Tag Archives: WP17

Shanshan Strengthens to a Typhoon Southeast of Japan

Former Tropical Storm Shanshan strengthened into a typhoon southeast of Japan on Saturday.  At 5:00 a.m. EDT on Saturday the center of Typhoon Shanshan was located at latitude 21.2°N and longitude 148.5°E which put it about 245 miles (395 km) northeast of Agrihan.  Shashan was moving toward the north-northwest at 10 m.p.h. (16 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.

A primary rainband wrapped around the center of circulation and an eye was developing at the center of Typhoon Shanshan.  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 Shanshan.  The strongest rainbands were south and east of the center of circulation.  Bands north and west of the center consisted primarily of showers and lower clouds.  Storms around the core were generating upper level divergence which was pumping mass away from the typhoon.  Shanshan has a large circulation.  Winds to tropical storm force extend out about 190 miles (305 km) from the center of circulation.

Typhoon Shanshan will move through an environment favorable for intensification during the next 24 to 48 hours.  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 weak and there will be little vertical wind shear.  Typhoon Shanshan will intensify and it could strengthen into the equivalent of a major hurricane.

Typhoon Shanshan will move around the western portion of a subtropical ridge over the Western North Pacific Ocean.  The ridge will steer Shanshan in a north-northwesterly direction.  On its anticipated track the center of Typhoon Shanshan will pass east of Iwo To in 24 to 36 hours.  Shanshan could be just southeast of Honshu in about four days.

Tropical Storm Jongdari Makes Landfall South of Shanghai, Shanshan Forms Northeast of Guam

Tropical Storm Jongdari made landfall south of Shanghai on Thursday, while Tropical Storm Shanshan formed northeast of Guam.  At 11:00 p.m. EDT on Thursday the center of Tropical Storm Jongdari was located at latitude 30.7°N and longitude 121.4°E which put it about 40 miles (65 km) south of Shanghai, China.  Jongdari was moving toward the west at 19 m.p.h. (30 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 994 mb.

The center of Tropical Storm Jongdari made landfall on the east coast of China near Zhoushan and Ningbo on Thursday.  Jongdari retained a distinct low level center of circulation while it made landfall.  The tropical storm brought gusty winds to the coast of Zhejiang and Shanghai Shi provinces.  Tropical Storm Jongdari dropped locally heavy rain over parts of those provinces and some flooding could occur.  The center of Jongdari will move quickly toward Hangzhou and the risk of flooding will continue as the tropical storm moves inland and weakens.

Elsewhere over the Western North Pacific Ocean, Tropical Storm Shanshan formed northeast of Guam.  At 11:00 p.m. EDT on Thursday the center of Tropical Storm Shanshan was located at latitude 17.9°N and longitude 150.1°E which put it about 460 miles (740 km) northeast of Guam.  Shanshan was moving toward the west-southwest 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. (65 km/h).  The minimum surface pressure was 998 mb.

A distinct low level center of circulation formed in a cluster of thunderstorms east of the Northern Marianas on Thursday and the Japan Meteorological Agency designated the system as Tropical Storm Shanshan.  The circulation of Shanshan was still organizing.  Several bands of showers and thunderstorms developed southwest of the center of circulation.  Bands northeast of the center consisted mostly of showers and lower clouds.  Storms near the center of circulation started to generate upper level divergence.

Tropical Storm Shanshan will move through an environment favorable for intensification.  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 weak and there will be little vertical wind shear.  Tropical Storm Shanshan will intensify and it could strengthen into a typhoon during the weekend.

Tropical Storm Shashan will move around the western end of a subtropical high pressure system.  The high will steer Shanshan in a general northwesterly direction during the next 12 to 24 hours.  It will turn more toward the north during the weekend.  On its anticipated track Tropical Storm Shanshan will move near the Northern Marianas during the next 24 to 36 hours.

