Category Archives: Western North Pacific

Western Pacific Typhoons and Tropical Storms

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.

Typhoon Jelawat Rapidly Intensifies Into Equivalent of Major Hurricane

Typhoon Jelawat intensified rapidly on Friday into the equivalent of a major hurricane.  At 11:00 a.m. EDT on Friday the center of Typhoon Jelawat was located at latitude 17.1°N and longitude 139.5°E which put it about 440 miles (710 km) northwest of Guam.  Jelawat was moving toward the east-northeast at 13 m.p.h. (21 km/h).  The maximum sustained wind speed was 150 m.p.h. (240 km/h) and there were wind gusts to 185 m.p.h. (295 km/h).  The minimum surface pressure was 926 mb.

Typhoon Jelawat intensified rapidly on Friday.  There was a small circular eye at the center of circulation.  A ring of very strong storms surrounded the eye and the strongest winds were occurring in that ring of storms.  Several spiral bands were revolving around the core of the circulation.  Storms near the core were generating well developed upper level divergence which was pumping large quantities of mass away to the east of the typhoon.  The removal of mass allowed the surface pressure to decrease rapidly and that produced a a rapid increase in wind speed.

Winds to typhoon force extend out about 45 miles (75 km) from the center of Typhoon Jelawat.  Winds to tropical storm force extend out about 175 miles (280 km) from the center of circulation.  The Hurricane Intensity Index (HII) for Typhoon Jelawat is 31.6.  The Hurricane Size Index (HSI) is 17.7 and the Hurricane Wind Intensity Size Index (HWISI) is 49.3.

Typhoon Jelawat is in an environment favorable for strong typhoons, but it may be near its peak in intensity.  Jelawat will move over water where the Sea Surface Temperature is near 28°C.  Typhoon Jelwat has moved around the western end of an upper level ridge which is producing easterly winds that are blowing toward the top of the circulation.  The winds are causing some vertical wind shear, but the shear has not inhibited intensification.  When Typhoon Jelawat moves farther to the northeast it will move under stronger easterly and the wind shear will increase.  More shear will cause Jelawat to weaken during the next few days.

A subtropical ridge to the east of Typhoon Jelawat is steering the typhoon toward the east-northeast.  A general motion toward the east-northeast is expected to continue for several more days.  On its anticipated track Typhoon Jelawat could approach the northernmost islands in the Marianas in about 48 hours.

Typhoon Jelawat Strengthens West-Northwest of Guam

Former Tropical Storm Jelawat strengthened into a typhoon as it moved west-northwest of Guam on Thursday.  At 11:00 p.m. EDT on Thursday the center of Typhoon Jelawat was located at latitude 15.9°N and longitude 137.7°E which put it about 520 miles (840 km) west-northwest of Guam.  Jelawat was moving toward the east-northeast at 7 m.p.h. (11 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 972 mb.

Typhoon Jelawat strengthened quickly on Thursday night.  A small eye developed at the center of circulation.  A ring of strong thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms.  Several bands of showers and thunderstorms were revolving around the core of Typhoon Jelawat.  Storms in the core of the circulation were generating upper level divergence which was pumping mass away to the northeast of the typhoon.  Winds to typhoon force extended out about 45 miles (75 km) from the center of circulation.  Winds to tropical storm force extended out about 145 miles (230 km) from the center.

Typhoon Jelawat will move through an area favorable for intensification on Friday.  Jelawat will move over water where the Sea Surface Temperature is near 28°C.  Typhoon Jelawat has moved around the western end of an upper level ridge which is producing southwesterly winds which are blowing toward the top of the circulation.  Those winds are producing some vertical wind shear, but the wind shear is not strong enough to prevent intensification.   Typhoon Jelwat is likely to intensify further on Friday.

The upper level ridge is steering Typhoon Jelawat toward the east-northeast and that general motion is expected to continue for several more days.  On its anticipated track Typhoon Jelawat is expected to pass northwest of Guam.  Jelawat could approach the northernmost islands in the Marianas in about two or three days.

Tropical Storm Jelawat Strengthens West of Guam

Tropical Storm Jelawat strengthened west of Guam late on Tuesday.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Jelawat was located at latitude 12.3°N and longitude 135.5°E which put it about 230 miles (375 km) northwest of Yap and about 600 miles (970 km) west of Guam.  Jelawat was moving toward the north at 10 m.p.h. (16 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 994 mb.

After being affected by strong vertical wind shear for about 36 hours, Tropical Storm Jelawat began to strengthen late on Tuesday.  Many more thunderstorms formed near the center of circulation.  The circulation became much more symmetrical.  Bands of showers and thunderstorms formed in all parts of the circulation.  The storms near the center of circulation started to generate upper level divergence which pumped mass away from the tropical storm.

Tropical Storm Jelawat will be moving through an environment favorable for intensification during the next several days.  Jelawat will move over water where the Sea Surface Temperature is near 28°C.  Tropical Storm Jelawat is moving around the western end of an upper level ridge.  The ridge is producing southerly winds which are blowing toward the tropical storm.  The winds are producing some vertical wind shear, but the shear is not as strong as it has been.  Tropical Storm Jelawat will intensify during the next day or two and it could strengthen into a typhoon.

The ridge is steering Tropical Storm Jelawat toward the north and the northerly motion is expected to continue for another 12 to 24 hours.  Jelawat will move more toward the northeast in a day or so after it rounds the western end of the ridge.  On its anticipated track Tropical Storm Jelawat will move away from Yap and it will remain west of Guam.