Former Tropical Depression One-C strengthened to Tropical Storm Iona over the Central Pacific Ocean southeast of Hawaii on Sunday.  At 11:00 p.m. EDT on Sunday the center of Tropical Storm Iona was located at latitude 10.9°N and longitude 148.3°W which put the center about 965 miles (1545 km) southeast of Honolulu, Hawaii.  Iona 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 1005 mb.

Former Tropical Depression One-C strengthened to Tropical Storm Iona over the Central Pacific Ocean southeast of Hawaii on Sunday.  More stronger thunderstorms formed near the center of Iona’s circulation.  Thunderstorms were also occurring in bands revolving around the center of Tropical Storm Iona.  Storms near the center of Iona started to generate upper level divergence that pumped mass away from the tropical storm.

The strongest winds were occurring in the northern half of Tropical Storm Iona.  Winds to tropical storm force extended out 35 miles (55 km) in the northern side of Iona’s circulation.  The winds in the southern half of Tropical Storm Iona were blowing at less than tropical storm force.

Tropical Storm Iona will move through an environment favorable for intensification during the next 24 hours.  Iona will move over water where the Sea Surface Temperatures are near 28°C.  It will move under the southern part of an upper level ridge over the Central Pacific Ocean.  The upper level ridge will produce easterly winds that will blow toward the top of Iona’s circulation.  Those winds will cause some vertical wind shear.  The vertical wind shear will inhibit intensification, but the wind shear will not be enough to prevent intensification.  Tropical Storm Iona will intensify during the next 24 hours.

Tropical Storm Iona will move around the southern side of a high pressure system over the Central Pacific Ocean.  The high pressure system will steer Iona toward the west during the next 24 hours.  On its anticipated track, Tropical Storm Iona will pass south of Hawaii on Tuesday.