Category Archives: Western North Pacific

Western Pacific Typhoons and Tropical Storms

Rai Intensifies to a Typhoon East of the Philippines

Former Tropical Storm Rai intensified to a typhoon east of the Philippines on Tuesday night. At 10:00 p.m. EST on Tuesday the center of Typhoon Rai was located at latitude 9.0°N and longitude 131.7°E which put it about 180 miles (290 km) northwest of Koror, Palau. Rai was moving toward the west at 12 m.p.h. (19 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 981 mb.

Former Tropical Storm Rai intensified steadily on Tuesday over the Western North Pacific Ocean and it reached typhoon intensity on Tuesday night. A small circular eye formed at the center of Rai. 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 Rai. Storms near the core generated upper level divergence that pumped mass away to the west and north of the typhoon. Winds to typhoon force extended out 45 miles (75 km) from the center of Rai’s circulation. Winds to tropical storm force extended out 180 miles (290 km) from the center.

Typhoon Rai will move through an environment favorable for intensification during the next 24 hours. Rai will move over water where the Sea Surface Temperatures are near 30˚C. It will move under the southern side of an upper level ridge over the Western North Pacific Ocean. The ridge will produce easterly winds that will blow toward the top of Typhoon Rai’s circulation. Those winds will cause some vertical wind shear but the wind shear will be too small to prevent intensification. Typhoon Rai will continue to strengthen. Rai could intensify more rapidly now that an inner core with an eye and an eyewall has formed.

Typhoon Rai will move south of a surface high pressure system over the Western North Pacific Ocean. The high pressure system will steer Rai toward the west-northwest during the next several days. On its anticipated track the center of Typhoon Rai could approach northern Mindanao in 24 hours. Rai will be a typhoon when it reaches the Philippines. Typhoon Rai will bring strong winds and locally heavy rain to northern Mindanao, Siargao Island, Dinegat Island, Samar, Leyte, Cebu, Negros, Bohol and Panay Island. Rai will cause a significant storm surge along coasts where the wind blows the water toward the shore.

Tropical Storm Rai Strengthens East of Palau

Tropical Storm Rai strengthened east of Palau on Monday night. At 10:00 p.m. EST on Monday the center of Tropical Storm Rai was located at latitude 7.7°N and longitude 136.3°E which put it about 170 miles (275 km) east of Koror, Palau. Rai was moving toward the west-northwest at 21 m.p.h. (33 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 990 mb.

Tropical Storm Rai strengthened steadily over the Western North Pacific Ocean on Monday. Although Rai intensified, the distribution of thunderstorms was asymmetrical. The strongest thunderstorms were occurring in bands in the western half of Tropical Storm Rai’s circulation. The inner end of a rainband wrapped around the western and southern side of the center of Rai’s circulation. Bands in the eastern half of the tropical storm consisted primarily of showers and lower clouds. Storms near the center of circulation generated upper level divergence that pumped mass away to the west and north of the tropical storm. Winds to tropical storm force extended out 200 miles (320 km) from the center of Rai.

Tropical Storm Rai will move through an environment favorable for intensification during the next 48 hours. Rai will move over water where the Sea Surface Temperatures are near 30˚C. It will move under the southern side of an upper level ridge over the Western North Pacific Ocean. The ridge will produce easterly winds that will blow toward the top of Tropical Storm Rai’s circulation. Those winds will cause some vertical wind shear and the shear is already contributing to the current asymmetrical distribution of thunderstorms. The upper level winds are forecast to weaken, and the vertical wind shear will be too small to prevent intensification. Tropical Storm Rai will intensify and it likely to strengthen to a typhoon during the next 24 hours. Rai could strengthen more rapidly once an inner core with an eye and an eyewall forms.

Tropical Storm Rai will move south of a surface high pressure system over the Western North Pacific Ocean. The high pressure system will steer Rai toward the west-northwest during the next several days. On its anticipated track the center of Tropical Storm Rai will north of Palau during the next 12 hours. Rai could bring gusty winds and locally heavy rain to Palau. Tropical Storm Rai could approach the Philippines in 60 hours. Rai is likely to be a typhoon when it reaches the Philippines.

