Category Archives: Western North Pacific

Western Pacific Typhoons and Tropical Storms

Nokaen Strengthens Back to a Tropical Storm

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Former Tropical Depression Nokaen strengthened back to a tropical storm over the Western North Pacific Ocean on Monday night.  At 10:00 a.m. EST on Tuesday the center of the Tropical Storm Nokaen was located at latitude 17.4°N and longitude 132.3°E which put the center about 700 miles (1130 km) northwest of Yap.  Nokaen was moving toward the east at 17 m.p.h. (28 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.

After weakening to a tropical depression on Sunday, Nokaen strengthened back to a tropical storm on Monday night.  Thunderstorms developed in several bands in the eastern side of Tropical Storm Nokaen.  Bands in the western side of Nokaen’s circulation still consisted primarily of showers and lower clouds.  The thunderstorms in the eastern side of Nokaen started to generate some upper level divergence that pumped mass away to the east of the tropical storm.

The strongest winds were occurring in the western side of Tropical Storm Nokaen.  Winds to tropical storm force extended out 115 miles (185 km) in the western half of Nokaen’s circulation.  The winds in the the eastern side of Tropical Storm Nokaen were blowing at less than tropical storm force.

Tropical Storm Nokaen will move through an environment that will be unfavorable for intensification during the next 24 hours.  Nokaen will move over water where the Sea Surface Temperatures are near 28°C.  However, it will continue to be surrounded by drier air.  In addition, Tropical Storm Nokaen will move under the southern portion of the midlatitude upper level westerly winds.  Those winds will cause vertical wind shear.  The drier air and the vertical wind shear will prevent Tropical Storm Nokaen from intensifying.

Tropical Storm Nokaen will move around the northwestern part of a high pressure system that is over the Western North Pacific Ocean.  The high pressure system will steer Nokaen toward the east during the next 24 hours.  On its anticipated track, Tropical Storm Nokaen will remain northwest of Yap.

Nokaen Weakens to a Tropical Depression

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Former Tropical Storm Nokaen weakened to a tropical depression over the Western North Pacific Ocean east of Luzon on Monday morning.  At 10:00 a.m. EST on Monday the center of the Tropical Depression Nokaen was located at latitude 17.1°N and longitude 127.4°E which put the center about 365 miles (530 km) east-southeast of Aparri, Philippines.  Nokaen was moving toward the northeast at 6 m.p.h. (10 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 1000 mb.

Former Tropical Storm Nokaen continued to move through an environment containing drier air on Monday.  The drier air caused most of the thunderstorms in Tropical Depression Nokaen to dissipate.  A few thunderstorms were still occurring in a band in the far northern periphery of Nokaen’s circulation.  The bands in the other parts of Tropical Depression Nokaen consisted primarily of showers and lower clouds.

Tropical Depression Nokaen will move through an environment that will be unfavorable for intensification during the next 24 hours.  Nokaen will move over water where the Sea Surface Temperatures are near 28°C.  However, it will continue to be surrounded by drier air.  In addition, Tropical Depression Nokaen will move under the southern portion of the midlatitude upper level westerly winds.  Those winds will cause vertical wind shear.  The drier air and the vertical wind shear will cause the circulation around Tropical Depression Nokaen to continue to weaken.

Tropical Depression Nokaen will move around the western end of a high pressure system that is over the Western North Pacific Ocean.  The high pressure system will steer Nokaen toward the east-northeast during the next 24 hours.  On its anticipated track, Tropical Depression Nokaen will continue to move farther away from Luzon as it gradually spins down.

Tropical Storm Nokaen Weakens East of the Philippines

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Tropical Storm Nokaen weakened east of the Philippines on Sunday morning.  At 10:00 a.m. EST on Sunday the center of the Tropical Storm Nokaen was located at latitude 15.5°N and longitude 125.9°E which put the center about 310 miles (500 km) east-southeast of Casiguran, Philippines.  Nokaen was moving toward the north-northeast at 8 m.p.h. (13 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.

A combination of drier air and vertical wind shear caused Tropical Storm Nokaen to weaken east of the Philippines on Sunday morning.  A large high pressure system over eastern Asia was transporting drier air into the environment around Tropical Storm Nokaen.  The drier air caused many of the thunderstorms in Nokaen’s circulation to dissipate.  An upper level ridge over the Western North Pacific Ocean was producing southerly winds that blew the tops off of many of the thunderstorms remaining in Tropical Storm Nokaen.

