Category Archives: Western North Pacific

Western Pacific Typhoons and Tropical Storms

Typhoon Prapiroon Brings Winds and Rain to Okinawa

Typhoon Prapiroon brought wind and rain to Okinawa on Sunday.  At 5:00 p.m. EDT on Sunday the center of Typhoon Prapiroon was located at latitude 26.8°N and longitude 126.8°E which put it about 65 miles (100 km) west-southwest of Okinawa.  Prapiroon was moving toward the north at 10 m.p.h. (16 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 978 mb.

The circulation of former Tropical Storm Prapiroon became much more well organized on Sunday.  A circular eye formed at the center of circulation and Prapiroon strengthened into a typhoon.  A ring of thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms.  Several bands of showers and thunderstorms in the eastern half of the typhoon were revolving around the center of circulation.  Bands northwest of the center consisted mostly of showers and low clouds.  Storms in the core of the circulation were generating upper level divergence which was pumping mass away to the east of the typhoon.

Typhoon Prapiroon will move through an environment favorable for intensification during the next 12 to 24 hours.  Prapiroon will move over water where the Sea Surface Temperature is near 29°C.  It will move through a region where the upper level winds are weak and there will be little vertical wind shear.  Typhoon Prapiroon could intensify during the next 12 to 24 hours.  Prapiroon will move over cooler water in a day or so.  It will also reach a location where an upper level trough west of South Korea will cause more vertical wind shear.  An environment of cooler water and more wind shear will cause Typhoon Prapiroon to weaken at that time.

Typhoon Prapiroon is moving around the western end of a subtropical ridge which is steering it toward the north.  On its anticipated track the center of Typhoon Prapiroon will pass west of Okinawa and the northern Ryukyu Islands.  Winds to typhoon force extend out about 30 miles (50 km) east of the center of circulation.  Winds to tropical storm force extend out about 150 miles (240 km) east of the center.  So, even though the center of Typhoon Prapiroon will pass west of the northern Ryukyu Islands, it will bring gusty winds and heavy rain.  Typhoon Prapiroon could approach western Kyushu in 24 hours.  When Prapiroon moves farther north the trough west of South Korea will start to steer the typhoon more toward the northeast.

Tropical Storm Prapiroon Moves Toward Okinawa

Tropical Storm Prapiroon moved closer to Okinawa on Saturday.  At 11:00 a.m. EDT on Saturday the center of Tropical Storm Prapiroon was located at latitude 22.4°N and longitude 128.3°E which put it about 315 miles (510 km) south of Okinawa.  Prapiroon was moving toward the northwest at 8 m.p.h. (13 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 992 mb.

There was a distinct center of circulation in the middle of Tropical Storm Prapiroon, but the distribution of thunderstorms was asymmetrical.  The stronger thunderstorms were occurring in bands south and east of the center of circulation.  The bands north and west of the center consisted primarily of showers and low clouds.  A large upper level ridge over Asia was producing northerly winds which were blowing toward the top of Tropical Storm Prapiroon.  Those winds were causing moderate vertical wind shear and they were probably the reason for the asymmetric distribution of thunderstorms.  Those winds were also blocking upper level divergence to the north and west of Prapiroon.

Tropical Storm Prapiroon will move through an area marginally favorable for intensification during the next 24 to 36 hours.  Prapiroon will move over water where the Sea Surface Temperature is near 29°C.  So, there will be enough energy in the upper ocean to support intensification.  The upper level ridge will continue to cause some vertical wind shear, but Tropical Storm Prapiroon could move into an area where the upper level winds are a little weaker on Sunday.  If the wind shear decreases, then Tropical Storm Prapiroon will intensify.  There is still a chance that Prapiroon could strengthen into a typhoon when it passes near Okinawa.

Tropical Storm Prapiroon is moving around the western end of a subtropical ridge over the Pacific Ocean which is steering the tropical storm toward the northwest.  Prapiroon is forecast to move more toward the north when it reaches the western end of the ridge in 12 to 24 hours.  On its anticipated track the center of Tropical Storm Prapiroon could approach Okinawa in 12 to 18 hours.  The center of Prapiroon will likely pass west of Okinawa which would bring the strongest winds and heaviest rain over Okinawa.

Tropical Storm Prapiroon Forms South-Southeast of Okinawa

A distinct center of circulation formed within an area of thunderstorms south-southeast of Okinawa on Thursday night and the Japan Meteorological Agency designated the system as Tropical Storm Prapiroon.  At 8:00 p.m. EDT on Thursday the center of Tropical Storm Prapiroon was located at latitude 20.0°N and longitude 130.2°E which put it about 500 miles (800 km) south-southeast of Okinawa.  Prapiroon was moving toward the west at 7 m.p.h. (11 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 circulation of Tropical Storm Prapiroon was still organizing.  More thunderstorms were forming close to the center of circulation.  There were more thunderstorms west of the center than there were east of the center.  Several bands of showers and thunderstorms in the outer part of the circulation were revolving around the core of Tropical Storm Prapiroon.  The storms in the core were generating upper level divergence which was pumping mass away from the tropical storm.

