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Tropical Storm Koto Weakens East of Vietnam

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Tropical Storm Koto weakened as it meandered over the South China Sea east of Vietnam on Sunday.  At 10:00 p.m. EST on Sunday the center of Tropical Storm Koto was located at latitude 14.7°N and longitude 111.6°E which put the center about 200 miles (320 km) east-northeast of Quy Nhon, Vietnam.  Koto was moving toward the southwest at 4 m.p.h. (6 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1004 mb.

Tropical Storm Koto weakened on Sunday as it moved through a mass of drier air over the western part of the South China Sea.  The drier air caused thunderstorms near the center of Koto’s circulation to dissipate.  Many of the bands revolving around the center of Tropical Storm Koto consisted of showers and lower clouds.  Thunderstorms were still occurring in a couple of bands in the southern part of Koto’s circulation.

There were no thunderstorms near the center of Tropical Storm Koto to generate upper level divergence.  Mass was still converging in the lower levels of the atmosphere.  So, the surface pressure increased on Sunday.

The size of the circulation around Tropical Storm Koto decreased as Koto weakened on Sunday.  Winds to tropical storm force extended out 65 miles (105 km) from the center of Koto’s circulation.

Tropical Storm Koto will be in an environment that will be unfavorable for intensification during the next 24 hours.  Koto 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 that is over the Southeast Asia.  The upper level ridge will produce northeasterly winds that will blow toward the top of Koto’s circulation.  Those winds will cause strong vertical wind shear.  In addition, Tropical Storm Koto will continue to be in a region of drier air that is over the western part of the South China Sea.  The strong vertical wind shear and drier air will continue to cause Tropical Storm Koto to weaken during the next 24 hours.

Since there are no thunderstorms near the center of Tropical Storm Koto, Koto will be steered by the winds in the lower level of the atmosphere.  Koto will move around the southeastern side of a high pressure system that is over Southeast Asia.  The high pressure system will steer Koto toward the southwest during the next 24 hours.  On its anticipated track, Tropical Storm Koto will move toward southern Vietnam.

Tropical Storm Koto Stalls East of Vietnam

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Tropical Storm Koto stalled over the South China Sea east of Vietnam on Saturday.  At 4:00 p.m. EST on Saturday the center of Tropical Storm Koto was located at latitude 13.8°N and longitude 112.2°E which put the center about 200 miles (320 km) east of Quy Nhon, Vietnam.  Koto was moving toward the north at 3 m.p.h. (5 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 998 mb.

Tropical Storm Koto was showing signs of more organization on Saturday afternoon.  More thunderstorms developed near the center of Koto’s circulation.  New thunderstorms also formed in some of the bands revolving around the center of Tropical Storm Koto.  Storms near the center of Koto were not yet generating much upper level divergence.  Mass was still converging in the lower levels of the atmosphere.  So, the surface pressure was increasing.

The distribution of wind speeds around Tropical Storm Koto continued to be asymmetrical. Winds to tropical storm force extended out 125 miles (200 km) in the western side of Koto’s circulation.  Winds to tropical storm force extended out 65 miles (105 km) in the eastern side of Tropical Storm Koto.

Tropical Storm Koto will be in an environment that will be marginally favorable for intensification during the next 24 hours.  Koto will move over water where the Sea Surface Temperatures are near 29°C.  It will move under the southern part of an upper level ridge that is over the South China Sea.  The upper level ridge will produce southeasterly winds that will blow toward the top of Koto’s circulation.  Those winds will cause some vertical wind shear.  In addition, Tropical Storm Koto will be in a region of drier air that is over the South China Sea.  The vertical wind shear and drier air will inhibit intensification.  Tropical Storm Koto is likely to maintain its intensity during the next 24 hours.  Koto could strengthen a little if the new thunderstorms near the center of circulation begin to generate more upper level divergence.

Tropical Storm Koto will start to move around the southern side of a high pressure system that is over China.  The high pressure system will begin to steer Koto toward the west during the next 24 hours.  On its anticipated track, Tropical Storm Koto will start to move toward Vietnam on Sunday.

Elsewhere, Tropical Depression Senyar was weakening south of Vietnam.  At 4:00 p.m. EST on Saturday the center of Tropical Depression Senyar was located at latitude 6.0°N and longitude 108.9°E which put the center about 380 miles (615 km) south-southeast of Ho Chi Minh City, Vietnam.  Senyar was moving toward the east-northeast at 12 m.p.h. (19 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 1006 mb.

