Tropical Storm Thelma - Meteorological History

Meteorological History

In late October 1991, a tropical disturbance developed near the Caroline Islands. Tracking generally west-northwestward, the system gradually became more defined. On October 31, convection associated with the system quickly increased, prompting the issuance of a Tropical Cyclone Formation Alert from the Joint Typhoon Warning Center (JTWC). Early on November 1, the Japan Meteorological Agency (JMA) began monitoring the system as a tropical depression, at which time the system was situated roughly 415 km (260 mi) north-northeast of Palau. Following a satellite-derived surface wind estimate of 45 km/h (30 mph) later that day, the JTWC also began monitoring the low as a tropical depression. Initially, forecast models showed the system continuing on an arcing path out to sea; however, the system turned westward on November 2 and threatened the Philippines. Due to the cyclone's proximity to the country, the Philippine Atmospheric, Geophysical and Astronomical Services Administration also monitored the storm and assigned it with the local name Uring. Late on November 3, the depression turned west-southwestward towards the Visayas in response to an approaching cold front, an event typical of late-season cyclones in the basin. On November 4, both the JTWC and JMA upgraded the system to a tropical storm, with the latter assigning it the name Thelma.

Hours before striking the Philippines on November 4, both agencies estimated Thelma to have reached its peak intensity. The JTWC estimated the storm to have attained one-minute sustained winds of 85 km/h (50 mph) while the JMA estimated ten-minute sustained winds at 75 km/h (45 mph). Additionally, its barometric pressure reached 992 mbar (hPa; 29.29 inHg). Thelma soon made landfall in Samar before weakening to a minimal tropical storm. Maintaining gale-force winds, the system eventually passed over Palawan Island on November 6 before moving over the South China Sea. Despite being back over water, strong wind shear prevented re-intensification and caused Thelma to weaken to a tropical depression by November 7. Now moving westward, the depression eventually made its final landfall over the Mekong River Delta in Southern Vietnam on November 8. Within hours of moving onshore, the system dissipated.