Tropical Storm Krosa was spinning northwest of the Marianas on Saturday.  At 5:00 p.m. EDT on Saturday the center of Tropical Storm Krosa was located at latitude 19.8°N and longitude 144.8°E which put the center about 90 miles (145 km) northwest of Agrihan.  Krosa was moving toward the north at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 80 m.p.h. (130 km/h).  The minimum surface pressure was 987 mb.

Tropical Storm Krosa strengthened on Saturday as it moved northwest of the Marianas.  More thunderstorms formed near the center of Krosa’s circulation.  Bands of showers and thunderstorms were revolving around the center of Tropical Storm Krosa.  Storms near the center of Krosa 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.

The distribution of wind speeds in Tropical Storm Krosa was asymmetrical.  Tropical storm force winds extended out 260 miles (420 km) in the southern side of Krosa’s circulation.  Tropical Storm force winds extended out 110 miles (175 km) in the northern side of Krosa.

Tropical Storm Krosa will move through and environment mostly favorable for intensification during the next 24 hours.  Krosa will move over water where the Sea Surface Temperatures are near 28°C.  It will move under the eastern side of an upper level low centered south of Japan.  The upper level low will produce southerly winds that will blow toward the top of Krosa’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 Krosa will intensify during the next 24 hours.  Krosa could strengthen to a typhoon on Sunday.

Tropical Storm Krosa will move around the western end of a high pressure system over the Western North Pacific Ocean.  The high pressure system will steer Krosa toward the north during the next 24 hours.  On its anticipated track, the center of Tropical Storm Krosa will pass east of Iwo To.