Tag Archives: Vietnam

Typhoon Mangkhut Makes Landfall West of Hong Kong

Typhoon Mangkhut made landfall west of Hong Kong on Sunday.  At 11:00 a.m. EDT on Sunday the center of Typhoon Mangkhut was located at latitude 22.3°N and longitude 111.0°E which put it about 65 miles (105 km) east-southeast of Yulin, China.  Mangkhut was moving toward the west-northwest at 20 m.p.h. (32 km/h).  The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 979 mb.

Typhoon Mangkhut made landfall on the coast of China near Yangjiang on Sunday.  The maximum sustained wind speed was near 90 m.p.h. (145 km/h) and there were wind gusts to 115 m.p.h. (185 km/h).  There were reports that strong winds blew out windows in high rise buildings in Hong Kong.  There were strong gusty winds along the coast between Hong Kong and Yangjiang.  Strong winds blowing water toward the coast also produced a storm surge along that section of the coast.  The highest surge occurred just to the east of where the center made landfall.

Typhoon Mangkhut will drop heavy rain over Zizhiqu, Zhaungzu and Guangxi provinces while it moves farther inland.  Mangkhut will weaken slowly as it moves slowly across southern China.  The locally heavy rain could cause flash floods, especially in regions of steeper terrain.  Reports of damage and casualties caused when Typhoon Mangkhut move across northern Luzon were still coming in.

Typhoon Mangkhut Approaches Southern China

After causing significant destruction over northern Luzon, Typhoon Mangkhut approached southern China on Saturday night.  At 11:00 p.m. EDT on Saturday the center of Typhoon Mangkhut was located at latitude 21.0°N and longitude 114.4°E which put it about 130 miles (205 km) south-southeast of Hong Kong.  Mangkhut was moving toward the west-northwest at 21 m.p.h. (34 km/h).  The maximum sustained wind speed was 100 m.p.h. (160 km/h) and there were wind gusts to 125 m.p.h. (200 km/h).  The minimum surface pressure was 961 mb.

The inner core of Typhoon Mangkhut was disrupted when it moved across the northern end of Luzon.  The inner eyewall weakened and a larger ragged eye was at the center of the typhoon.  Recent visible satellite images seemed to show an inner rainband wrapping more tightly around the center of circulation and the inner core of Typhoon Mangkhut could be reorganizing.  A smaller eye could be redeveloping at the center of circulation.

Even though it has weakened since yesterday, Typhoon Mangkhut has a very large circulation.  Winds to typhoon force extend out about 70 miles (110 km) from the center of circulation.  Winds to tropical storm force extend out about 350 miles (565 km) from the center.  The Hurricane Intensity Index (HII) for Typhoon Mangkhut is 16.5.  The Hurricane Size Index (HSI) is 28.5 and the Hurricane Wind Intensity Index (HWISI) is 45.0.  Typhoon Mangkhut is capable of causing widespread serious damage.

Typhoon Mangkhut is moving southwest of a subtropical ridge which is steering the typhoon quickly toward the west-northwest.  On its anticipated track Typhoon Mangkhut will pass south of Hong Kong in a few hours.  Mangkhut will make landfall on the coast of south China near Yangjiang in about 12 hours.  Typhoon Mangkhut will bring strong gusty winds to southern China.  It will cause a storm surge of up to 10 feet (3 meters) along the coast.  Mangkhut will also drop heavy rain and it will cause flash floods.

Powerful Typhoon Mangkhut Hits Northern Luzon

Powerful Typhoon Mangkhut hit northern Luzon on Friday.  At 5:00 p.m. EDT on Friday the center of Typhoon Mangkhut was located at latitude 18.2°N and longitude 121.5°W which put it about 60 miles (95 km) east of Laoag, Philippines.  Mangkhut was moving toward the west-northwest at 21 m.p.h. (35 km/h).  The maximum sustained wind speed was 165 m.p.h. (270 km/h) and there were wind gusts to 200 m.p.h. (320 km/h).  The minimum surface pressure was 908 mb.