Most of the bands in Tropical Storm Nokaen consisted primarily of showers and lower clouds on Sunday morning.  A few new thunderstorms formed northeast of the center of Nokaen’s circulation.  The dissipation of many of the thunderstorms in Nokaen reduced the upper level divergence.   Without thunderstorms to pump mass away from Nokaen, convergence in the lower levels of the atmosphere caused the surface pressure to increase.

The distribution of wind speeds in Tropical Storm Nokaen remained asymmetrical.  Winds to tropical storm force extended out 115 miles (185 km) in the northern half of Nokaen’s circulation.  Winds to tropical storm force extended out only 25 miles (40 km) in the southern half of Tropical Storm Nokaen.

Tropical Storm Nokaen will move through an environment that will be unfavorable for intensification during the next 24 hours.  Nokaen will move over water where the Sea Surface Temperatures are near 28°C.  However, the western end of the upper level ridge over the Western North Pacific Ocean will continue to produce southerly winds that will blow toward the top of Nokaen’s circulation.  Those winds will cause strong vertical wind shear.  In addition drier air will continue to surround Tropical Storm Nokaen.  Tropical Storm Nokaen is likely to continue to weaken slowly during the next 24 hours.

Tropical Storm Nokaen will move around the western end of a high pressure system that is over the Western North Pacific Ocean.  The high pressure system will steer Nokaen toward the northeast during the next 24 hours.  On its anticipated track, the center of Tropical Storm Nokaen will move farther away from Luzon.

Tropical Storm Nokaen Passes East of Luzon

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Tropical Storm Nokaen was passing just to the east of Luzon on Saturday morning.  At 10:00 a.m. EST on Saturday the center of the Tropical Storm Nokaen was located at latitude 15.2°N and longitude 124.1°E which put the center about 185 miles (300 km) east-southeast of Casiguran, Philippines.  Nokaen was moving toward the northwest at 13 m.p.h. (21 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 993 mb.

Tropical Storm Nokaen strengthened a little more as it moved east of Luzon on Saturday morning.  Even though Nokaen was stronger, the distribution of thunderstorms remained asymmetrical.  Thunderstorms were occurring in bands in the western and northern parts of Tropical Storm Nokaen.  Bands in the eastern and southern parts of Nokaen’s circulation consisted primarily of showers and lower clouds.  Storms near the center of Nokaen generated upper level divergence that pumped mass away from the tropical storm.  The removal of mass caused the surface pressure to decrease.

The circulation around Tropical Storm Nokaen was interacting with a high pressure system over eastern Asia.  The interaction was causing a large area of strong winds in the northwestern quadrant of Nokaen’s circulation.  Winds to tropical storm force extended out 150 miles (240 km) in the northwestern quadrant of Tropical Storm Nokaen.  Winds to tropical storm force only extended out 60 miles (95 km) in the other quadrants of Nokaen’s circulation.

Tropical Storm Nokaen will move through an environment that will become unfavorable for intensification during the next 24 hours.  Nokaen will move over water where the Sea Surface Temperatures are near 28°C.  It will move under the western end of an upper level ridge that is over the Western North Pacific Ocean.  The upper level ridge will produce southeasterly winds that will blow toward the top of Nokaen’s circulation.  Those winds will cause the vertical wind shear to increase.  Tropical Storm Nokaen will start to weaken when the vertical wind shear increases.

Tropical Storm Nokaen will move around the western end of a high pressure system that is over the Western North Pacific Ocean.  The high pressure system will steer Nokaen toward the north during the next 24 hours.  On its anticipated track, the center of Tropical Storm Nokaen will remain east of Luzon.

Bands in the western side of Tropical Storm Nokaen will bring gusty winds and locally heavy rain to parts of Luzon.  Heavy rain could cause flash floods in some locations.

Tropical Cyclone Nokaen Nears the Philippines

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Tropical Storm Nokaen moved nearer to the Philippines on Friday morning.  At 10:00 a.m. EST on Friday the center of the Tropical Storm Nokaen was located at latitude 12.4°N and longitude 126.7°E which put the center about 115 miles (185 km) east of Laoang, Philippines.  Nokaen was moving toward the west-northwest at 11 m.p.h. (17 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 997 mb.

