Category Archives: Western North Pacific

Western Pacific Typhoons and Tropical Storms

Tropical Storm Wipha Brings Wind and Rain to South China

Tropical Storm Wipha brought wind and rain to south China on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Wipha was located at latitude 20.5°N and longitude 110.6°E which put it about 50 miles (80 km) southeast of Leizhou, China.  Wipha was moving toward the west-northwest at 8 m.p.h. (13 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 990 mb.

The circulation around Tropical Storm Wipha contained a large rainband in the southern half of the tropical storm and another large rainband in the northern half of the circulation.  The rainband in the southern half of Wipha brought wind and rain to Hainan Island.  The rainband in the northern part of the tropical storm brought wind and rain to south China including Hong Kong.  Persistent heavy rain was creating the potential for flash floods in parts of southern China.

Tropical Storm Wipha was moving around the southwestern part of a subtropical ridge over the Western North Pacific Ocean.  The ridge will steer Wipha toward the west-northwest during the next 24 to 36 hours.  On its anticipated track Tropical Storm Wipha will move close to the coast of south China and northeastern Vietnam.  Wipha will continue to bring gusty winds and drop locally heavy rain over those regions on Thursday.

Tropical Storm Wipha Forms South of Macau

Tropical Storm Wipha formed south of Macau late on Tuesday.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Wipha was located at latitude 18.8°N and longitude 112.6°E which put it about 175 miles (285 km) south of Macau.  Wipha was moving toward the northwest at 6 m.p.h. (10 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 Tropical Storm Wipha was large, but Wipha did not have a well formed inner core.  Winds to tropical storm force extended out about 200 miles (320 km) from the center of circulation.  However, there were no strong thunderstorms near the center.  Stronger thunderstorms were occurring in bands well to the south and east of the center of circulation.  Bands northwest of the center consisted primarily of showers and lower clouds.

The large lower level circulation of Tropical Storm Wipha was just to the southeast of an upper low over the northwestern part of the South China Sea.  The upper low was circulating some drier air over the northwestern part of Wipha.  It was also causing some vertical wind shear.  The drier air and wind shear were inhibiting the formation of thunderstorms in the northwestern part of Tropical Storm Wipha.

Tropical Storm Wipha will move through an environment somewhat favorable for intensification during the next 24 hours.  Wipha will move over water where the Sea Surface Temperature is near 30°C.  The upper low will continue to inhibit the strengthening of Tropical Storm Wipha.  If thunderstorms begin to develop near the center of Wipha, then the tropical storm could strengthen.

Tropical Storm Wipha will move around the southwestern part of a subtropical ridge over the Western North Pacific Ocean.  The ridge will steer Wipha toward the northwest during the next 24 hours.  On its anticipated track the center of Tropical Storm Wipha will be near the northern part of Hainan Island and the south coast of China in 18 to 24 hours.  Wipha could move more toward the west when it reaches the Gulf of Tongking.  Although Tropical Storm Wipha will bring gusty winds to southern China and northern Vietnam, locally heavy rain and the potential for floods will be greater risks.

Tropical Storm Nari Drops Heavy Rain on Honshu

Tropical Storm Nari dropped locally heavy rain and producing gusty winds on Honshu on Friday night.  At 11:00 p.m. EDT on Friday the center of Tropical Storm Nari was located at latitude 35.2°N and longitude 137.0°E which put it about 10 miles (15 km) east of Nagoya, Japan.  Nari was moving toward the north-northeast 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 1000 mb.

Tropical Storm Nari was dropping locally heavy rain over parts of central Honshu.  The heaviest rain was falling in bands located in the western half of the circulation.  Heavier rain was falling in the area between Nagoya, Osaka and Kyoto.  Bands of heavier rain were also falling north of Nagoya.  Most of the bands in the eastern half of Tropical Storm Nari consisted primarily lighter showers and lower clouds.  The heavier rain could produce flash flooding in some locations.

Tropical Storm Nari will move more toward the east-northeast on Saturday.  The center of Nari is forecast to pass north of Tokyo.  Tropical Storm Nari will continue to drop locally heavy rain over central and eastern Honshu when it moves over those locations.

Tropical Storm Nari Develops South of Japan

Tropical Storm Nari developed south of Japan on Thursday night.  The Japan Meteorological Agency designated a low pressure system south of Honshu as Tropical Storm Nari when the maximum sustained wind speed reached 40 m.p.h. (65 km/h).  At 11:00 p.m. EDT on Thursday the center of Tropical Storm Nari was located at latitude 30.2°N and longitude 136.9°E which put it about 350 miles (565 km) south of Nagoya, Japan.  Nari was moving toward the north at 14 m.p.h. (22 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.