Mangkhut is a large and dangerous typhoon.  Winds to typhoon force extend out about 110 miles (175 km) from the center of circulation.  Winds to tropical storm force extend out about 330 miles (530 km) from the center.  The outer rainbands around Typhoon Mangkhut stretch from Manila, Philippines to southern Taiwan.

The Hurricane Intensity Index (HII) is 36.8.  The Hurricane Size Index (HSI) is 38.5 and the Hurricane Wind Intensity Size Index (HWISI) is 75.3.  Typhoon Mangkhut is bigger than Hurricane Katrina was when Katrina was a Category 5 hurricane on the Saffir-Simpson Scale over the Gulf of Mexico in 2005.  Typhoon Mangkhut has the potential to cause extensive catastrophic damage over parts of Luzon.

Typhoon Mangkhut will cause extensive catastrophic wind damage over northern Luzon.  It will also drop heavy rain and there will be flash floods.  The flooding will be worse in areas of steeper slopes.  There will be a significant storm surge on the coast of extreme northeastern Luzon.

Typhoon Mangkhut will weaken while it crosses northern Luzon.  Mangkhut will then move quickly off to the west-northwest. On its anticipated track Typhoon Mangkhut could be near Hong Kong in about 30 hours.

Dangerous Typhoon Mangkhut Approaches Northern Luzon

Dangerous Typhoon Mangkhut approached northern Luzon on Thursday night.  At 11:00 p.m. EDT on Thursday the center of Typhoon Mangkhut was located at latitude 16.2°N and longitude 126.2°E which put it about 400 miles (645 km) east-northeast of Manila.  Mangkhut was moving toward the northwest at 14 m.p.h.  The maximum sustained wind speed was 170 m.p.h. (280 km/h) and there were wind gusts to 205 m.p.h. (335 km/h).  The minimum surface pressure was 905 mb.

Typhoon Mangkhut has a large powerful circulation.  There is a circular eye with a diameter of about 30 miles (50 km) at the center of circulation.  A number of bands of showers and thunderstorms are revolving around the core of the circulation.  Storms around the core were generating strong upper level divergence which was pumping mass away from the typhoon in all directions.

Winds to typhoon force extended out about 100 miles (160 km) from the center of circulation.  Winds to tropical storm force extended out about 265 miles (425 km) from the center.  The Hurricane Intensity Index (HII) for Typhoon Mangkhut was 38.5.  The Hurricane Size Index (HSI) was 33.7 and the Hurricane Wind Intensity Size Index (HWISI) was 72.2.  Those indices indicate that Typhoon Mangkhut is very similar in size and strength to what Hurricane Katrina was when Katrina was a Category 5 hurricane over the Gulf of Mexico in 2005.

Typhoon Mangkhut will move through an environment that is very favorable for strong typhoons during the next 12 to 18 hours.  Mangkhut will move over water where the Sea Surface Temperature is near 30°C.  It will move through an area where there will be little vertical wind shear.  It is difficult for a typhoon or hurricane to continue to generate enough upper level divergence to stay extremely strong for a long period of time.  However, Typhoon Mangkhut could remain the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale until it reaches northern Luzon.  Mangkhut will weaken when the center moves over northern Luzon.

Typhoon Mangkhut is moving south of a subtropical ridge over the Western North Pacific Ocean.  The ridge is steering Mangkhut toward the northwest and that general motion is forecast to continue.  On its anticipated track Typhoon Mangkhut will reach northern Luzon east of Tuguegarao in about 18 hours.  Mangkhut is capable of causing extensive catastrophic damage.  It will produce extremely strong winds over northern Luzon.  There will be a significant storm surge at the coast.  Locally heavy rain will cause flash floods.

