Tropical Storm Ma-on developed near northern Luzon on Sunday night. At 5:00 a.m. EDT on Monday the center of Tropical Storm Ma-on was located at latitude 16.3°N and longitude 123.4°E which put it about 100 miles (160 km) southeast of Tuguegarao, Philippines. Ma-on was moving toward the west at 11 m.p.h. (17 km/h). The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h). The minimum surface pressure was 997 mb.

Former Tropical Depression 10W strengthened to Tropical Storm Ma-on just to the east of northern Luzon on Sunday night. The distribution of thunderstorms in Ma-on continued to be asymmetrical. Most of the thunderstorms were in bands in the southern half of Ma-on’s circulation. The bands in the northern half of the circulation consisted primarily of showers and lower clouds. A strong upper level ridge over China was producing strong northerly winds that were blowing toward the top of Tropical Storm Ma-on. Those winds were causing moderate vertical wind shear and the wind shear was causing the asymmetrical distribution of thunderstorms.

Tropical Storm Ma-on will move through an environment favorable for intensification during the next 12 hours. Ma-on will move over water where the Sea Surface Temperatures are 30˚C. The upper level ridge over China will continue to produce northerly winds that will blow toward the top of Ma-on’s circulation. However, Tropical Storm Ma-on could strengthen during the next 12 hours. Ma-on will weaken when the center passes over northern Luzon, but it could strengthen again over the South China Sea later this week.

Tropical Storm Ma-on will move around the southwestern part of a high pressure system over the Western North Pacific Ocean. The high pressure system will steer Ma-on toward the west-northwest during the next 24 hours. On its anticipated track Tropical Storm Ma-on will hit northern Luzon in 12 hours. Ma-on will bring gusty winds and locally heavy rain to northern Luzon. Heavy rain could cause flash floods in some locations.

Elsewhere over the Western North Pacific Ocean, Tropical Storm Tokage formed southeast of Japan. At 5:00 a.m. EDT on Monday the center of Tropical Storm Tokage was located at latitude 25.5°N and longitude 151.6°E which put it about 1010 miles (1635 km) southeast of Tokyo, Japan. Tokage was moving toward the north at 11 m.p.h. (17 km/h). The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h). The minimum surface pressure was 998 mb.