Tropical Storm Koto Meanders East of Vietnam

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Tropical Storm Koto meandered over the South China Sea east of Vietnam on Friday.  At 4:00 p.m. EST on Friday the center of Tropical Storm Koto was located at latitude 13.0°N and longitude 112.5°E which put the center about 235 miles (380 km) east-northeast of Nha Trang, Vietnam.  Koto was moving toward the north at 3 m.p.h. (5 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 993 mb.

Tropical Storm Koto was maintaining its intensity on Friday.  New thunderstorms develop west of the center of Koto’s circulation.  Bands in the other parts of Tropical Storm Koto consisted primarily of showers and lower clouds.  Storms west of the center of Koto generated some upper level divergence that pumped mass away to the northwest of the tropical storm.  The removal of mass in the upper levels was nearly equal to the inflow of mass in the lower levels of the atmosphere.  So, the surface pressure was nearly steady.

The distribution of wind speeds around Tropical Storm Koto continued to be very asymmetrical.  Winds to tropical storm force extended out 180 miles (290 km) in the western side of Koto’s circulation.  Winds to tropical storm force extended out 65 miles (105 km) in the eastern side of Tropical Storm Koto.

Tropical Storm Koto will be in an environment that will be unfavorable for intensification during the next 24 hours.  Koto will move over water where the Sea Surface Temperatures are near 29°C.  It will move under the southern part of an upper level ridge that is over the South China Sea.  The upper level ridge will produce southeasterly winds that will blow toward the top of Koto’s circulation.  Those winds will cause moderate vertical wind shear.  In addition, Tropical Storm Koto will continue to move through the region of drier air that is over the South China Sea.  Tropical Storm Koto in likely to maintain its intensity during the next 24 hours because of the moderate vertical wind shear and the effects of the drier air.

Tropical Storm Koto will continue to be in a region where the steering currents are weak during the next 24 hours.  On its anticipated track, Tropical Storm Koto will meander slowly over the South China Sea on Friday.

Elsewhere, Tropical Cyclone Senyar moved across Malaysia and over the extreme southwestern part of the Western North Pacific Ocean.  Both the U.S. Joint Typhoon Warning Center and the Japan Meteorological Agency were classifying Senyar as a tropical depression.  At 4:00 p.m. EST on Friday the center of Tropical Depression Senyar was located at latitude 4.8°N and longitude 105.5°E which put the center about 160 miles (260 km) east-northeast of Kuantan, Malaysia.  Senyar was moving toward the east-northeast at 7 m.p.h. (11 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 1003 mb.

Koto Weakens Back to a Tropical Storm

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Former Typhoon Koto weakened back to a tropical storm over the South China Sea on Thursday.  At 4:00 p.m. EST on Thursday the center of Tropical Storm Koto was located at latitude 12.3°N and longitude 113.5°E which put the center about 435 miles (705 km) southeast of Da Nang, Vietnam.  Koto was moving toward the south-southwest at 5 m.p.h. (8 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 986 mb.

Former Typhoon Koto moved into a region of drier air and weakened back to a tropical storm over the South China Sea on Thursday.  A high pressure system over China was pumping drier air over the South China Sea.  Many of the thunderstorms in Tropical Storm Koto weakened when the drier air was pulled into Koto’s circulation.  Most of the remaining thunderstorms were occurring in bands in the northwestern part of Tropical Storm Koto.  Bands in the other parts of Koto’s circulation consisted primarily of showers and lower clouds.

Storms near the center of Tropical Storm Koto generated less upper level divergence.  The removal of mass in the upper levels of Koto’s circulation was less than the inflow of mass in the lower levels of the atmosphere.  As a result, the surface pressure was increasing.

The distribution of wind speeds in Tropical Storm Koto continued to be very asymmetrical.  Winds to tropical storm force extended out 205 miles (335 km) in the northern side of Koto’s circulation.  Winds to tropical storm force extended out 70 miles (110 km) in the southern side of Tropical Storm Koto.

Tropical Storm Koto will move through an environment that will be unfavorable for intensification during the next 24 hours.  Koto will move over water where the Sea Surface Temperatures are near 29°C.  It will move under the southern part of an upper level ridge that is over the Western North Pacific Ocean.  The upper level ridge will produce southeasterly winds that will blow toward the top of Koto’s circulation.  Those winds will cause moderate vertical wind shear.  In addition, Tropical Storm Koto will continue to move through the region of drier air that is over the western part of the South China Sea.  Moderate vertical wind shear and the effects of drier air will cause Tropical Storm Koto to continue to weaken during the next 24 hours.

