Tropical Storm Alvin weakened on Friday as it moved over the Eastern North Pacific Ocean south of Baja California.  At 5:00 p.m. EDT on Friday the center of Tropical Storm Alvin was located at latitude 18.1°N and longitude 109.0°W which put the center about 335 miles (540 km) south of the southern tip of Baja California.  Alvin was moving toward the north-northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 1001 mb.

An upper level low over Baja California produced southwesterly winds that blew toward the top of Tropical Storm Alvin on Friday.  Those winds caused the vertical wind shear to increase.  The increase in vertical wind shear caused Alvin to weaken.  The increase in wind shear also caused the distribution of thunderstorm around Tropical Storm Alvin to become asymmetrical.  Thunderstorms were still occurring in bands in the northern side of Alvin’s circulation.  Bands in the southern side of Tropical Storm Alvin consisted primarily of showers and lower clouds.

Even though Tropical Storm Alvin weakened on Friday,  the size of the circulation did not change much.  Winds to tropical storm force extended out 140 miles (225 km) from the center of Alvin’s circulation.

Tropical Storm Alvin will move through an environment that will become even more unfavorable for intensification during the next 24 hours.  Alvin will move over water where where the Sea Surface Temperatures are near 25°C.  It will move under the southeastern part of the upper level low over Baja California.  The upper level low will continue to produce southwesterly winds that will blow toward the top of Alvin’s circulation.  Those winds will cause strong vertical wind shear on Saturday.  The combination of cool Sea Surface Temperatures and strong vertical wind shear will cause Tropical Storm Alvin to continue to weaken during the next 24 hours.

Tropical Storm 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 Storm Alvin will closer to the southern end of Baja California.