Tropical Storm Prapiroon formed beneath an upper level ridge that developed between an upper level low northwest of the Philippines and a much larger upper low east of the Marianas.  The winds in the upper ridge will be weak and there will be little vertical wind shear.  Prapiroon will move over water where the Sea Surface Temperature is near 29°C.  Tropical Storm Prapiroon will move through an environment very favorable for intensification.  Prapiroon will strengthen and it could intensify rapidly once the inner core organizes.  Tropical Storm Prapiroon could strengthen into a typhoon in 24 to 48 hours.

Tropical Storm Prapiroon was moving around the southwestern part of a subtropical ridge which was steering the tropical storm toward the west.  Prapiroon will turn toward the north in 12 to 24 hours when it reaches the western end of the ridge.  On its anticipated track Tropical Storm Prapiroon could approach Okinawa in about 36 hours.  Prapiroon could be a typhoon when it nears Okinawa.

Tropical Storm Gaemi Brings Wind and Rain to Okinawa

Tropical Storm Gaemi brought wind and rain to Okinawa late on Friday.  At 11:00 p.m. EDT on Friday the center of Tropical Storm Gaemi was located at latitude 26.7°N and longitude 127.9°E which put it near Okinawa.  Gaemi was moving toward the east-northeast at 19 m.p.h (30 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.

Tropical Storm Gaemi became better organized after it moved across southern Taiwan early on Friday.  The center of circulation was more evident on microwave satellite images.  A primary band of showers and thunderstorms formed in the eastern side of circulation.  Other showers and thunderstorms were located farther to the northeast of the center of Tropical Storm Gaemi.  An upper level trough west of Gaemi was producing string southwesterly winds which were blowing toward the top of the tropical storm.  Those winds were causing moderate vertical wind shear and they were likely the reason why most of the heavier rain was occurring northeast of the center of circulation.

The upper level trough was also steering Tropical Storm Gaemi quickly toward the east-northeast.  On its anticipated track Gaemi will move over the middle Ryukyu Islands including Amami-O-Shima during the next 12 hours.  Tropical Storm Gaemi will continue to produce gusty winds and locally heavy rain.  Most of the rain will fall before the center of circulation reaches a location.  Gaemi is likely to make a transition to an extratropical cyclone when it moves south of the larger islands of Japan during the weekend.

Tropical Storm Gaemi Forms Near Southwest Taiwan

Tropical Storm Gaemi formed near Kaohsiung on the southwest coast of Taiwan late on Thursday.  At 8:00 p.m. EDT on Thursday the center of Tropical Storm Gaemi was located at latitude 22.8°N and longitude 120.2°E which put it near Kaohsiung, Taiwan.  Gaemi was moving toward the northeast 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 992 mb.

A distinct low level center of circulation developed in an area of showers and thunderstorms southwest of Taiwan on Thursday and the Japan Meteorological Agency designated the system as Tropical Storm Gaemi.  Thunderstorms developed near the core of the circulation.  Several short bands of showers and thunderstorms were revolving around the core.  Mountains in eastern Taiwan may have deflected the flow in the lower levels and contributed to the organization of a center of circulation.  Storms around the center were generating some upper level divergence which was pumping mass away to the east of the tropical storm.

Tropical Storm Gaemi is likely to weaken during the next few hours while the center of circulation moves across southern Taiwan.  Mountains in eastern Taiwan could disrupt the lower portions of the circulation when it moves over them.  If the circulation still exists when it moves east of Taiwan in a few hours, then Tropical Storm Gaemi will move into a more favorable environment for intensification.  Gaemi will move over water where the Sea Surface Temperature is near 29°C.  An upper level trough over eastern Asia is producing southwesterly winds which are blowing toward the top of the circulation.  Those winds will cause some vertical wind shear, but the shear will probably not be strong enough to tear the circulation apart.  Gaemi could remain a tropical storm for another 24 to 36 hours.  When Tropical Storm Gaemi moves farther north in a day or two, it will move over colder water and into an area with stronger vertical wind shear.  Gaemi will likely make a transition to an extratropical cyclone at that time.

