Category Archives: Western North Pacific

Western Pacific Typhoons and Tropical Storms

Namtheun Strengthens to a Typhoon North of Wake Island

Former Tropical Storm Namtheun strengthened to a typhoon over the Western North Pacific Ocean north of Wake Island on Saturday morning. At 5:00 a.m. EDT on Saturday the center of Typhoon Namtheun was located at latitude 31.4°N and longitude 165.6°E which put it about 800 miles (1290 km) north of Wake Island. Namtheun was moving toward the north-northeast at 18 m.p.h. (29 km/h). The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (150 km/h). The minimum surface pressure was 979 mb.

Former Tropical Storm Namtheun passed over water where the Sea Surface Temperatures are near 27˚C during the past 24 hours and it was able to extract enough energy to strengthen to a typhoon. A small eye formed at the center of Typhoon Namtheun. The eye was surrounded by a broken ring of thunderstorms and the strongest winds were occurring in that ring of storms. Storms near the center of Namtheun generated upper level divergence that pumped mass away from the typhoon. The circulation around Typhoon Namtheun was relatively small. Winds to typhoon force extended out 20 miles (30 km) from the center of Namtheun. Winds to tropical storm force extended out 115 miles (185 km) from the center of circulation.

An upper level trough east of Japan will steer Typhoon Namtheun toward the north-northeast during the weekend. On its anticipated track Namtheun will move toward the Aleutian Islands. Typhoon Namtheun will move into an environment unfavorable for intensification during the weekend. Namtheun will move over much cooler water. The upper level trough east of Japan will produce strong southwesterly winds that will blow toward the top of Namtheun’s circulation. Those winds will cause moderate vertical wind shear. The combination of cooler water and more vertical wind shear will cause Typhoon Namtheun to make a transition to an extratropical cyclone as it moves toward the Aleutian Islands.

Tropical Storm Namtheun Spins Southeast of Japan

Tropical Storm Namtheun was spinning southeast of Japan on Friday morning. At 5:00 a.m. EDT on Friday the center of Tropical Storm Namtheun was located at latitude 26.6°N and longitude 161.9°E which put it about 495 miles (800 km) east-northeast of Minami Tori Shima. Namtheun was moving toward the east-northeast at 18 m.p.h. (29 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 994 mb.

Tropical Storm Namtheun was the only current tropical cyclone on Friday morning as it churned over the Western North Pacific Ocean between Japan and Hawaii. Namtheun intensified during the past 24 hours as it moved well to the east of the main islands of Japan. The inner end of a rainband wrapped around the center of Tropical Storm Namtheun. A broken ring of thunderstorms was around the center of circulation. The strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Namtheun. Storms near the core generated upper level divergence that pumped mass away from the tropical storm. Winds to tropical storm force extended out 85 miles (135 km) from the center of circulation.

Tropical Storm Namtheun will move through an environment somewhat favorable for intensification during the next 24 hours. Namtheun will move over water where the Sea Surface Temperatures are near 27˚C. An upper level trough southeast of Japan will produce southwesterly winds that will blow toward the top of Namtheun’s circulation. Those winds will cause some vertical wind shear and the wind shear will inhibit intensification. Tropical Storm Namtheun could strengthen during the next 24 hours. Namtheun will move over colder water during the weekend. It will also move in a region where the upper level winds will be stronger. Tropical Storm Namtheun will weaken during the weekend.

The upper level trough southeast of Japan will steer Tropical Storm Namtheun toward the northeast during the next several days. On its anticipated track Namtheun will move farther away from Japan.

Tropical Storm Kompasu Brings Wind and Rain to Hainan

Tropical Storm Kompasu brought wind and rain to Hainan on Wednesday. At 5:00 a.m. EDT on Wednesday the center of Tropical Storm Kompasu was located at latitude 19.2°N and longitude 110.0°E which put it about 50 miles (80 km) southwest of Haikou, China. Kompasu was moving toward the west at 22 m.p.h. (35 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 981 mb.

Tropical Storm Kompasu brought wind and rain as it moved over Hainan on Wednesday. The strongest thunderstorms were in bands on the western side of Kompasu’s circulation. Bands on the eastern side of the circulation consisted primarily of showers and lower clouds. Winds to tropical storm force extended out 200 miles (320 km) from the center of Tropical Storm Kompasu.

