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Tropical Storm Shanshan Drops Heavy Rain on Japan

Tropical Storm Shanshan dropped heavy on parts of southwestern Japan on Thursday.  At 11:00 p.m. EDT on Thursday the center of Tropical Storm Shanshan was located at latitude 33.8°N and longitude 131.6°E which put the center about 20 miles (30 km) west of Matsuyama, Japan.  Shanshan was moving toward the east-northeast at 3 m.p.h. (5 km/h).  The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 990 mb.

Former Typhoon Shanshan weakened to a tropical storm as it moved across Kyushu on Thursday.  Bands in the eastern side of Tropical Storm Shanshan dropped heavy rain on parts of Kyushu, Shikoku and southwestern Honshu.  The heaviest rain fell in locations where southerly winds pushed air up the slopes of mountains.  A weather station in Yosuhara reported 16.37 inches (416 mm) of rain.  A weather station in Hongawa reported 13.05 inches (331.5 mm) of rain.  Heavy rainfall caused flash floods in some locations.

Tropical Storm Shanshan weakened on Thursday as the center moved over land.  Bands of showers and thunderstorms were revolving around the center of Shanshan’s circulation.  The heaviest rain was falling in bands in the eastern side of Tropical Storm Shanshan.  Winds to tropical storm force extended out 100 miles (160 km) from the center of Shanshan.

An upper level trough over northeastern Asia will steer Tropical Storm Shanshan toward the east-northeast during the next 24 hours.  On its anticipated track, the center Tropical Storm Shanshan will move across Shikoku during the next 24 hours.

Tropical Storm Shanshan will continue to drop heavy rain on parts of southwestern Japan on Friday.  Heavy rain will fall in parts of Shikoku and southwestern Honshu.  The heaviest rain will fall where southerly winds push air up the slopes of mountains.  Heavy rain is likely to cause additional flash floods.

Typhoon Shanshan Brings Wind and Rain to Kyushu

Typhoon Shanshan brought wind and rain to Kyushu on Wednesday.  At 5:00 p.m. EDT on Wednesday the center of Typhoon Shanshan was located at latitude 31.6°N and longitude 130.2°E which put the center about 35 miles (55 km) west of Kagoshima, Japan.  Shanshan was moving toward the north at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 100 m.p.h. (160 km/h) and there were wind gusts to 120 m.p.h. (195 km/h).  The minimum surface pressure was 957 mb.

Typhoon Shanshan brought wind and rain to Kyushu on Wednesday.  The eastern side of the eyewall of Shanshan moved over Makurazaki, Japan.  A weather station in Makurazaki reported a sustained wind speed of 69 m.p.h. (111 km/h).  The weather station also reported 8.42 inches (214 mm) of rain.  A weather station in Kaseda reported 10.95 inches (278 mm) of rain.  A weather station in Ibusuki reported 9.33 inches (237 mm) of rain.

Typhoon Shanshan was weakening gradually when it reached the west coast of Kyushu.  An upper level trough over northeastern Asia was producing southwest winds that were blowing toward the top of Shanshan’s circulation.  Those winds caused more vertical wind shear.  The increase in wind shear caused Typhoon Shanshan to start to weaken.

An eye was no longer visible at the center of Typhoon Shanshan on conventional satellite images.  The former eye was still being detected by radars operated by the Japan Meteorological Agency.  There were breaks in the ring of thunderstorms that surrounded the former eye.  The strongest winds were still occurring in that broken ring of storms.  Bands of showers and thunderstorms were revolving around the core of Typhoon Shanshan.

The circulation around Typhoon Shanshan was still symmetrical.  Winds to typhoon force extended out 30 miles (50 km) from the center of Shanshan’s circulation.  Winds to tropical storm force extended out 125 miles (200 km) from the center of Typhoon Shanshan.

The Hurricane Intensity Index (HII) for Typhoon Shanshan was 16.5.  The Hurricane Size Index (HSI) was 11.8 and the Hurricane Wind Intensity Size Index (HWISI) was 28.3.  Typhoon Shanshan was similar in intensity to Hurricane Idalia when Idalia hit Florida in 2023.  Shanshan was bigger than Idalia was.

Typhoon Shanshan will move around the western end of a high pressure system over the Western North Pacific Ocean.  The high pressure system will steer Shanshan toward the north during the next 12 hours.  The upper level trough over northeastern Asia will steer Shanshan toward the northeast on Thursday.  On its anticipated track, the center Typhoon Shanshan will move near the west coast of Kyushu during the next 12 hours.  Shanshan will move inland over Kyushu on Thursday.