Typhoon Sanvu Brings Wind and Rain to Chichi Jima

Typhoon Sanvu is bringing a prolonged period of gusty winds and heavy rain to Chichi JIma, Japan.  Sanvu strengthened during the past several days while it meandered around Chichi Jima.  At 11:00 a.m. EDT on Thursday the center to Typhoon Sanvu was located at latitude 28.1°N and longitude 142.0°E which put it about 60 miles (95 km) north-northwest of Chichi Jima, Japan.  Sanvu was moving toward the north at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 85 m.p.h. (135 km/h) and there were wind gusts to 105 m.p.h. (170 km/h).  The minimum surface pressure was 967 mb.

The organization of Typhoon Sanvu has been slowly improving.  An eye developed at the center of Sanvu as the typhoon moved slowly over Chichi Jima.  A broken ring of thunderstorms surrounds the eye.  The strongest winds are occurring in the ring of storms.  A primary band of thunderstorms wraps around the western and southern sides of the center of circulation.  Other bands of showers and thunderstorms are developing outside the core of Typhoon Sanvu.  Most of the bands are developing in the southern half of the circulation.  Thunderstorms in the core of Sanvu are producing upper level divergence which is pumping mass away to the north of the typhoon.

Typhoon Sanvu will move through an environment favorable for intensification for several more days.  It will move over water where the Sea Surface Temperature is near 30°C.  An upper level ridge east of Sanvu is producing southerly winds which are blowing toward the top of the circulation, but there is not much vertical wind shear.  Typhoon Sanvu is likely to continue to strengthen for another 24 to 48 hours.  Eventually, Sanvu will move over colder water and the wind shear will increase.  It will start to weaken when that happens.

Sanvu is moving around the western end of a subtropical ridge which steering the typhoon toward the north.  When Typhoon Sanvu moves farther north, it will be steered by an upper level trough over Japan.  Southwesterly winds will steer Sanvu toward the northeast at a faster speed in a day or two.  On its anticipated track Typhoon Sanvu would stay east of Tokyo, but it could affect the northernmost islands of Japan in four or five days.  Conditions in Chichi Jima should improve slowly as Typhoon Sanvu moves farther away.

Tropical Storm Sanvu Forms Over Northern Marianas

Tropical Storm Sanvu formed over the northern Marianas on Monday.  At 11:00 a.m. EDT on Monday the center of Tropical Storm Sanvu was located at latitude 20.4°N and longitude 146.4°E which put it about 100 miles (160 km) north-northeast of Agrihan.  Sanvu was moving toward the north-northeast at 3 m.p.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 994 mb.

Tropical Storm Sanvu developed when a distinct center of circulation formed within a much larger area of low pressure over the northern Marianas.  The circulation of Sanvu is still in the early stages of consolidation around the center.  Most of the showers and thunderstorms were forming in bands in the southern half of the circulation.  The bands in the northern half of the circulation were weaker.  The showers and thunderstorms south of the center were beginning to generate some upper level divergence which was pumping mass away to the south of the tropical storm.

Tropical Storm Sanvu will be moving through an environment that is somewhat favorable for intensification.  Sanvu will move over water where the Sea Surface Temperature is near 30.5°C.  Sanvu is under the axis of a narrow upper level ridge and the winds over the southern half of the circulation are fairly weak.  There is little vertical wind shear over that part of the tropical storm.  An upper level trough north of the ridge is producing stronger winds over that half of the circulation.  The stronger winds may be responsible for the lack of strong rainbands in the northern half of Sanvu.  The trough is forecast to move east and the shear in that region should decrease.  When the shear decreases Sanvu could intensify at a faster rate and it is forecast to become a typhoon in two or three days.

The trough is currently steering Tropical Storm Sanvu slowly toward the north-northeast.  When the trough moves away to the east a ridge if forecast to steer Sanvu more toward the north.  On its anticipated track Tropical Storm Sanvu will gradually move away from the northern Marianas and the weather should improve in that region.