Tropical Storm Nokaen strengthened on Friday morning as it moved closer to the Philippines.  More thunderstorms formed near the center of Nokaen’s circulation.  More thunderstorms also developed in bands in the western side of Tropical Storm Nokaen.  Bands in the eastern side of Nokaen’s circulation still consisted primarily of showers and lower clouds.  Storms near the center of Nokaen generated more upper level divergence that pumped mass away from the tropical storm.  The removal of more mass caused the surface pressure to decrease.

The strongest winds were occurring in the northwestern part of Tropical Storm Nokaen.  Winds to tropical storm force extended out 150 miles (240 km) in the northwestern quadrant of Nokaen’s circulation.  The winds in the other parts of Tropical Storm Nokaen were blowing at less than tropical storm force.

Tropical Storm Nokaen will move through an environment somewhat favorable for intensification during the next 24 hours.  Nokaen will move over water where the Sea Surface Temperatures are near 29°C.  It will move under the western end of an upper level ridge that is over the Western North Pacific Ocean.  The upper level ridge will produce southeasterly winds that will blow toward the top of Nokaen’s circulation.  Those winds will cause moderate vertical wind shear.  The moderate vertical wind shear will inhibit intensification, but the wind shear may not be enough to prevent intensification.  Tropical Storm Nokaen could continue to intensify during the next 24 hours.

Tropical Storm Nokaen will move around the western end of a high pressure system that is over the Western North Pacific Ocean.  The high pressure system will steer Nokaen toward the northwest during the next 24 hours.  On its anticipated track, the center of Tropical Storm Nokaen will be near Samar on in 24 hours.

Bands in the western side of Nokaen’s circulation are already bringing gusty winds and locally heavy rain to Samar, Catanduanes Island, and southeastern Luzon.  Heavy rain is likely to cause flash floods in some locations.

Tropical Storm Nokaen Develops East of the Philippines

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Tropical Storm Nokaen developed over the Western North Pacific Ocean east of the Philippines on Thursday morning.  At 10:00 a.m. EST on Thursday the center of the Tropical Storm Nokaen was located at latitude 10.2°N and longitude 128.8°E which put the center about 220 miles (335 km) east of Dinagat, Philippines.  Nokaen was moving toward the northwest at 2 m.p.h. (3 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.

A low pressure system over the Western North Pacific Ocean east of the Philippines strengthened on Thursday morning and the Japan Meteorological Agency designated the system as Tropical Storm Nokaen.

Thunderstorms were occurring near the center of Tropical Storm Nokaen.  Thunderstorms were also occurring in bands in the western and northern parts of Nokaen’s circulation.  Bands in the eastern and southern parts of Tropical Storm Nokaen consisted primarily of showers and thunderstorms.  Storms near the center of Nokaen generated upper level divergence that pumped mass away from the tropical storm.  The removal of mass caused the surface pressure to decrease.

The distribution of winds speeds in Tropical Storm Nokaen was asymmetrical.  Winds to tropical storm force extended out 150 miles (240 km) in the northern half of Nokaen’s circulation.  Winds to tropical storm force extended out 45 miles (75 km) in the southern half of Tropical Storm Nokaen.

Tropical Storm Nokaen will move through an environment somewhat favorable for intensification during the next 24 hours.  Nokaen will move over water where the Sea Surface Temperatures are near 29°C.  It will move under the western end of an upper level ridge that is over the Western North Pacific Ocean.  The upper level ridge will produce southeasterly winds that will blow toward the top of Nokaen’s circulation.  Those winds will cause moderate vertical wind shear.  The moderate vertical wind shear will inhibit intensification, but the wind shear may not be enough to prevent intensification.  Tropical Storm Nokaen could intensify slowly during the next 24 hours.

Tropical Storm Nokaen will move around the western end of a high pressure system that is over the Western North Pacific Ocean.  The high pressure system will steer Nokaen toward the northwest during the next 24 hours.  On its anticipated track, Tropical Storm Nokaen will move closer to the central Philippines.

Bands in the western side of Nokaen’s circulation will bring gusty winds and locally heavy rain to Samar, Cataduanes Island, and southeastern Luzon.  Heavy rain could cause flash floods in some locations.

Tropical Storm Koto Weakens East of Vietnam

Tropical Storm Koto weakened as it meandered over the South China Sea east of Vietnam on Sunday.  At 10:00 p.m. EST on Sunday the center of Tropical Storm Koto was located at latitude 14.7°N and longitude 111.6°E which put the center about 200 miles (320 km) east-northeast of Quy Nhon, Vietnam.  Koto was moving toward the southwest 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 1004 mb.

