Tag Archives: Sepat

Sepat Weakens to a Tropical Depression

Former Tropical Storm Sepat weakened to a tropical depression over the Western North Pacific Ocean south of Japan on Tuesday.  At 11:00 p.m. EDT on Tuesday the center of Tropical Depression Sepat was located at latitude 32.4°N and longitude 139.5°E which put the center about 230 miles (370 km) south of Tokyo, Japan.  Sepat was moving toward the north-northwest at 8 m.p.h. (13 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 1005 mb.

Former Tropical Storm Sepat weakened to a tropical depression on Tuesday as it moved over the Western North Pacific Ocean south of Japan.  Many of the thunderstorms in Sepat’s circulation dissipated.  A few thunderstorms were still occurring in the southeastern quadrant of Tropical Depression Sepat.  Most of the bands revolving around the center of Sepat’s circulation consisted primarily of showers and lower clouds.

Tropical Depression Sepat will move through an environment that will be unfavorable for intensification during the next 24 hours.  Sepat will move over water where where the Sea Surface Temperatures are near 25°C.  It will move under the northern part of an upper level ridge south of Japan.  The upper level ridge will produce west-southwesterly winds that will blow toward the top of Sepat’s circulation.  Those winds will cause strong vertical wind shear.  The strong vertical wind shear and marginal Sea Surface Temperatures will cause Tropical Depression Sepat to continue to weaken during the next 24 hours.

Tropical Depression Sepat will move around the western end of a high pressure system over the Western North Pacific Ocean.  The high pressure system will steer Sepat toward the north during the next 24 hours.  On its anticipated track, Tropical Depression Sepat will approach eastern Honshu in 12 hours.  The center of Sepat’s circulation is likely to pass just to the southeast of Tokyo.

Tropical Depression Sepat is likely to bring gusty winds and rain to the part of Honshu southeast of Tokyo.

Tropical Storm Sepat Moves Toward Honshu

Tropical Storm Sepat moved toward Honshu on Monday.  At 11:00 p.m. EDT on Monday the center of Tropical Storm Sepat was located at latitude 29.7°N and longitude 140.7°E which put the center about 420 miles (680 km) south of Tokyo, Japan.  Sepat was moving toward the northwest at 14 m.p.h. (22 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 1003 mb.

Tropical Storm Sepat strengthened a little on Monday morning, but Sepat was showing signs of weakening on Monday evening.  Thunderstorms were still occurring near the center of Tropical Storm Sepat.  Thunderstorms were also occurring bands revolving around the center of Sepat’s circulation.  Storms near the center of Sepat generated upper level divergence that pumped mass away from the tropical storm.  The removal of mass in the upper levels was balanced by the inflow of mass in the lower levels of Tropical Storm Sepat.  The balance of upper level divergence and inflow in the lower levels caused the surface pressure to remain steady.

The distribution of wind speeds in Tropical Storm Sepat was asymmetrical.  Winds to tropical storm force extended out 110 miles (175 km) in the eastern side of Sepat’s circulation.  The winds in the western side of Tropical Storm Sepat were blowing at less than tropical storm force.

Tropical Storm Sepat will move through an environment that will become unfavorable for intensification during the next 24 hours.  Sepat will move over water where where the Sea Surface Temperatures are near 26°C.  It will move under the northern part of an upper level low south of Japan.  The upper level low will produce northeasterly winds that will blow toward the top of Sepat’s circulation.  Those winds will cause moderate vertical wind shear.  The vertical wind shear  and marginal Sea Surface Temperatures will cause Tropical Storm Sepat to weaken during the next 24 hours.  Sepat is likely to weaken to a tropical depression on Tuesday.

Tropical Storm Sepat will move around the western end of a high pressure system over the Western North Pacific Ocean.  The high pressure system will steer Sepat toward the north-northwest during the next 24 hours.  On its anticipated track, Tropical Storm Sepat will continue to move toward Honshu.