The circulation around Tropical Storm Nari exhibited more of a hybrid structure than the structure of a pure tropical cyclone.  Tropical Storm Nari developed when an upper level low pressure system stalled south of the Japan.  A surface circulation formed beneath the upper low and then more thunderstorms formed closer to the center of circulation.  The original upper level low was located southwest of the surface low on Thursday night.  The upper level low was producing southwesterly winds which were blowing across the surface low.  Those winds were creating vertical wind shear.  The circulation around Tropical Storm Nari showed evidence of the effect of that wind shear.  The stronger thunderstorms were in a band that curved around north and west of the center of circulation.  Bands south and east of the center consisted primarily of showers and lower clouds.  The wind field around Tropical Storm Nari was also asymmetric.  Winds to tropical storm force extended out about 115 miles (185 km) to the east of the center of circulation, but only extended out about 60 miles (95 km) to the west of the center.

Tropical Storm Nari will move through an environment only marginally favorable for intensification.  Nari will move over water where the Sea Surface Temperature is near 28°C.  The upper low will continue to cause vertical wind shear, which will inhibit intensification.  The upper low will also pull some drier air around the southern side of the circulation.  Nari could strengthen a little during the next 24 hours if more thunderstorms develop closer to the center of circulation.  Tropical Storm Nari will move under stronger westerly winds in about a day or so.  Those winds will cause more vertical wind shear and they should prevent further intensification.

Tropical Storm Nari will be steered by the interaction of the upper low and a subtropical ridge over the western North Pacific Ocean.  Those two features are likely to steer Nari toward the north during the next 24 hours.  On its anticipated track Tropical Storm Nari could approach the coast of Honshu near Nagoya in about 24 hours.  Nari will move more toward the east when it reaches the stronger westerly winds in a day or so.  Tropical Storm Nari could bring gusty winds and locally heavy rain to central Honshu on Saturday.

Tropical Storm Danas Speeds Toward South Korea

Tropical Storm Danas sped toward South Korea on Friday as it moved quickly north-northeast over the East China Sea.  At 11:00 a.m. EDT on Friday the center of Tropical Storm Danas was located at latitude 32.3°N and longitude 125.1°E which put it about 190 miles (305 km) south-southwest of Mopko, South Korea.  Danas was moving toward the north-northeast at 19 m.p.h. (30 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 987 mb.

The distribution of thunderstorms around Tropical Storm Danas remained asymmetrical on Friday.  The strongest thunderstorms were occurring in bands well to the east of the center of circulation.  Bands closer to the center and on the western side of the circulation consisted primarily of showers and lower clouds.  An upper level trough over eastern China was producing southwesterly winds which were blowing toward the top of the circulation.  Those winds were causing moderate vertical wind shear and they were the reason for the asymmetrical distribution of thunderstorms.  The wind field also exhibited the effects of the wind shear.  Winds to tropical storm force extended out about 200 miles (320 km) from the center of Danas on the eastern side of the circulation, but only extended out about 120 miles (195 km) on the western side of the tropical storm.

Tropical Storm Danas will remain in an environment only marginally favorable for intensification until it makes landfall in South Korea.  Danas will move over water where the Sea Surface Temperature is near 30°C.  The upper level trough over eastern China will continue to cause moderate vertical wind shear.  Tropical Storm Danas could intensify a little during the next 12 hours, but it will weaken after the center moves over South Korea.

Tropical Storm Danas will move around the western end of a subtropical ridge over the western North Pacific Ocean.  The ridge and the upper level trough will interact to steer Danas rapidly toward the north-northeast.  On its anticipated track the center of Tropical Storm Danas will make landfall on the southwestern coast of South Korea in about 12 hours.  Danas will bring gusty winds and locally heavy rain to South Korea on Saturday.  The heaviest rain will fall over the southeastern half of South Korea.  Locally heavy rain in that region could cause flash floods.  The outer rainbands of Tropical Storm Danas could also drop locally heavy rain over western Kyushu.

Tropical Storm Danas Nears Southern Ryukyu Islands

Tropical Storm Danas moved near the southern Ryukyu Islands late on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Danas was located at latitude 23.9°N and longitude 124.1°E which put it about 30 miles (50 km) south of Ishigaki, Japan.  Danas was moving toward the north at 21 m.p.h. (34 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 990 mb.

The circulation around Tropical Storm Danas exhibited a little more organization on Wednesday.  More thunderstorms formed near the center of circulation and several bands of showers and thunderstorms formed in the eastern half of the circulation.  The bands north and west of the center consisted primarily of showers and lower clouds.  Storms near the center began to generate upper level divergence which pumped mass away to the northeast of the tropical storm.  Winds to tropical storm force extended out about 125 miles (200 km) from the center of circulation.

