Category Archives: Western North Pacific

Western Pacific Typhoons and Tropical Storms

Typhoon Koinu Moves Toward Hong Kong

Typhoon Koinu moved toward Hong Kong on Thursday. At 11:00 p.m. EDT on Thursday the center of Typhoon Koinu was located at latitude 21.5°N and longitude 117.4°E which put it about 225 miles (365 km) east of Hong Kong. Koinu was moving toward the west at 8 m.p.h. (13 km/h). The maximum sustained wind speed was 85 m.p.h. (135 km/h) and there were wind gusts to 105 m.p.h. (165 km/h). The minimum surface pressure was 967 mb.

Typhoon Koinu moved over the South China Sea toward Hong Kong on Thursday. Koinu was weaker and smaller after passing over southern Taiwan on Wednesday. The circulation around Typhoon Koinu started to exhibit more organization again on Thursday evening. A circular eye with a diameter of 18 miles (30 km) was at the center of Koinu’s circulation. The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms revolved around the core of Typhoon Koinu. Storms near the core generated upper level divergence that pumped mass away from the typhoon.

Wins to typhoon force extended out 35 miles (55 km) from the center of Typhoon Koinu. Winds to tropical storm force extended out 285 miles (460 km) in the northeast quadrant of Koinu’s circulation. Winds to tropical storm force extended out 130 miles (210 km) in the other parts of Typhoon Koinu.

Typhoon Koinu will move through an environment somewhat favorable for intensification during the next 24 hours. Koinu will move over water where the Sea Surface Temperatures are near 28°C. It will move under the southern part of an upper level ridge over China. The ridge will produce easterly winds that will blow toward the top of Koinu’s circulation. Those winds will cause some vertical wind shear. The wind shear will inhibit intensification but the shear may not be strong enough to prevent intensification. The circulation around the northern side of Typhoon Koinu could start to draw in some drier air from China. Typhoon Koinu could intensify during the next 24 hours if the drier air does not reach the inner core of the circulation.

Typhoon Koinu will move will move around the southern part of a high pressure system over eastern Asia and the Western North Pacific Ocean. The high pressure system will steer Koinu toward the west during the next 24 hours. On its anticipated track the center Typhoon Koinu will move closer to Hong Kong on Friday.

Typhoon Koinu Brings Wind and Rain to Taiwan

Typhoon Koinu brought wind and rain to Taiwan on Wednesday night. At 11:00 p.m. EDT on Wednesday the center of Typhoon Koinu was located at latitude 22.1°N and longitude 120.6°E which put it about 10 miles (15 km) west of Hengchun, Taiwan. Koinu was moving toward the west-northwest at 5 m.p.h. (8 km/h). The maximum sustained wind speed was 125 m.p.h. (200 km/h) and there were wind gusts to 155 m.p.h. (250 km/h). The minimum surface pressure was 945 mb.

Typhoon Koinu brought strong winds and heavy rain to southern Taiwan on Wednesday night. The eye of Koinu passed over the southern tip of Taiwan. The northern half of the eyewall moved across southern Taiwan. Typhoon Koinu was the equivalent of a major hurricane when it moved across Taiwan. Winds to typhoon force extended out 70 miles (110 km) from the center of Koinu’s circulation. Winds to tropical storm force extended out 230 miles (370 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Koinu was 23.6. The Hurricane Size Index (HSI) was 21.6 and the Hurricane Wind Intensity Size Index (HWISI) was 45.2. Typhoon Koinu was stronger than Hurricane Rita was when Rita hit southwest Louisiana in 2005. Koinu was a little smaller than Rita was.

Easterly winds blowing around the northern side of Typhoon Koinu will rise up the eastern slopes of mountains in Taiwan. The enhanced rising motion will produce very heavy rainfall on those eastern slopes. The heavy rain is likely to cause flash floods in some locations.

Typhoon Koinu will move will move around the southern part of a high pressure system over eastern Asia and the Western North Pacific Ocean. The high pressure system will steer Koinu toward the west during the next 24 hours. On its anticipated track the center Typhoon Koinu will move over the South China Sea on Thursday.