Typhoon Mangkhut Strengthens Into Equivalent of Cat. 5 Hurricane

Typhoon Mangkhut strengthened into the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale on Tuesday.  At 11:00 a.m. EDT on Tuesday the center of Typhoon Mangkhut was located at latitude 13.7°N and longitude 138.0°E which put it about 290 miles (470 km) north of Yap.  Mangkhut was moving toward the west at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 160 m.p.h. (260 km/h) and there were wind gusts to 190 m.p.h. (305 km/h).  The minimum surface pressure was 915 mb.

Typhoon Mangkhut is strong and well organized.  It has a symmetrical circulation with a circular eye at the center.  A ring of strong thunderstorms surround the eye and the strongest winds are occurring in the ring of storms.  Several bands of showers and thunderstorms were revolving around the core of Typhoon Mangkhut.  Storms near the core were generating strong upper level divergence which was pumping large quantities of mass away from the typhoon in all directions.

Typhoon Mangkhut has a large circulation.  Winds to typhoon force extend out about 65 miles (105 km) from the center of circulation.  Winds to tropical storm force extend out about 210 miles (375 km) from the center.  The Hurricane Intensity Index (HII) for Typhoon Mangkhut is 35.0.  The Hurricane Size Index (HSI) is 22.1 and the Hurricane Wind Intensity Size Index (HWISI) is 57.1.  Typhoon Mangkhut is capable of causing extensive catastrophic damage.

Typhoon Mangkhut will be moving through an environment very favorable for powerful typhoons.  Mangkhut will be moving over water where the Sea Surface Temperature is near 30°C.  It will move through an area were the upper level winds are weak and there will be little vertical wind shear.  Typhoon Mangkhut could maintain its intensity for several more days unless eyewall replacement cycles cause fluctuations in the wind speed.

Typhoon Mangkhut is moving south a ridge of high pressure over the Western North Pacific Ocean.  The ridge will steer Mangkhut in a general west-northwesterly direction during the next few days.  On its anticipated track Typhoon Mangkhut could approach northern Luzon in about three days.  Mangkhut could be near Hong Kong in about five days.

Elsewhere over the Western North Pacific Ocean, Tropical Storm Barijat was moving southeast of Hong Kong.  At 11:00 a.m. EDT on Tuesday the center of Tropical Storm Barijat was located at latitude 20.5°N and longitude 116.5°E which put it about 215 miles (345 km) southeast of Hong Kong.  Barijat was moving toward the west-southwest 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 1000 mb.

Tropical Storm Rumbia Makes Landfall Near Shanghai, Bebinca Hits Vietnam

Tropical Storm Rumbia made landfall on the east coast of China just south of Shanghai on Thursday, and Tropical Storm Babinca hit Vietnam.  At 5:00 p.m. EDT on Thursday the center of Tropical Storm Rumbia was located at latitude 30.5°N and longitude 121.0°E which put it about 60 miles (95 km) southwest of Shanghai, China.  Rumbia was moving toward the west at 14 m.p.h. (22 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 987 mb.

Tropical Storm Rumbia strengthened before it made landfall.  Thunderstorms developed near the center of circulation and a band wrapped around the center.  The circulation became more circular and storms near the center began to generate upper level divergence.  In the western half off the circulation where the winds were blowing toward the land, increased friction enhanced rising motion and heavier rain fell.

Tropical Storm Rumbia caused some gusty winds near the coast, but the greater risks were the locally heavy rain and the potential for floods.  Tropical Storm Rumbia is forecast to move slightly north of due west as it moves inland over eastern China.  Rumbia will drop locally heavy rain over the area around Shanghai, and over parts Zhejiang, Jiangsu and Anhui provinces.  Some of those regions have received heavy rain from previous storms and the potential for serious flooding exists.

Tropical Storm Bebinca made landfall on the coast of Vietnam on Thursday.  At 5:00 p.m. EDT on Thursday the center of Tropical Storm Bebinca was located at latitude 19.9°N and longitude 106.3°E which put it about 70 miles (110 km) southeast of Ninh Binh, Vietnam.  Bebinca was moving toward the west-southwest at 8 m.p.h. (13 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 979 mb.

