Former Tropical Storm Alvin weakened to a tropical depression over the Eastern North Pacific Ocean south of Baja California on Saturday morning. At 11:00 a.m. EDT on Saturday the center of Tropical Depression Alvin was located at latitude 20.7°N and longitude 109.5°W which put the center about 155 miles (250 km) south of the southern tip of Baja California. Alvin was moving toward the north at 9 m.p.h. (15 km/h). The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h). The minimum surface pressure was 1006 mb.
Former Tropical Storm Alvin weakened to a tropical depression over the Eastern North Pacific Ocean south of Baja California on Sunday morning. An upper level low over Baja California caused strong southwesterly winds that blew across the top of Alvin’s circulation. Those winds caused strong vertical wind shear. In addition, Alvin moved over water where the Sea Surface Temperatures are near 24°C. Strong vertical wind shear and cool Sea Surface Temperatures caused former Tropical Storm Alvin to weaken.
Most of the thunderstorms in former Tropical Storm Alvin dissipated due to the strong vertical wind shear and cooler Sea Surface Temperatures. The circulation around Tropical Depression Alvin existed primarily in the lower levels of the atmosphere. Bands of showers and lower clouds were revolving around the center of Alvin’s circulation. Since there were no thunderstorms to generate upper level divergence and to pump mass away, the surface pressure was increasing gradually.
Tropical Depression Alvin will move through an environment very unfavorable for intensification during the next 24 hours. Alvin will move over water where where the Sea Surface Temperatures are near 24°C. The upper level low over Baja California will continue to produce southwesterly winds that will blow across the top of Alvin’s circulation. Those winds will continue to cause strong vertical wind shear. The combination of cool Sea Surface Temperatures and strong vertical wind shear will cause Tropical Depression Alvin to continue to weaken during the next 24 hours.
Tropical Depression Alvin will move around the western part of a high pressure system over Mexico. The high pressure system over Mexico and the upper level low over Baja California will steer Alvin toward the north during the next 24 hours. On its anticipated track, Tropical Depression Alvin will closer to the southern end of Baja California.
