Tropical Storm Estelle developed late Friday over the Eastern North Pacific as Hurricane Darby neared its peak intensity farther west. At 11:00 p.m. EDT on Friday the center of Tropical Storm Estelle was located at latitude 15.2°N and longitude 108.3°W which put it about 370 miles (600 km) southwest of Manzanillo, Mexico. Estelle was moving toward the west-northwest at 12 m.p.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. Estelle is the fifth tropical storm to form over the Eastern North Pacific during the month of July.
Meanwhile, about 950 miles west of Estelle, Hurricane Darby neared its peak intensity. At 11:00 p.m. EDT on Friday the center of Hurricane Darby was located at latitude 17.3°N and longitude 122.1°W which put it about 880 miles (1415 km) west-southwest of the southern tip of Baja California. Darby was moving toward the west-northwest at 9 m.p.h. The maximum sustained wind speed was 105 m.p.h. (165 km/h) and there were wind gusts to 125 m.p.h. (200 km/h). The minimum surface pressure was 972 mb.
The large circulation around Tropical Storm Estelle is still organizing. A primary rainband is wrapping around the western side of the center. Several spiral bands of thunderstorms are forming farther away from the core of the tropical storm. Storms near the center are beginning to produce upper level divergence, but it is not currently well developed.
The environment around Estelle is favorable for gradual intensification. Estelle is moving over water where the Sea Surface Temperature is near 29°C. An upper level ridge north of Estelle is generating easterly winds which are blowing over the top of the tropical storm. There is enough vertical wind shear to slow the rate of intensification, but the shear is probably not strong enough to keep Estelle from intensifying. Storms like Estelle with large initial circulations can intensify slowly as a tighter core develops within the larger circulation.
Hurricane Darby is a well formed mature hurricane. It has a well developed eye surrounded by a narrow ring of strong thunderstorms. Several spiral bands are rotating around the core of Darby. The thunderstorms near the center of circulation are generating upper level divergence which is pumping out mass in all directions.
Hurricane Darby is probably close to its peak intensity. It is moving over water where the Sea Surface Temperature is near 27°C and Darby will be moving over cooler water during the next few days. There is not much vertical wind shear, and Darby may have a chance to intensify during the next 12 to 24 hours. However, Darby will reach cooler water in about a day and then the hurricane will being to weaken.
A subtropical ridge located north of Hurricane Darby and Tropical Storm Estelle is expected to steer both cyclones toward the west during the next few days.