Tropical Storm Nokaen weakened east of the Philippines on Sunday morning. At 10:00 a.m. EST on Sunday the center of the Tropical Storm Nokaen was located at latitude 15.5°N and longitude 125.9°E which put the center about 310 miles (500 km) east-southeast of Casiguran, Philippines. Nokaen was moving toward the north-northeast at 8 m.p.h. (13 km/h). The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h). The minimum surface pressure was 998 mb.
A combination of drier air and vertical wind shear caused Tropical Storm Nokaen to weaken east of the Philippines on Sunday morning. A large high pressure system over eastern Asia was transporting drier air into the environment around Tropical Storm Nokaen. The drier air caused many of the thunderstorms in Nokaen’s circulation to dissipate. An upper level ridge over the Western North Pacific Ocean was producing southerly winds that blew the tops off of many of the thunderstorms remaining in Tropical Storm Nokaen.
Most of the bands in Tropical Storm Nokaen consisted primarily of showers and lower clouds on Sunday morning. A few new thunderstorms formed northeast of the center of Nokaen’s circulation. The dissipation of many of the thunderstorms in Nokaen reduced the upper level divergence. Without thunderstorms to pump mass away from Nokaen, convergence in the lower levels of the atmosphere caused the surface pressure to increase.
The distribution of wind speeds in Tropical Storm Nokaen remained asymmetrical. Winds to tropical storm force extended out 115 miles (185 km) in the northern half of Nokaen’s circulation. Winds to tropical storm force extended out only 25 miles (40 km) in the southern half of Tropical Storm Nokaen.
Tropical Storm Nokaen will move through an environment that will be unfavorable for intensification during the next 24 hours. Nokaen will move over water where the Sea Surface Temperatures are near 28°C. However, the western end of the upper level ridge over the Western North Pacific Ocean will continue to produce southerly winds that will blow toward the top of Nokaen’s circulation. Those winds will cause strong vertical wind shear. In addition drier air will continue to surround Tropical Storm Nokaen. Tropical Storm Nokaen is likely to continue to weaken slowly during the next 24 hours.
Tropical Storm Nokaen will move around the western end of a high pressure system that is over the Western North Pacific Ocean. The high pressure system will steer Nokaen toward the northeast during the next 24 hours. On its anticipated track, the center of Tropical Storm Nokaen will move farther away from Luzon.
