Category Archives: Western North Pacific

Western Pacific Typhoons and Tropical Storms

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.

Dujuan Reaches Typhoon Intensity South of Okinawa

Tropical Storm Dujuan continued to strengthen on Thursday and it reached typhoon intensity.  At 11:00 p.m. EDT on Thursday the center of Typhoon Dujuan was located at latitude 19.4°N and longitude 132.1°E which put it about 575 miles (930 km) south-southeast of Okinawa.  Dujuan was moving toward the north-northwest at 4 m.p.h. (6 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 980 mb.

The circulation around Typhoon Dujuan is becoming increasingly well organized.  A spiral band wrapped entirely around the center of circulation creating a large eye in the middle of the typhoon.  Additional spiral bands are forming, especially in the southern half of the circulation.  Thunderstorms in the eyewall are generating upper level divergence which is increasing with time.  Recent satellite images suggest that they eye may be contracting which would be another sign of intensification.

Dujuan is in an environment that favors intensification.  The Sea Surface Temperatures are warm and the speed of the upper level winds is decreasing.  An upper level ridge west of Dujuan is producing some northerly winds over the top of the typhoon, but the vertical wind shear is decreasing.  Intensification is likely and a period of rapid intensification is possible.  Dujuan could become the equivalent of a major hurricane in 24 to 48 hours.

Typhoon Dujuan is between a subtropical ridge to its northeast and another ridge to its northwest.  As a result, it moved slowly toward the northwest on Thursday.  Dujuan is expected to continue to move in a general northwesterly direction for another day or two.  The ridge west of Dujuan is expected to extend north of the typhoon during the weekend.  When the ridge extends north of Dujuan, it will steer the typhoon more toward the west.

On its anticipated track Typhoon Dujuan could approach the southwestern Ryukyu Islands including Ishigaki JIma in 60 to 72 hours.  Dujuan could be near Taiwan in about three and a half days and it could reach the coast of China in less than five days.  Dujuan could be a large and powerful typhoon capable of bringing strong winds and heavy rain by the time it reaches those areas.

Tropical Storm Dujuan Intensifying Southeast of Okinawa

After several days where vertical wind shear pushed most of the thunderstorms west of the core of the circulation, Tropical Storm Dujuan began to intensify on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Dujuan was located at latitude 18.9°N and longitude 132.7°E which put it about 620 miles (1000 km) southeast of Okinawa.  Dujuan was moving toward the west-northwest at 10 m.p.h. (16 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.

The circulation near the core of Tropical Storm Dujuan is showing more organization.  Thunderstorms are developing closer to the center of circulation, although most of the stronger storms are still south and southwest of the center.  The distribution of thunderstorms is an indication that an upper level ridge west of Dujuan is still generating northeasterly winds over the top of the tropical storm.  Some of the storms closer to the center of circulation are starting to generate upper level divergence.

Dujuan is over water where the Sea Surface Temperatures are near 30°C.  Intensification is likely but vertical wind shear could limit the rate of intensification in the short term.  The wind shear is likely to decrease in a day or two as Dujuan moves into an area where the upper level winds are lighter.  Dujuan could become a typhoon within 24 to 36 hours and it could reach the equivalent of a major hurricane during the weekend.

Tropical Storm Dujuan is being steered toward the west-northwest by a subtropical ridge located to its northeast,  That general steering patter is expected to continue for another 24 to 36 hours.  At that time Dujuan will be between the ridge to its east and another upper level ridge to its west, and it could turn toward the northwest for a day or so.  The western ridge is expected to build north of Dujuan and turn it more toward the west in three or four days.  On its anticipated track Dujuan could approach the southern islands of Japan in three or four days.  It could be near Taiwan in five days.  Dujuan could be a strong typhoon by that time.

Typhoon Krovanh Nearing Iwo To

Typhoon Krovanh continued to intensify on Thursday and it is now the equivalent of a Major Hurricane.  At 11:00 p.m. EDT on Thursday the center of Typhoon Krovanh was located at latitude 24.1°N and longitude 142.5°E which put it about 105 miles (170 km) southeast of Iwo To.  Krovanh was moving toward the north-northwest at 10 m.p.h. (16 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 935 mb.  The weather station on Iwo To is currently reporting sustained winds of 33 m.p.h. (53 km/h) with wind gusts to 48 m.p.h. (77 km/h).

Typhoon Krovanh has probably reached its peak intensity.  It may be pulling in some drier air from the northwest.  It also looks like an upper level trough near Japan is beginning to cause southwesterly winds over the top of the typhoon.  There is a gap in the eyewall on the south side and clouds are beginning to obscure the eye on satellite imagery.  Vertical wind shear will increase as Krovanh moves farther north and it gets closer to the upper level trough.  Krovanh will also start to move over cooler Sea Surface Temperatures which will increase the rate at which it weakens.

