Category Archives: Western North Pacific

Western Pacific Typhoons and Tropical Storms

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.

Tropical Storm Jongdari Heads Toward China

Tropical Storm Jongdari headed toward China late on Tuesday.  After dropping heavy rain on parts of Honshu and Kyushu, former Typhoon Jongdari weakened to a tropical storm.  Jongdari then was caught by the circulation of an upper level low south of Japan and the tropical storm made a slow counterclockwise loop south of Kyushu.  Tropical Storm Jongdari completed the loop and moved west toward China on Tuesday.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Jongdari was located at latitude 30.0°N and longitude 126.7°E which put it about 360 miles (575 km) east-southeast of Shanghai, China.  Jongdari was moving toward the west at 11 m.p.h. (17 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.

Tropical Storm Jongdari moved around the circulation of an upper level low south of Japan on Sunday and Monday.  Strong upper winds rotating around the upper level low caused vertical wind shear which disrupted the upper part of Jongdari’s circulation.  However, the integrity of the lower level circulation remained intact.  There is a well defined low level circulation with bands of showers and thunderstorms revolving around the center of circulation.  Stronger upper level winds have periodically sheared the tops off of the taller thunderstorms.  New thunderstorms were forming near the center of circulation but it is unclear if those storms will persist.

Tropical Storm Jongdari will move through an environment marginally favorable for intensification on Wednesday.  Jongdari will move over water where the Sea Surface Temperature is near 28°C.  However the upper level low south of Japan and an upper level ridge over East Asia will combine to produce strong easterly winds which will blow across the top of the circulation.  Those winds will cause strong vertical wind shear which will inhibit intensification.  Tropical Storm Jongdari could intensify a little during the next 24 hours.

Tropical Storm Jongdari will move south of a high pressure system near East Asia which will steer Jongdari in a general westerly direction.  On its anticipated track Tropical Storm Jongdari could approach the coast of China southeast of Shanghai in about 24 hours.  The center of Jongdari could be near Shanghai in about 36 hours.  Tropical Storm Jongdari will bring some gusty winds, but the greater risk will be locally heavy rainfall.  Heavy rain falling on very moist ground could cause flash floods over parts of eastern China.

Typhoon Jongdari Makes Landfall on Honshu

Typhoon Jongdari made landfall on Honshu near Ise in the Mie Prefecture on Saturday.  The maximum sustained wind speed was 80 m.p.h. (130 km/h) at the time of landfall.  Jongdari weakened to a tropical storm after the center moved over Honshu.  At 5:00 p.m. EDT on Saturday the center of Tropical Storm Jongdari was located at latitude 34.7°N and longitude 135.0°E which put it about 20 miles (30 km) southwest of Kobe, Japan.  Jongdari was moving toward the west-northwest at 25 m.p.h. (40 km/h).  The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were wind gusts to 85 m.p.h. (135 km/h).  The minimum surface pressure was 980 mb.

The center of Typhoon Jongdari made landfall in the Mie Prefecture on Honshu near Ise and Toba.  Jongdari then moved west-northwest near Matsusaka and Tsu.  It passed near Nara and Osaka before moving to its current position southwest of Kobe.  Typhoon Jongdari brought gusty winds and it dropped locally heavy rain over parts of the Mie, Nara, Shiga, Kyoto, Osaka and Hyogo Prefectures.  The ground in some of those places is very moist from recent rains and flash flooding could occur if more heavy rain falls.  The relatively rapid movement of Tropical Storm Jongdari will help to reduce the amount of rain that falls over specific locations.

Tropical Storm Jongdari will continue to weaken as it moves over western Honshu and northern Kyushu.  Jongdari is moving around the northern side of an upper level low south of Japan.  The upper level low will steer Tropical Storm Jongdari quickly to the west during the next 12 hours.  Jongdari will move southwest on Sunday when it moves around the northwestern part of the upper low.  On its anticipated track Tropical Storm Jongdari will move near Okayama, Hiroshima, Yamaguchi, Kitakyushu and Fukuoka.  The tropical storm will continue to drop locally heavy rain while it weakens over western Japan.