Tropical Storm Kompasu was moving under the southern part of an upper level ridge over China. The ridge was producing strong easterly winds that were blowing toward the top of Kompasu’s circulation. Those winds were causing moderate vertical wind shear. The flow around the northern side of Tropical Storm Kompasu was pulling drier air from Asia into the circulation. The combination of moderate vertical wind shear and drier air was causing the stronger thunderstorms to be on the western side of Kompasu.

Tropical Storm Kompasu will move around the southern side of a high pressure system over China. The high pressure system will steer Kompasu quickly toward the west during the next 24 hours. On its anticipated track the center of Kompasu will move quickly across the Gulf of Tonkin. Tropical Storm Kompasu will reach the coast of northern Vietnam in 18 hours. Gusty winds and rain will reach the coast before the center arrives because the stronger thunderstorms are on the western side of Kompasu. Vertical wind shear and drier air will prevent intensification of Tropical Storm Kompasu. Kompasu will bring gusty winds and locally heavy rain to northern Vietnam and Laos. Locally heavy rain could cause flash floods in some locations.

Tropical Storm Kompasu Brings Wind and Rain to Northern Luzon

Tropical Storm Kompasu brought wind and rain to northern Luzon on Monday. At 11:00 a.m. EDT on Monday the center of Tropical Storm Kompasu was located at latitude 18.9°N and longitude 120.9°E which put it about 35 miles (55 km) north of Claveria, Philippines. Kompasu was moving toward the west at 16 m.p.h. (26 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 981 mb.

Rainbands in the southern side of Tropical Storm Kompasu brought wind and rain to northern Luzon on Monday. The center of Kompasu passed just north of Luzon. Thunderstorms in bands in southern half of Tropical Storm Kompasu passed over the northern end of Luzon. Kompasu strengthened as it approached northern Luzon. More thunderstorms developed in bands revolving around the center of Tropical Storm Kompasu. Storms near the center of circulation generated upper level divergence that pumped mass away from the tropical storm. Winds to tropical storm force extended out 145 miles (235 km) from the center of Kompasu.

Tropical Storm Kompasu will move through an environment somewhat favorable for intensification during the next 36 hours. Kompasu will move over water where the Sea Surface Temperatures are near 29˚C. It will move south of an upper level ridge over China. The ridge will produce northeasterly winds that will blow toward the top of Kompasu’s circulation. Those winds will cause moderate vertical wind shear and the wind shear will inhibit intensification. Tropical Storm Kompasu is likely to strengthen gradually during the next 24 hours. Kompasu could intensify to a typhoon over the South China Sea.

Tropical Storm Kompasu will move south of a high pressure system over China. The high pressure system will steer Kompasu toward the west during the next several days. On its anticipated track the center of Tropical Storm Kompasu will pass south of Hong Kong in 24 hours. Kompasu could approach Hainan in 36 hours.

Elsewhere over the Western North Pacific Ocean, Tropical Storm Namtheun intensified east of the northern Marianas. At 11:00 a.m. EDT on Monday the center of Tropical Storm Namtheun was located at latitude 19.4°N and longitude 154.0°E which put it about 555 miles (895 km) east of Agrihan. Namtheun was moving toward the west-northwest at 16 m.p.h. (26 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 988 mb.

Tropical Storm Lionrock Drops Heavy Rain on Northern Vietnam

Tropical Storm Lionrock dropped heavy rain on parts of northern Vietnam on Saturday night. At 11:00 p.m. EDT on Saturday the center of Tropical Storm Lionrock was located at latitude 20.4°N and longitude 107.1°E which put it about 25 miles (40 km) southeast of Haiphong, Vietnam. Lionrock was moving toward the west-northwest at 15 m.p.h. (24 km/h). The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h). The minimum surface pressure was 995 mb.

Tropical Storm Lionrock dropped heavy rain over the part of northern Vietnam between Hanoi and Haiphong on Saturday night. The heaviest rain was falling in bands in the western half of Tropical Storm Lionrock. Bands in the eastern side of Lionrock consisted primarily of showers and lower clouds. Winds to tropical storm force extended out 120 miles (195 km) from the center of Lionrock’s circulation.

