The first tropical cyclone to develop during October 1991, Typhoon Orchid formed a broad monsoon trough that extended from the South China Sea eastward through the Caroline Islands.
The Joint Typhoon Warning Center (JTWC) started monitoring the system at 06:00 UTC on October 1 while it was located northwest of Guam.
A mid-latitude trough weakened a subtropical ridge to its north, allowing the tropical disturbance to slowly gain latitude.
Following a surge in the monsoon trough, a Tropical Cyclone Formation Alert was issued at 08:00 UTC on October 3.
At the same time, the Japan Meteorological Agency (JMA) classified the system as a tropical depression, with the JTWC doing the same at 00:00 UTC on October 4.
Post-storm analysis from the JTWC indicated, however, that the depression had attained tropical storm midday on October 3.
The JMA upgraded Orchid into a tropical storm early on October 4, and twenty-four hours later, the JMA upgraded Orchid into a severe tropical storm.
At around this time, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) also monitored the storm and assigned it with the local name Sendang.
On the evening of October 5, Orchid was upgraded into a typhoon by the JTWC, and on the following morning, the JMA followed suit.

Continuing to intensify, Typhoon Orchid tracked due westward south of subtropical ridge.
Late on October 6, the JTWC raised the intensity of the storm to 185 km/h (115 mph), equal to a Category 3 hurricane on the United States-based Saffir-Simpson Hurricane Wind Scale (SSHWS).
Increased convergence in the southern quadrant enhanced convection, and dual outflow channels aloft were present.
The next day, the JTWC and JMA estimated that Orchid attained its peak intensity of 210 km/h (130 mph) and 175 km/h (110 mph).
Shortly after its peak, Orchid began to recurve near 130°E as the ridge receded eastward, allowing Orchid to move north.
Typhoon Orchid slowly accelerated after recurvature, only to slow down south of Japan on October 10 as a binary interaction started with Typhoon Pat.
Over a 42-hour period from October 10–12, Orchid took a "stair-stepped” track - moving to the north then back to the northeast due to interaction with Typhoon Pat.
At 00:00 UTC on October 12, both the JTWC and JMA agreed that Pat lost typhoon intensity.
Orchid subsequently started speeding up, following Pat to the northwest while slowly weakening.
At 00:00 UTC on October 13, the final warning was issued by the JTWC since Orchid had transitioned into an extratropical cyclone, though according to the JMA, this process did not occur until 24 hours later.
The JMA stopped keeping an eye on the system late on October 15.
The first tropical cyclone to develop during October 1991, Typhoon Orchid formed a broad monsoon trough that extended from the South China Sea eastward through the Caroline Islands. The Joint Typhoon Warning Center (JTWC) started monitoring the system at 06:00 UTC on October 1 while it was located northwest of Guam. A mid-latitude trough weakened a subtropical ridge to its north, allowing the tropical disturbance to slowly gain latitude. Following a surge in the monsoon trough, a Tropical Cyclone Formation Alert was issued at 08:00 UTC on October 3. At the same time, the Japan Meteorological Agency (JMA) classified the system as a tropical depression, with the JTWC doing the same at 00:00 UTC on October 4. Post-storm analysis from the JTWC indicated, however, that the depression had attained tropical storm midday on October 3. The JMA upgraded Orchid into a tropical storm early on October 4, and twenty-four hours later, the JMA upgraded Orchid into a severe tropical storm. At around this time, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) also monitored the storm and assigned it with the local name Sendang. On the evening of October 5, Orchid was upgraded into a typhoon by the JTWC, and on the following morning, the JMA followed suit.
Continuing to intensify, Typhoon Orchid tracked due westward south of subtropical ridge. Late on October 6, the JTWC raised the intensity of the storm to 185 km/h (115 mph), equal to a Category 3 hurricane on the United States-based Saffir-Simpson Hurricane Wind Scale (SSHWS). Increased convergence in the southern quadrant enhanced convection, and dual outflow channels aloft were present. The next day, the JTWC and JMA estimated that Orchid attained its peak intensity of 210 km/h (130 mph) and 175 km/h (110 mph). Shortly after its peak, Orchid began to recurve near 130°E as the ridge receded eastward, allowing Orchid to move north. Typhoon Orchid slowly accelerated after recurvature, only to slow down south of Japan on October 10 as a binary interaction started with Typhoon Pat. Over a 42-hour period from October 10–12, Orchid took a "stair-stepped” track - moving to the north then back to the northeast due to interaction with Typhoon Pat. At 00:00 UTC on October 12, both the JTWC and JMA agreed that Pat lost typhoon intensity. Orchid subsequently started speeding up, following Pat to the northwest while slowly weakening. At 00:00 UTC on October 13, the final warning was issued by the JTWC since Orchid had transitioned into an extratropical cyclone, though according to the JMA, this process did not occur until 24 hours later. The JMA stopped keeping an eye on the system late on October 15.
Typhoon Orchid (1991)