Tropical Cyclone Ruby Hits New Caledonia

Tropical Cyclone Ruby hit New Caledonia on Monday. At 4:00 p.m. EST on Monday the center of Tropical Cyclone Ruby was located at latitude 20.5°S and longitude 164.5°E which put it about 20 miles (30 km) east of Koumac, New Caledonia and about 200 miles (320 km) northwest of Noumea. Ruby was moving toward the southeast at 18 m.p.h. (29 km/h). The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were wind gusts to 85 m.p.h. (135 km/h). The minimum surface pressure was 984 mb.

The center of Tropical Cyclone Ruby made landfall on the northwest end of New Caledonia near Poum on Monday. Ruby was the equivalent of a strong tropical storm when it made landfall. Winds to tropical storm force extended out 140 miles (225 km) in the northeastern quadrant of Ruby’s circulation. Winds to tropical storm force extended out 80 miles from the center of Tropical Cyclone Ruby in the other quadrants. A band of heavy rain wrapped around the southern and western sides of the center of circulation. Other bands of showers and thunderstorms were revolving around the center of Ruby.

An upper level trough east of Australia will produce northwesterly winds that will steer Tropical Cyclone Ruby toward the southeast during the next 36 hours. On its anticipated track the center of Ruby will move over almost the entire length of New Caledonia. Ruby could maintain much of its intensity as it moves over New Caledonia because most of the circulation will be over water. Tropical Cyclone Ruby will bring strong winds and heavy rain to much of New Caledonia. Locally heavy rain is likely to cause flash floods. Strong winds and locally heavy rain could cause widespread electrical outages. Winds blowing water toward the east coast of New Caledonia could cause storm surges.

Tropical Storm Rai Forms Southeast of Yap

Tropical Storm Rai formed over the Western North Pacific Ocean southeast of Yap on Monday morning. At 4:00 a.m. EST on Monday the center of Tropical Storm Rai was located at latitude 5.5°N and longitude 140.5°E which put it about 355 miles (575 km) southeast of Yap. Rai was moving toward the west-northwest at 11 m.p.h. (17 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 around a low pressure system strengthened on Monday morning and the Japan Meteorological Agency designated the system as Tropical Storm Rai. Thunderstorms formed near the center of Tropical Storm Rai. More thunderstorms also developed in bands revolving around the center of Rai. Storms near the center of circulation generated upper level divergence that pumped mass away from the tropical storm. Winds to tropical storm force extended out 150 miles (240 km) from the center of Tropical Storm Rai.

Tropical Storm Rai will move through an environment favorable for intensification during the next several days. Rai will move over water where the Sea Surface Temperatures are near 30˚C. It will move under the southern side of an upper level ridge over the Western North Pacific Ocean. The ridge will produce easterly winds that will blow toward the top of Tropical Storm Rai’s circulation. Those winds will cause some vertical wind shear, but the shear will be too small to prevent intensification. Tropical Storm Rai will intensify during the next several days. Rai could strengthen to a typhoon within 36 hours. It could strengthen more rapidly once an inner core with an eye and an eyewall forms.

Tropical Storm Rai will move south of a surface high pressure system over the Western North Pacific Ocean. The high pressure system will steer Rai toward the west-northwest during the next several days. On its anticipated track the center of Tropical Storm Rai will south of Yap during the next 24 hours. Rai could bring gusty winds and locally heavy rain to Yap. Tropical Storm Rai could affect Palau within 36 hours. Rai could approach the Philippines within 72 hours. Rai is likely to be a typhoon when it reaches the Philippines.

Typhoon Nyatoh Brings Wind and Rain to Iwo To

Typhoon Nyatoh brought wind and rain to Iwo To on Friday. At 10:00 a.m. EST on Friday the center of Typhoon Nyatoh was located at latitude 24.3°N and longitude 142.9°E which put it about 80 miles (130 km) southeast of Iwo To. Nyatoh was moving toward the northeast at 24 m.p.h. (39 km/h). The maximum sustained wind speed was 125 m.p.h. (200 km/h) and there were wind gusts to 155 m.p.h. (250 km/h). The minimum surface pressure was 947 mb.