Tropical Storm Bebinca also strengthened before it made landfall.  An eye started to form at the center of circulation and Bebinca was on the threshold of becoming a typhoon when it made landfall.  Tropical Storm Bebinca produced gusty winds and a storm surge near the coast.  However, the greatest risks are locally heavy rain and the potential for floods.  Tropical Storm Bebinca is forecast to move in a general westerly direction.  Bebinca will drop locally heavy rain over parts of Vietnam, northern Laos and extreme northern Thailand.

Elsewhere over the Western North Pacific Ocean, Tropical Storm Soulik moved quickly toward Iwo To and strengthened.  At 5:00 p.m. EDT on Thursday the center of Tropical Storm Soulik was located at latitude 20.9°N and longitude 141.3°E which put it about 315 miles (510 km) south of Iwo To.  Soulik was moving toward the north at 20 m.p.h. (32 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 981 mb.

Tropical Storm Rumbia Nears Shanghai, Bebinca Strengthens East of Vietnam

Tropical Storm Rumbia moved closer to Shanghai on Wednesday, while Tropical Storm Bebinca strengthened east of Vietnam and Tropical Storm Soulik formed west of Guam.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Rumbia was located at latitude 30.1°N and longitude 124.2°E which put it about 160 miles (260 km) southeast of Shanghai, China.  Rumbia was moving toward the west-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 999 mb.

Tropical Storm Rumbia has about 12 to 18 hours before it makes landfall near Shanghai.  It will move through an environment somewhat favorable for intensification.  Rumbia will move over water where the Sea Surface Temperature is near 28°C.  The circulation of Rumbia is broad.  There is a distinct center of circulation, but there are few thunderstorms close to the center.  Most of the stronger thunderstorms were occurring in rainbands revolving around the center of Rumbia.  The broad circulation will limit the potential for intensification, but Tropical Storm Rumbia could get stronger before it reaches the east coast of China on Thursday.

Tropical Storm Bebinca strengthened on Wednesday while it moved south of China.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Bebinca was located at latitude 19.9°N and longitude 108.2°E which put it about 125 miles (200 km) east-southeast of Hai Phong, Vietnam.  Bebinca was moving toward the west-southwest at 15 m.p.h. (24 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 980 mb.

Tropical Storm Bebinca intensified quickly on Wednesday after it moved west of Hainan Island.  A primary rainband wrapped around the center of circulation and an eye appeared to be forming.  Several bands of showers and thunderstorms were revolving around the core of Bebinca.  Tropical Storm Bebinca has about 18 hours before it reaches the coast of Vietnam.  It will move through an environment favorable for intensification.  Bebinca will move over water where the Sea Surface Temperature is near 29°C.  It will move through an area where the upper level winds are weak and there is little vertical wind shear.  Bebinca could strengthen into a typhoon before it reaches Vietnam.

Tropical Storm Bebinca could make landfall on the coast of  Vietnam between Hai Phong and Vinh within 24 hours.  It could be a typhoon when it makes landfall.  Bebinca will bring strong winds capable of causing damage.  it could generate a storm surge of 6 to 9 feet (2 to 3 meters) at the coast.  Bebinca will drop heavy rain over parts of Vietnam and it could cause serious flooding.

Tropical Storm Soulik formed west of Guam on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Soulik was located at latitude 15.9°N and longitude 142.7°E which put it about 165 miles (265 km) northwest of Guam.  Soulik was moving toward the north-northwest at 20 m.p.h. (32 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 999 mb.

Tropical Storm Soulik will move through an environment favorable for intensification.  Soulik will move over water where the Sea Surface Temperature is near 29°C.  It will move east of an upper level low that will produce southerly winds.  Those winds will move blow toward the top of the circulation and they will cause some vertical wind shear, but they will not be strong enough to prevent intensification.  Soulik could strengthen into a typhoon within 48 hours.  The upper low will pull Tropical Storm Soulik toward Iwo To.

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 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.