Typhoon Jongdari Turns Toward Honshu

Typhoon Jongdari turned toward Honshu on Friday.  At 5:00 p.m. EDT on Friday the center of Typhoon Jongdari was located at latitude 31.0°N and longitude 143.7°E which put it about 415 miles (665 km) southeast of Tokyo, Japan.  Jongdari was moving toward the north at 24 m.p.h. (39 km/h).  The maximum sustained wind speed was 105 m.p.h. (170 km/h) and there were wind gusts to 125 m.p.h. (205 km/h).  The minimum surface pressure was 957 mb.

An upper level low west of Typhoon Jongdari was affecting the circulation.  Winds blowing around the eastern side of the upper low were cutting under the upper level divergence at the top of the circulation of Jongdari.  In addition, drier flowing around the southern half of the upper low was being pulled into the western side of the circulation of Typhoon Jongdari.  The effects of the upper low were causing the circulation of Typhoon Jongdari to become asymmetrical.  Many of the stronger thunderstorms and stronger winds were occurring in bands in the eastern half of the circulation.  Bands in the western half of the circulation consisted primarily of showers and lower clouds.  With fewer strong thunderstorms in the western part of the typhoon with downdrafts to bring stronger winds to the surface the wind field was also becoming asymmetrical.  Winds to typhoon force extended out about 100 miles (160 km) from the center of circulation on the eastern side of Jongdari, but they only extended out about 50 miles (80 km) on the western side.  Winds to tropical storm force extended out about 230 miles (370 km) to the east of the center, but only extended out about 170 miles (280 km) to the west of the center of circulation.

The upper level low will continue to affect Typhoon Jongdari.  Jongdari will move over water where the Sea Surface Temperature is near 28°C.  So, there will be sufficient energy in the upper ocean to support a strong typhoon.  However, the upper low will inhibit upper level divergence to the west of the circulation.  Upper level divergence will be strong to the southeast of Typhoon Jongdari.  Drier air flowing around the upper low will inhibit the formation of thunderstorms in bands in the southwestern part of the circulation.  Typhoon Jongdari is likely to weaken slowly, although it could maintain its intensity at times as it moves around the northern side of the upper low.

The upper low will also steer Typhoon Jongdari during the weekend.  Jongdari will turn more toward the west-northwest when it moves around the northern part of the upper low.  On its anticipated track Typhoon Jongdari could pass south of Tokyo in about 18 hours.  The center of Jongdari could be very close to Hamamatsu in about 24 hours.  It could make landfall near Matsuzaka in a little over a day.  Typhoon Jongdari could pass very close to Osaka and Kobe and it could pass just south of Kyoto.  Heavy rain fell on parts of Japan earlier this month and Typhoon Jongdari could cause serious flooding in some locations.

Typhoon Jongdari Nears Iwo To

Typhoon Jongdari neared Iwo To on Thursday.  At 11:00 a.m. EDT on Thursday the center of Typhoon Jongdari was located at latitude 24.2°N and longitude 140.5°E which put it about 105 miles (170 km) southwest of Iwo To.  Jongdari was moving toward the northeast at 13 m.p.h. (21 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.

Former Tropical Storm Jongdari strengthened as it neared Iwo To on Thursday.  An eye developed at the center of circulation and the Japan Meteorological Agency classified Jongdari as a typhoon.  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 Jongdari.  Thunderstorms in the core of Jongdari were generating strong upper level divergence which was pumping mass away from the typhoon.  Winds to typhoon force extended out about 20 miles (30 km) from the center of circulation.  Winds to tropical storm force extended out about 130 miles (210 km) from the center.