Tropical Storm Lionrock will move south of a high pressure system over China during the next 24 hours. The high pressure system will steer Lionrock toward the west during the next day or so. On its anticipated track Tropical Storm Lionrock will move across northern Vietnam and northern Laos. Lionrock will bring gusty winds and locally heavy rain to parts of northern Vietnam and northern Laos. Heavy rain could cause flash floods in some locations.

Elsewhere over the Western North Pacific Ocean, Tropical Storm Kompasu was spinning east of Luzon and Tropical Storm Namtheun formed east of the northern Marianas. At 11:00 p.m. EDT on Saturday the center of Tropical Storm Kompasu was located at latitude 15.9°N and longitude 129.8°E which put it about 470 miles (760 km) east of Luzon. Kompasu was moving toward the northwest at 9 m.p.h. (15 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. Kompasu is forecast to move toward the west-northwest and to strengthen.

At 11:00 p.m. EDT on Saturday the center of Tropical Storm Namtheun was located at latitude 17.0°N and longitude 160.3°E which put it about 980 miles (1580 km) east of Alamagan. Namtheun was moving toward the west 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 1000 mb. Namtheun was forecast to move toward the northwest and to strengthen.

Tropical Storm Lionrock Drops Heavy Rain on Hainan

Tropical Storm Lionrock dropped heavy rain on Hainan on Friday. At 11:00 a.m. EDT on Friday the center of Tropical Storm Lionrock was located at latitude 19.1°N and longitude 110.2°E which put it about 50 miles (80 km) south of Haikou, China. Lionrock was moving toward the north at 7 m.p.h. (11 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 991 mb.

Tropical Storm Lionrock brought gusty winds and heavy rain to Hainan on Friday. The center of Lionrock was over Hainan. Bands of showers and thunderstorms on the northern and western sides of Tropical Storm Lionrock were dropping heavy rain over much of Hainan. Bands on the southern and eastern sides of Lionrock consisted primarily of showers and lower clouds. Storms near the center of circulation generated upper level divergence that pumped mass away from the tropical storm. The circulation around Tropical Storm Lionrock was large. Winds to tropical storm force extended out 220 miles (350 km) from the center of circulation.

Tropical Storm Lionrock is likely to weaken during the next 12 hours while the center of circulation moves over Hainan. Lionrock will move into an environment favorable for intensification when the center moves over the Gulf of Tonkin. Lionrock will move over water where the Sea Surface Temperatures are near 29˚C. It will move under the western side of a small upper level ridge. The ridge will produce southerly winds that will blow toward the top of Lionrock’s circulation. Those winds will cause some vertical wind shear, but the shear will not be strong enough to prevent intensification. Tropical Storm Lionrock is likely to intensify slowly after the center of circulation moves over the Gulf of Tonkin.

Tropical Storm Lionrock will move around the southwestern part of a subtropical high pressure system over the Western North Pacific Ocean during the next 12 hours. The subtropical high will steer Lionrock toward the northwest. On its anticipated track the center of Tropical Storm Lionrock will move across Hainan and it will emerge over the Gulf of Tonkin on Saturday. Lionrock will continue to bring gusty winds and locally heavy rain to Hainan during the next 12 hours. Heavy rain could cause flash floods in some locations. Tropical Storm Lionrock will move south of a second high pressure system that is centered over China during the weekend. The second high pressure system will steer Lionrock toward the west. Tropical Storm Lionrock could approach the coast of northern Vietnam in 36 hours.

Elsewhere over the Western North Pacific Ocean, a former tropical depression east of the Philippines strengthened to Tropical Storm Kompasu. At 11:00 a.m. EDT on Friday the center of Tropical Storm Kompasu was located at latitude 13.8°N and longitude 131.5°E which put it about 570 miles (920 km) east of Daet, Philippines. Kompasu was stationary. 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.

Tropical Storm Lionrock Forms Southeast of Hainan

Tropical Storm Lionrock formed over the South China Sea southeast of Hainan on Thursday. At 5:00 p.m. EDT on Thursday the center of Tropical Storm Lionrock was located at latitude 17.5°N and longitude 111.0°E which put it about 95 miles (150 km) southeast of Lingshui, China. Lionrock was moving toward the north-northwest at 5 m.p.h. (8 km/h). The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h). The minimum surface pressure was 994 mb.

