Category Archives: Western North Pacific

Western Pacific Typhoons and Tropical Storms

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 Fung-Wong Clips Southern Taiwan

Tropical Storm Fung-wong clipped the southern part of Taiwan on Wednesday.  At 4:00 p.m. EST on Wednesday the center of Tropical Storm Fung-wong was located at latitude 23.5°N and longitude 122.5°E which put the center about 140 miles (225 km) south of Taipei, Taiwan.  Fung-wong was moving toward the northeast at 13 m.p.h. (21 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.

The center of Tropical Storm Fung-wong moved across southern Taiwan on Wednesday.  Fung-wong brought gusty winds and locally heavy rain as it moved across Taiwan.

Tropical Storm Fung-wong continued to weaken as it moved across southern Taiwan on Wednesday.  Drier air from Asia was pulled into many parts of Fung-wong’s circulation.  A few thunderstorms were occurring near the center of Tropical Storm Fung-wong.  Other thunderstorms were located northeast of the center where Fung-wong’s circulation was interacting with a frontal boundary.  There was little upper level divergence.  Since mass was not being transported away from Tropical Storm Fung-wong, the surface pressure was increasing.

The distribution of wind speeds around Tropical Storm Fung-wong was very asymmetrical.  The pressure gradient between a high pressure system over eastern Asia and Tropical Storm Fung-wong was causing a large area of tropical storm winds to the north of Fung-wong.  Winds to tropical storm force extended out 320 miles (520 km) in the northern side of Fung-wong’s circulation.  Winds to tropical storm force extended out 90 miles (145 km) in the southern side of Tropical Storm Fung-wong.

Tropical Storm Fung-wong will move through an environment that will be unfavorable for intensification during the next 24 hours.  Fung-wong will move over water where the Sea Surface Temperatures are near 27°C.  It will move under the southeastern part of an upper level trough that is over eastern China.  The upper level trough will produce southwesterly winds that will blow across the top of Fung-wong’s circulation.  Those winds will cause strong vertical wind shear.  In addition, the drier air that is already in the circulation around Fung-wong will suppress the formation of new thunderstorms.  Strong vertical wind shear and the drier air will cause Tropical Storm Fung-wong to continue to weaken during the next 24 hours.

Tropical Storm Fung-wong will move around the western end of a high pressure system that is over the Western North Pacific Ocean.  The high pressure system will steer Fung-wong toward the northeast during the next 24 hours.  On its anticipated track, Tropical Storm Fung-wong will move over the southern Ryukyu Island.

Tropical Storm Fung-wong will bring gusty winds and rain showers to the southern Ryukyu Islands.

Fung-wong Weakens to a Tropical Storm

Former Typhoon Fung-wong weakened to a tropical storm over the South China Sea southwest of Taiwan on Tuesday morning.  At 10:00 a.m. EST on Tuesday the center of Tropical Storm Fung-wong was located at latitude 20.8°N and longitude 11934°E which put the center about 165 miles (265 km) southwest of Kaohsiung, Taiwan.  Fung-wong was moving toward the north-northwest at 8 m.p.h. (13 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.

Former Typhoon Fung-wong weakened to a tropical storm southwest of Taiwan on Tuesday morning.  Drier air from Asia was pulled into the core of Tropical Storm Fung-wong.  The drier air caused many of the thunderstorms in Fung-wong to dissipate.  The dissipation of the thunderstorms significantly reduced the amount of upper level divergence.  Since the upper level divergence pumped less mass away from Tropical Storm Fung-wong, the surface pressure increased.

An upper level ridge over the Western North Pacific Ocean was producing southerly winds that were blowing toward the top of Fung-wong’s circulation.  Those winds were causing strong vertical wind shear.  The strong vertical wind shear was blowing the upper part of Fung-wong’s circulation toward the north of the circulation in the lower levels.  Many of the bands in Tropical Storm Fung-wong consisted primarily of showers and lower clouds.

Even though Tropical Storm Fung-wong was weakening, the circulation around Fung-wong was still large.  Winds to tropical storm force extended out 275 miles (445 km) in the northern side of Fung-wong’s circulation.  Winds to tropical storm force extended out 160 miles (260 km) in the southern half of Tropical Storm Fung-wong.

Tropical Storm Fung-wong will move through an environment that will be unfavorable for intensification during the next 24 hours.  Fung-wong will move over water where the Sea Surface Temperatures are near 27°C.  The upper level ridge that is over the Western North Pacific Ocean will continue to produce southerly winds that will blow toward the top of Fung-wong’s circulation.  Those winds will continue to cause strong vertical wind shear.  In addition, the drier air that is already in the circulation around Fung-wong will suppress the formation of new thunderstorms.  Strong vertical wind shear and the drier air will cause Tropical Storm Fung-wong to continue to weaken during the next 24 hours.

Tropical Storm Fung-wong will move around the western end of a high pressure system that is over the Western North Pacific Ocean.  The high pressure system will steer Fung-wong toward the northeast during the next 24 hours.  On its anticipated track, Tropical Storm Fung-wong will move across Taiwan during the next 24 hours.