Tropical Storm Danas will move into an environment somewhat favorable for intensification.  Danas will move over water where the Sea Surface Temperature is near 30°C.  A small upper level low near Taiwan will produce southwesterly winds which blow toward the top of the circulation around Tropical Storm Danas.  Those winds were the reason why the stronger rainbands were in the eastern half of the circulation.  Those winds will cause moderate vertical wind shear, which will inhibit intensification.  However, the shear will have less of an effect since Danas will move in the same direction as the upper level winds.  Tropical Storm Danas is likely to intensify during the next 24 hours and there is a chance it could strengthen into a typhoon.

Tropical Storm Danas will move around the western end of a subtropical ridge over the western North Pacific Ocean.  The ridge will steer Danas toward the north-northeast.  On its anticipated track Tropical Storm Danas will move through the southern Ryukyu Islands during the next few hours.  Danas will bring gusty winds and locally heavy rain when it passes over those islands.  Tropical Storm Danas will move over the East China Sea toward southwestern Japan and South Korea during the next several days.

Tropical Storm Danas Forms East of Luzon

Tropical Storm Danas formed east of Luzon on Tuesday.  A distinct low level center of circulation developed in an area of low pressure east of Luzon and the Japan Meteorological Agency designated the system as Tropical Storm Danas.  At 5:00 p.m. EDT on Tuesday the center of Tropical Storm Danas was located at latitude 17.5°N and longitude 123.1°E which put it about 80 miles (130 km) east of Tuguegarao, Philippines.  Danas was moving toward the west at 4 m.p.h. (6 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 distribution of thunderstorms around Tropical Storm Danas was highly asymmetrical.  There were a few thunderstorms just to the southwest of the center of circulation, but most of the thunderstorms were occurring in a band on the far western edge of the circulation around Danas.  Bands in other parts of the circulation consisted primarily of showers and lower clouds.  Tropical Storm Danas was moving around the southeastern portion of an upper level ridge over east Asia.  The ridge was producing strong easterly winds which were blowing across the top of the circulation around Danas.  The easterly winds were causing strong vertical wind shear and the wind shear was causing the asymmetric distribution of thunderstorms.  The circulation around Tropical Storm Danas was large.  Winds to tropical storm force extended out about 200 miles (320 km) from the center of circulation.

Tropical Storm Danas will move into an environment that is only marginally favorable for intensification.  Danas will move over water where the Sea Surface Temperature is near 31°C.  So, there is plenty of energy in the upper ocean.  The strong upper level easterly winds are expected to weaken somewhat during the next several days.  If those winds weaken, then there will be less vertical wind shear and Tropical Storm Danas could strengthen.  If the upper level winds remain strong, then Danas will not strengthen and it could weaken to a tropical depression.  The forecast is for very slow intensification during the next 24 to 48 hours.

Since there are not a lot of taller thunderstorms near the center of Tropical Storm Danas, it will be steered by the winds in the lower troposphere.  Danas will move around the western end of a subtropical ridge over the Western North Pacific Ocean.  The ridge will turn Danas toward the north on Wednesday.  On its anticipated track the center of Tropical Storm Danas will remain east of Luzon.  The center of Danas could be near southeastern Taiwan in 24 to 36 hours.  Tropical Storm Danas could be near the east coast of China in about three days.  The primary risks will be locally heavy rain and flash floods.

Tropical Storm Mun Develops Near Hainan Island

Tropical Storm Mun developed near Hainan Island on Tuesday when the Japan Meteorological Agency designated an area of low pressure as a tropical storm.  At 5:00 p.m. EDT on Tuesday the center of Tropical Storm Mun was located at latitude 19.4°N and longitude 109.8°E which put the center over Hainan Island and it was about 225 miles (365 km) east-southeast of Hai Phong, Vietnam.  Mun was moving toward the west at 12 m.p.h. (19 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 Tropical Storm Mun was very large but it did not have a well developed inner core.  Winds to tropical storm force extended out several hundred miles from the center of circulation.  However, there were few thunderstorms near the center.  The strongest thunderstorms were in two bands in the western periphery of the circulation.  Other bands around Tropical Storm Mun consisted primarily of showers and lower clouds.

Tropical Storm Mun will move through an environment that is not favorable for intensification.  After Mun moves west of Hainan Island the tropical storm will move over water where the Sea Surface Temperature is near 30°C.  So, there is plenty of energy in the upper ocean to support intensification.  However, Tropical Storm Mun will move south of an upper level ridge over eastern Asia.  The ridge will produce strong northeasterly winds which will cause strong vertical wind shear.  The wind shear will prevent significant intensification of Tropical Storm Mun.