The core of Typhoon Koinu was partially disrupted when the eye and northern part of the eyewall moved across southern Taiwan. The disruption of the inner core of Koinu’s circulation is likely to cause Typhoon Koinu to weaken during the next 24 hours even though Koinu will move through an environment favorable for intensification. Koinu will move over water where the Sea Surface Temperatures are near 28°C. It will move under the southern part of an upper level ridge over China. The ridge will produce easterly winds that will blow toward the top of Koinu’s circulation. Those winds will cause some little vertical wind shear, but the wind shear will not be too strong. Typhoon Koinu is likely to weaken gradually during the next 24 hours because of the disruption of its inner core.

Typhoon Koinu Approaches Taiwan

Typhoon Koinu approached Taiwan from east on Tuesday night. At 11:00 p.m. EDT on Tuesday the center of Typhoon Koinu was located at latitude 22.1°N and longitude 123.3°E which put it about 175 miles (280 km) east of Hengchun, Taiwan. Koinu was moving toward the west-northwest at 7 m.p.h. (11 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. (230 km/h). The minimum surface pressure was 953 mb.

Typhoon Koinu was the equivalent of a major hurricane as it approached Taiwan on Tuesday night. A circular eye with a diameter of 30 miles (50 km) was at the center of Koinu’s circulation. The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Typhoon Koinu. Storms near the core generated strong upper level divergence that pumped large quantities of mass away from the typhoon.

The size of the circulation around Typhoon Koinu increased on Tuesday. Winds to typhoon force extended out 90 miles (145 km) from the center of Koinu’s circulation. Winds to tropical storm force extended out 200 miles (320 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Koinu was 20.6. The Hurricane Size Index (HSI) was 29.2 and the Hurricane Wind Intensity Size Index (HWISI) was 49.8. Typhoon Koinu was similar in size and intensity to Hurricane Frances when Frances hit southeast Florida in 2004.

Typhoon Koinu will move through an environment favorable for intensification during the next 12 hours. Koinu will move over water where the Sea Surface Temperatures are near 28°C. It will move through a region where the upper level winds are weak and there will be little vertical wind shear. Typhoon Koinu is likely to intensify during the next 12 hours.

Typhoon Koinu will move around the southern part of a high pressure system over eastern Asia and the Western North Pacific Ocean. The high pressure system will steer Koinu toward the west during the next 24 hours. On its anticipated track the center Typhoon Koinu will reach the coast of southeast Taiwan in less than 24 hours. Typhoon Koinu is likely to be the equivalent of a major hurricane when it approaches Taiwan. Koinu will bring strong, gusty winds and locally heavy rain to Taiwan. Heavy rain will cause flash floods in some locations. Typhoon Koinu could also cause widespread outages of electricity.

Typhoon Koinu Rapidly Intensifies to Equivalent of a Major Hurricane

Typhoon Koinu rapidly intensified to the equivalent of a major hurricane over the Western North Pacific Ocean east-southeast of Taiwan on Sunday night. At 5:00 a.m. EDT on Monday the center of Typhoon Koinu was located at latitude 19.9°N and longitude 126.4°E which put it about 405 miles (650 km) east-southeast of Hengchun, Taiwan. Koinu was moving toward the northwest at 9 m.p.h. (15 km/h). The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 150 m.p.h. (240 km/h). The minimum surface pressure was 953 mb.

Typhoon Koinu rapidly intensified to the equivalent of a major hurricane during the past 24 hours. A circular eye with a diameter of 10 miles (16 km) was at the center of Koinu’s circulation. The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the center of Typhoon Koinu. Storms near the center generated upper level divergence that pumped mass away from the typhoon.

The size of the circulation around Typhoon Koinu increased when Koinu rapidly intensified. Winds to typhoon force extended out 50 miles (80 km) from the center of Koinu’s circulation. Winds to tropical storm force extended out 150 miles (240 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Koinu was 22.1. The Hurricane Size Index (HSI) was 17.3 and the Hurricane Wind Intensity Size Index (HWISI) was 39.4.

