Category Archives: Western North Pacific

Western Pacific Typhoons and Tropical Storms

Typhoon Malou Brings Strong Winds, Rain to Ogasawara Islands

Typhoon Malou brought strong winds and heavy rain to the Ogasawara Islands on Thursday morning. At 5:00 a.m. EDT on Thursday the center of Typhoon Malou was located at latitude 25.6°N and longitude 141.2°E which put it about 15 miles (25 km) east of Iwo To. Malou was moving toward the north-northeast at 16 m.p.h. (26 km/h). The maximum sustained wind speed was 100 m.p.h. (165 km/h) and there were wind gusts to 125 m.p.h. (200 km/h). The minimum surface pressure was 967 mb.

The strong inner core of Typhoon Malou passed directly over Iwo To on Thursday morning. An eye with a diameter of 35 miles (55 km) was at the center of Malou. The eye was surrounded by a broken ring of thunderstorms and the strongest winds were occurring in that ring of storms. Winds to typhoon force extended out 70 miles (110 km) from the center of Malou. Winds to tropical storm force extended out 175 miles (280 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Malou was 16.5. The Hurricane Size Index (HSI) was 20.6 and the Hurricane Wind Intensity Size Index (HWISI) was 37.1.

An upper level trough near Japan will steer Typhoon Malou toward the northeast during the next several days. On its anticipated track Malou will move away from the Ogasawara Islands. Typhoon Malou will pass well to the southeast of the larger islands of Japan.

Typhoon Malou will move into an environment unfavorable for tropical cyclones during the next few days. Malou will move over water where the Sea Surface Temperatures are cooler. The upper level trough near Japan will produce stronger southwesterly winds that will blow toward the top of Malou’s circulation. The vertical wind shear will increase as the upper level winds get stronger. The combination of cooler water and stronger vertical wind shear will cause Typhoon Malou to weaken. The cooler water and stronger shear will also cause Malou to make a transition to an extratropical cyclone during the next few days.

Typhoon Malou Nears Iwo To

Typhoon Malou neared Iwo To on Wednesday night. At 11:00 p.m. EDT on Wednesday the center of Typhoon Malou was located at latitude 24.2°N and longitude 141.3°E which put it about 100 miles (160 km) south-southwest of Iwo To. Malou was moving toward the north-northeast at 14 m.p.h. (22km/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 970 mb.

Typhoon Malou strengthened as it moved closer to Iwo To on Wednesday night. A very large eye with a diameter of 90 miles (145 km) was at the center of Malou. Several smaller counterclockwise circulations were rotating within the eye. 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 large core of Typhoon Malou. Storms near the core generated upper level divergence that pumped mass away to the northeast of the typhoon.

The size of Typhoon Malou’s circulation increased on Wednesday. Winds to typhoon force extended out 60 miles (95 km) from the center of Malou. Winds to tropical storm force extended out 175 miles (280 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Malou was 13.9. The Hurricane Size Index (HSI) was 14.6 and the Hurricane Wind Intensity Size Index (HWISI) was 28.5.

Typhoon Malou will move through an environment favorable for intensification during the next 18 hours. Malou will move over water where the Sea Surface Temperatures are near 28˚C. An upper level trough near Japan will produce southwesterly winds that will blow toward the top of Malou’s circulation. However, the winds in the lower levels of the atmosphere will also blow from the southwest and so there will not be a lot of vertical wind shear. Typhoon Malou is could strengthen during the next 18 hours. The upper level winds will get stronger on Friday and the vertical wind shear will increase. Malou is likely to weaken and to begin a transition to an extratropical cyclone when the wind shear increases.

An upper level trough over Japan will steer Typhoon Malou toward the north-northeast during the next 24 hours. On its anticipated track Typhoon Malou could make a direct hit on Iwo To in a few hours. Typhoon Malou will bring strong winds and heavy rain to Iwo To. The eyewall with the strongest winds is likely to pass over Iwo To. The wind could blow at tropical storm force or greater for several hours. Malou will be capable of causing serious damage on Iwo To. In addition, heavy rain could also cause flash floods.

Malou Strengthens to a Typhoon South-southwest of Iwo To

Former Tropical Storm Malou strengthened to a typhoon over the Western North Pacific Ocean south-southwest of Iwo To on Tuesday night. At 11:00 p.m. EDT on Tuesday the center of Typhoon Malou was located at latitude 21.0°N and longitude 139.4°E which put it about 310 miles (500 km) south-southwest of Iwo To. Malou was moving toward the north-northeast at 3 m.p.h. (5 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. 145 km/h). The minimum surface pressure was 981 mb.

Former Tropical Storm Malou intensified to a typhoon on Tuesday night. The inner end of a rainband wrapped around the center of Typhoon Malou and an eye appeared intermittently on satellite images. A broken ring of thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Malou’s circulation. Storms near the core generated upper level divergence that pumped mass away from the typhoon. Winds to typhoon force extended out 80 miles (130 km) from the center of Malou. Winds to tropical storm force extended out 165 miles (270 km) from the center of circulation.

Typhoon Malou will move through an environment favorable for intensification during the next 24 hours. Malou will move over water where the Sea Surface Temperatures are near 29˚C. It will move under an upper level ridge south of Japan. The upper level winds are weak in the ridge and there will be little vertical wind shear. The upper level ridge will enhance divergence which will cause the surface pressure to decrease. Typhoon Malou is likely to strengthen during the next 24 hours. Malou could intensify rapidly if an inner core with an eye and a complete eyewall develops.

An upper level trough over Japan will steer Typhoon Malou toward the north-northeast during the next 24 hours. On its anticipated track Typhoon Malou could make a direct hit on Iwo To in 24 hours. Typhoon Malou will bring strong winds and heavy rain to Iwo To. Malou will be capable of causing serious damage on Iwo To. Heavy rain could also cause flash floods.

Tropical Storm Malou Forms West of the Marianas

Tropical Storm Malou formed west of the Marianas on Sunday night. At 11:00 p.m. EDT on Sunday the center of Tropical Storm Malou was located at latitude 16.5°N and longitude 138.1°E which put it about 515 miles (830 km) west-northwest of Saipan. Malou was moving toward the north-northwest 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 1003 mb.

The circulation around a low pressure system over the Western North Pacific Ocean west of the Marianas strengthened on Sunday night and the Japan Meteorological Agency designated the system as Tropical Storm Malou. The circulation around Tropical Storm Malou was still organizing. There was a broad center of circulation, but there were not many thunderstorms near the center of Malou. Several long rainbands were revolving around the broad center of circulation. The strongest winds were occurring in the eastern half of Malou. Winds to tropical storm force extended out 185 miles (295 km) on the eastern side of Malou. The winds in the western half of Malou’s circulation were blowing at less than tropical storm force.

Tropical Storm Malou will move through an environment favorable for intensification during the next 48 hours. Malou will move over water where the Sea Surface Temperatures are near 29˚C. It will move under an upper level ridge near the Marianas. The upper level winds are weak in the ridge and there will be little vertical wind shear. Tropical Storm Malou is likely to intensify steadily during the next 48 hours. Malou could strengthen to a typhoon in 48 hours.

Tropical Storm Malou will move around the western end of a high pressure system over the Western North Pacific Ocean. The high pressure system will steer Malou toward the west-northwest during the next 48 hours. Tropical Storm Malou will turn toward the northeast after it moves around the western end of the ridge. On its anticipated track Malou could approach Iwo To in three days. Malou could be a typhoon when it approaches Iwo To.

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.