Typhoon Krovanh is moving around the western end of the subtropical ridge that has been steering it.  It will start to turn toward the northeast on Friday as the upper level trough begins to steer the typhoon.  On its anticipated track the center of Krovanh will pass within about 50 to 60 miles (80 to 95 km) of Iwo To during the next few hours and then it will be very near Chichi Jima in about 18 hours.  Krovanh could cause gusty winds, heavy rain and large waves as it passed near those two islands.

Krovanh Becomes a Typhoon Southeast of Iwo To

Krovanh continued to intensify rapidly on Wednesday and it reached typhoon status.  At 11:00 p.m. EDT on Wednesday the center of Typhoon Krovanh was located at latitude 21.5°N and longitude 144.5°E which put it about 330 miles (530 km) southeast of Iwo To.  Krovanh was moving toward the northwest at 13 m.p.h. (21 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 961 mb.

Typhoon Krovanh remains in a very favorable environment.  It is over water with warm Sea Surface Temperatures and the upper level winds are light.  The absence of significant vertical wind shear has allowed upper level divergence to continue to pump away mass in all directions.  The structure of the inner core of Krovanh improved as it intensified and the typhoon now has a well developed eye surrounded by a nearly complete eyewall.  The favorable environment could allow Krovanh to intensify for another 24 to 36 hours.  When the typhoon begins to approach latitude 30°N, it will begin to be affected by the upper level westerly winds in the middle latitudes.  The increased vertical wind shear will begin to weaken Krovanh.

Typhoon Krovanh is moving around the western end of a subtropical ridge.  The ridge should steer Krovanh toward the northwest for another 24 hours.  When it reaches the western end of the ridge, the typhoon will start moving toward the north.  As the upper level westerly winds start to affect Krovanh, those winds will accelerate it toward the northeast.  On its anticipated track Krovanh could be approaching Iwo To in about 24 hours and it could be near Chichi Jima in about 36 hours.  Krovanh could be a strong typhoon when it passes those islands.

Tropical Storm Krovanh Organizing Quickly Near Northern Marianas

The circulation around Tropical Storm Krovanh is organizing quickly as it passes near the northern Marianas.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Krovanh was located at latitude 19.3°N and longitude 148.1°E which put it about 170 miles (275 km) east-northeast of Agrihan in the northern Mariana Islands.  Krovanh was moving toward the northwest at 11 m.p.h. (18 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 995 mb.  A Tropical Storm Watch has been issued for Alamagan, Pagan and Agrihan in the northern Marianas.

The circulation near the center of Krovanh organized quickly on Tuesday.  A primary spiral rainband wrapped around the southern side of the center and an eyelike feature has appeared intermittently on visible satellite imagery.  Additional rainbands are developing around the circulation.  The thunderstorms near the core of the tropical storm are producing upper level outflow in all directions which is pumping out mass and is allowing the surface pressure to decrease.

Tropical Storm Krovanh is moving over water where the Sea Surface Temperature is near 30°C.  Upper levels winds are light and there is little vertical wind shear.  The environment is very favorable for further intensification and rapid intensification is likely.  Krovanh could become a typhoon within 24 hours and it could be a strong typhoon within several days.

A subtropical ridge located northeast of Krovanh is steering the tropical storm toward the northwest.  That general steering pattern is expected to continue for the next 48 hours.  After that time Krovanh will reach the western end of the subtropical ridge and it will turn toward the north.  On its anticipated track Krovanh will pass through the extreme northern Marianas on Wednesday and it be approaching Iwo To in about 48 hours.  Krovanh could be a strong typhoon at that time.

Tropical Storm Vamco Forms East of Vietnam

A large area of low pressure east of Vietnam developed enough organization on Sunday to be classified as Tropical Storm Vamco.  At 11:00 p.m. EDT on Sunday the center of Tropical Storm Vamco was located at latitude 14.8°N and longitude 110.0°E which put it about 160 miles (260 km) east-southeast of Da Nang, Vietnam.  Vamco was moving toward the west at 10 m.p.h. (16 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.

Although there is a large area of low pressure, the circulation around Tropical Storm Vamco is not well organized.  Most of the thunderstorms are located in a large rainband about 100 miles (160 km) from the center of circulation that wraps around the northern and western parts of the storm.  There are not many thunderstorms located near the center of the circulation.  Vamco is located over water where the Sea Surface Temperature is near 30°C.  However, an upper level ridge is generating northeasterly winds over the top of the storm and the vertical wind shear is inhibiting development.  Some intensification is possible in the short term, but the lack of a well formed inner core and proximity to land will limit strengthening.

A subtropical ridge north of Vamco is steering the tropical storm toward the west and that steering pattern is expected to continue.  On its anticipated track the center of Vamco will reach the central coast of Vietnam in about 18 hours.  The primary impacts will be locally heavy rainfall and the potential for flooding.