Typhoon Chan-hom, known in the Philippines as Typhoon Falcon, was a large, powerful and long-lived tropical cyclone that affected most countries in the western Pacific basin. The ninth named storm of the 2015 Pacific typhoon season, Chan-hom developed on June 29 from a westerly wind burst that also spawned Tropical Cyclone Raquel in the southern hemisphere. Chan-hom slowly developed while moving to the northwest, aided by warm waters but disrupted by wind shear. The storm meandered near the Northern Marianas Islands, passing over the island of Rota before beginning a steady northwest track. While near the island, the storm dropped heavy rainfall on neighboring Guam, causing flooding and minor power outages. Chan-hom intensified into a typhoon on July 7, and two days later passed between the Japanese islands of Okinawa and Miyako-jima. There, strong winds left 42,000 people without power, while 27 people were injured. Around that time, the storm caused a surge in the monsoon trough, in conjunction with Tropical Storm Linfa, which caused flooding and killed 16 people in the Philippines.

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Typhoon Chan-hom (Falcon)

Typhoon Chan-hom at peak intensity on July 10
Meteorological history
Formed	June 29, 2015
Dissipated	July 13, 2015
Very strong typhoon
10-minute sustained (JMA)
Highest winds	165 km/h (105 mph)
Lowest pressure	935 hPa (mbar); 27.61 inHg
Category 4-equivalent typhoon
1-minute sustained (SSHWS/JTWC)
Highest winds	220 km/h (140 mph)
Lowest pressure	933 hPa (mbar); 27.55 inHg
Overall effects
Fatalities	18
Damage	$1.59 billion (2015 USD)
Areas affected	Guam, Northern Mariana Islands, Philippines, Japan, Taiwan, China, Korea, Russian Far East
IBTrACS
Part of the 2015 Pacific typhoon season

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After passing by Okinawa, the typhoon reached peak winds of 165 km/h (103 mph), according to the Japan Meteorological Agency. It passed north of Taiwan, where it brought beneficial rainfall that replenished reservoirs. On July 11, Chan-hom became the strongest typhoon to make landfall in the Chinese province of Zhejiang in the month of July. About 1.1 million people were evacuated ahead of the storm, and across the country, the storm left ¥9.84 billion (US$1.58 billion) in damage, as well as one death. Later, the storm turned to the northeast toward the Korean Peninsula. Jeju Island offshore South Korea recorded 1,250 mm (49 in) of rainfall, and one person died due to a thunderstorm in the country. On July 12, the storm struck the Ongjin peninsula in North Korea, and became an extratropical cyclone shortly thereafter. The remnants later caused flooding and power outages in the Russian Far East.

During June 2015, a near record strength pulse in the Madden–Julian oscillation, lead to a period of significant weather across the Western Pacific.^[1][2] This significant weather included a major westerly wind burst during late June, which caused a set of twin tropical cyclones to develop.^[3] The first tropical cyclone developed in the Southern Hemisphere during June 28, before it later developed into Tropical Cyclone Raquel during June 30.^[3] The second tropical cyclone was first noted by the United States Joint Typhoon Warning Center (JTWC) as a tropical disturbance during June 25, while it was located about 345 km (215 mi) to the south-southeast of Pohnpei State in the Federated States of Micronesia.^{[4][nb 1]}

Drifting generally northward, the disturbance slowly organized within a region of low to moderate wind shear and favorable outflow aloft. The circulation was enhanced by a surge of westerly winds to the south.^[5] At 06:00 UTC on June 29, the Japan Meteorological Agency (JMA)^{[nb 2]} classified the system as a tropical depression.^[7] Following further organization, the JTWC issued a Tropical Cyclone Formation Alert that day at 22:30 UTC with the system located about 345 km (214 mi) northeast of Pohnpei.^[8] Convection steadily deepened over the center and banding features began consolidating around the periphery.^[9] On June 30, the JMA upgraded the cyclone to Tropical Storm Chan-hom.^{[7][10][nb 3]} The JTWC assessed Chan-hom to be slightly weaker at this time, initiating it as a tropical depression.^[9]