Tropical Storm Fung-wong will bring strong winds and isolated heavy rain to Taiwan.  Heavy rain could cause flash floods in some locations.

Tropical Storm Fung-wong will move across the southern Ryukyu Islands on Wednesday.

Typhoon Fung-wong Moves over South China Sea

Typhoon Fung-wong moved over the South China Sea on Monday.  At 10:00 a.m. EST on Monday the center of Typhoon Fung-wong was located at latitude 18.8°N and longitude 118.4°E which put the center about 285 miles (460 km) south-southwest of Kaohsiung, Taiwan.  Fung-wong was moving toward the north-northwest at 11 m.p.h. (17 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 969 mb.

Typhoon Fung-wong was weakening as it moved over the South China Sea on Monday.  Even though Fung-wong was weakening, thunderstorms were still developing near the center of Fung-wong’s circulation.  Bands of showers and thunderstorms were revolving around the center of Typhoon Fung-wong.  Storms near the center of Fung-wong continued to generate upper level divergence that pumped mass away from the typhoon.  However, the removal of mass in the upper levels of the atmosphere was less than the convergence of mass in the lower levels.  So, the surface pressure was increasing.

The circulation around Typhoon Fung-wong was large.  Winds to typhoon force extended out 100 miles (160 km) from the center of Fun-wong’s circulation.  Winds to tropical storm force extended out 300 miles (485 km) from the center of Typhoon Fung-wong.

Typhoon Fung-wong will move through an environment that will be unfavorable for intensification during the next 24 hours.  Fung-wong will move over water where the Sea Surface Temperatures are near 28°C.  It will move under the western end of an upper level ridge that is over the Western North Pacific Ocean.  The upper level ridge will produce southerly winds that will blow toward the top of Fung-wong’s circulation.  Those winds will cause the vertical wind shear to increase.  In addition, drier air from Asia is over the South China Sea.  The drier air will gradually get pulled into the circulation around Fung-wong.  More vertical wind shear and drier air will cause Typhoon Fung-wong to weaken slowly during the next 24 hours.

Typhoon Fung-wong will move around the western end of a high pressure system that is over the Western North Pacific Ocean.  The high pressure system will steer Fung-wong toward the north during the next 24 hours.  On its anticipated track, Typhoon Fung-wong will move toward Taiwan.

Typhoon Fung-wong is likely to weaken to a tropical storm before it reaches Taiwan.  Fung-wong will bring strong winds and locally heavy rain to Taiwan.  Heavy rain could cause flash floods in some locations.

Typhoon Fung-wong Hits Luzon

Typhoon Fung-wong hit Luzon on Sunday.  At 10:00 a.m. EST on Sunday the center of Typhoon Fung-wong was located at latitude 16.4°N and longitude 121.3°E which put the center about 25 miles (40 km) east of Bayombong, Philippines.  Fung-wong was moving toward the northwest at 21 m.p.h. (33 km/h).  The maximum sustained wind speed was 115 m.p.h. (185 km/h) and there were wind gusts to 145 m.p.h. (235 km/h).  The minimum surface pressure was 945 mb.

The center of Typhoon Fung-wong made landfall on the east coast of Luzon between Baler and Casiguran on Sunday.  Fung-wong was the equivalent of a major hurricane when it made landfall.

The circulation around Typhoon Fung-wong was large.  Winds to typhoon force extended out 80 miles (130 km) from the center of Fung-wong’s circulation.  Winds to tropical storm force extended out 230 miles (370 km) from the center of Typhoon Fung-wong.

The Hurricane Intensity Index (HII) for Typhoon Fung-wong is 20.6.  The Hurricane Size Index (HSI) is 27.1 and the Hurricane Wind Intensity Size Index (HWISI) is 47.7.  Typhoon Fung-wong is similar in size and intensity to Hurricane Irma when Irma hit Southwest Florida in 2017.

Typhoon Fung-wong will move around the western end of a high pressure system that is over the Western North Pacific Ocean.  The high pressure system will steer Fung-wong toward the northwest during the next 24 hours.  On its anticipated track, Typhoon Fung-wong will move across northern Luzon during the next few hours.  Fung-wong will move over the South China Sea.

Typhoon Fung-wong will bring strong, gusty winds and very heavy rain to Luzon.  Heavy rain will cause widespread flash floods.  Fung-wong will cause widespread electricity outages.  Typhoon Fung-wong could also cause a storm surge of up to 13 feet (4 meters) along portions of the coast of Luzon.

Typhoon Fung-wong will move into an environment that will be less favorable for intensification when it moves over the South China Sea.  Fung-wong will move over water where the Sea Surface Temperatures are near 28°C.  It will move under the middle of an upper level ridge that is over eastern China.  The upper level winds are weak near the middle of the ridge and there will be little vertical wind shear.  However, drier air from Asia has spread over the South China Sea.  The drier air will gradually get pulled into the circulation around Fung-wong.  The drier air is likely to cause Typhoon Fung-wong to weaken slowly when it moves over the South China Sea.