Tropical Storm Hernan formed over the Eastern North Pacific Ocean west of Baja California on Wednesday night.  At 5:00 a.m. EDT on Thursday the center of Tropical Storm Hernan was located at latitude 18.1°N and longitude 131.9°W which put the center about 1460 miles (2350 km) west of the the southern tip of Baja California.  Hernan was moving toward the west at 2 m.p.h. (3 km/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 1006 mb.

A low pressure system over the Eastern North Pacific Ocean strengthened on Wednesday night and the U.S. National Hurricane Center designated the system as Tropical Storm Hernan.

The distribution of thunderstorms in Tropical Storm Hernan was asymmetrical.  An upper level trough near the West Coast of the U.S. was producing westerly winds that were blowing toward the top of Hernan’s circulation.  Those winds were causing moderate vertical wind shear.  The moderate vertical wind shear was causing the asymmetrical distribution of thunderstorms in Tropical Storm Hernan.

Thunderstorms were occurring in bands in the eastern side of Tropical Storm Hernan.  Bands in the western side of Hernan’s circulation consisted primarily of showers and lower clouds.  Storms near the center of Hernan generated upper level divergence that pumped mass away to the east of the tropical storm.  The removal of mass caused the surface pressure to decrease.

Even though the thunderstorms were in the eastern side of Tropical Storm Hernan, the strongest winds were occurring in the western side of Hernan.  Winds to tropical storm force extended out 40 miles (65 km) in the western side of Hernan’s circulation.  The winds in the eastern side of Tropical Storm Hernan were blowing at less than tropical storm force.

Tropical Storm Hernan will move through an environment that will be unfavorable for intensification during the next 24 hours.  Hernan will move over water where the Sea Surface Temperatures are near 26°C.  However, the upper level trough near the West Coast of the U.S. will continue to cause moderate vertical wind shear.  Tropical Storm Hernan is unlikely to intensify during the next 24 hours because of the vertical wind shear.

Tropical Storm Hernan will move around the southern part of a high pressure system over the Eastern North Pacific Ocean.  The high pressure system will steer Hernan toward the southwest during the next 24 hours.  On its anticipated track, Tropical Storm Hernan will remain far to the west of Baja California.

Elsewhere, Potential Tropical Cyclone One-C moved closer to Hawaii.  At 5:00 a.m. EDT on Thursday the center of Potential Tropical Cyclone One-C was located at latitude 14.8°N and longitude 144.5°W which put the center about 775 miles (1250 km) east-southeast of Hilo,Hawaii.   It was moving toward the west at 10 m.p.h. (16 km/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 1002 mb.