Typhoon Koinu will move through an environment favorable for intensification during the next 24 hours. Koinu 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 over the Western North Pacific Ocean and eastern Asia. The upper level ridge will produce easterly winds that will blow toward the top of Koinu’s circulation. Those winds will cause some vertical wind shear, but the wind shear will not be strong enough to prevent intensification. Typhoon Koinu is likely to intensify during the next 24 hours.

Typhoon Koinu will move around the southern part of a high pressure system over eastern Asia. The high pressure system will steer Koinu toward the northwest during the next 24 hours. On its anticipated track Typhoon Koinu will move closer to Taiwan. Koinu will approach southern Taiwan in 48 hours. Typhoon Koinu is likely to be the equivalent of a major hurricane when it approaches Taiwan. Koinu will bring strong, gusty winds and locally heavy rain to Taiwan. Heavy rain will cause flash floods in some locations.

Koinu Strengthens to a Typhoon

Former Tropical Storm Koinu strengthened to a typhoon over the Western North Pacific Ocean east-southeast of Taiwan on Sunday morning. At 11:00 a.m. EDT on Sunday the center of Typhoon Koinu was located at latitude 18.6°N and longitude 128.5°E which put it about 570 miles (920 km) east-southeast of Hengchun, Taiwan. Koinu was moving toward the northwest at 7 m.p.h. (11 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. (165 km/h). The minimum surface pressure was 977 mb.

Former Tropical Storm Koinu intensified rapidly during the past 24 hours. The inner end of a rainband wrapped around the center of Typhoon Koinu. A circular eye with a diameter off 17 miles (28 km) developed at the center of Koinu’s circulation. The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the center of Typhoon Koinu, Storms near the center generated upper level divergence that pumped mass away to the west of the typhoon. Winds to typhoon force extended out 20 miles (30 km) from the center of Koinu’s circulation. Winds to tropical storm force extended out 85 miles (135 km) from the center of circulation.

Tropical Storm Koinu will move through an environment favorable for intensification during the next 24 hours. Koinu will move over water where the Sea Surface Temperatures are near 30°C. ‘ It will move under the southeastern part of an upper level ridge centered west of Taiwan. The ridge will produce northeasterly winds that will blow toward the top of Koinu’s circulation. Those winds will cause some vertical wind shear. The wind shear will inhibit intensification, but the shear will not be strong enough to completely stop intensification. Typhoon Koinu will intensify during the next 24 hours. Koinu could strengthen to the equivalent of a major hurricane.

Tropical Storm Koinu will move around the southern part of a high pressure system over eastern Asia. The high pressure system will steer Koinu toward the northwest during the next 24 hours. On its anticipated track Tropical Storm Koinu will move closer to Taiwan. Koinu could approach southern Taiwan in three days. Typhoon Koinu is likely to be the equivalent of a major hurricane when it approaches Taiwan.

Tropical Storm Koinu Forms Southeast of Taiwan

Tropical Storm Koinu formed over the Western North Pacific Ocean southeast of Taiwan on Friday night. At 5:00 a.m. EDT on Saturday the center of Tropical Storm Koinu was located at latitude 16.0°N and longitude 130.9°E which put it about 850 miles (1730 km) southeast of Taipei, Taiwan. Koinu was moving toward the west-northwest at 11 m.p.h. (17 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 997 mb.

A low pressure system over the Western North Pacific Ocean southeast of Taiwan strengthened on Friday night and the Japan Meteorological Agency designated the system as Tropical Storm Koinu. The distribution of thunderstorms around Tropical Storm Koinu was asymmetrical. Many of the thunderstorms were occurring in bands in the western half of Koinu’s circulation. Bands in the eastern side of Tropical Storm Koinu consisted primarily of showers and lower clouds. Storms near the center of Koinu’s circulation generated upper level divergence that pumped mass away to the west of the tropical storm. Winds to tropical storm force extended out 170 miles (275 km) from the center of circulation.

Tropical Storm Koinu will move through an environment favorable for intensification during the next 24 hours. Koinu 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 over the Western North Pacific Ocean. The ridge will produce easterly winds that will blow toward the top of Koinu’s circulation. Those winds will cause moderate vertical wind shear. The wind shear will inhibit intensification, but the shear will not be strong enough to completely stop intensification. Tropical Storm Koinu is likely to intensify gradually during the next 24 hours.