Bands in the northwestern side of Typhoon Nyatoh brought strong winds and heavy rain to Iwo To on Friday. The core of Nyatoh’s circulation where the strongest winds were occurring passed to the southeast of Iwo To. An upper level trough over Japan was producing strong southwesterly winds that were blowing toward the top of Typhoon Nyatoh’s circulation. Those winds caused strong vertical wind shear and the shear started to weaken Nyatoh when it approached Iwo To. A circular eye was still present at the center of Typhoon Nyatoh, but the distribution of thunderstorms was asymmetrical. The strongest thunderstorms were occurring around the eye and in bands in the northern half of Nyatoh. Bands in the southern half of the typhoon consisted primarily of showers and lower clouds.

Even though Typhoon Nyatoh was weakening, it was still the equivalent of a major hurricane. Winds to typhoon force extended out 60 miles (95 km) from the center of Nyatoh. Winds to tropical storm force extended out 200 miles (320 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Nyatoh was 23.6. The Hurricane Size Index (HSI) was 22.2 and the Hurricane Wind Intensity Size Index (HWISI) was 45.8.

The upper level trough over Japan will steer Typhoon Nyatoh quickly toward the northeast during the next 24 hours. On its anticipated track Nyatoh will move away from Iwo To and the weather conditions should improve. Typhoon Nyatoh will move through an environment that will be unfavorable for a typhoon. Nyatoh will move over water where the Sea Surface Temperatures are near 24.5˚C. The upper level trough will continue to produce strong vertical wind shear. A surface high pressure system over eastern Asia will transport drier air toward the western side of Nyatoh’s circulation. Cooler water, strong vertical wind shear, and drier air will cause Typhoon Nyatoh to weaken rapidly during the next 24 hours.

Typhoon Nyatoh Strengthens to Equivalent of a Major Hurricane

Typhoon Nyatoh strengthened to the equivalent of a major hurricane over the Western North Pacific Ocean southwest of Iwo To on Thursday. At 10:00 a.m. EST on Thursday the center of Typhoon Nyatoh was located at latitude 18.7°N and longitude 137.1°E which put it about 540 miles (875 km) southwest of Iwo To. Nyatoh was moving toward the northeast at 15 m.p.h. (24 km/h). The maximum sustained wind speed was 115 m.p.h. (185 km/h) and there were wind gusts to 145 m.p.h. (230 km/h). The minimum surface pressure was 955 mb.

Typhoon Nyatoh rapidly intensified to the equivalent of a major hurricane on Thursday. A circular eye with a diameter of 35 miles (55 km) formed at the center of Nyatoh. 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 Nyatoh. Storms near the core generated strong upper level divergence that pumped mass away to the northeast of the typhoon.

The circulation around Typhoon Nyatoh increased in size on Thursday. Winds to typhoon force extended out 65 miles (105 km) from the center of Nyatoh. Winds to tropical storm force extended out 220 miles (355 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Nyatoh was 20.6. The Hurricane Size Index (HSI) was 22.1 and the Hurricane Wind Intensity Size Index (HWISI) was 42.7.

Typhoon Nyatoh will move through an environment that will become unfavorable for intensification during the next 24 hours. Nyatoh will move over water where the Sea Surface Temperatures are near 28˚C. An upper level trough near Japan will produce southwesterly winds that will blow toward the top of Nyatoh’s circulation. Those winds will cause the vertical wind shear to increase during the next 24 hours. Clockwise flow around a surface high pressure system centered over eastern Asia will transport drier air toward the northwestern part of Nyatoh’s circulation. The drier air will begin to be pulled into the northwestern part of Typhoon Nyatoh’s circulation during the next 24 hours. The combination of more vertical wind shear and drier air will cause Typhoon Nyatoh to start to weaken.

