Category Archives: Western North Pacific

Western Pacific Typhoons and Tropical Storms

Intensifying Typhoon Koppu Moving Toward Northern Luzon

Typhoon Koppu intensified on Thursday as it continued to move steadily toward Northern Luzon.  At 11:00 p.m. EDT the center of Typhoon Koppu was located at latitude 15.6°N and longitude 126.9°E which put it about 425 miles (685 km) east of Manila, Philippines.  Koppu was moving toward the west at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 90 m.p.h. (145 km/h) and there were wind gusts to 115 m.p.h. (185 km/h).  The minimum surface pressure was 969 mb.

Typhoon Koppu is moving over water where the Sea Surface Temperature is near 30°C.  The upper level winds lessened on Thursday which decreased the vertical wind shear and allowed Koppu to intensify more quickly.  The core of the circulation consolidated and there are suggestions that an eyewall may be forming.  Koppu is expected to move through a favorable environment until it reaches northern Luzon and further intensification is very likely.

A subtropical ridge is steering Koppu toward the west and that general steering pattern is expected to continue for another 36 to 48 hours.  On its anticipated track, Typhoon Koppu will approach northern Luzon in 36 to 42 hours.  It could bring strong winds, heavy rain and a storm surge when it reaches that area.  The heavy rain could produce floods and mudslides as Koppu moves over northern Luzon.

Tropical Storm Champi Passing Through the Northern Marianas

Tropical Storm Champi is bringing gusty winds and heavy rain as it moves through the Northern Marianas.  At 11:00 p.m. EDT on Thursday the center of Tropical Storm Champi was centered near latitude 15.9°N and longitude 146.3°E which put it about 80 miles (135 km) east-northeast of Saipan.  Champi was moving toward the west at 19 m.p.h. (31 km/h).  The maximum sustained wind speed was 70 m.p.h. (115 km/h) and there were wind gusts to 85 m.p.h. (135 km/h).  The minimum surface pressure was 980 mb.  A Tropical Storm Warning remains in effect for Rota, Tinian, Saipan, Alamagan, Pagan and Agrihan.  The weather station at the airport on Saipan was reporting southwesterly winds at 46 m.p.h. (74 km/h) with gusts to 78 m.p.h. (126 km/h).

Although an upper level ridge north of Champi continued to cause vertical wind shear over the tropical storm, it slowly intensified on Thursday.  More thunderstorms formed near the center of circulation and those storms are generating more upper level divergence.  The core of the circulation is consolidating and more spiral bands are forming outside the core.  Champi is on the threshold of becoming a typhoon.  It is moving over water where the Sea Surface Temperature is near 29°C.  Champi is likely to move into an area where the upper level winds are lighter during the weekend and it will continue to intensify during the next several days.

A subtropical ridge is steering Champi toward the west and that motion is expected to continue for the next 12 to 24 hours.  After that time Champi will reach the western end of the ridge and turn toward the north.  Champi could be a strong typhoon south of Iwo To in about three days.

Tropical Storm Champi Intensifies, Warnings Issued for Northern Marianas

Tropical Storm Champi intensified on Wednesday and the National Weather Service issued watches and warnings for the northern Marianas.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Champi was located at latitude 15.5°N and longitude 151.9°E which put it about 450 miles (730 km) east of Saipan.  Champi was moving toward the west-northwest at 13 m.p.h. (21 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 984 mb.  Tropical Storm Warnings have been issued for Rota, Tinian, Saipan, Alamagan, Pagan and Agrihan.  A Typhoon Watch has been issued for Alamagan, Pagan and Agrihan.

The circulation of Tropical Storm Champi is still organizing.  An upper level ridge north of the tropical storm is causing easterly winds to blow over the top of Champi.  The resulting vertical wind shear is causing most of the stronger thunderstorms to form in the western half of the circulation.  Champi is over water where the Sea Surface Temperature is near 29°C.  The vertical wind shear will inhibit intensification on Thursday, but Champi could reach typhoon intensity within 24 hours.  It is expected to move into an area where the upper level winds are lighter on Friday and the rate of intensification could increase.

A subtropical ridge is steering Champi on a track that is a little north of due west.  That general motion is expected to continue for the next several days.  Champi will reach the western end of the subtropical ridge and turn toward the north later in the weekend.  On its anticipated track Champi will approach the northern Marianas in 24 to 30 hours.  It could bring strong winds and heavy rain to those islands.  Since the strongest thunderstorms are west of the center of circulation, conditions could start to deteriorate on some of the islands in less than 24 hours.

Tropical Storm Koppu Forms North of Yap

In spite of significant vertical wind shear a surface circulation has been consolidating inside an area of thunderstorms north of Yap.  The system has been designated Tropical Storm Koppu.  At 5:00 p.m. EDT on Tuesday the center of Tropical Storm Koppu was located at latitude 15.7°N and longitude 137.1°E which put it about 430 miles (690 km) north of Yap.  Koppu was moving toward the west at 14 m.p.h. (23 km/h).  The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 993 mb.