Typhoon Jongdari will move through an environment favorable for intensification during the next day or two.  Jongdari will move over water where the Sea Surface Temperature is near 28°C.  An upper level low southeast of Honshu will cause easterly winds which will blow over the northern part of the circulation.  Those winds will cause some vertical wind shear, but the shear will be less over the core of the typhoon.  Typhoon Jongdari will strengthen during the next 24 to 48 hours and it could become the equivalent of a major hurricane.

Typhoon Jongdari is moving around the western end of a subtropical ridge over the Western North Pacific and the ridge is steering Jongdari toward the northeast.  A general motion toward the northeast is forecast for the next 12 to 24 hours.  The upper low southeast of Honshu will move slowly toward the west.  When Jongdari moves farther north, it will begin to be steered more by the upper level low.  Typhoon Jongdari is forecast to turn more toward the north on Friday.  Jongdari will start to move toward the northwest in about 36 hours, when it moves northeast of the upper level low.

On its anticipated track Typhoon Jongdari will move over Iwo To in a few hours.  It will bring gusty winds and heavy rain.  Typhoon Jongdari could approach Honshu in about 48 hours and it could cause flooding in addition to strong winds and heavy rain.

Elsewhere over the Western North Pacific, Tropical Storm Wokung was weakening east of northern Japan.  At 11:00 a.m. EDT on Thursday the center of Tropical Storm Wokung was located at latitude 42.2°N and longitude 152.5°E which put it about 600 miles (960 km) east of Misawa, Japan.  Wokung was moving toward the north-northwest at 19 m.p.h. (31 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 995 mb.

Tropical Storm Wukong Forms Southeast of Japan

Tropical Storm Wukong formed southeast of Japan on Monday.  At 5:00 p.m. EDT on Monday the center of Tropical Storm Wukong was located at latitude 29.0°N and longitude 159.0°E which put it about 1370 miles (2210 km) east-southeast of Tokyo, Japan.  Wukong was moving toward the north at 24 m.p.h. (39 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and the were wind gusts to 75 m.p.h. (120 km/h).  The minimum surface pressure was 984 mb.

A cluster of thunderstorms developed southeast of Japan during the weekend and a low level center of circulation formed near the southwestern edge of the cluster of storms.  However, strong upper level winds blowing from the southwest kept blowing the top of the circulation northeast of the low level center and the system was unable to develop.  The upper level winds slowed on Monday and a band of showers and thunderstorms wrapped around the northern and western sides of the center of circulation.  The Japan Meteorological Agency designated the system as Tropical Storm Wukong.

The circulation of Tropical Storm Wukong organized quickly after the upper level winds weakened.   As mentioned above, a primary rainband wrapped around the northern and western sides of the center of circulation.  Storms in the primary rainband generated upper level divergence which was pumping mass away to the north of the tropical storm.  Several other bands of showers and thunderstorms developed in the eastern half of the circulation.  Bands south and west of the center consisted primarily of showers and lower clouds.

Tropical Storm Wukong will move through an environment favorable for intensification during the next day or so.  Wukong will move over water where the Sea Surface Temperature is near 27°C.  Wukong is moving along the eastern portion of an upper level trough.  The trough is producing southwesterly winds which are blowing toward the top of the circulation.  However, those winds weakened on Monday and they will not cause enough vertical wind shear to prevent further intensification.  Tropical Storm Wukong could strengthen into a typhoon during the next 24 to 36 hours.  Eventually, Wukong will move over cooler water and it will begin to weaken.

Tropical Storm Wukong is moving between an upper level trough to the west and an upper level ridge to the east.  The trough and ridge were combining to steer Wukong toward the north and a general northerly motion is expected to continue.  On its anticipated track Tropical Storm Wukong will stay west of the larger islands of Japan.  Wukong could approach the Kuril Islands in about three days.

