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Through Atmospheric pressure

Megi killed 31 people and caused $255.1 million (2010 USD) in damage over Luzon, making it top twenty of the costliest typhoons in the Philippines. After moving to the South China Sea, the outflow of Megi and a weather front together brought torrential rainfall, caused $42.2 million (2010 USD) in damage and killed 38 people in Yilan, Taiwan, making Megi the deadliest typhoon of 2010s in Taiwan. Megi also caused US$411.7 million in damage over Fujian, China, although there were no deaths by the storm in the province. Total losses from Megi were estimated at US$709 million, and a total of 69 people killed as a result of the typhoon. Despite the intensity and destruction, the name Megi was not retired, and was used again in 2016 until its retirement in 2022, although the name Juan was retired by PAGASA.

Meteorological history

Late on October 10, a tropical disturbance formed east-southeast of Guam. There were favorable environmental conditions, such as low vertical wind shear, good upper-level divergence and poleward outflow. The system began to significantly develop on October 12, prompting the Joint Typhoon Warning Center (JTWC) issuing a Tropical Cyclone Formation Alert at 09:00 UTC. Several hours later, the Japan Meteorological Agency (JMA) began monitoring the system as a tropical depression. Early on October 13, JTWC also classified the system as a tropical depression and designated it 15W. Hours later, well-defined convective banding features developed around the system and thunderstorm activity over the center of circulation increased. Sea surface temperatures above 28 °C (82 °F) and high oceanic heat content allowed for further strengthening. Situated to the southwest of a subtropical ridge, the system slowly tracked west-northwest towards the Philippines. Around 12:00 UTC, the system further intensified into a tropical storm, earning the name Megi from JMA.

Late on October 13, Tropical Storm Megi became quasi-stationary, but a mid-latitude trough moving from the west caused the storm to resume a northwestward track around the periphery of the subtropical ridge. Throughout the morning of October 14, a central dense overcast developed over the center of Megi, allowing for intensification. Later that day, microwave imagery showed a developing mid-level eye feature, resulting in JMA upgrading the system to a severe tropical storm and JTWC upgrading it to a typhoon. Around this time, Megi began to be observed by Hurricane Hunters from the United States Air Force's (USAF) 53rd Weather Reconnaissance Squadron, as part of a field campaign researching typhoon impacts on the ocean. On their first flight, they verified the microwave data of a developing eye within the cyclone. On October 15, JMA upgraded Megi to a typhoon, and the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) began to mention the typhoon and named it Juan as it entered the Philippine Area of Responsibility, with improved outflow over the western semi-circle and a well-defined low-level circulation center with tightly curved banding; steady intensification continued thereafter. By the afternoon of October 16, Megi began to undergo rapid intensification with a well-defined eye developing, and enhanced poleward outflow developing due to a transitory mid-latitude trough.

Early on October 17, Megi started to moved westward and then west-southwestward because of the subtropical ridge. Based on aircraft data, increased satellite estimates and a circular 20 nautical miles (37 km; 23 mi) diameter eye, JTWC upgraded Megi to a category 5-equivalent super typhoon on the Saffir–Simpson hurricane wind scale, becoming the only super typhoon in 2010. Hurricane Hunters later that morning found Megi to have become extremely intense, measuring near-record-high flight-level winds of 352 km/h (219 mph), while the Stepped-Frequency Microwave Radiometer (SFMR) found surface winds near 305 km/h (190 mph), in addition to the pressure dropping to 890 mb (26 inHg). They also noted that there was frequent lightning within Megi's eyewall. Additionally, a dropsonde recorded a maximum wind gust aloft of 399 km/h (248 mph); this stood as a world record until surpassed by the North Atlantic's Hurricane Melissa in 2025 fifteen years later. Based on the measurements, the JTWC set Megi's maximum intensity at 295 km/h (185 mph), although the pressure was listed in post-analysis as nearly 20 millibars (0.59 inHg) higher than what the Hurricane Hunters actually observed. Six hours later at 18:00 UTC, the JMA assessed that Megi had strengthened slightly afterwards and reached peak intensity with maximum sustained winds at 230 km/h (145 mph) and a minimum pressure of 885 hPa (26.13 inHg), making Megi one of the most intense tropical cyclones on record. An eyewall replacement cycle began to commence later that day, though Megi remained steady in intensity until it made landfall over Isabela, Philippines at 03:25 UTC (11:25 PST) on October 18. When passing the Sierra Madre, the eye filled due to land interaction, but tightly curved banding and excellent radial outflow remained.