The circulation around a low pressure system over the South China Sea strengthened on Thursday and the Japan Meteorological Agency designated the system as Tropical Storm Lionrock. There was a broad center of circulation in the middle of Tropical Storm Lionrock. Many of the thunderstorms were occurring in bands northeast and southwest of the broad center. Storms in the bands generated upper level divergence that pumped mass away from the tropical storm. Winds to tropical storm force extended out 150 miles (240 km) on the eastern side of Lionrock. Winds to tropical storm force extended out 75 miles (120 km) on the western side of the circulation.

Tropical Storm Lionrock will move through an environment somewhat favorable for intensification during the next 24 hours. Lionrock will move over water where the Sea Surface Temperatures are near 29˚C. It will move under the eastern side of a small upper level ridge. The ridge will produce northeasterly winds that will blow toward the top of Lionrock’s circulation. Those winds will cause some vertical wind shear, but the shear will not be strong enough to prevent intensification. Tropical Storm Lionrock is likely to intensify slowly during the next 24 hours because of the broad center of circulation.

Tropical Storm Lionrock will move around the southwestern part of a subtropical high pressure system over the Western North Pacific Ocean during the next 24 hours. The subtropical high will steer Lionrock toward the north-northwest. On its anticipated track the center of Tropical Storm Lionrock will reach Hainan in 24 hours. Lionrock will bring gusty winds and locally heavy rain to Hainan. Heavy rain could cause flash floods in some locations.

Elsewhere over the Western North Pacific Ocean, a tropical depression formed east of the Philippines. At 5:00 p.m. EDT on Thursday the center of the tropical depression was located at latitude 13.3°N and longitude 129.7°E which put it about 400 miles (645 km) east of Legazpi, Philippines. The tropical depression 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 1002 mb.

Typhoon Mindulle Passes South of Tokyo

Typhoon Mindulle passed south of Tokyo on Thursday. At 5:00 p.m. EDT on Thursday the center of Typhoon Mindulle was located at latitude 31.1°N and longitude 140.0°E which put it about 340 miles (545 km) south of Tokyo, Japan. Mindulle was moving toward the northeast at 17 m.p.h. (28 km/h). The maximum sustained wind speed was 90 m.p.h. (145 km/h) and there were wind gusts to 105 m.p.h. (165 km/h). The minimum surface pressure was 969 mb.

The core of Typhoon Mindulle passed well to the south of Tokyo on Thursday. However, the circulation around Typhoon Mindulle was so large, that bands of showers and thunderstorms on the northern periphery of Mindulle were bringing gusty winds and rain to parts of Honshu. Winds to typhoon force extended out 130 miles (210 km) on the eastern side of Typhoon Mindulle. Winds to typhoon force extended out 75 miles in the western half of Mindulle. Winds to tropical storm force extended out 310 miles (500 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Mindulle was 13.9. The Hurricane Size Index (HSI) was 37.6 and the Hurricane Wind intensity Size Index (HWISI) was 51.5.

Typhoon Mindulle weakened as it moved over cooler water and into a region where westerly winds in the upper levels caused more vertical wind shear. A larger eye was present at the center of Mindulle, but breaks were developing in the ring of thunderstorms around the eye. The upper level westerly winds in the middle latitudes were beginning to affect the structure of Typhoon Mindulle. Those winds were blowing toward the top of Mindulle’s circulation and they were causing increasing vertical wind shear. The strongest thunderstorms were occurring in bands north and east of the center of the typhoon. Bands south and west of the center consisted primarily of showers and lower clouds. The combination of cooler water and more wind shear was causing Typhoon Mindulle to start a transition to an extratropical cyclone.

The westerly winds in the upper levels will steer Typhoon Mindulle quickly toward the northeast during the next 48 hours. On its anticipated track the core of Mindulle will pass well to the east of Honshu and Hokkaido. Bands on the northern side of Typhoon Mindulle could bring gusty winds and heavy rain to coastal parts of northern Honshu and eastern Hokkaido. Big waves will affect shipping southeast of Japan. Mindulle will weaken gradually during the next 48 hours while it makes a transition to an extratropical cyclone.