Typhoon Shanshan will weaken gradually as it moves inland over Kyushu.  Even though Shanshan will weaken it will still produce strong winds and drop heavy rain over much of Kyushu.  Heavy rain is likely to cause flash floods in some locations,

Typhoon Shanshan Strengthens to Equivalent of a Cat. 4 Hurricane

Typhoon Shanshan strengthened to the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale over the northern Ryukyu Islands on Tuesday.  At 5:00 p.m. EDT on Tuesday the center of Typhoon Shanshan was located at latitude 29.2°N and longitude 130.0°E which put the center about 90 miles (145 km) south-southwest of Kamiyaku, Japan.  Shanshan was moving toward the north-northwest at 5 m.p.h. (8 km/h).  The maximum sustained wind speed was 130 m.p.h. (210 km/h) and there were wind gusts to 160 m.p.h. (260 km/h).  The minimum surface pressure was 932 mb.

Typhoon Shanshan intensified to the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale on Tuesday.  A circular eye with a diameter of 30 miles (50 km) was at the center of Shanshan’s circulation.  The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Typhoon Shanshan.  Storms near the core generated strong upper level divergence that pumped mass away from the typhoon.  The removal of mass caused the surface pressure to decrease.

The circulation around Typhoon Shanshan was symmetrical.  Winds to typhoon force extended out 30 miles (50 km) from the center of Shanshan’s circulation.  Winds to tropical storm force extended out 145 miles (230 km) from the center of Typhoon Shanshan.

The Hurricane Intensity Index (HII) for Typhoon Shanshan was 25.1.  The Hurricane Size Index (HSI) was 12.1 and the Hurricane Wind Intensity Size Index (HWISI) was 37.2.  Typhoon Shanshan was similar in size and intensity to Hurricane Harvey when Harvey hit Texas in 2017.

Typhoon Shanshan will move through an environment that will be favorable for intensification during the next 24 hours.  Shanshan will move over water where the Sea Surface Temperatures are near 29°C.  It will through a region where the upper level winds are weak and there will be little vertical wind shear.  Typhoon Shanshan could intensify during the next 24 hours.

Typhoon Shanshan will move around the western end of a high pressure system over the Western North Pacific Ocean.  The high pressure system will steer Shanshan toward the north-northwest during the next 24 hours.  On its anticipated track, Typhoon Shanshan will toward western Kyushu.  Shanshan could approach western Kyushu in 36 hours.

Typhoon Shanshan will continue to produce strong winds and heavy rain in the northern Ryukyu Islands.  The eastern side of the eyewall of Shanshan will move near Yakushima.  Shanshan will be capable of causing severe damage.  Heavy rain is likely to cause flash floods in some locations.  Typhoon Shanshan will also cause a storm surge in the northern Ryukyu Islands where the wind blows the water toward the shore.

 

Typhoon Shanshan Intensifies to the Equivalent of a Major Hurricane

Typhoon Shanshan intensified to the equivalent of a major hurricane near the northern Ryukyu Islands on Monday evening.  At 11:00 p.m. EDT on Monday the center of Typhoon Shanshan was located at latitude 28.3°N and longitude 130.6°E which put the center about 75 miles (120 km) east of Naze, Japan.  Shanshan was moving toward the northwest at 4 m.p.h. (6 km/h).  The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 150 m.p.h. (240 km/h).  The minimum surface pressure was 943 mb.

Typhoon Shanshan intensified to the equivalent of a major hurricane on Monday evening as it moved slowly near the northern Ryukyu Islands.  A small circular eye with a diameter of 12 miles (19 km) was at the center of Shanshan’s circulation.  The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Typhoon Shanshan.  Storms near the core generated strong upper level divergence that pumped mass away from the typhoon.  The removal of mass caused the surface pressure to decrease.

The circulation around Typhoon Shanshan was symmetrical.  Winds to typhoon force extended out 40 miles (65 km) from the center of Shanshan’s circulation.  Winds to tropical storm force extended out 125 miles (200 km) from the center of Typhoon Shanshan.

The Hurricane Intensity Index (HII) for Typhoon Shanshan was 22.1.  The Hurricane Size Index (HSI) was 13.7 and the Hurricane Wind Intensity Size Index (HWISI) was 35.8.  Typhoon Shanshan was similar in size to Hurricane Delta when Delta hit southwest Louisiana in 2020.  Shanshan was stronger than Delta was.