The upper level trough is forecast to steer Tropical Storm Gaemi toward the northeast.  Gaemi will move across southern Taiwan during the next few hours.  It will cause gusty winds, but the greater risks will be heavy rain and flash floods.  On its anticipated track Tropical Storm Gaemi will move near the southern Ryukyu Islands of Japan.  It could pass near Ishigaki Jima and Miyako Jima in the next 12 to 18 hours.  Gaemi could be near Okinawa later on Friday.

Maliksi Strengthens Into a Typhoon East of Okinawa

Former Tropical Storm Maliksi strengthened into a typhoon east of Okinawa near Minami Daito Jima late on Saturday.  At 11:00 p.m. EDT on Saturday the center of Typhoon Maliksi was located at latitude 25.7°N and longitude 131.7°E which put it about 210 miles (335 km) east of Okinawa.  Maliksi was moving toward the northeast at 24 m.p.h. (39 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 970 mb.

The circulation of Typhoon Maliksi became more organized on Saturday.  An inner rainband wrapped around the center of circulation and an eye was apparent on satellite images.  There were intermittent breaks in the rings of thunderstorms around the eye.  Several bands of showers and thunderstorms in the eastern half of the circulation were revolving around the core of the typhoon.  Bands west of the center consisted primarily of showers and low clouds.  Storms near the core of Maliksi were generating upper level divergence which was pumping mass away to the northeast of the typhoon.  The circulation of Typhoon Maliksi was large and winds to tropical storm force extended out about 250 miles (400 km) from the center of circulation.

Typhoon Maliksi will move through an environment favorable for intensification during the next 12 to 24 hours.  Maliksi will move over water where the Sea Surface Temperature is near 30°C.  An upper level trough to the west of Maliksi will produce southwesterly winds which will blow toward the top of the circulation.  Those winds will produce some vertical wind shear, but the shear will not be strong enough to prevent intensification on Sunday.  The shear will increase after 18 to 24 hours and that will likely cause Maliksi to start to weaken.

The upper level trough is steering Maliksi toward the northeast and that general motion is expected to continue for another two or three days.  Typhoon Maliksi will speed past Minami Daito Jima during the next few hours.  On its anticipated track Maliksi will reach some of the islands south of Honshu in about 24 hours.  Typhoon Maliksi will produce gusty winds and locally heavy rain.

Tropical Storm Maliksi Forms East of Luzon, Ewiniar Brings Rain to South China.

Tropical Storm Maliksi formed east of Luzon on Thursday while Tropical Storm Ewiniar brought rain to parts of South China.  At 8:00 p.m. EDT on Thursday the center of Tropical Storm Maliksi was located at latitude 17.4°N and longitude 127.7°E which put it about 330 miles (535 km) east of Luzon.  Maliksi was moving toward the north 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 996 mb.

The Japan Meteorological Agency designated an area of low pressure east of Luzon as Tropical Storm Maliksi late on Thursday.  There was a large counterclockwise circulation east of Luzon, but there were few thunderstorms near the center of the circulation.  Most of the thunderstorms were occurring in three bands in the outer portions of the circulation.  One band was located well to the west of the center of circulation, a second band was located well to the north of the center and the third band was located well to the east of the center.  The winds to tropical storm force were occurring in those bands.

Tropical Storm Maliksi will move through an environment favorable for intensification during the next 24 to 48 hours.  Maliksi will move over water where the Sea Surface Temperature is near 30°C.  Maliksi will move underneath an upper level ridge where the winds are weak and there will be little vertical wind shear.  The large circulation will be the primary factor inhibiting intensification in the short term.  Maliksi will intensify slowly until thunderstorms develop near the center of circulation and the strongest winds occur closer to the center.

Tropical Storm Maliksi will move around the western end of a subtropical ridge.  The ridge will steer Maliksi slowly toward the north.  When Tropical Storm Maliksi moves farther to the north westerly winds will begin to steer it toward the northeast.  On its anticipated track Tropical Storm Maliksi will remain east of Luzon.  The circulation of Maliksi is so large that rainbands on the western side of the circulation could affect the northern Philippines.

Elsewhere over the western North Pacific Ocean, Tropical Storm Ewiniar brought heavy rain to parts of South China.  Ewiniar made landfall on the coast of China near Yangjiang on Thursday.  At 8:00 p.m. EDT on Thursday the center of Tropical Storm Ewiniar was located at latitude 22.6°N and longitude 112.1°E which put it about 50 miles (80 km) northeast of Yangjiang, China.  Ewiniar was moving toward the north at 9 m.p.h. (15 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 center of Tropical Storm Ewiniar was moving farther inland over South China.  The winds to tropical storm force were occurring in rainbands that were still over the South China Sea.  Ewiniar was dropping heavy rain over parts of western Guangdong province and over southern Zizhiqu province.  The heavy rain could cause flooding in those areas.