Tropical Storm Koto will be in a region where the steering currents are weak during the next 24 hours.  On its anticipated track, Tropical Storm Koto is likely to meander slowly over the South China Sea on Friday.

Koto Intensifies to a Typhoon Over South China Sea

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Former Tropical Storm Koto intensified to a typhoon over the South China Sea on Wednesday.   At 4:00 p.m. EST on Wednesday the center of Typhoon Koto was located at latitude 13.2°N and longitude 114.5°E which put the center about 475 miles (765 km) east-southeast of Da Nang, Vietnam.  Koto was moving toward the northwest at 12 m.p.h. (19 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 982 mb.

Former Tropical Storm Koto intensified to a typhoon on Wednesday.  Thunderstorms continued to develop around the center of Typhoon Koto.  Bands of showers and thunderstorms were revolving around the center of Koto’s circulation.  Storms near the center of Koto generated upper level divergence that pumped mass away from the tropical storm.  The removal of mass caused the surface pressure to decrease.

The distribution of wind speeds around Typhoon Koto was asymmetrical.  Winds to typhoon force extended out 30 miles from the center of Koto’s circulation.  Winds to tropical storm force extended out 205 miles (335 km) in the northern side of Koto’s circulation.  Winds to tropical storm force extended out 70 miles (110 km) in the southern side of Typhoon Koto.

Typhoon Koto will move through an environment that will become unfavorable for intensification during the next 24 hours.  Koto will move over water where the Sea Surface Temperatures are near 30°C.  It will move under the southern part of an upper level ridge that is over the Western North Pacific Ocean.  The upper level ridge will produce easterly winds that will blow toward the top of Koto’s circulation.  Those winds will cause the vertical wind shear to increase.  In addition, Typhoon Koto will move into a region of drier air that is flowing over the western part of the South China Sea.  Some of the drier air is likely to get pulled into the western side of Koto’s circulation.  More vertical wind shear and the effects of drier air will cause Typhoon Koto to start to weaken during the next 24 hours.

Typhoon Koto will move around the southern side of a high pressure system over the Western North Pacific Ocean.  The high pressure system will steer Koto toward the west during the next 24 hours.  On its anticipated track, Typhoon Koto will move closer to Vietnam.  A second high pressure system over China and Southeast Asia that is transporting the drier air over the western part of the South China Sea will impede the progress of Koto later this week.  Koto could meander over the South China Sea for several days at the end of the week.

Tropical Storm Koto Develops Over Sulu Sea

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Tropical Storm Koto developed over the northern Sulu Sea on Tuesday.  At 10:00 a.m. EST on Tuesday the center of Tropical Storm Koto was located at latitude 11.6°N and longitude 119.5°E which put the center about 55 miles (90 km) northwest of Coron, Philippines.  Koto was moving toward the west-northwest at 13 m.p.h. (21 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 996 mb.

A low pressure system over the northern Sulu Sea strengthened on Tuesday and the Japan Meteorological Agency designated the system as Tropical Storm Koto.

The circulation around Tropical Storm Koto exhibited more organization on Tuesday.  More thunderstorms developed near the center of Koto’s circulation.  Bands of showers and thunderstorms were revolving around the center of Tropical Storm Koto.  Storms near the center of Koto generated upper level divergence that pumped mass away from the tropical storm.  The removal of mass caused the surface pressure to decrease.

The distribution of wind speeds around Tropical Storm Koto was asymmetrical.  Winds to tropical storm force extended out 125 miles (200 km) in the northern side of Koto’s circulation.  Winds to tropical storm force extended out 45 miles (75 km) in the southern side of Tropical Storm Koto.

Tropical Storm Koto will move through an environment favorable for intensification during the next 24 hours.  Koto will move over water where the Sea Surface Temperatures are near 30°C.  It will move under the middle of an upper level ridge that is over the Western North Pacific Ocean.  The upper level winds are weak near the middle of the ridge and there will be little vertical wind shear.  Tropical Storm Koto will intensify during the next 24 hours.

Tropical Storm Koto will move around the southern side of a high pressure system over the Western North Pacific Ocean.  The high pressure system will steer Koto toward the west-northwest during the next 24 hours.  On its anticipated track, Tropical Storm Koto will move over northern Palawan.  Koto will move over the South China Sea on Wednesday.

