japan Meteorological Agency (JMA) also recognised the system as a tropical depression a few hours later. By this time, however, both the PAGASA and the JTWC had already classified the system as a tropical storm. The JMA subsequently followed suit, upgrading it to tropical storm status and assigning it the international name Co-may, the replacement name for Lekima, which had been retired in 2019. The storm then turned west-southwestwards towards the northwestern tip of Pangasinan. After overnight rapid intensification, by the morning of July 24, Co-may was upgraded to a severe tropical storm by both the PAGASA and the JMA, and later in the day, it reached minimal typhoon strength according to both the PAGASA and the JTWC. The storm then altered its course, turning southeastwards towards the area between Pangasinan and La Union.
On July 24, the JMA also upgraded Co-may to typhoon status. Then at 22:40 PHT (14:40 UTC), Co-may made its first landfall over Agno, Pangasinan, bringing strong winds and heavy rainfall.[3] This made Co-may the most powerful typhoon to strike Pangasinan since Chan-hom in 2009.[4] After landfall, the interaction with the mountainous terrain of the Cordillera Range weakened it into a severe tropical storm as it moved northeastwards. Co-may later made its second landfall over Candon, Ilocos Sur at 05:10 PHT on July 25 (21:10 UTC on July 24).[5] The system weakened further as it entered the Babuyan Channel[6] and was downgraded into a depression[7] as it moved through the Ryukyu Islands. On July 27, Co-may re-strengthened into a tropical storm, as per all agencies near Okinawa. The storm then turned westwards, where it struck Zhujiajian Island, Zhejiang on July 29 and Fengxian, Shanghai on July 30 before weakening and becoming a remnant low on July 31.[citation needed] It maintained its strength, passing through Yancheng before entering the Yellow Sea, and eventually dissipating when it moved inland over South Korea on August 3.
Preparations
Philippines
Shortly after the system was named by the PAGASA, the agency issued Tropical Cyclone Wind Signal #1 over Ilocos Norte, the northwestern portion of La Union, and the western portion of Pangasinan, due to the depression’s proximity to northern Luzon.[8] As the system rapidly intensified into a severe tropical storm, PAGASA subsequently raised Signal #3 over the entire province Abra, Apayao, Ilocos Norte, central portion of Pangasinan, extreme northern portion of Zambales, northern and western portion of Cagayan, western portion of Benguet; Kalinga; and Mountain Province, as well as the remaining areas of the provinces that were placed in Signal #4. Signal #2 was later hoisted over the entire provinces of Babuyan Islands, Batanes, Ifugao, as well as the northern portion of Tarlac and Zambales, northern and western portions of Isabela, northwestern portion of Nueva Ecija and Quirino, and the western and central portions of Nueva Vizcaya. This signal also covered the remaining areas already placed under Signal #3.[9]
Meanwhile, Signal #1 was raised over the northern portion of Bataan, northern and central portions of Aurora, western and central portions of Pampanga and the remaining localities of each province that were previously placed under Signal #2. Classes in Metro Manila and in some areas in Luzon and Western Visayas were suspended from July 24 and 25 due to Co-may and the enhanced southwest monsoon.[10][11] Around 70 domestic and international flights were cancelled as Co-may nears Northern Luzon and the persistent heavy rain brought by the southwest monsoon.[12]
When Co-may was upgraded into a typhoon by the PAGASA at 11:00 PHT (03:00 UTC), a Signal #4 warning was issued over the northern portion of Pangasinan, the northern and central portions of La Union, and the southwestern portion of Ilocos Sur. All the storm signal warnings were later discontinued on July 26.[13][14]
Impact
Philippines
Recent tropical cyclone activity from Wipha and Co-may in Southeast Asia
Co-may generated strong winds and floods in parts of the Philippines, resulting in extensive damage in Alaminos, Pangasinan[15] and Naval Station Ernesto Ogbinar in San Fernando, La Union. Five people were rescued from floods in Burgos, Ilocos Norte.[16] Flooding also blocked a highway in Bauang, La Union.[17] A widespread power outage occurred in Baguio and nearby areas in Benguet at around 02:00 PHT on July 25 (18:00 UTC on July 24) as Co-may battered the Cordillera Central mountain range.[18] Many provinces in Luzon and Visayas were placed under a state of calamity due to the severe damages caused by Co-may, including the effects of the southwest monsoon.[19] In Calumpit, one person was killed due to flooding and incessant rains. Some portions of the area saw water reach 4 feet (1.2m) high. Two people were electrocuted after touching a live electrical wire amid the storm.[20] In Navotas, a navigational guide keeping water from overflowing the Navotas River was severely damaged. A sea wall in Barangay collapsed due to the storm, causing major flooding.[21]
China
Co-may brought torrential rainfall and strong winds to eastern China, resulting in evacuations and widespread transport disruptions in Shanghai and the provinces of Zhejiang and Jiangsu, which experienced the most severe effects of the storm. On the afternoon of 30 July, the Shanghai Meteorological Bureau issued an orange rainstorm warning, the second-highest level in China's four-tier warning system. A total of 640 flights were cancelled, including 410 at Shanghai Pudong International Airport and 230 at Shanghai Hongqiao International Airport.[22] Approximately 283,000 people were evacuated from coastal and low-lying areas as Co-may made its first landfall.[23]
Typhoon Parma (Pepeng; 2009) – A stronger and equally erratic but deadlier typhoon which impacted northern Philippines for several days, also due to a Fujiwhara interaction with another typhoon.
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