During late August and early September 1986, the Western Pacific monsoon trough became displaced to the east.
Lower than normal pressures favored the building of convection over the trough.
By the evening of September 9, a pronounced area of disturbed weather developed southwest of the Truk Atoll.
Aided by low wind shear, the disturbance developed slowly, even though the Hurricane Hunters initially failed to find a well-defined center.
The disturbance drifted towards the northwest, and early on September 12, the Japan Meteorological Agency (JMA) started monitoring the system.
Based on ship reports, the Joint Typhoon Warning Center (JTWC) classified the system as a tropical depression at 06:00 UTC on September 13.
Both the JMA and JTWC upgraded the depression into Tropical Storm Abby at 00:00 UTC on September 14.

On September 14, Abby, while moving west-northwest, began to develop a central dense overcast and thus began to intensify.
On the morning of September 15, the JMA upgraded the system into a severe tropical storm.
Despite reports from Hurricane Hunter aircraft indicating that low-and upper-level circulations were not properly aligned, both the JTWC and JMA estimated that Abby became a typhoon early on September 16.

At 06:00 UTC on September 18, the JMA reported that Abby attained its maximum intensity of 160 km/h (100 mph).
Six hours later, the JTWC estimated that Abby reached its peak intensity of 175 km/h (110 mph).
Moving northwest, the storm weakened slightly before making landfall in the eastern portion of Taiwan on September 19; the JTWC estimated winds of 170 km/h (105 mph) at the time of landfall.
Due to land interaction, the storm rapidly weakened, with the low-level center re-curving towards the northeast.
At 00:00 UTC on September 20, the JMA estimated that Abby weakened below typhoon intensity.
Twelve hours later, the JTWC stopped monitoring the system while located 410 km (255 mi) southeast of Shanghai.
Around this time, the JMA reported that Abby transitioned into an extratropical cyclone, although the JMA continued to track the system through the morning hours of September 24.
During late August and early September 1986, the Western Pacific monsoon trough became displaced to the east. Lower than normal pressures favored the building of convection over the trough. By the evening of September 9, a pronounced area of disturbed weather developed southwest of the Truk Atoll. Aided by low wind shear, the disturbance developed slowly, even though the Hurricane Hunters initially failed to find a well-defined center. The disturbance drifted towards the northwest, and early on September 12, the Japan Meteorological Agency (JMA) started monitoring the system. Based on ship reports, the Joint Typhoon Warning Center (JTWC) classified the system as a tropical depression at 06:00 UTC on September 13. Both the JMA and JTWC upgraded the depression into Tropical Storm Abby at 00:00 UTC on September 14.
On September 14, Abby, while moving west-northwest, began to develop a central dense overcast and thus began to intensify. On the morning of September 15, the JMA upgraded the system into a severe tropical storm. Despite reports from Hurricane Hunter aircraft indicating that low-and upper-level circulations were not properly aligned, both the JTWC and JMA estimated that Abby became a typhoon early on September 16.
At 06:00 UTC on September 18, the JMA reported that Abby attained its maximum intensity of 160 km/h (100 mph). Six hours later, the JTWC estimated that Abby reached its peak intensity of 175 km/h (110 mph). Moving northwest, the storm weakened slightly before making landfall in the eastern portion of Taiwan on September 19; the JTWC estimated winds of 170 km/h (105 mph) at the time of landfall. Due to land interaction, the storm rapidly weakened, with the low-level center re-curving towards the northeast. At 00:00 UTC on September 20, the JMA estimated that Abby weakened below typhoon intensity. Twelve hours later, the JTWC stopped monitoring the system while located 410 km (255 mi) southeast of Shanghai. Around this time, the JMA reported that Abby transitioned into an extratropical cyclone, although the JMA continued to track the system through the morning hours of September 24.
Typhoon Abby (1986)