Category Archives: Western North Pacific

Western Pacific Typhoons and Tropical Storms

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.

Tropical Cyclone Pola Organizes Quickly Between Fiji and Tonga

Tropical Cyclone Pola organized quickly between Fiji and Tonga on Tuesday.  At 4:00 p.m. EST on Tuesday the center of Tropical Cyclone Pola was located at latitude 18.8°S and longitude 176.7°W which put it about 185 miles (295 km) north-northwest of Nuku’alofa, Tonga.  Pola was moving toward the south at 16 m.p.h. (26 km/h).  The maximum sustained wind speed was 55 m.p.h. (90 km/h) and there were wind gusts to 70 m.p.h. (110 km/h).  The minimum surface pressure was 988 mb.

A well organized low level center of circulation consolidated within a much larger area of showers and thunderstorms north of Tonga on Tuesday and the Fiji Meteorological Service classified the system as Tropical Cyclone Pola.  A small circular eye was beginning to appear at the center of circulation on some satellite images.  The eye was surrounded by a narrow ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Storms near the center 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.  Winds to tropical storm force extended out about 175 miles (280 km) from the center of circulation.

Tropical Cyclone Pola will move through an environment favorable for intensification during the next 24 to 36 hours.  Pola 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.  Tropical Cyclone Pola will intensify during the next day or so and it could strengthen into the equivalent of a hurricane/typhoon.  Pola will move over colder water and into a region where the upper level winds are stronger later this week and it will start to weaken at that time.

Tropical Cyclone Pola will move around the northwestern portion of a subtropical ridge over the South Pacific Ocean.  The ridge will steer Pola in a southward direction.  On its anticipated track the core and strongest part of Tropical Cyclone Pola will pass west of Tonga.  The outer rainbands on the western side of the circulation could bring gusty winds and locally heavy rain to parts of southeastern Fiji.  Rainbands on the eastern side of the circulation could also bring gusty winds and locally heavy rain to parts of Tonga.

Elsewhere, Typhoon Wutip was weakening west of the Marianas.  At 4:00 p.m. EST on Tuesday the center of Typhoon Wutip was located at latitude 15.7°N and longitude 139.9°E which put it about 345 miles (560 km) west-northwest of Guam.  Wutip was moving toward the north at 3 m.p.h. (5 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 972 mb.

Typhoon Wutip Strengthens to Equivalent of a Category 5 Hurricane

Typhoon Wutip strengthened into the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale on Monday.  At 5:00 a.m. EST on Monday the center of Typhoon Wutip was located at latitude 14.0°N and longitude 140.1°E which put it about 300 miles (480 km) west-northwest of Guam.  Wutip was moving toward the north-northwest at 5 m.p.h. (8 km/h).  The maximum sustained wind speed was 160 m.p.h. (260 km.h) and there were wind gusts to 195 m.p.h. (315 km/h).  The minimum surface pressure was 929 mb.

Typhoon Wutip completed an eyewall replacement cycle on Sunday and then it rapidly intensified into the equivalent of a Category 5 hurricane.  The inner eyewall dissipated completely and the outer eyewall contracted around a circular, symmetrical eye.  A ring of strong thunderstorms surrounded the new eye and the strongest winds were occurring in that ring of storms.  Storms near the core of Typhoon Wutip were generating strong upper level divergence which was pumping mass away from the typhoon.  Bands of showers and thunderstorms were revolving around the core of Wutip.

Winds to typhoon force extended out about 45 miles (75 km) from the center of Typhoon Wutip.  Winds to tropical storm force extended out about 160 miles (260 km) from the center.  The Hurricane Intensity Index (HII) for Typhoon Wutip was 35.0.  The Hurricane Size Index (HSI) was 16.6 and the Hurricane Wind Intensity Size Index (HWISI) was 51.6.

Typhoon Wutip will remain in an environment capable of supporting a strong typhoon for another 12 to 24 hours.  Wutip 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 be little vertical wind shear.  A band of stronger westerly winds north of the Philippines will approach Typhoon Wutip in another day or so.  Those winds will cause the vertical wind shear to increase and the increased shear will cause Wutip to weaken.

Typhoon Wutip will move southwest of a subtropical ridge over the Western North Pacific Ocean.  The ridge is forecast to steer Wutip in a west-northwesterly direction.  On its forecast track Typhoon Wutip will gradually move farther away from the Northern Marianas.

Powerful Typhoon Wutip Moving West of Guam

Powerful Typhoon Wutip moved west of Guam on Saturday.  At 10:00 p.m. EST on Saturday the center of Typhoon Wutip was located at latitude 12.9°N and longitude 141.9°E which put it about 170 miles (280 km) west-southwest of Guam.  Wutip was moving toward the northwest at 5 m.p.h. (8 km/h).  The maximum sustained wind speed was 155 m.p.h. (250 km/h) and there were wind gusts to 190 m.p.h. (305 km/h).  The minimum surface pressure was 924 mb.  Typhoon Wutip was the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale.

Visible and microwave satellite imagery  indicated that Typhoon Wutip may have started an eyewall replacement cycle.  An inner rainband wrapped around the original eye and eyewall.  An outer eyewall formed around the original inner eyewall.  The strongest winds were occurring in the inner eyewall.  The eyewall replacement cycle and the formation of an outer eyewall contributed to an increase in the size of Typhoon Wutip.  Winds to typhoon force extended out about 60 miles (95 km) from the center of circulation.  Winds to tropical storm force extended out about 200 miles (320 km) from the center.