Typhoon Shanshan will move through an environment that will be favorable for intensification during the next 24 hours. Shanshan will move over water where the Sea Surface Temperatures are near 29°C.  It will through a region where the upper level winds are weak and there will be little vertical wind shear.  Typhoon Shanshan is likely to continue to intensify during the next 24 hours.

Typhoon Shanshan will move around the western end of a high pressure system over the Western North Pacific Ocean.  The high pressure system will steer Shanshan slowly toward the northwest during the next 24 hours.  On its anticipated track, Typhoon Shanshan will move over the northern Ryukyu Islands.  Shanshan could approach southwestern Japan in 48 hours. Shanshan could be a strong typhoon when it approaches Kyushu.

Typhoon Shanshan will bring strong winds and heavy rain to the northern Ryukyu Islands.  Shanshan will be capable of causing major damage.  Heavy rain is likely to cause flash floods in some locations.  Typhoon Shanshan will also cause a storm surge on the northern Ryukyu Islands where the wind blows the water toward the shore.

Typhoon Shanshan Continues to Strengthen

Typhoon Shanshan continues to strengthen over the Western North Pacific Ocean south of Japan on Sunday.  At 11:00 p.m. EDT on Sunday the center of Typhoon Shanshan was located at latitude 27.3°N and longitude 133.5°E which put the center about 350 miles (565 km) south-southeast of Kagoshima, Japan.  Shanshan was moving toward the west-northwest at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 90 m.p.h. (145 km/h) and there were wind gusts to 115 m.p.h. (185 km/h).  The minimum surface pressure was 968 mb.

Typhoon Shanshan strengthened gradually on Sunday as it moved over the Western North Pacific Ocean south of Japan.  A large circular eye was present at the center of Shanshan’s circulation.  The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Typhoon Shanshan.  Storms near the core of Shanshan’s circulation generated more upper level divergence that pumped mass away from the typhoon.  The removal of more mass caused the surface pressure to decrease.

The size of the circulation around typhoon Shanshan increased slightly on Sunday.  Winds to typhoon force extended out 35 miles (55 km) from the center of Shanshan’s circulation.  Winds to tropical storm force extended out 145 miles (230 km) from the center of Typhoon Shanshan.

The Hurricane Intensity Index (HII) for Typhoon Shanshan was 13.9.  The Hurricane Size Index (HSI) was 11.7 and the Hurricane Wind Intensity Size Index (HWISI) was 25.6.

Typhoon Shanshan will move through an environment that will be favorable for intensification during the next 24 hours.  Shanshan will move over water where the Sea Surface Temperatures are near 29°C.  It will move under the northern periphery of an upper level low south of Japan.  The upper level low will produce easterly winds that will blow toward the top of Shanshan’s circulation.  Those winds will cause some vertical wind shear, but the wind shear will not be enough to prevent intensification.  Typhoon Shanshan will intensify during the next 24 hours.

Typhoon Shanshan will move around the western end of a high pressure system over the Western North Pacific Ocean.  The high pressure system will steer Shanshan toward the northwest during the next 24 hours.  On its anticipated track, Typhoon Shanshan will move closer to Kyushu and Shikoku.  Shanshan could approach southwestern Japan in 48 hours.  Shanshan could be a strong typhoon when it approaches Japan.

 

Typhoon Shanshan Passes West of Iwo To

The center of Typhoon Shanshan passed west of Iwo To on Saturday night.  At 11:00 p.m. EDT on Saturday the center of Typhoon Shanshan was located at latitude 25.4°N and longitude 138.4°E which put the center about 150 miles (240 km) west of Iwo To.  Shanshan was moving toward the northwest at 15 m.p.h. (24 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 974 mb.

Typhoon Shanshan maintained its intensity on Saturday as it moved over the Western North Pacific Ocean west of Iwo To.  Shanshan moved under the eastern side of an upper level low south of Japan.  The upper level low produced southerly winds that blew toward the top of Shanshan’s circulation.  Those winds caused moderate vertical wind shear, and the wind shear prevented intensification of Typhoon Shanshan.

