Tropical Storms Hilary and Irwin started to interact on Thursday as both storms began to weaken. At 11:00 p.m. EDT on Thursday the center of Tropical Storm Hilary was located at latitude 18.3°N and longitude 117.3°W which put it about 575 miles (925 km) west-southwest of the southern tip of Baja California. Hilary was moving toward the west-northwest at 8 m.p.h. (13 km/h). The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were gust to 85 m.p.h. (140 m.p.h.). The minimum surface pressure was 992 mb.
At 11:00 p.m. EDT on Thursday the center of Tropical Storm Irwin was located at latitude 14.9°N and longitude 124.6°W which put it about 1105 miles (1780 km) west-southwest of the southern tip of Baja California. Irwin was moving toward the west at 2 m.p.h. (3 km/h). The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were gusts to 75 m.p.h. (120 km/h). The minimum surface pressure was 1000 mb.
Hilary weakened below hurricane intensity on Thursday. It appeared that the circulation drew in drier more stable air around the northwestern side of the circulation. The drier air reduced the formation of showers and thunderstorms and the core of the circulation weakened. At the same time upper level divergence from Tropical Storm Hilary increased the vertical wind shear over Tropical Storm Irwin. Irwin was over water where the Sea Surface Temperature is near 28.5°C and it was able to extract enough energy from the ocean to maintain most of its intensity.
Tropical Storms Hilary and Irwin will move over water where the Sea Surface Temperature is near 28°C on Friday. However, the combination of drier, more stable air and vertical wind shear is likely to keep both of the storms from strengthening. Hilary and Irwin will move over cooler water during the weekend and both tropical storms are likely to weaken when that occurs.
Tropical Storm Hilary is being steering toward the west-northwest by a subtropical high pressure system to the north of the tropical storm. Hilary is forecast to continue moving toward the west-northwest. Tropical Storm Hilary is larger than Irwin. Winds to tropical storm force extend out about 110 miles (180 km) in Tropical Storm Hilary. Winds to tropical storm force extend out about 70 miles (110 km) in Tropical Storm Irwin.
The centers of the two tropical storms are only about 540 miles (870 km) apart. When Tropical Storm Hilary passes north of Irwin, Tropical Storm Irwin is forecast to start to revolve around the larger Tropical Storm Hilary. Irwin is expected to turn toward the north after Tropical Storm Hilary passes by. Some models are forecasting the that the centers of the two tropical storms will approach each other and the larger Tropical Storm Hilary will eventually absorb Tropical Storm Irwin.