Elsewhere over the Western North Pacific former Tropical Storm Ampil weakened to a tropical depression over land southeast of Beijing, China, Tropical Storm Son-tinh meandered near the coast of southeastern China and Tropical Depression 15W organized southwest of Iwo To, Japan.  At 5:00 p.m. EDT on Monday the center of Tropical Depression Ampil was located at latitude 38.8°N and longitude 117.6°E which put it about 110 miles (175 km) southeast of Beijing, China.  Ampil was moving toward the north-northwest at 18 m.p.h. (29 km/h).  The maximum sustained wind speed was 35 m.p.h. (55k km/h) and there were wind gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 998 mb.  Tropical Depression Ampil was still dropping locally heavy rain over parts of eastern China.

At 5:00 p.m. EDT on Monday the center of Tropical Storm Son-tinh was located at latitude 21.2°N and longitude 109.0°E which put it about 40 miles (65 km) southeast of Beihai, China.  Son-tinh was moving toward the west-northwest at 6 m.p.h. (10 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 996 mb.  Tropical Storm Son-tinh was dropping locally heavy rain over parts of southeastern China and Hainan Island.

At 5:00 p.m. EDT on Monday the center of Tropical Depression 15W was located at latitude 17.6°N and longitude 136.3°E which put it about 585 miles (945 km) southwest of Iwo To, Japan.  It was moving toward the north-northwest at 10 m.p.h. (16 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 998 mb.  The circulation of Tropical Depression 15W became more organized on Monday and it could eventually strengthen into a typhoon when it moves toward Iwo To later this week.

Tropical Storm Ampil Nears Landfall Southeast of Shanghai

Tropical Storm Ampil neared landfall on the coast of China southeast of Shanghai on Saturday night.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm Ampil was located at latitude 31.0°N and longitude 122.3°E which put it about 60 miles (95 km) southeast of Shanghai, China.  Ampil was moving toward the west-northwest at 14 m.p.h. (22km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h).  The minimum surface pressure was 990 mb.

Tropical Storm Ampil moved steadily toward the coast of China on Saturday with little change of structure or intensity.  Drier air continued to circulate around the tropical storm and it limited the development of taller thunderstorms in much of Ampil.  The strongest thunderstorms were occurring in the inner portion of a band northwest of center of circulation.  The strongest winds were associated with those storms.  Bands around the rest of Tropical Storm Ampil consisted of showers and lower clouds.  Winds to tropical storm force extended out about 165 miles (270 km) from the center.

Tropical Storm Ampil will make landfall on the coast of China southeast of Shanghai in a few hours.  Ampil will cause gusty winds and the strong band of thunderstorms will drop locally heavy rain.  The heavy rain could cause flash floods in parts of eastern China.

Elsewhere the tropics became more active over the Western North Pacific Ocean on Saturday.  The remnants of former Tropical Storm Son-tinh were reorganizing west of Hainan Island over the Gulf of Tongking, Tropical Depression 13W moved east of Taiwan, and Tropical Depression 14W formed northwest of Wake Island and Tropical Depression 15W formed west of Guam.

At 11:00 p.m. EDT on Saturday the center of Tropical Depression Son-tinh was located at latitude 19.2°N and longitude 108.2°E which put it about 45 miles (75 km) west of Dongfeng, China.  Son-tinh was moving toward the east-southeast at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 999 mb.

Former Tropical Storm Son-tinh completed a slow clockwise loop over Laos and Vietnam which during the past several days and it emerged back over the Gulf of Tongking on Saturday.  There was a distinct low level center of circulation.  Bands of showers and thunderstorms were circulating around the enter.  The rainbands were dropping heavy rain over Hainan Island and creating the potential for flash floods.

At 11:00 p.m. EDT on Saturday the center of Tropical Depression 13W was located at latitude 21.6°N and longitude 122.9°E which put it about 165 miles (265 km) south-southeast of Hualien, Taiwan.  It was moving toward the northwest at 18 m.p.h. (29 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 998 mb.

At 11:00 p.m. EDT on Saturday the center of Tropical Depression 14W was located at latitude 22.5°N and longitude 159.4°E which put it about 370 miles (600 km) east-southeast of Minami Tori Shima.  It was moving toward the north at 4 m.p.h. (6 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 998 mb.