The vertical wind shear also affected the structure of Typhoon Shanshan.  A small circular eye was present at the center of Shanshan’s circulation.  The eye was surrounded by a broken ring of thunderstorms and the strongest winds were occurring in that ring of storms.  Thunderstorms were occurring in bands in the northern side of Typhoon Shanshan.  Bands in the southern part of Shanshan’s circulation consisted primarily of showers and lower clouds.  Storms near the center of Shanshan generated upper level divergence that pumped mass away to the north of the typhoon.  The removal of mass in the upper levels was balanced by the inflow of mass in the lower levels of the atmosphere.  The balance of the outflow and inflow of mass caused the surface pressure to remain steady on Saturday.

Winds to typhoon force extended out 35 miles (55 km) from the center of Typhoon Shanshan.  Winds to tropical storm force extended out 125 miles (200 km) from the center of Shanshan’s circulation.

Typhoon Shanshan will move through an environment that will become more favorable for intensification during the next 24 hours.  Shanshan will move over water where the Sea Surface Temperatures are near 29°C.  It will move farther away from the upper level low south of Japan.  The upper level low will still produce southerly winds that will blow toward the top of Shanshan’s circulation.  However, there will be less vertical wind shear on Sunday.  Typhoon Shanshan is likely to intensify during the next 24 hours.

Typhoon Shanshan will move around the western end of a high pressure system over the Western North Pacific Ocean.  The high pressure system will steer Shanshan toward the northwest during the next 24 hours.  On its anticipated track, Typhoon Shanshan will move closer to Kyushu and Shikoku.  Shanshan could approach southwestern Japan in 48 hours.  Shanshan could be a strong typhoon when it approaches Japan.

 

Shanshan Strengthens to a Typhoon

Former Tropical Storm Shanshan strengthened to a typhoon over the Western North Pacific Ocean south of Iwo To.  At 11:00 p.m. EDT on Friday the center of Typhoon Shanshan was located at latitude 20.5°N and longitude 141.2°E which put the center about 330 miles (535 km) south of Iwo To.  Shanshan was moving toward the north at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 974 mb.

Former Tropical Storm Shanshan strengthened to a typhoon south of Iwo To on Friday.  The inner end of a raindband wrapped around the center of Shanshan’s circulation.  A circular eye formed at the center of Typhoon Shanshan.  The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the center of Shanshan’s circulation.  Storms near the center of Shanshan generated more upper level divergence that pumped mass away from the typhoon.  The removal of more mass caused the surface pressure to decrease.

Winds to typhoon force extended out 30 miles (50 km) from the center of Typhoon Shanshan.  Winds to tropical storm force extended out 115 miles (185 km) from the center of Shanshan’s circulation.

Typhoon Shanshan will move through an environment favorable for intensification during the next 24 hours.  Shanshan will move over water where the Sea Surface Temperatures are near 29°C.  It will move through a region where the upper level winds are weak and there will be little vertical wind shear.  Typhoon Shanshan will intensify during the next 24 hours.

Typhoon Shanshan will move around the western end of a high pressure system over the Western North Pacific Ocean.  The high pressure system will steer Shanshan toward the north-northwest during the next 24 hours.  On its anticipated track, the center of Typhoon Shanshan will be near Iwo To in 24 hours.  Shanshan could approach central Japan in 72 hours.

 

Tropical Storm Shanshan Forms South of Iwo To

Tropical Storm Shanshan formed over the Western North Pacific Ocean south of Iwo To on Wednesday evening.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Shanshan was located at latitude 17.2°N and longitude 141.5°E which put the center about 505 miles (810 km) south of Iwo To.  Shanshan was moving toward the west at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 1001 mb.

A low pressure system over the Western North Pacific Ocean south of Iwo To strengthened on Wednesday evening and the Japan Meteorological Agency designated the system as Tropical Storm Shanshan.  The circulation around Tropical Storm Shanshan exhibited more organization on satellite images, but the distribution of thunderstorms was asymmetrical.  Thunderstorms were occurring in bands in the eastern side of Shanshan’s circulation.  Bands in the western side of Tropical Storm Shanshan consisted primarily of showers and lower clouds.  Storms near the center of Shanshan began to generate upper level divergence that pumped mass away from the tropical storm.

The circulation around Tropical Storm Shanshan was small.  Winds to tropical storm force extended out 45 miles (75 km) from the center of Shanshan’s circulation.