Tropical Storm Koto weakened on Sunday as it moved through a mass of drier air over the western part of the South China Sea.  The drier air caused thunderstorms near the center of Koto’s circulation to dissipate.  Many of the bands revolving around the center of Tropical Storm Koto consisted of showers and lower clouds.  Thunderstorms were still occurring in a couple of bands in the southern part of Koto’s circulation.

There were no thunderstorms near the center of Tropical Storm Koto to generate upper level divergence.  Mass was still converging in the lower levels of the atmosphere.  So, the surface pressure increased on Sunday.

The size of the circulation around Tropical Storm Koto decreased as Koto weakened on Sunday.  Winds to tropical storm force extended out 65 miles (105 km) from the center of Koto’s circulation.

Tropical Storm Koto will be in an environment that will be unfavorable for intensification during the next 24 hours.  Koto will move over water where the Sea Surface Temperatures are near 29°C.  It will move under the southeastern part of an upper level ridge that is over the Southeast Asia.  The upper level ridge will produce northeasterly winds that will blow toward the top of Koto’s circulation.  Those winds will cause strong vertical wind shear.  In addition, Tropical Storm Koto will continue to be in a region of drier air that is over the western part of the South China Sea.  The strong vertical wind shear and drier air will continue to cause Tropical Storm Koto to weaken during the next 24 hours.

Since there are no thunderstorms near the center of Tropical Storm Koto, Koto will be steered by the winds in the lower level of the atmosphere.  Koto will move around the southeastern side of a high pressure system that is over Southeast Asia.  The high pressure system will steer Koto toward the southwest during the next 24 hours.  On its anticipated track, Tropical Storm Koto will move toward southern Vietnam.

Tropical Storm Koto Stalls East of Vietnam

Tropical Storm Koto stalled over the South China Sea east of Vietnam on Saturday.  At 4:00 p.m. EST on Saturday the center of Tropical Storm Koto was located at latitude 13.8°N and longitude 112.2°E which put the center about 200 miles (320 km) east of Quy Nhon, Vietnam.  Koto was moving toward the north at 3 m.p.h. (5 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 998 mb.

Tropical Storm Koto was showing signs of more organization on Saturday afternoon.  More thunderstorms developed near the center of Koto’s circulation.  New thunderstorms also formed in some of the bands revolving around the center of Tropical Storm Koto.  Storms near the center of Koto were not yet generating much upper level divergence.  Mass was still converging in the lower levels of the atmosphere.  So, the surface pressure was increasing.

The distribution of wind speeds around Tropical Storm Koto continued to be asymmetrical. Winds to tropical storm force extended out 125 miles (200 km) in the western side of Koto’s circulation.  Winds to tropical storm force extended out 65 miles (105 km) in the eastern side of Tropical Storm Koto.

Tropical Storm Koto will be in an environment that will be marginally favorable for intensification during the next 24 hours.  Koto will move over water where the Sea Surface Temperatures are near 29°C.  It will move under the southern part of an upper level ridge that is over the South China Sea.  The upper level ridge will produce southeasterly winds that will blow toward the top of Koto’s circulation.  Those winds will cause some vertical wind shear.  In addition, Tropical Storm Koto will be in a region of drier air that is over the South China Sea.  The vertical wind shear and drier air will inhibit intensification.  Tropical Storm Koto is likely to maintain its intensity during the next 24 hours.  Koto could strengthen a little if the new thunderstorms near the center of circulation begin to generate more upper level divergence.

Tropical Storm Koto will start to move around the southern side of a high pressure system that is over China.  The high pressure system will begin to steer Koto toward the west during the next 24 hours.  On its anticipated track, Tropical Storm Koto will start to move toward Vietnam on Sunday.

Elsewhere, Tropical Depression Senyar was weakening south of Vietnam.  At 4:00 p.m. EST on Saturday the center of Tropical Depression Senyar was located at latitude 6.0°N and longitude 108.9°E which put the center about 380 miles (615 km) south-southeast of Ho Chi Minh City, Vietnam.  Senyar was moving toward the east-northeast at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 1006 mb.

Tropical Storm Koto Meanders East of Vietnam

Tropical Storm Koto meandered over the South China Sea east of Vietnam on Friday.  At 4:00 p.m. EST on Friday the center of Tropical Storm Koto was located at latitude 13.0°N and longitude 112.5°E which put the center about 235 miles (380 km) east-northeast of Nha Trang, Vietnam.  Koto was moving toward the north at 3 m.p.h. (5 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 993 mb.