Tropical Storm Sepat Forms Southeast of Japan

Tropical Storm Sepat formed over the Western North Pacific Ocean southeast of Japan on Sunday night.  At 11:00 p.m. EDT on Sunday the center of Tropical Storm Sepat was located at latitude 25.1°N and longitude 144.3°E which put the center about 215 miles (345 km) east of Iwo To.  Sepat was moving toward the northwest at 12 m.p.h. (19 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 1004 mb.

A low pressure system over the Western North Pacific Ocean southeast of Japan strengthened on Sunday night and the Japan Meteorological Agency designated the system as Tropical Storm Sepat.  The distribution of thunderstorms in Tropical Storm Sepat was asymmetrical.  Thunderstorms were occurring in bands in the northern side of Sepat’s circulation.  The bands in the southern side of Tropical Storm Sepat consisted primarily of showers and lower clouds.

Tropical Storm Sepat was under the eastern side of an upper level low that was south of Japan.  The upper level low was producing southerly winds that were blowing toward the top of Sepat’s circulation.  Those winds were causing moderate vertical wind shear.  The wind shear was causing the asymmetrical distribution of thunderstorms.

The distribution of wind speeds in Tropical Storm Sepat was also asymmetrical.  Winds to tropical storm force extended out 110 miles (175 km) in the eastern side of Sepat’s circulation.  The winds in the western side of Tropical Storm Sepat were blowing at less than tropical storm force.

Tropical Storm Sepat will move through an environment somewhat favorable for intensification during the next 24 hours.  Sepat will move over water where where the Sea Surface Temperatures are near 28°C.  The upper level low south of Japan will continue to cause moderate vertical wind shear.  The vertical wind shear will inhibit intensification, but the wind shear will not be enough to prevent intensification.  Tropical Storm Sepat is likely to intensify during the next 24 hours.

Tropical Storm Sepat will move around the western end of a high pressure system over the Western North Pacific Ocean.  The high pressure system and the upper low south of Japan will steer Sepat toward the north-northwest during the next 24 hours.  On its anticipated track, Tropical Storm Sepat will move toward Honshu.

Tropical Storm Sepat Forms Near Honshu

Tropical Storm Sepat formed near Honshu on Thursday.  More thunderstorms formed near the center of a low pressure system near the southeast coast of Honshu on Thursday and the Japan Meteorological Agency designated the system as Tropical Storm Sepat.  At 8:00 a.m. EDT on Thursday the center of Tropical Storm Sepat was located at latitude 32.6°N and longitude 134.7°E which put it about 100 miles (160 km) southwest of Susami, Japan.  Sepat was moving toward the northeast at 32 m.p.h. (50 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 998 mb.

The distribution of thunderstorms around Tropical Storm Sepat was asymmetrical.  The strongest thunderstorms were in several bands south and east of the center of circulation.  Bands in the other parts of the circulation consisted primarily of showers and lower clouds.  Storms southeast of the center of Sepat were generating upper level divergence which was pumping mass away to the northeast of the tropical storm.  Winds to tropical storm force extended out about 150 miles (240 km) to the east of the center of circulation.

Tropical Storm Sepat will move through an environment marginally favorable for intensification during the next 12 to 24 hours.  Sepat will move over water where the Sea Surface Temperature is near 24°C.  An upper level trough west of Japan will produce strong southwesterly winds which will blow toward the top of the circulation.  Those winds will cause moderate vertical wind shear, which is the primary reason for the asymmetrical distribution of thunderstorms.  Moderate vertical wind shear and cooler water will cause the structure of Tropical Storm Sepat to change to that of an extratropical cyclone.  Sepat could strengthen during the extratropical transition because upper level divergence will cause the surface pressure to decrease.

The upper level trough will steer Tropical Storm Sepat rapidly toward the northeast.  On its anticipated track the center of Tropical Storm Sepat will pass near the coast of Honshu.  Sepat will bring gusty winds and it could drop locally heavy rain.