During June 30, a tropical disturbance developed about 463 km (288 mi) to the north-northeast of Palau.
Noting some organization within the system, the Joint Typhoon Warning Center (JTWC) issued a Tropical Cyclone Formation Alert (TCFA) early on July 1.
Six hours later, the Japan Meteorological Agency (JMA) classified it as a tropical depression.
Later that day, the JMA began to issue advisories, predicting that the system could intensify into a tropical storm within the next 24 hours.
Shortly after, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) upgraded the system to a tropical depression, assigning the local name Emong.

Early on July 2, the JMA upgraded the system to a tropical storm, and assigned the official name Nanmadol.
The PAGASA also upgraded the system to a tropical storm.
Soon after, the JTWC gave the system the internal designation of 05W. Satellite imagery depicted convective banding wrapping tightly into Nanmadol's low-level circulation center (LLCC), prompting the JTWC to upgrade it to a tropical storm in their next advisory.
Nanmadol later entered a favorable environment with low vertical wind shear and high sea surface temperatures (SSTs) of 30–31 °C (86–88 °F), allowing it to develop a deep and symmetric core surrounded by deep convection.
At this time, the JMA stated that Nanmadol had intensified into a severe tropical storm.
The PAGASA also upgraded Nanmadol to a severe tropical storm in their final advisory on the system as it exited the Philippine Area of Responsibility.

Nanmadol continued to intensify while moving northward just to the east of Taiwan, with satellite imagery capturing a small, developing eye.
At 06:00 UTC on July 3, Nanmadol reached its peak intensity with the JTWC assessing the cyclone to have 1-minute sustained winds of 110 km/h (70 mph); the JMA estimated 10-minute sustained winds of 100 km/h (65 mph) and a minimum barometric pressure of 985 hPa (29.09 inHg).
However, the JTWC assessed that Nanmadol reached its peak intensity as a Category 1-equivalent typhoon with 1-minute sustained winds of 120 km/h (75 mph) six hours later in a post-analysis report.
Nanmadol maintained its peak intensity for several hours until just before July 4, when the system began curving eastwards and its satellite presentation deteriorated.
Around that time, Nanmadol made landfall approximately 40 km (25 mi) to the east of Nagasaki in Kyushu.
Despite the system still displaying a well-defined center, cloud tops began to warm, in line with the rapid weakening trend of the system.
After several hours, Nanmadol began to interact with the mid-latitude westerlies; the JTWC downgraded the system further to a low-end  of tropical storm intensity, though the JMA still maintained it at severe tropical storm intensity.
By 21:00 UTC on the same day, the JTWC issued its final advisory on Nanmadol, mentioning that the system was embedded within the cold baroclinic zone, and had thus lost its tropical characteristics and transitioned into a cold-core low.
The JMA soon followed suit with their final warning, declaring that Nanmadol had fully become an extratropical cyclone at 00:00 UTC on July 5.
Its extratropical remnants later left the basin on July 8.
During June 30, a tropical disturbance developed about 463 km (288 mi) to the north-northeast of Palau. Noting some organization within the system, the Joint Typhoon Warning Center (JTWC) issued a Tropical Cyclone Formation Alert (TCFA) early on July 1. Six hours later, the Japan Meteorological Agency (JMA) classified it as a tropical depression. Later that day, the JMA began to issue advisories, predicting that the system could intensify into a tropical storm within the next 24 hours. Shortly after, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) upgraded the system to a tropical depression, assigning the local name Emong.
Early on July 2, the JMA upgraded the system to a tropical storm, and assigned the official name Nanmadol. The PAGASA also upgraded the system to a tropical storm. Soon after, the JTWC gave the system the internal designation of 05W. Satellite imagery depicted convective banding wrapping tightly into Nanmadol's low-level circulation center (LLCC), prompting the JTWC to upgrade it to a tropical storm in their next advisory. Nanmadol later entered a favorable environment with low vertical wind shear and high sea surface temperatures (SSTs) of 30–31 °C (86–88 °F), allowing it to develop a deep and symmetric core surrounded by deep convection. At this time, the JMA stated that Nanmadol had intensified into a severe tropical storm. The PAGASA also upgraded Nanmadol to a severe tropical storm in their final advisory on the system as it exited the Philippine Area of Responsibility.
Nanmadol continued to intensify while moving northward just to the east of Taiwan, with satellite imagery capturing a small, developing eye. At 06:00 UTC on July 3, Nanmadol reached its peak intensity with the JTWC assessing the cyclone to have 1-minute sustained winds of 110 km/h (70 mph); the JMA estimated 10-minute sustained winds of 100 km/h (65 mph) and a minimum barometric pressure of 985 hPa (29.09 inHg). However, the JTWC assessed that Nanmadol reached its peak intensity as a Category 1-equivalent typhoon with 1-minute sustained winds of 120 km/h (75 mph) six hours later in a post-analysis report. Nanmadol maintained its peak intensity for several hours until just before July 4, when the system began curving eastwards and its satellite presentation deteriorated. Around that time, Nanmadol made landfall approximately 40 km (25 mi) to the east of Nagasaki in Kyushu. Despite the system still displaying a well-defined center, cloud tops began to warm, in line with the rapid weakening trend of the system. After several hours, Nanmadol began to interact with the mid-latitude westerlies; the JTWC downgraded the system further to a low-end  of tropical storm intensity, though the JMA still maintained it at severe tropical storm intensity. By 21:00 UTC on the same day, the JTWC issued its final advisory on Nanmadol, mentioning that the system was embedded within the cold baroclinic zone, and had thus lost its tropical characteristics and transitioned into a cold-core low. The JMA soon followed suit with their final warning, declaring that Nanmadol had fully become an extratropical cyclone at 00:00 UTC on July 5. Its extratropical remnants later left the basin on July 8.
Tropical Storm Nanmadol (2017)