Significant vertical wind shear is inhibiting the organization of Tropical Storm Koppu.  An upper level ridge north of Koppu is generating strong northeasterly winds over the top of the tropical storm.  The vertical wind shear is causing most of the strong thunderstorms to be located southwest of the center of circulation.  The only other deep convection is occurring in a band that is west of the core of the circulation.

Koppu is over water where the Sea Surface Temperature is near 30°C and so there is plenty of energy in the upper ocean.  The wind shear will inhibit intensification for another 24 to 48 hours before it starts to subside.  Koppu could intensify much more quickly later this week when it moves into an area where the upper level winds are lighter.  Koppu could become a typhoon withing 36 to 48 hours and it could be a strong typhoon by the end of the week.

A subtropical ridge is steering Tropical Storm Koppu quickly to the west.  That general motion is expected to continue for the rest of the week.  On its anticipated track Koppu could be approaching northern Luzon in about three or four days.  It could be a significant typhoon by that time.

Tropical Storm Choi-Wan Organizing Southeast of Japan

Tropical Storm Choi-Wan exhibited better organization on Monday as it moved southeast of Japan.  At 5:00 p.m. EDT on Monday the center of Tropical Storm Choi-Wan was located at latitude 23.4°N and longitude 151.4°W which put it about 615 miles (990 km) east of Iwo To.  Choi-Wan was moving toward the west-northwest at 12 m.p.h. (19 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 981 mb.

Tropical Storm Choi-Wan has a broad center of circulation without a tight inner core.  A rainband appears to be trying to wrap entirely around the broad center and other rainbands are forming outside the center.  Satellite images seem to indicate that Choi-Wan is slowly organizing.  Thunderstorms near the center of circulation are producing upper level divergence.

The environment favors intensification.  Choi-Wan is over water where the Sea Surface Temperature (SST) is near 29°C.  The upper level winds are light and there is little vertical wind shear.  Upper level outflow channels appear to be developing northeast and southwest of Choi-Wan.  If the tropical storm had a tight core, rapid intensification would be likely.  With a broader center of circulation, intensification will be more gradual.  Choi-Wan could become a typhoon on Tuesday.  When Choi-Wan moves farther north it will move over cooler SSTs and the wind shear will increase, which will weaken it.

Tropical Storm Choi-Wan is moving around the western end of a subtropical ridge.  The ridge is expected to steer Choi-Wan mainly toward the north during the next several days.  On its anticipated track, Choi-Wan could approach some of the northern islands of Japan in about three days.  Choi-Wan could be a tropical storm or a strong extratropical low pressure system at that time.

Typhoon Mujigae Making Landfall in China

Strong Typhoon Mujigae is making landfall on the coast of China near Zhanjiang.  At 11:00 p.m. EDT on Saturday the center of Typhoon Jiang was located at latitude 20.8°N and longitude 111.1°E which put it about 55 miles (90 km) southeast of Zhanjiang.  Mujigae was moving toward the northwest at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 110 m.p.h. (175 km/h) and there were wind gusts to 130 m.p.h. (215 km/h).  The minimum surface pressure was 949 mb.

The northwestern side of the eyewall is beginning to affect the coast of China.  Mujigae will bring strong winds and heavy rain as it moves inland over southern China.  The typhoon will begin to weaken as soon as the center moves over land and it will gradually spin down over southern China.

Tropical Storms Mujigae and Choi-Wan Form Over NW Pacific

Two new tropical storms with the names of Mujigae and Choi-Wan have formed over the western North Pacific Ocean.  At 11:00 a.m. EDT on Friday the center of Tropical Storm Mujigae was located at latitude 17.4°N and longitude 117.3°E which put it about 275 miles (445 km) northwest of Manila, Philippines.  Mujigae was moving toward the west-northwest at 17 m.p.h.  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 990 mb.

At 11:00 a.m. EDT on Friday the center of Tropical Storm Choi-Wan was located at latitude 19.2°N and longitude 166.4°E which put it about 15 miles (20 km) south-southeast of Wake Island.  Choi-Wan was moving toward the west-northwest at 3 m.p.h. (5 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.

Tropical Storm Mujigae organized quickly after the system move west of the Philippines.  A primary curved rainband wrapped around the western and southern sides of the center of circulation.  A possible eye is apparent intermittently on infrared satellite imagery.  Upper level divergence is beginning to occur both north and south of the center.  Mujigae is moving over water where the Sea Surface Temperature is near 28°C and there is not enough vertical wind shear to prevent intensification.  A period of rapid intensification is possible and Mujigae could become a typhoon in 12 to 24 hours.

A subtropical ridge is steering Mujigae toward the west-northwest and that general motion is expected to continue for the next several days.  On its anticipated track, Mujigae could be approaching the southern coast of China in 36 hours.  It could bring strong winds and heavy rain when it makes landfall.