Tropical Storm Koinu will move around the southwestern part of a high pressure system over the Western North Pacific Ocean. The high pressure system will steer Koinu toward the northwest during the next 24 hours. On its anticipated track Tropical Storm Koinu will move closer to Taiwan. Koinu could approach southern Taiwan in four days. It could be a typhoon when it approaches Taiwan.

Tropical Storm Yun-yeung Moves Toward Honshu

Tropical Storm Yun-Yeung moved toward Honshu on Wednesday. At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Yun-yeung was located at latitude 30.2°N and longitude 136.7°E which put it about 430 miles (695 km) south-southwest of Tokyo, Japan. Yun-yeung was moving toward the north-northeast at 15 m.p.h. (24 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 994 mb.

Tropical Storm Yun-yeung consisted primarily of a low level circulation on Wednesday night. The bands revolving around the center of Yun-yeung’s circulation contained primarily showers and lower clouds. A strong upper level trough northwest of Japan produced strong southwesterly winds that blew across the top of Tropical Storm Yun-Yeung. Those winds caused strong vertical wind shear and the winds blew the upper part of Yun-Yeung’s circulation to the northeast of the circulation near the surface . There was a band of thunderstorms near the northern periphery of Tropical Storm Yun-yeung. Winds to tropical storm force extended out 100 miles (160 km) in the eastern side of Yun-Yeung’s circulation. The winds in the western side of Yun-yeung were blowing at less than tropical storm force.

Tropical Storm Yun-yeung will move through an environment unfavorable for intensification of a tropical storm during the next 36 hours. Yun-yeung will move over water where the Sea Surface Temperatures are near 28°C. However, the upper level trough northwest of Japan will continue to cause strong vertical wind shear. The strong vertical wind shear will prevent intensification of Tropical Storm Yun-yeung. Yun-yeung could get a little stronger, if it makes a transition to an extratropical cyclone.

Tropical Storm Yun-yeung will move around the northwestern part of high pressure system over the Western North Pacific. The high pressure system and the upper level trough northwest of Japan will steer Yun-yeung toward the northeast during the next 36 hours. On its anticipated track, Tropical Storm Yun-yeung will approach Tokyo in 36 hours.

Tropical Storm Yun-yeung Forms South of Japan

Tropical Storm Yun-yeung formed over the Western North Pacific Ocean south of Japan on Tuesday night. At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Yun-yeung was located at latitude 26.2°N and longitude 133.6°E which put it about 810 miles (1305 km) south-southwest of Tokyo, Japan. Yun-yeung was moving toward the north at 17 m.p.h. (28 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 998 mb.

A low pressure system over the Western North Pacific Ocean strengthened on Tuesday and the Japan Meteorological Agency designated the system as Tropical Storm Yun-yeung. More thunderstorms developed near the center of Yun-yeung’s circulation on Tuesday evening, but the distribution of thunderstorms was asymmetrical. Most of the thunderstorms were occurring in bands in the southern half of Tropical Storm Yun-yeung. Bands in the northern half of the circulation consisted primarily of showers and lower clouds. The distribution of wind speeds was also asymmetrical. Winds to tropical storm force extended out 40 miles (65 km) in the eastern side of Yun-yeung’s circulation. The winds in the eastern side of Yun-yeung were blowing at less than tropical storm force.

Tropical Storm Yun-yeung will move through an environment somewhat favorable for intensification during the next 24 hours. Yun-yeung will move over water where the Sea Surface Temperatures are near 28°C. It will move under the eastern side on an upper level ridge south of Japan. The upper level ridge will produce northeasterly winds that will blow toward the top of Yun-yeung’s circulation. Those winds will cause moderate vertical wind shear. The wind shear is already contributing to the asymmetrical distribution of thunderstorms. The vertical wind shear will inhibit intensification, but the shear will probably not be strong enough to prevent Yun-yeung from strengthening. Tropical Storm Yun-yeung is likely to intensify gradually during the next 24 hours.