The upper level trough near Japan will steer Typhoon Nyatoh toward the northeast during the next 24 hours. On its anticipated track Typhoon Nyatoh could approach Iwo To on Friday. Although Nyatoh will weaken, it will bring strong winds and locally heavy rain to Iwo To.

Nyatoh Strengthens to a Typhoon West of the Marianas

Former Tropical Storm Nyatoh strengthened to a typhoon west of the Marianas on Wednesday. At 10:00 a.m. EST on Wednesday the center of Typhoon Nyatoh was located at latitude 15.5°N and longitude 135.6°E which put it about 580 miles (935 km) west-northwest of Guam. Nyatoh was moving toward the north-northwest at 11 m.p.h. (17 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 981 mb.

Former Tropical Storm Nyatoh continued to strengthen over the Western North Pacific Ocean west of the Marianas on Wednesday. The inner end of a rainband wrapped around the center of Typhoon Nyatoh and microwaves satellite images indicated that an eye was forming. The developing eye was surrounded by a broken ring of thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Nyatoh. Storms near the core generated upper level divergence that pumped mass away from the typhoon. Winds to typhoon force extended out 35 miles (55 km) from the center of Nyatoh. Winds to tropical storm force extended out 150 miles (240 km) from the center of circulation.

Typhoon Nyatoh will move through an environment mostly favorable for intensification during the next 24 hours. Nyatoh will move over water where the Sea Surface Temperatures are near 28˚C. It will move under the western part of the axis of an upper level ridge centered near the Marianas. The upper level winds are weak near the axis of the ridge and there will be little vertical wind shear. Clockwise flow around a high pressure system centered over eastern Asia will transport drier air toward the northwestern part of Nyatoh’s circulation. The drier air is likely to remain northwest of Typhoon Nyatoh during the next 24 hours. Nyatoh could intensify more rapidly once the eye and eyewall become fully formed. Typhoon Nyatoh will continue to strengthen and it could intensify to the equivalent of a major hurricane during the next 24 hours. An upper level trough west of Japan will produce southwesterly winds that will begin to affect Nyatoh later this week. Those winds will create more vertical wind shear and the shear will cause Typhoon Nyatoh to weaken.

Typhoon Nyatoh will move around the western part of a high pressure system over the Western North Pacific Ocean during the next 24 hours. The high pressure system will steer Nyatoh toward the north during the next 24 hours. The upper level trough will steer Typhoon Nyatoh toward the northeast after Nyatoh moves around the western end of the high pressure system. On its anticipated track Tropical Storm Nyatoh will remain west of the Marianas during the next 24 hours. Nyatoh could approach Iwo To in 48 hours.

Tropical Storm Nyatoh Strengthens West of the Marianas

Tropical Storm Nyatoh strengthened over the Western North Pacific Ocean west of the Marianas on Tuesday. At 4:00 p.m. EST on Tuesday the center of Tropical Storm Nyatoh was located at latitude 13.4°N and longitude 136.7°E which put it about 510 miles (825 km) west of Guam. Nyatoh was moving toward the west-northwest at 7 m.p.h. (11 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 991 mb.

Tropical Storm Nyatoh continued to strengthen west of the Marianas on Tuesday. The inner end of a rainband wrapped around the northern and western sides of the center of Nyatoh. Additional bands of showers and thunderstorms were revolving around the center of Tropical Storm Nyatoh. Storms near the center of circulation generated strong upper level divergence that pumped mass away from the tropical storm. Winds to tropical storm force extended out 130 miles (210 km) from the center of Nyatoh’s circulation.

Tropical Storm Nyatoh will move through an environment mostly favorable for intensification during the next 24 hours. Nyatoh will move over water where the Sea Surface Temperatures are near 29˚C. It will move under the western part of the axis of an upper level ridge centered east of the Marianas. The upper level winds are weak near the axis of the ridge and there will be little vertical wind shear. Clockwise flow around a high pressure system centered over eastern Asia could transport drier air toward the northwestern part of Nyatoh’s circulation. The drier air is likely to remain northwest of Tropical Storm Nyatoh during the next 24 hours. Nyatoh could intensify more rapidly once the inner end of the rainband wraps around the center of circulation and a core with an eye and an eyewall develops. Tropical Storm Nyatoh will continue to strengthen and it will intensify to a typhoon during the next 24 hours.