Tropical Storm Choi-Wan is still in the organizational stage.  It has a large broad circulation without a well developed inner core.  Winds to tropical storm force are occurring in clusters of thunderstorms.  Choi-Wan is over Sea Surface Temperatures near 29°C, but there is moderate vertical wind shear over the northern part of the tropical storm.  The wind shear is expected to decrease in a day or two and Choi-Wan is forecast to become a typhoon.

Choi-Wan is between two subtropical ridges and the steering currents are relatively weak.  In a day or two the western ridge is expected to steer Choi-Wan toward the northwest.  Choi-Wan will cause squally weather on Wake Island for 24 to 48 hours.

Typhoon Dujan Making Landfall in China

Typhoon Dujuan moved across Taiwan on Monday and it is currently making another landfall on the east coast of China.  At 11:00 p.m. EDT the center of Typhoon Dujuan was located at latitude 25.3°N and longitude 118.6°E which put it near Putian, China.  Dujuan was moving toward the northwest at 13 m.p.h.  The maximum sustained wind speed was 85 m.p.h. (135 m.p.h.) and there were wind gusts to 105 m.p.h. (170 km/h).  The minimum surface pressure was 976 mb.

Dujuan brought strong winds and heavy rain when it moved across Taiwan.  It weakened as the center moved over the mountains on Taiwan, but its large size and intensity allow Dujuan to survive.  Dujuan was still a typhoon as it moved into the coast of eastern China near Putian.  It could produce heavy rainfall and flooding as it moves inland.  Dujuan should spin down gradually during the next few days as it moves farther into eastern China.

Large Dangerous Typhoon Dujuan Nearing Taiwan

Large and dangerous Typhoon Dujuan is nearing Taiwan.  At 11:00 p.m. EDT on Sunday the center of Typhoon Dujuan was located at latitude 23.5°N and longitude 123.2°W which put it about 185 miles (300 km) southeast of Taipei, Taiwan.  Dujuan was moving toward the west-northwest at 13 m.p.h. (21 km/h).  The maximum sustained wind speed was 145 m.p.h. (235 km/h) and there were wind gusts to 170 m.p.h. (275 km/h).  The minimum surface pressure was 912 mb.

Typhoon Dujuan is a very symmetrical storm with a large eye.  Winds to hurricane force extend out 60 miles from the center.  A weather station on Ishigaki Jima, Japan has reported winds over 54 m.p.h. (87 km/h) for the past five hours even though the center is passing south of that island.  The upper level winds around the typhoon are light and upper level divergence is pumping out mass in all directions  Typhoon Dujuan is likely to maintain its intensify until it makes landfall in Taiwan.  When the core of the typhoon moves over the mountains on Taiwan it will weaken.  However, given Dujuan’s size and intensity, it is likely to still be a typhoon when it moves west of Taiwan.

A subtropical ridge north of Dujuan is steering the typhoon toward the west-northwest and that general steering pattern is expected to continue.  On its anticipated track Dujuan will make landfall in northeastern Taiwan in less than 12 hours.  It will move across Taiwan and the center could reform northwest of that island.  Dujuan could make a landfall in China between Xiamen and Fuzhou in less than 24 hours.

Dujuan has the potential to be a very destructive typhoon.  It has a Hurricane Intensity Index of 29.9 and a Hurricane Size Index of 21.3.  Those numbers produce a Hurricane Wind Intensity Size Index of 51.2.  Those Indices suggest it is capable of producing widespread significant damage.  In addition to wind damage, Dujuan is capable of producing very heavy rainfall and floods.

Powerful Typhoon Dujuan Heads Toward Taiwan

Powerful Typhoon Dujuan turned west on Saturday and headed for Taiwan.  At 11:00 p.m. EDT on Saturday the center of Typhoon Dujuan was located at latitude 22.3°N and longitude 127.0°E which put it about 380 miles (610 km) east-southeast of Taipei, Taiwan and about 300 miles (480 km) south of Okinawa.  Dujuan was moving toward the west at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 130 m.p.h. (210 km/h) and there were wind gusts to 160 m.p.h. (260 km/h).  The minimum surface pressure was 925 mb.

Dujuan continued to intensify on Saturday and it is a powerful well organized typhoon.  Dujuan has a large symmetrical eye which is surrounded by strong thunderstorms.  Upper level divergence is pumping out mass and the surface pressure is decreasing.  Dujuan is over warm Sea Surface Temperatures and there is not much vertical wind shear.  Further intensification is possible, although if concentric eyewalls form, it could disrupt the intensification trend.

An upper level ridge north of Dujuan steered the typhoon a little north of due west on Saturday.  That general motion is expected to continue for another day or two.  On its anticipated track Dujuan will pass near the southwestern Ryukyu Islands in about 24 hours.  It will approach Taiwan in about 30 hours and it could reach China in less than two days.  Dujuan is a large powerful typhoon and it will bring strong winds and heavy rain.  It could produce flooding in parts of Taiwan and eastern China.