Typhoon Mindulle Strengthens Back to Equivalent of a Major Hurricane

Typhoon Mindulle strengthened back to the equivalent of a major hurricane west-southwest of Iwo To on Tuesday. At 5:00 p.m. EDT on Tuesday the center of Typhoon Mindulle was located at latitude 23.0°N and longitude 135.6°E which put it about 390 miles (630 km) west-southwest of Iwo To. Mindulle was moving toward the north at 7 m.p.h. (11 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 950 mb.

Typhoon Mindulle strengthened back to the equivalent of a major hurricane after it completed several Eyewall Replacement Cycles. A large circular eye with a diameter of 45 miles (75 km) was present at the center of Typhoon Mindulle. The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Mindulle. Storms near the core generated upper level divergence that pumped mass away from the typhoon.

The circulation around Typhoon Mindulle grew even larger after it completed the Eyewall Replacement Cycles. Winds to typhoon force extended out 70 miles (110 km) from the center of Mindulle. Winds to tropical storm force extended out 235 miles (380 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Mindulle was 22.1. The Hurricane size Index (HSI) was 27.4 and the Hurricane Wind Intensity Size Index (HWISI) was 49.5.

Typhoon Mindulle will move through an environment capable of sustaining a powerful typhoon during the next 36 hours. Mindulle will move over water where the Sea Surface Temperatures are near 29˚C. It will move into a region where the upper level winds are weak and there will be little vertical wind shear. Typhoon Mindulle could strengthen gradually during the next 36 hours.

Typhoon Mindulle will move around the western end of a subtropical high pressure system over the Western North Pacific Ocean during the next 48 hours. The high pressure system will steer Mindulle toward the north during the next 24 hours. Typhoon Mindulle will start to move toward the northeast after it moves around the western end of the high. On its anticipated track Typhoon Mindulle will pass west of Iwo To during the next 24 hours. Mindulle cold be south of Tokyo in 48 hours.

Typhoon Mindulle Develops Concentric Eyewalls

Large Typhoon Mindulle developed concentric eyewalls southwest of Iwo To on Sunday. At 11:00 p.m. EDT on Sunday the center of Typhoon Mindulle was located at latitude 19.9°N and longitude 136.4°E which put it about 445 miles (720 km) southwest of Iwo To. Mindulle moving toward the north at 3 m.p.h. (5 km/h). The maximum sustained wind speed was 125 m.p.h. (200 km/h) and there were wind gusts to 150 m.p.h. (240 km/h). The minimum surface pressure was 947 mb.

Typhoon Mindulle developed concentric eyewalls on Sunday when the inner end of a rainband wrapped around an existing eye and eyewall. When the larger outer eyewall formed, much of the low level convergence of air shifted to the outer eyewall. The inner eyewall began to weaken because there was less low level convergence into it. Since the strongest winds were occurring in the existing inner eyewall, the maximum wind speed decreased when it weakened. The inner eyewall was still present, although it was much weaker. There was a break in the northwestern part of the outer eyewall. The existence of the two eyewalls was disrupting the inner core of Typhoon Mindulle.

The ongoing Eyewall Replacement Cycle was causing the circulation around Typhoon Mindulle to get larger. Winds to typhoon force extended out 65 miles (105 km) from the center of Mindulle. Winds to tropical storm force extended out 205 miles (330 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Mindulle was 23.6. The Hurricane size Index (HSI) was 23.2 and the Hurricane Wind Intensity Size Index (HWISI) was 46.8.

Typhoon Mindulle will move through an environment capable of sustaining a powerful typhoon during the next 36 hours. Mindulle will move over water where the Sea Surface Temperatures are near 30˚C. It will move into a region where the upper level winds are weak and there will be little vertical wind shear. The ongoing Eyewall Replacement Cycle will likely cause Typhoon Mindulle to weaken during the next 12 hours. If the inner eyewall dissipates and the outer eyewall becomes more well developed, then Mindulle could strengthen again. Typhoon Mindulle will move slowly. The strong winds in Mindulle could mix cooler water to the surface. Cooler water and an Eyewall Replacement Cycle could limit the potential for Typhoon Mindulle to intensify.

Typhoon Mindulle will move around the western end of a subtropical high pressure system over the Western North Pacific Ocean during the next several days. The high will steer Mindulle slowly toward the north-northwest during the next 36 hours. On its anticipated track Typhoon Mindulle could be west of Iwo To in 48 hours. Mindulle could be south of Tokyo in four days.