The Hurricane Intensity Index (HII) for Typhoon Wutip was 33.3.  The Hurricane Size Index (HSI) was 21.5 and the Hurricane Wind Intensity Size Index (HWISI) was 54.8.

Typhoon Wutip will move into an environment that will gradually become less favorable for strong typhoons.  Wutip will move over water where the Sea Surface Temperature is near 27°C.  The eyewall replacement cycle will cause Typhoon Wutip to weaken when the inner eyewall starts to dissipate.  Wutip also appears to be moving toward a region of drier air.  Rainbands in the western side of Typhoon Wutip seemed to be weakening as they moved into the region of drier air.  Typhoon Wutip will weaken during the next few days.

Typhoon Wutip will move southwest of a subtropical ridge over the Western North Pacific Ocean.  The ridge will steer Wutip toward the northwest during the next several days.  On its anticipated track Typhoon Wutip will move away from the Marianas.

Typhoon Wutip Strengthens to Equivalent of a Major Hurricane South of Guam

Typhoon Wutip strengthened into the equivalent of a major hurricane south of Guam on Friday.  At 10:00 a.m. EST on Friday the center of Typhoon Wutip was located at latitude 10.1°N and longitude 144.7°E which put it about 240 miles (385 km) south of Guam.  Wutip was moving toward the northwest at 15 m.p.h. (24 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 949 mb.

Tropical Storm Warnings were in effect for Guam, Rota and Faraulep.  Tropical Storm Watches have been issued for Tinian, Saipan, Agrihan and Pagan.

Typhoon Wutip was a very well organized tropical cyclone.  A small eye was at the center of circulation.  The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Typhoon Wutip.  Storms near the core were generating upper level divergence which was pumping mass away from the typhoon.

Typhoon Wutip had a large circulation.  Winds to typhoon force extended out about 45 miles (75 km) from the center of circulation.  Winds to tropical storm force extended out about 185 miles (295 km) from the center.  The Hurricane Intensity Index (HII) for Typhoon Wutip was 22.1.  The Hurricane Size Index (HSI) was 17.3 and The Hurricane Wind Intensity Size Index (HWISI) was 39.4.  Typhoon Wutip was capable of causing major damage.

Typhoon Wutip may be near its peak intensity.  Wutip will move over water where the Sea Surface Temperature is near 29°C.  So, there is enough energy in the upper ocean to support a strong typhoon.  Typhoon Wutip has been in an area where the upper level winds were weak and there was little vertical wind shear.  The shear will remain small for another 12 to 24 hours.  Then an upper level trough will approach Typhoon Wutip from the west in a day or so.  The trough will bring southwesterly winds and the vertical wind shear will increase.  Wutip will start to weaken when the shear increases.

Typhoon Wutip will move around the western end of a subtropical ridge over the Western North Pacific Ocean.  Wutip will gradually turn more toward the north while it moves around the end of the ridge.  On its anticipated track the core of Typhoon Wutip will pass west of Guam and the Northern Marianas.  Wutip could bring winds to tropical storm force to Guam and some of the other islands, which is why the warnings and watches were issued.

Wutip Intensifies Into a Typhoon Southeast of Guam

Former Tropical Storm Wutip intensified into a typhoon southeast of Guam on Wednesday.  At 10:00 p.m. EST on Wednesday the center of Typhoon Wutip was located at latitude 6.5°N and longitude 150.0°E which put it about 640 miles (1035 km) southeast of Guam.  Wutip was moving toward the west-northwest at 13 m.p.h. (20 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 979 mb.

Tropical Storm Watches have been issued for Guam, Rota, Tinian and Saipan.  A Typhoon Warning is in effect for Satawal and Puluwat.  A Tropical Storm Warning and a Typhoon Watch are in effect for Ulul and Faraulep.

Typhoon Wutip continued to exhibit better organization on Wednesday.  A cluster of thunderstorms remained near the center of circulation.  A band of storms wrapped around the southern side of the center, which could indicate the start of the formation of an eyewall.  Other bands of showers and thunderstorms were revolving around the core of Typhoon Wutip.  Storms near the core were generating upper level divergence which was pumping mass away from the typhoon.  Winds to typhoon force extended out about 35 miles (55 km) from the center of circulation.  Winds to tropical storm force extended out about 160 miles (260 km) from the center.

Typhoon Wutip will move through an environment favorable for intensification for several more days.  Wutip will move over water where the Sea Surface Temperature is near 30°C.  Typhoon Wutip will move around the western end of an upper level ridge.  The ridge will produce easterly winds which will blow toward the top of the circulation.  Those winds will create some vertical wind shear, but the wind shear will not be great enough to prevent intensification.  Typhoon Wutip will continue to intensify and it could strengthen into the equivalent of a major hurricane within 36 hours.

The ridge will steer Typhoon Wutip in a northwesterly direction during the next 48 hours.  Wutip is likely to turn more toward the north-northwest when it approaches the western end of the ridge.  On its anticipated track Typhoon Wutip could be south of Guam in 36 to 48 hours.  Wutip could be the equivalent of a major hurricane at that time.

Elsewhere, Tropical Cyclone Oma continued to spin over the Coral Sea between New Caledonia and Australia.  At 10:00 p.m. EST on Wednesday the center of Tropical Cyclone Oma was located at latitude 22.7°S and longitude159.8°E which put it about 560 miles (905 km) northeast of Brisbane, Australia.  Oma was moving toward the southwest at 6 m.p.h. (10 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 981 mb.