Tropical Storm Nyatoh will move around the western part of a high pressure system over the Western North Pacific Ocean during the next 24 hours. The high pressure system will steer Nyatoh toward the north during the next 24 hours. Nyatoh could move toward the northeast after it moves around the western end of the high pressure system. On its anticipated track Tropical Storm Nyatoh will remain west of the Marianas during the next 24 hours.

TD 27W Strengthens to Tropical Storm Nyatoh West of Guam

Former Tropical Depression 27W strengthened to Tropical Storm Nyatoh west of Guam on Monday night. At 10:00 p.m. EST on Monday the center of Tropical Storm Nyatoh was located at latitude 13.0°N and longitude 138.7°E which put it about 370 miles (600 km) west of Guam. Nyatoh was moving toward the west 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 former Tropical Depression 27W continued to strengthen on Monday night and the Japan Meteorological Agency upgraded the system to Tropical Storm Nyatoh. More thunderstorms developed near the center of circulation and in the bands revolving around the center of Nyatoh. Storms near the center generated upper level divergence that pumped mass away from the tropical storm. Winds to tropical storm force extended out 125 miles (200 km) from the center of Tropical Storm Nyatoh.

Tropical Storm Nyatoh will move through an environment mostly favorable for intensification during the next 36 hours. Nyatoh will move over water where the Sea Surface Temperatures are near 29˚C. It will move under the western part of the axis of an upper level ridge centered east of the Marianas. The upper level winds are weak near the axis of the ridge and there will be little vertical wind shear. Clockwise flow around a high pressure system centered over eastern Asia could transport drier air toward the northwestern part of Nyatoh’s circulation. The drier air is likely to remain northwest of the core of Tropical Storm Nyatoh during the next 36 hours. Tropical Storm Nyatoh will continue to strengthen and it could intensify to a typhoon during the next 36 hours.

Tropical Storm Nyatoh will move around the southwestern part of a high pressure system over the Western North Pacific Ocean during the next 36 hours. The high pressure system will steer the tropical depression toward the northwest during the next 36 hours. On its anticipated track Tropical Storm Nyatoh will move farther away from the Marianas and Yap.

Tropical Depression Forms Southwest of the Marianas

A tropical depression formed southwest of the Marianas on Monday morning. At 7:00 a.m. EST on Monday the center of Tropical Depression 27W was located at latitude 11.8°N and longitude 141.1°E which put it about 270 miles (435 km) west-southwest of Guam. The tropical depression was moving toward the west-northwest at 12 m.p.h. (19 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.

The circulation around a low pressure system west-southwest of Guam exhibited more organization on Monday morning and the Japan Meteorological Agency designated the system as a tropical depression. The circulation around Tropical Depression 27W was gradually becoming more organized. A distinct low level center of circulation was evident on conventional and microwave satellite images. More thunderstorms were beginning to develop near the center of circulation. Storms near the center began to generate upper level divergence that pumped mass away from the tropical depression. Additional thunderstorms were forming in bands revolving around the center of the depression.

Tropical Depression 27W will move through an environment favorable for intensification during the next 24 hours. The tropical depression will move over water where the Sea Surface Temperatures are near 29˚C. It will move under the western part of the axis of an upper level ridge centered east of the Marianas. The upper level winds are weak near the axis of the ridge and there will be little vertical wind shear. Tropical Depression 27W will strengthen gradually and it is likely to intensify to a tropical storm during the next 24 hours.

Tropical Depression 27W will move around the southwestern part of a high pressure system over the Western North Pacific Ocean during the next 24 hours. The high pressure system will steer the tropical depression toward the west-northwest during the next day or so. On its anticipated track Tropical Depression 27W will move farther away from the Marianas. It will pass north of Yap.