Tropical Cyclone Palawan will bring strong winds and locally heavy rain to northern Palawan.  Koto will also bring strong winds and heavy rain to Busuanga Island, Culion Island, Linapacan Island and the Calamian Group of islands.  Heavy rain is likely to cause flooding in some locations.

Tropical Storm Usagi Makes Landfall South of Ho Chi Minh City

Tropical Storm Usagi made landfall south of Ho Chi Minh City, Vietnam on Saturday night.  At 10:00 p.m. EST on Saturday the center of Tropical Storm Usagi was located at latitude 10.2°N and longitude 107.1°E which put it about 60 miles (995 km) south-southeast of Ho Chi Minh City, Vietnam.  Usagi was moving toward the west at 5 m.p.h. (8 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 984 mb.

Former Typhoon Usagi weakened as it approached the coast of southern Vietnam.  Moderate vertical wind shear caused by upper level winds blowing from the east caused Usagi to weaken slowly.  The core of Tropical Storm Usagi was still relatively intact.  A ring of strong thunderstorms surrounded the remnants of the small eye.  The strongest winds were occurring in that ring of storms.  Heavy rain was falling just to the southwest of the center of circulation.  Thunderstorms were also dropping heavy rain in a couple of bands on the northeastern periphery of the circulation.

Tropical Storm Usagi will bring gusty winds to the areas south and west of Ho Chi Minh City.  Some places in southern Vietnam and Cambodia will receive locally heavy rainfall and flash floods could occur in those areas.  Usagi will weaken slowly as it move inland over southern Vietnam.

Elsewhere over the Western North Pacific Ocean, Typhoon Man-yi was meandering slowly southeast of Okinawa.  At 10:00 p.m. EST on Saturday the center of Typhoon Man-yi was located at latitude 18.4°N and longitude 135.8°E which put it about 770 miles (1245 km) southeast of Okinawa.  Man-yi was moving toward the west at 2 m.p.h. (3 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 969 mb.

Usagi Strengthens to a Typhoon East of Southern Vietnam

Former Tropical Storm Usagi strengthened into a typhoon east of southern Vietnam on Friday night.  At 10:00 p.m. EST on Friday the center of Typhoon Usagi was located at latitude 9.6°N and longitude 109.2°E which put it about 205 miles (335 km) east-southeast of Ho Chi Minh City, Vietnam.  Usagi was moving toward the west-southwest at 10 m.p.h. (16 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 977 mb.

A small circular eye was visible at the center of Typhoon Usagi on both conventional and microwave satellite imagery.  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 Usagi.  The strongest rain bands were in the western half of the typhoon.  Storms near the core of Usagi were generating upper level divergence which was pumping mass away from the typhoon.  Winds to typhoon force extended out about 30 miles (50 km) from the center of circulation.  Winds to tropical storm force extended out about 125 miles (200 km) from the center.

Typhoon Usagi will move through an environment favorable for intensification during the next 24 hours.  Usagi will move over water where the Sea Surface Temperature is near 29°C.  It will move south of an upper level ridge.  The ridge will produce easterly winds which will blow toward the top of the circulation.  Those winds will cause some vertical wind shear, which will reduce the rate of intensification.  Typhoon Usagi will strengthen on Saturday.

The ridge north of Typhoon Usagi will steer the typhoon a little to the south of due west.  On its anticipated track the center of Typhoon Usagi will approach the Mouths of the Mekong River in about 24 hours.  Usagi will bring strong winds and drop heavy rain on southern Vietnam.  Winds to tropical storm force could affect Ho Chi Minh City.  There could be a storm surge of 6 to 9 feet (2 to 3 meters) along the coast.  Locally heavy rain could cause floods over portions of southern Vietnam and Cambodia.

Elsewhere over the Western North Pacific Typhoon Man-yi started to weaken southeast of Okinawa.  At 10:00 p.m. EST on Friday the center of Typhoon Man-yi was located at latitude 18.1°N and longitude 135.4°E which put it about 760 miles (1230 km) southeast of Okinawa.  Man-yi was moving toward the north at 5 m.p.h. (8 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 969 mb.

Tropical Storm Usagi Forms East of Vietnam

Tropical Storm Usagi formed over the South China Sea east of Vietnam on Thursday.  At 10:00 a.m. EST on Thursday the center of Tropical Storm Usagi was located at latitude 11.2°N and longitude 113.7°E which put it about 350 miles (565 km) east of Lien Huong, Vietnam.  Usagi was moving toward the west at 18 m.p.h. (29 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 1001 mb.