At 11:00 p.m. EDT on Saturday the center of Tropical Depression 15W was located at latitude 13.2°N and longitude 138.1°E which put it about 225 miles (365 km) north-northwest of Ulithi.  It was moving toward the northwest at 15 m.p.h. (24 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 998 mb.

Tropical Storm Ampil Moves Over Okinawa

Tropical Storm Ampil moved over Okinawa on Friday night.  At 11:00 p.m. EDT on Friday the center of Tropical Storm Ampil was located at latitude 27.3°N and longitude 127.4°E which put it about 25 miles (40 km) north-northwest of Okinawa.  Ampil was moving toward the northwest at 21 m.p.h. (34 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h).  The minimum surface pressure was 990 mb.

Drier air continued to circulated around Tropical Storm Ampil on Friday and the drier air prevented Ampil from intensifying.  Several bands of stronger thunderstorms were occurring northeast of the center of circulation and the strongest winds were occurring in those bands.  The bands in other parts of Tropical Storm Ampil consisted primarily of the showers and low clouds.  There was a distinct low level center of circulation, but there were few thunderstorms near the center.  Winds to tropical storm force extended out about 160 miles (260 km) from the center.

Tropical Storm Ampil is unlikely to intensify significantly before it makes landfall in China.  Ampil will move over water where the Sea Surface Temperature is near 28°C.  So, there will be enough energy in the ocean to support intensification.  There is a chance for some intensification on Saturday, if more thunderstorms develop near the center of circulation.  However, the drier air will inhibit the formation of taller thunderstorms and that will limit possible intensification..

Tropical Storm Ampil will move south of a subtropical ridge over the Western North Pacific Ocean.  The ridge will steer Ampil quickly toward the northwest.  On its anticipated track Tropical Storm Ampil will move quickly away from Okinawa and the Ryukyu Islands.  Ampil could approach the coast of China near Shanghai in about 24 hours.  Tropical Storm Ampil will bring gusty winds and locally heavy rain to the region of China around Shanghai.

Elsewhere over the Western North Pacific Ocean Tropical Depression 13W formed west of northern Luzon.  At 11:00 p.m. EDT on Friday the center of Tropical Depression 13W was located at latitude 18.0°N and longitude 118.9°E which put it about 140 miles (225 km) west of Laoag, Philippines.  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 998 mb.  The depression could bring locally heavy rain and cause flash floods over Luzon during the weekend.

Tropical Storm Ampil Moves Toward Okinawa

Tropical Storm Ampil moved toward Okinawa on Thursday.  At 11:00 p.m. EDT on Thursday the center of Tropical Storm Ampil was located at latitude 23.3°N and longitude 130.6°E which put it about 320 miles (520 km) southeast of Okinawa.  Ampil was moving toward the north-northwest at 11 m.p.h. (17 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h).  The minimum surface pressure was 984 mb.

Tropical Storm Ampil strengthened on Thursday, although its appearance on satellite imagery was not particularly impressive.  There was a distinct low level center of circulation, but the most of the stronger thunderstorms were occurring in a rainband southwest of the center of circulation.  Bands in other parts of the tropical storm consisted primarily of showers and low clouds.  It appeared that some drier air could have wrapped around the southern and eastern sides of the circulation.  The drier air may have inhibited the development of taller thunderstorms in those parts of Tropical Storm Ampil.  The circulation was fairly large and winds to tropical storm force extended out about 185 miles (295 km) from the center of circulation.

Tropical Storm Ampil will move through an environment that could support further intensification during the next day or two.  Ampil will move over water where the Sea Surface Temperature is near 29°C.  It will be near the eastern end of an upper level low, but Tropical Storm Ampil will move under a zone where the upper level winds will not be too strong.  There will be some vertical wind shear, but the shear will not be strong enough to prevent intensification.  The main factor that could inhibit intensification will be the drier air already around the circulation.  If the strong rainband in the southwestern part of Tropical Storm Ampil wraps around the center of circulation, it could prevent the drier air from affecting the core of the tropical storm.  If that happens, the Tropical Storm Ampil would be likely to intensify and it could become a typhoon.  However, if the drier air works its way into the center of circulation, then Ampil will not intensify.