Since Tropical Storm Mun does not have a well developed inner core with tall thunderstorms, it will be steered by the winds at lower levels in the atmosphere.  Southeasterly winds blowing as part of the monsoonal circulation will push Mun toward the border between Vietnam and China.  On its anticipated track the center of Tropical Storm Mun will move inland within 24 hours.  Mun will bring some gusty winds and locally heavy rain to portions of northeastern Vietnam and southeastern China.  Heavy rain could cause flash floods in some locations.

Tropical Storm Sepat Forms Near Honshu

Tropical Storm Sepat formed near Honshu on Thursday.  More thunderstorms formed near the center of a low pressure system near the southeast coast of Honshu on Thursday and the Japan Meteorological Agency designated the system as Tropical Storm Sepat.  At 8:00 a.m. EDT on Thursday the center of Tropical Storm Sepat was located at latitude 32.6°N and longitude 134.7°E which put it about 100 miles (160 km) southwest of Susami, Japan.  Sepat was moving toward the northeast at 32 m.p.h. (50 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.

The distribution of thunderstorms around Tropical Storm Sepat was asymmetrical.  The strongest thunderstorms were in several bands south and east of the center of circulation.  Bands in the other parts of the circulation consisted primarily of showers and lower clouds.  Storms southeast of the center of Sepat were generating upper level divergence which was pumping mass away to the northeast of the tropical storm.  Winds to tropical storm force extended out about 150 miles (240 km) to the east of the center of circulation.

Tropical Storm Sepat will move through an environment marginally favorable for intensification during the next 12 to 24 hours.  Sepat will move over water where the Sea Surface Temperature is near 24°C.  An upper level trough west of Japan will produce strong southwesterly winds which will blow toward the top of the circulation.  Those winds will cause moderate vertical wind shear, which is the primary reason for the asymmetrical distribution of thunderstorms.  Moderate vertical wind shear and cooler water will cause the structure of Tropical Storm Sepat to change to that of an extratropical cyclone.  Sepat could strengthen during the extratropical transition because upper level divergence will cause the surface pressure to decrease.

The upper level trough will steer Tropical Storm Sepat rapidly toward the northeast.  On its anticipated track the center of Tropical Storm Sepat will pass near the coast of Honshu.  Sepat will bring gusty winds and it could drop locally heavy rain.

Tropical Cyclone Pola Strengthens to Equivalent of Hurricane/Typhoon

Tropical Cyclone Pola strengthened to the equivalent of a hurricane/typhoon on Wednesday.  At 4:00 a.m. EST on Wednesday the center of Tropical Cyclone Pola was located at latitude 20.2°S and longitude 177.6°W which put it about 170 miles (275 km) west-northwest of Nuku’alofa, Tonga.  Pola was moving toward the south-southwest 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 969 mb.

There was a small, circular eye at the center of Tropical Cyclone Pola.  The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Storms near the core of Pola were generating upper level divergence which was pumping mass away from the tropical cyclone.  Bands of showers and thunderstorms were revolving around the core of Tropical Cyclone Pola.  The strongest rainbands were occurring in the northwestern half of the circulation.  Bands in the southeastern half of Pola consisted primarily of showers and lower clouds.  Winds to hurricane/typhoon force extended out about 40 miles (65 km) from the center of circulation.  Winds to tropical storm force extended out about 160 miles (260 km) from the center.

Tropical Cyclone Pola will move through an environment favorable for support a strong tropical cyclone for another day or so.  Pola will move over water where the Sea Surface Temperature is near 28°C.  It will move through a region where the upper level winds are weak and there will not be much vertical wind shear.  Tropical Cyclone Pola could strengthen during the next 24 hours.  Pola will stat to move over cooler water on Thursday.  An upper level trough will approach Tropical Cyclone Pola from the west.  The trough will produce northwesterly winds which will increase the vertical wind shear.  A combination of cooler water and more vertical wind shear will cause Pola to weaken.  Tropical Cyclone Pola could make a transition to an extratropical cyclone later this week.

Tropical Cyclone Pola will move around the western end of a subtropical ridge over the South Pacific Ocean.  The ridge will steer Pola toward the south-southwest during the next day or two.  Eventually, the upper level trough will turn Tropical Cyclone Pola toward the southeast.  On its anticipated track the core of Pola and the strongest winds will pass west of Tonga.  Rainbands on the eastern side of the circulation could bring gusty winds and heavy rain at times to parts of Tonga.

Elsewhere, Typhoo Wutip continued to weaken west-northwest of the Marianas.  At 4:00 a.m. EST on Wednesday the center of Typhoon Wutip was located at latitude 16.3°N and longitude 139.4°E which put it about 370 miles (595 km) west-northwest of Guam.  Wutip was moving toward the north-northwest at 6 m.p.h. (10 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 981 mb.