Tropical Storm Shanshan will move through an environment favorable for intensification during the next 24 hours.  Shanshan will move over water where the Sea Surface Temperatures are near 29°C.  It will move under the southeastern part of an upper level ridge over Japan.  The ridge will produce northerly winds that will blow toward the top of Shashan’s circulation.  Those winds will cause vertical wind shear, but the wind shear will not be enough to prevent intensification.  Tropical Storm Shanshan will intensify during the next 24 hours.  Shanshan is likely to strengthen to a typhoon within 36 hours/

Tropical Storm Shanshan will move around the western end of a high pressure system over the Western North Pacific Ocean.  The high pressure system will steer Shanshan toward the north-northwest during the next 24 hours.  On its anticipated track, Tropical Storm Shanshan will move closer to Iwo To.  Shanshan could approach Japan in five days.

Typhoon Shanshan Brushes East Coast of Honshu

Typhoon Shanshan brushed the east coast of Honshu late on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Typhoon Shanshan was located at latitude 36.8°N and longitude 141.5°E which put it about 40 miles (65 km) east of Iwaki, Japan.  Shanshan was moving toward the north at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 975 mb.

The center of Typhoon Shanshan moved very close to the east coast of Honshu near Choshi on Wednesday and then it moved nearly parallel to the coast.  The stronger winds and heavier rain were occurring on the eastern side of Shanshan, and they passed east of Honshu.  The winds were weaker and the rain was lighter in the western side of Typhoon Shanshan.  Winds to tropical storm force were occurring near the east coast of Honshu.  The typhoon had little effect on the weather near Tokyo.  Some locations near the coast did have a period of heavier rain after the center of Typhoon Shanshan passed and the winds blew from the southwest toward the coast.

Typhoon Shanshan will affect the coast of Honshu for another six to twelve hours, while the center moves nearly parallel to the coast.  Shanshan will reach an area where stronger westerly winds are blowing in the middle and upper troposphere.  Those winds will turn Typhoon Shanshan toward the east and they will push it away from Japan.  The stronger winds will also cause significant vertical wind shear.  Shanshan will move over cooler water when it turns eastward.  The combination of vertical wind shear and cooler water will cause Typhoon Shanshan to weaken and it could make a transition to an extratropical cyclone in a day or two.

Elsewhere over the Western North Pacific, Tropical Storm Yagi formed southeast of Okinawa on Wednesday.  At 11:00 p.m. EDT the center of Tropical Storm Yagi was located at latitude 21.3°N and longitude 133.6°E which put it about 530 miles (855 km) southeast of Okinawa.  Yagi was moving toward the northwest at 7 m.p.h. (11 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 993 mb.

Typhoon Shanshan Moves Closer to Honshu

Typhoon Shanshan moved steadily closer to Honshu on Tuesday.  At 11:00 p.m. EDT on Tuesday the center of Typhoon Shanshan was located at latitude 33.7°N and longitude 141.6°E which put it about 190 miles (305 km) southeast of Tokyo.  Shanshan was moving toward the north-northwest at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 90 m.p.h. (145 km/h) and there were wind gusts to 115 m.p.h. (185 km/h).  The minimum surface pressure was 965 mb.

Typhoon Shanshan intensified earlier on Tuesday and it started to weaken on Tuesday night.  There was a circular eye at the center of circulation.  The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Several bands of showers and thunderstorms were revolving around the core of Typhoon Shanshan.  The rainbands south and east of the center were stronger and the rainbands north and west of the center were weaker.  Storms near the core of Shanshan were generating upper level divergence which was pumping mass away from typhoon.  Winds to typhoon force extended out about 45 miles (75 km) from the center of circulation.  Winds to tropical storm force extended out about 220 miles (350 km) from the center.

Typhoon Shanshan will move through an environment on Wednesday that should allow it to remain a typhoon until it reaches Japan.  Shanshan will move over water where the Sea Surface Temperature is near 28°C.  It will move through a region where the upper level winds are weaker and there will be little vertical wind shear.  Typhoon Shanshan will move into a region in a day or so where stronger upper level winds will blow from the west.  Vertical wind shear will increase at that time and Typhoon Shanshan will start to weaken more quickly.

Typhoon Shanshan will move around the western end of a ridge over the North Pacific Ocean and the ridge will steer the typhoon toward the north on Wednesday.  When Shanshan gets close to the coast of Honshu, the westerly winds will turn the typhoon toward the east.  On its anticipated track Typhoon Shanshan could make landfall on the coast of Honshu east of Tokyo in 18 to 24 hours.  Shanshan will bring gusty winds and it could drop heavy rain over coastal regions of eastern Honshu.