Tropical Storm Koto was maintaining its intensity on Friday.  New thunderstorms develop west of the center of Koto’s circulation.  Bands in the other parts of Tropical Storm Koto consisted primarily of showers and lower clouds.  Storms west of the center of Koto generated some upper level divergence that pumped mass away to the northwest of the tropical storm.  The removal of mass in the upper levels was nearly equal to the inflow of mass in the lower levels of the atmosphere.  So, the surface pressure was nearly steady.

The distribution of wind speeds around Tropical Storm Koto continued to be very asymmetrical.  Winds to tropical storm force extended out 180 miles (290 km) in the western side of Koto’s circulation.  Winds to tropical storm force extended out 65 miles (105 km) in the eastern side of Tropical Storm Koto.

Tropical Storm Koto will be in an environment that will be unfavorable for intensification during the next 24 hours.  Koto will move over water where the Sea Surface Temperatures are near 29°C.  It will move under the southern part of an upper level ridge that is over the South China Sea.  The upper level ridge will produce southeasterly winds that will blow toward the top of Koto’s circulation.  Those winds will cause moderate vertical wind shear.  In addition, Tropical Storm Koto will continue to move through the region of drier air that is over the South China Sea.  Tropical Storm Koto in likely to maintain its intensity during the next 24 hours because of the moderate vertical wind shear and the effects of the drier air.

Tropical Storm Koto will continue to be in a region where the steering currents are weak during the next 24 hours.  On its anticipated track, Tropical Storm Koto will meander slowly over the South China Sea on Friday.

Elsewhere, Tropical Cyclone Senyar moved across Malaysia and over the extreme southwestern part of the Western North Pacific Ocean.  Both the U.S. Joint Typhoon Warning Center and the Japan Meteorological Agency were classifying Senyar as a tropical depression.  At 4:00 p.m. EST on Friday the center of Tropical Depression Senyar was located at latitude 4.8°N and longitude 105.5°E which put the center about 160 miles (260 km) east-northeast of Kuantan, Malaysia.  Senyar was moving toward the east-northeast at 7 m.p.h. (11 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.

Koto Weakens Back to a Tropical Storm

Former Typhoon Koto weakened back to a tropical storm over the South China Sea on Thursday.  At 4:00 p.m. EST on Thursday the center of Tropical Storm Koto was located at latitude 12.3°N and longitude 113.5°E which put the center about 435 miles (705 km) southeast of Da Nang, Vietnam.  Koto was moving toward the south-southwest at 5 m.p.h. (8 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 986 mb.

Former Typhoon Koto moved into a region of drier air and weakened back to a tropical storm over the South China Sea on Thursday.  A high pressure system over China was pumping drier air over the South China Sea.  Many of the thunderstorms in Tropical Storm Koto weakened when the drier air was pulled into Koto’s circulation.  Most of the remaining thunderstorms were occurring in bands in the northwestern part of Tropical Storm Koto.  Bands in the other parts of Koto’s circulation consisted primarily of showers and lower clouds.

Storms near the center of Tropical Storm Koto generated less upper level divergence.  The removal of mass in the upper levels of Koto’s circulation was less than the inflow of mass in the lower levels of the atmosphere.  As a result, the surface pressure was increasing.

The distribution of wind speeds in Tropical Storm Koto continued to be very asymmetrical.  Winds to tropical storm force extended out 205 miles (335 km) in the northern side of Koto’s circulation.  Winds to tropical storm force extended out 70 miles (110 km) in the southern side of Tropical Storm Koto.

Tropical Storm Koto will move through an environment that will be unfavorable for intensification during the next 24 hours.  Koto will move over water where the Sea Surface Temperatures are near 29°C.  It will move under the southern part of an upper level ridge that is over the Western North Pacific Ocean.  The upper level ridge will produce southeasterly winds that will blow toward the top of Koto’s circulation.  Those winds will cause moderate vertical wind shear.  In addition, Tropical Storm Koto will continue to move through the region of drier air that is over the western part of the South China Sea.  Moderate vertical wind shear and the effects of drier air will cause Tropical Storm Koto to continue to weaken during the next 24 hours.

Tropical Storm Koto will be in a region where the steering currents are weak during the next 24 hours.  On its anticipated track, Tropical Storm Koto is likely to meander slowly over the South China Sea on Friday.