Tropical Storm Ampil will move southwest of a subtropical ridge over the Western North Pacific Ocean.  The ridge will steer Ampil in a northwesterly direction during the next 24 to 48 hours.  On its anticipated track Tropical Storm Ampil could be near Okinawa and the Ryukyu Islands in less than 24 hours.  Ampil could reach the east coast of China south of Shanghai in about two days.  Tropical Storm Ampil will bring gusty winds to the Ryukyu Islands later on Friday.  Ampil could bring gusty winds and locally heavy rain to parts of eastern China during the weekend.

Tropical Storm Son-tinh Makes Landfall in Vietnam, Ampil Forms South of Okinawa

Tropical Storm Son-tinh made landfall in Vietnam on Wednesday while Tropical Storm Ampil formed south of Okinawa.  At 5:00 p.m. EDT on Saturday the center of Tropical Storm Son-tinh was located at latitude 19.1°N and longitude 105.5°E which put it about 30 miles (50 km) north-northwest of Vinh, Vietnam.  Son-tinh was moving toward the west at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 990 mb.

Tropical Storm Son-tinh strengthened on Wednesday after it moved away from Hainan Island.  A primary rainband wrapped around the western and southern side of the center of circulation and the inner end of the band began to evolve into a partial eyewall.  Thunderstorms in the core of Son-tinh generated upper level divergence which pumped away mass.  The removal of mass allowed the surface pressure to decrease.  A stronger pressure gradient force produced higher wind speeds.

Tropical Storm Son-tinh moved south of a ridge in the upper and middle troposphere.  The ridge steered Son-tinh steadily toward the west and the tropical storm made landfall just north of Vinh, Vietnam late on Wednesday.  Tropical Storm Son-tinh brought gusty winds and locally heavy rain to the coast of northern Vietnam around Vinh.  Son-tinh was also dropping locally heavy rain over portions of northern Vietnam and flash flooding could occur in some locations.

Tropical Storm Son-tinh will continue to move westward over northern Vietnam and northern Laos.  Son-tinh will weaken as the circulation moves inland.  It will continue to drop locally heavy rain and flash floods could occur in parts of northern Vietnam and northern Laos during the next several days.

The organization of former Tropical Depression 12W improved on Wednesday and the Japan Meteorological Agency designated the system as Tropical Storm Ampil.  At 5:00 p.m. EDT on Wednesday the center of Tropical Storm Ampil was located at latitude 19.9°N and longitude 129.6°E which put it about 480 miles (775 km) south-southeast of Okinawa.  Ampil was moving toward the east-northeast at 8 m.p.h. (13 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 996 mb.

The circulation of Tropical Storm Ampil was not particularly well organized.  It exhibited characteristics of a hybrid low pressure system.  There was an upper low northwest of the low level circulation.  The upper low was causing strong southwesterly winds which were blowing across the top of the lower level circulation.  Those winds were causing significant vertical wind shear and they were tilting the circulation strongly toward the northeast.  The strongest bands of showers and thunderstorms were occurring south and west of the low level circulation.  Bands north and west of the center consisted primarily of showers and lower clouds.

The upper low will gradually move toward the west.  As the low moves westward, the vertical wind shear over Tropical Storm Ampil will start to decrease.  Ampil will move over water where the Sea Surface Temperature is near 29°C.  So, when the vertical wind shear decreases, then Tropical Storm Ampil will likely intensify.  Ampil could eventually strengthen into a typhoon in two or three days.

The upper low will initially will steer Tropical Storm Ampil toward the northeast.  When the upper low moves farther to the west on Thursday, then Ampil will move toward the north.  On its anticipated track the center of Tropical Storm Ampil could be near Okinawa and the Ryukyu Islands in two or three days.