Hurricane Rosa moved toward Baja California on Saturday night. At 11:00 p.m. EDT on Saturday the center of Hurricane Rosa was located at latitude 22.4°N and longitude 118.9°W which put it about 440 miles (710 km) south-southwest of Punta Eugenia, Mexico. Rosa was moving toward the north at 12 m.p.h. (19 km/h). The maximum sustained wind speed was 100 m.p.h. (160 km/h) and there were wind gusts to 120 m.p.h. (195 km/h). The minimum surface pressure was 969 mb.
A Tropical Storm Warning was in effect for the portion of the coast from Punta Abreojos to Cabo San Quintin, Mexico. A Tropical Storm Watch was in effect for the portion of the coast from Bahia de los Angeles to San Felipe, Mexico.
Hurricane Rosa will move into an environment unfavorable for hurricanes on Sunday. Rosa will move over water where the Sea Surface Temperature is cooler than 26°C. In addition an upper level low near the west coast of the U.S. will produce southwesterly winds which will cause vertical wind shear. The combination of cooler water and more vertical wind shear will cause Hurricane Rosa to weaken. Rosa could weaken to a tropical storm by Sunday night.
The upper low will steer Hurricane Rosa toward the northeast during the next several days. On its anticipated track Rosa could reach Baja California on Monday. It will likely be a tropical storm at that time. Even though it will weaken, Rosa will drop heavy rain over parts northern Baja California and the southwestern U.S. The heavy rain could cause flash floods.
Elsewhere over the Eastern North Pacific Ocean Tropical Storm Sergio formed southwest of Acapulco, Mexico. At 11:00 p.m. EDT on Saturday the center of Tropical Storm Sergio was located at latitude 12.3°N and longitude 103.3°W which put it about 390 miles (630 km) southwest of Acapulco, Mexico. Sergio was moving toward the west at 10 m.p.h. (16 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 1003 mb.
Hurricane Rosa rapidly intensified into a major hurricane southwest of Baja California on Thursday. At 5:00 p.m. EDT on Thursday the center of Hurricane Rosa was located at latitude 16.9°N and longitude 115.9°W which put it about 570 miles (915 km) southwest of the southern tip of Baja California. Rosa was moving toward the west at 10 m.p.h. (16 km/h). The maximum sustained wind speed was 125 m.p.h. (200 km/h) and there were wind gusts to 145 m.p.h. (240 km/h). The minimum surface pressure was 953 mb.
Hurricane Rosa rapidly intensified into a powerful hurricane on Thursday and a circular eye developed at the center of circulation. The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in the ring of storms. The circulation around Hurricane Rosa was symmetrical. Several bands of showers and thunderstorms were revolving around the core of the hurricane. Storms around the core were generating strong upper level divergence which was pumping mass away from the hurricane.
The circulation around Hurricane Rosa was relatively small. Winds to hurricane force only extended out about 35 miles (55 km) from the center of circulation. Winds to tropical storm force extended out about 115 miles (185 km) from the center. The Hurricane Intensity Index (HII) for Hurricane Rosa was 23.6. The Hurricane Size Index (HSI) was 9.8 and the Hurricane Wind Intensity Size Index (HWISI) was 33.4.
Hurricane Rosa will continue to move through an environment favorable for intensification during the next 12 to 24 hours. Rosa will move over water where the Sea Surface Temperature is near 28°C. It will move through an area where the upper level winds are weak and there will be little vertical wind shear during the shorter term. If a rainband wraps around the existing eye and eyewall, an eyewall replacement cycle could halt the current period of rapid intensification. Hurricane Rosa will start to move over cooler water during the weekend. An upper level low west of California will produce southwesterly winds which will blow toward the top of Rosa’s circulation. Those winds will cause more vertical wind shear and they could cause Rosa to weaken more quickly.
Hurricane Rosa will move around the western end of a ridge of high pressure over northern Mexico on Friday. Rosa will start to move more toward the north when it moves around the western end of the ridge. The upper level trough east of California will turn Rosa more toward the northeast during the weekend. On its anticipated track Rosa could approach Baja California early next week. It may weaken to a tropical storm before it gets to Baja California, but it still will have the potential to drop heavy rain.