Tropical Storm Ewiniar Forms Near Coast of South China

Tropical Storm Ewiniar formed near the coast of South China late on Tuesday.  At 11:00 p.m. EDT on Monday the center of Tropical Storm Ewiniar was located at latitude 20.9°N and longitude 110.5°E which put it about 50 miles (80 km) southeast of Zhanjiang, China.  Ewiniar 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 1000 mb.

A distinct low level center of circulation consolidated in a cluster of showers and thunderstorms moving over the South China Sea near Hainan Island on Monday and the Japan Meteorological Agency designated the system as Tropical Storm Ewiniar.  Several bands of showers and thunderstorms developed west of the center of circulation.  Bands east of the center consisted primarily of showers and low clouds.  Winds to tropical storm force were occurring within 60 miles (95 km) of the center o circulation.

Tropical Storm Ewiniar has 12 to 24 hours during which it could intensify if the center remains over water.  The Sea Surface Temperature of the water near the coast of South China is about 30°C.  Ewiniar is under the southwestern portion of a narrow upper level ridge.  The ridge is producing weak southerly winds which are blowing toward the top of the circulation.  Those winds will cause some vertical wind shear but the shear will not be strong enough to prevent intensification.  Even though the atmospheric and oceanic environments are favorable for intensification, a portion of the circulation of Tropical Storm Ewiniar is already over land.  The friction caused by the flow of air over the land will inhibit intensification.  Tropical Storm Ewiniar could intensify a little more if the center remains over water.

The upper level ridge was steering Tropical Storm Ewiniar toward the northwest.  A general motion toward the north is expected for the next 24 to 48 hours.  On its anticipated track the center of Tropical Storm Ewiniar will move near the east coast of the Leizhou Peninsula.  Ewiniar could move inland near Wuchuan and Dianbai.  Tropical Storm Ewiniar will bring some gust winds to South China, but the greater risks are the potential for heavy rain and floods.

Tropical Depression 04W Forms East of the Northern Marianas

Tropical Depression 04W formed east of the Northern Marianas very late on Friday.  At 11:00 p.m. EDT on Friday the center of Tropical Depression 04W was located at latitude 18.8°N and longitude 148.5°E which put it about 185 miles (300 km) east of Agrihan.  It was moving toward the northwest at 11 m.p.h. (17 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 1003 mb.

An area of showers and thunderstorms persisted for much of the past week east of the Northern Marianas.  Several smaller centers of circulation formed within the area of showers and storms, but those centers ran into strong upper level winds and weakened because strong vertical wind shear and they dissipated.  Another center formed on Friday, but the upper level winds were a little weaker and the center persisted.  An upper level trough south of Japan was still producing southwesterly winds which were blowing toward the top of the circulation.  Those winds were producing moderate vertical wind shear, but the center of circulation persisted.  Most of the thunderstorms were occurring in bands east of the center of circulation.  The bands west of the center consisted primarily of low clouds and showers.

Tropical Depression will move through an area marginally favorable for intensification during the next 24 hours.  it will move over water where the Sea Surface Temperatures are near 28°C.  So, there will be enough energy in the upper ocean to support some intensification.  The upper level trough south of Japan will continue to cause moderate vertical wind shear, but the upper level winds could be weak enough to allow for further intensification.  Tropical Depression 04W could strengthen into a tropical storm on Saturday.

Tropical Depression 04W is moving near the southwestern part of a ridge over the North Pacific Ocean.  The ridge is steering the depression toward the northwest and that general motion is expected to continue for another day or two.  On its anticipated track Tropical Depression 04W is expected to pass near the northernmost Mariana Islands.  It could pass near Asuncion Island, the Maug Islands, Supply Reef and Farallon de Pajaros.  Tropical Depression 04W could bring gust winds, locally heavy rain and higher waves to those places.

Tropical Storm Jelawat Weakens Rapidly Over the Northern Marianas

Tropical Storm Jelawat weakened rapidly over the Northern Marianas on Saturday.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm Jelawat was located at latitude 19.3°N and longitude 145.5°E which put it about 50 miles (80 km) north-northwest of Agrihan.  Jelawat was moving toward the east-northeast at 14 m.p.h. (22 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 993 mb.

Former Typhoon Jelawat moved into an area where there were upper level westerly winds blowing at 50 m.p.h. (80 km/h).  Those strong upper level winds created enough vertical wind shear to blow the upper two thirds of the circulation east of the lower part of the circulation.  The remaining strong thunderstorms were weakening well to the east of the lower level circulation.  Tropical Storm Jelawat consisted primarily of narrow bands of showers and low clouds that were revolving around the center of circulation.  Jelawat may bring brief gusty winds and showers to the northernmost islands in the Marianas.