More thunderstorms developed near the center of former Tropical Depression 33W and the Japan Meteorological Agency designated the system as Tropical Storm Usagi.  Satellite imagery indicated that the inner end of a rainband was wrapping around the center of circulation.  Several other bands of showers and thunderstorms were in the western half of Tropical Storm Usagi.  Bands in the eastern half of the circulation consisted primarily of showers and low clouds.  An upper level ridge north Usagi was producing southeasterly winds which were blowing toward the top of the circulation.  Those winds were causing moderate vertical wind shear and they were the reason why the stronger thunderstorms were developing west of the center of circulation.  Storms near the center were producing upper level divergence which was pumping mass away to the west of the tropical storm.

Tropical Storm Usagi will move through an environment favorable for intensification during the next 24 to 36 hours.  Usagi will move over water where the Sea Surface Temperature is near 29°C.  It will continue to move south of an upper level ridge and moderate vertical wind shear will continue to affect Tropical Storm Usagi.  The wind shear will slow intensification, but Usagi will strengthen during the next day or so.  It could intensify into a typhoon during the next 36 hours.

The ridge north of Tropical Storm Usagi will steer the tropical storm on a track a little to the south of due west.  On its anticipated track the center of Tropical Storm Usagi will approach the coast of southern Vietnam in about 36 hours.  Usagi could make landfall on the portion of the coast between Cam Ranh and Vung Tau.  Tropical Storm Usagi will bring gusty winds and it could drop locally heavy rain over southern Vietnam and Cambodia.  Heavy rain could cause flash foods in some locations.

Elsewhere over the Western North Pacific, Typhoon Man-yi was moving away from the Marianas after causing power outages in southern Guam.  At 10:00 a.m. EST on Thursday the center of Typhoon Man-yi was located at latitude 13.5°N and longitude 137.8°E which put it about 1155 miles (1860 km) southeast of Okinawa.  Man-yi was moving toward the northwest at 21 m.p.h. (34 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 969 mb.

Man-yi Strengthens to a Typhoon Southwest of Guam

Former Tropical Storm Man-yi strengthened to a typhoon southwest of Guam on Wednesday.  At 10:00 p.m. EST on Wednesday the center of Typhoon Man-yi was located at latitude 11.1°N and longitude 141.1°E which put it about 300 miles (485 km) southwest of Guam.  Man-yi was moving toward the west-northwest at 27 m.p.h. (44 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 973 mb.

Typhoon Man-yi strengthened quickly on Wednesday.  An inner band of thunderstorms wrapped around the center of circulation.  A small eye appeared intermittently on satellite imagery.  The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Other bands of showers and thunderstorms were revolving around the core of Typhoon Man-yi.  Storms near the core were generating upper level divergence which was pumping mass away from the typhoon.  Winds to typhoon force extended out about 40 miles (65 km) from the center of circulation.  Winds to tropical storm force extended out about 145 miles (230 km) from the center.

Typhoon Man-yi will move through an environment somewhat favorable for intensification on Thursday.  Man-yi will move over water where the Sea Surface Temperature is near 29°C.  So, there will be enough energy in the upper ocean to support further intensification.  Typhoon Man-yi will move south of an upper level ridge.  The ridge will produce strong east-southeasterly winds which will blow toward the top of the circulation.  Those winds will produce moderate vertical wind shear.  The wind shear will inhibit upper level outflow to the east of the typhoon and they will slow the rate of intensification.  Despite the moderate vertical wind shear, Typhoon Man-yi is likely to strengthen during the next 24 hours and it could become the equivalent of a major hurricane.

The ridge will steer Typhoon Man-yi rapidly toward the northwest during the next 24 to 36 hours.  On its anticipated track Typhoon Man-yi will move quickly away from Guam and the Marianas.  Man-yi could move southeast of Okinawa this weekend.

Elsewhere over the rest of the Western North Pacific Ocean, Tropical Depression 33W was moving quickly westward over the South China Sea.  At 10:00 p.m. EDT on Wednesday the center of Tropical Depression 33W was located at latitude 11.1°N and longitude 116.2°E which put it about 505 miles (815 km) east of Cam Ranh, Vietnam.  It was moving toward the west at 25 m.p.h. (40 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 1004 mb.