Tropical Storm Yun-yeung will move around the northwestern part of high pressure system over the Western North Pacific. The high pressure system will steer Yun-yeung toward the north-northeast during the next 24 hours. On its anticipated track, Tropical Storm Yun-yeung will move closer to Honshu. Yun-yeung could be near Tokyo in 48 hours.

Tropical Storm Haikui Makes Landfall near Shantou, China

The center of Tropical Storm Haikui made landfall on the coast of eastern China near Shantou on Monday. At 5:00 p.m. EDT on Monday the center of Tropical Storm Haikui was located at latitude 23.7°N and longitude 117.0°E which put it about 15 miles (20 km) northeast of Shantou, China. Haikui was moving toward the west 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 996 mb.

Former Typhoon Haikui weakened to a tropical storm as it moved across the Taiwan Strait. The lower levels of circulation around Haikui were disrupted by the mountains on Taiwan. The disruption caused Haikui to weaken steadily before it made landfall in China. Many of the bands revolving around the center of Tropical Storm Haikui consisted primarily of showers and lower clouds. There were thunderstorms in a band just to the south of the center of Haikui’s circulation. There were also thunderstorms in a band in the eastern side of Tropical Storm Haikui.

Tropical Storm Haikui will move toward the west over eastern China. Haikui will weaken to a tropical depression as it moves inland. Tropical Storm Haikui will bring gusty winds and isolated heavy rain to eastern Guangdong province.

Typhoon Haikui Moves over the Taiwan Strait

Typhoon Haikui moved over the Taiwan Strait on Sunday night. At 11:00 p.m. EDT on Sunday the center of Typhoon Haikui was located at latitude 23.3°N and longitude 119.6°E which put it about 70 miles (110 km) northwest of Kaohsiung, Taiwan. Haikui was moving toward the west-northwest at 6 m.p.h. (10 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. (165 km/h). The minimum surface pressure was 966 mb.

Typhoon Haikui brought strong winds and heavy rain to Taiwan on Sunday. A weather station at the airport in Taipei (RCTP) reported a sustained wind speed of 35 m.p.h. (55km/h) and a wind gust of 49 m.p.h. (79 km/h). A weather station in Taitung (RCFN) reported a sustained wind speed of 56 m.p.h. (91 km/h) and a wind gust of 87 m.p.h. (140 km/h). A weather station in Kaohsiung (RCKH) reported a sustained wind speed of 39 m.p.h. (63 km/h) and a wind gust of 62 m.p.h. (100 km/h). Bands in the eastern part of Typhoon Haikui were still dropping heavy rain over parts of Taiwan on Sunday night.

The lower levels of the circulation of Typhoon Haikui were disrupted when Haikui moved over the mountains on Taiwan. There was no longer an eye at the center of Haikui’s circulation. The circulation in the middle and upper level of Typhoon Haikui remained relatively intact. Bands of showers and thunderstorms were revolving around the center of Haikui’s circulation. Winds to typhoon force extended out 30 miles (50 km/h) from the center of circulation. Winds to tropical storm force extended out 165 miles (265 km) from the center of Typhoon Haikui.

Typhoon Haikui will move around the southern side of a high pressure system over the Western North Pacific Ocean. The high pressure system will steer Haikui toward the west-northwest during the next 24 hours. On its anticipated track, the center of Typhoon Haikui will approach the east coast of China between Shantou and Xiamen within 24 hours.

Typhoon Haikui will move through an environment favorable for intensification during the next 24 hours. Haikui will move over water where the Sea Surface Temperatures are near 30°C. It will move under an upper level ridge centered northwest of Taiwan. The upper level winds are weak in the ridge and the will be little vertical wind shear. Typhoon Haikui may not intensify during the next 24 hours even though it will move through a favorable environment. The lower levels of Haikui’s circulation will gradually reorganize now that the center of circulation is back over water. However, there may not be enough time for an eye to develop again before Haikui reaches the east coast of China. If the inner core of Typhoon Haikui does not develop again, then it will be unlikely to strengthen.