The weakened typhoon emerged into the South China Sea late on October 18, and it began to reorganize. On October 19, Megi formed an enlarged but ragged eye. Late on the same day, Megi turned northwestward and moved slowly due to the significantly weakening western subtropical ridge in response to a deepening mid-latitude shortwave trough moving into Southeast China. Megi turned northward then north-northeastward towards a break in the subtropical ridge caused by an approaching mid-latitude trough on October 20. By low vertical wind shear and good radial outflow especially on the poleward channel, the typhoon started to gradually intensify. On October 21, JMA reported that Megi attained its secondary peak intensity by the 10-minute maximum sustained winds reaching 95 knots (175 km/h; 110 mph) and the atmospheric pressure decreasing to 935 hPa (27.61 inHg). On October 22, the eye of Typhoon Megi became cloud-filled and convection begun eroding due to increasing vertical wind shear. Late on the same day, JMA downgraded Megi to a severe tropical storm in the Taiwan Strait because of subsidence induced by a developing upper-level trough west of the storm. On October 23, Megi made landfall over Zhangpu in Fujian, China at 04:55 UTC. Soon, Megi weakened to a tropical storm in mainland China, as the majority of convection associated with the system has dissipated, prompting JTWC issuing a final warning. Megi further weakened to a tropical depression late on October 23. On October 24, the tropical depression dissipated completely around 12:00 UTC, though according to the JTWC Best Track Data analysis, Megi became extratropical at 00:00 UTC on the next day.

Records

The Japan Meteorological Agency (JMA) analysed that the 10-minute maximum sustained winds of Typhoon Megi in 2010 was 125 knots (232 km/h; 144 mph), making it the second strongest tropical cyclone in the Northwest Pacific Ocean on record along with Bess in 1982 and Haiyan in 2013, only after Tip in 1979. The Hong Kong Observatory analysed that Megi was the strongest tropical cyclone in the Northwest Pacific Ocean since Tip in 1979 by attaining the 10-minute maximum sustained winds at 270 km/h (145 knots, 165 mph). A hurricane hunter aircraft indicated 1-minute maximum sustained surface winds of 165 knots (306 km/h; 190 mph) and minimum pressure was 890 hPa (26.3 inHg) at peak intensity, which was equivalent to Tip in 1979.

Megi's atmospheric pressure estimated by JMA was 885 hPa (26.13 inHg), the lowest since Vanessa in 1984 and the eighth lowest in the Northwest Pacific Ocean on record; in addition, Megi was the first tropical cyclone in the Northwest Pacific Ocean having the atmospheric pressure below 900 hPa (27 inHg) since Yuri in 1991. When reaching peak intensity at 18:00 UTC on October 17 and 00:00 UTC on October 18, Megi's Current Intensity (CI) number of the Dvorak technique was 8.0, the highest number. According to JMA's advisory, Megi still maintained its peak strength at 03:00 UTC on October 18, making it one of the strongest tropical cyclones to make landfall on record at 03:25 UTC. Moreover, Megi was the latest-forming storm to make landfall over Fujian, China since 1949.

In addition, a dropsonde positioned in the eyewall recorded a wind gust of 215.51 knots (399.12 km/h; 248.00 mph), which was the highest wind speed ever measured by dropsonde until the North Atlantic's Hurricane Melissa surpassed it in 2025.

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