Tropical Storm Boris developed east-southeast of Hawaii on Thursday afternoon. At 5:00 p.m. EDT on Thursday the center of Tropical Storm Boris was located at latitude 11.2°N and longitude 137.1°W which put it about 1330 miles (2145 km) east-southeast of Hilo, Hawaii. Boris was moving toward the west-northwest at 9 m.p.h. (15 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 1005 mb.
More thunderstorms developed Thursday afternoon near a low pressure system southeast of Hawaii that was previously designated as Tropical Depression Three-E. A scatterometer on board a satellite detected winds to 40 m.p.h. (65 km) near the center of the low pressure system and the National Hurricane Center designated the system as Tropical Storm Boris. A band of showers and thunderstorms wrapped around the southern and eastern sides of the center of circulation and the strongest winds were occurring in that band of storms. A few other short bands of showers and thunderstorms developed in the eastern half of Boris. Bands in the western half of the circulation consisted primarily of showers and lower clouds. Winds to tropical storm force extended out about 50 miles from the center of circulation.
Tropical Storm Boris will move through an environment marginally favorable for intensification during the next 12 to 24 hours. Boris will move over water where the Sea Surface Temperature is near 26.5°C. A large upper level trough between Hawaii and the West Coast of the U.S. will produce southwesterly winds which will blow toward the top of the circulation. Those winds will cause moderate vertical wind shear and the shear will limit intensification. In addition, there is drier air north and west of Tropical Storm Boris. Boris could intensify during the next 12 hours in spite of the moderate vertical wind shear and drier air. However, Tropical Storm Boris will move into a region where the upper level winds are stronger during the weekend. When the vertical wind shear increases, Boris will weaken.
Tropical Storm Boris will move south of a subtropical high pressure system over the Eastern North Pacific Ocean. The will steer Boris toward the west-northwest during the next 24 hours. When Tropical Storm Boris weakens during the weekend, it will be steered by winds closer to the surface. Those winds will steer Boris toward the west. On its anticipated track the weakening Tropical Storm Boris will pass southeast of Hawaii.