Situated along the southern periphery of a subtropical ridge, Chan-hom moved steadily to the west.^[9] Upper-level ventilation allowed for growth of the cyclone,^[12] but moderate wind shear displaced the center from the deepest convection for much of July 1.^[13] That day, the JMA upgraded the system to a severe tropical storm.^[7] Early on July 2, the large circulation of Chan-hom absorbed a smaller disturbance to its southeast,^[14] and the storm turned to the west-southwest. Dvorak satellite classifications indicated that the system reached typhoon intensity following an expansion of the central dense overcast; the JTWC classified Chan-hom as such by 15:00 UTC,^[15] although the JMA maintained it as a severe tropical storm.^[7] Shortly thereafter, strong wind shear from a tropical upper tropospheric trough (TUTT) cell to the northeast dramatically weakened the storm. Convection was stripped away from Chan-hom's center and the storm's forward motion abruptly slowed.^[16][17] Alongside the shear, subsidence over the cyclone, a trough to the north, and a remnant vortex to the northeast all served to suppress convection.^[18] By 12:00 UTC on July 3, Chan-hom had weakened to a tropical storm with winds of 85 km/h (53 mph).^[19]

Coinciding with Chan-hom's abrupt collapse on July 3, the system turned northeast as it entered a weakness in the steering ridge.^[16][18] Later that day, the broad circulation turned north-northwest.^[20] Wind shear eased early on July 4 as the TUTT cell retreated to the north and the subtropical ridge steadily re-established itself. Convection started redeveloping over the tropical storm.^[21] Late on July 4 into July 5, the center of Chan-hom skirted the southern coast of Rota in the Mariana Islands.^[22][23] While near the island, Chan-hom executed an unusual counter-clockwise loop owing to interaction with a monsoon trough.^[24][25] Once clear of the Mariana Islands, steady development ensued owing to low wind shear and good outflow.^[26] Early on July 7, Chan-hom attained typhoon intensity according to the JMA,^[7] following to a burst in central convection.^[27][28] Microwave satellite imagery indicated the formation of an eye as convection deepened and banding features tightened around the circulation.^[29]

On July 7, the typhoon entered the Philippine area of Responsibility and was assigned the local name Falcon.^[30] Chan-hom's eye briefly improved in structure before entering a state of flux and collapsing later that day; convection on the northern side of the storm diminished simultaneously.^[31][32] The 65 km (40 mi) wide eye soon re-established itself and slowly contracted to a diameter of 40 km (25 mi) by July 8.^[33][34] A large storm, gale-force winds extended 445 km (277 mi) from Chan-hom's center on July 9.^[35] Late on July 9 into July 10, Chan-hom passed between the Japanese islands of Okinawa and Miyako-jima.^[36] The typhoon reached its peak strength during this time with estimated winds of 165 km/h (103 mph) and a barometric pressure of 935 mbar (hPa; 27.61 inHg).^[37] Featuring multiple intense feeder bands and a well-defined 27 km (17 mi) eye, the JTWC assessed Chan-hom to have peaked as a Category 4-equivalent typhoon on the Saffir–Simpson hurricane wind scale with one-minute sustained winds of 220 km/h (140 mph).^[38]

An eyewall replacement cycle and weakening convection along the northern side resulted in steady weakening starting on July 10.^[39][40] Increasing wind shear prevented the system from reorganizing as it neared East China.^[41] Early on July 11, the typhoon reached the southwestern edge of the subtropical ridge and began turning to the north and later north-northeast.^[42] Chan-hom made landfall in Zhoushan, Zhejiang, or roughly 140 km (87 mi) south-southeast of Shanghai, around 08:40 UTC.^[43] The JMA assessed the storm to have had winds of 140 km/h (87 mph) while the JTWC estimated one-minute sustained winds at 155 km/h (96 mph).^[42][44] Based on the JTWC estimate, Chan-hom was the strongest typhoon to pass within 160 km (99 mi) of Shanghai in at least 35 years,^[43] and it was the strongest landfall in Zhejiang in the month of July since recordkeeping began in 1949.^[45] Thereafter the storm accelerated north-northeast and moved over the cool waters of the Yellow Sea, prompting further degradation of its structure.^[46] Chan-hom weakened below typhoon-force around 18:00 UTC on July 11.^[7] The system's low-level center completely exposed on July 12 as it approached the Korean Peninsula.^[47][48] Around 18:00 UTC, Chan-hom moved ashore on the Ongjin peninsula in North Korea, southwest of the capital Pyongyang, with winds of 85 km/h (53 mph).^[49][50] By 00:00 UTC on July 13 the system transitioned into an extratropical cyclone while retaining gale-force winds,^[51] and six hours later the system dissipated over north-central North Korea.^[7]

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