Category Archives: Tropical Cyclones

Information about tropical cyclones

Tropical Storm Koto Weakens East of Vietnam

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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 Cyclone Ditwah Weakens

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Tropical Cyclone Ditwah was weakening on Sunday as it moved slowly over the southwestern Bay of Bengal east of southern India.  At 10:00 a.m. EST on Sunday the center of Tropical Cyclone Ditwah was located at latitude 11.8°N and longitude 80.6°E which put the center about 55 miles (90 km) east-southeast of Puducherry, India.  Ditwah was moving toward the north at 2 m.p.h. (3 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 1004 mb.

Tropical Cyclone Ditwah was weakening slowly on Sunday.  A few new thunderstorms developed near the center of Ditwah’s circulation.  However, most of the bands revolving around the center of Tropical Cyclone Ditwah consisted of showers and lower clouds.  Thunderstorms were occurring in a couple of bands in the northeastern periphery of Ditwah’s circulation.

Tropical Cyclone Ditwah will move through an environment mostly unfavorable for intensification during the next 24 hours.  Ditwah will move over water where the Sea Surface Temperatures are near 29°C.  It will move under the western part of an upper level ridge that is over Southeast Asia and the Bay of Bengal.  The upper level ridge will produce southeasterly winds that will blow toward the top of Ditwah’s circulation.  Those winds will cause moderate vertical wind shear.  The moderate vertical wind shear will inhibit intensification.  In addition, drier air being pulled into Ditwah’s circulation is likely to limit the formation of new thunderstorms.  Tropical Cyclone Ditwah is likely to continue to weaken slowly during the next 24 hours because of the moderate vertical wind shear and the effects of the drier air.

Tropical Cyclone Ditwah will move around the southwestern part of a high pressure system over the Bay of Bengal.  The high pressure system will steer Ditwah slowly toward the north during the next 24 hours.  On its anticipated track, Tropical Cyclone Ditwah will move nearly parallel to the coast of southeast India.

Tropical Cyclone Ditwah will bring gusty winds and isolated heavy rain to parts of Tamil Nadu and Puducherry.

Tropical Storm Koto Stalls East of Vietnam

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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 Cyclone Ditwah Moves North of Sri Lanka

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Tropical Cyclone Ditwah moved north of Sri Lanka on Saturday.  At 10:00 a.m. EST on Saturday the center of Tropical Cyclone Ditwah was located at latitude 10.2°N and longitude 80.8°E which put the center about 150 miles (240 km) southeast of Puducherry, India.  Ditwah was moving toward the north at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 40 m.p.h. (50 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1004 mb.

The circulation around Tropical Cyclone Ditwah was pulling in drier air from over India.  The drier air caused the thunderstorms near the center of Ditwah’s circulation to weaken.  Thunderstorms were still occurring in bands in the northern and eastern periphery of Tropical Cyclone Ditwah.  Bands in the other parts of Ditwah’s circulation consisted primarily of showers and lower clouds.

Even though the thunderstorms near the center of Tropical Cyclone Ditwah weakened, Ditwah was still producing winds to tropical storm force.  Winds to tropical storm force extended out 140 miles (225 km) from the center of Ditwah’s circulation.

Tropical Cyclone Ditwah will move through an environment marginally favorable for intensification during the next 24 hours.  Ditwah will move over water where the Sea Surface Temperatures are near 29°C.  It will move under the western part of an upper level ridge that is over Southeast Asia and the Bay of Bengal.  The upper level ridge will produce southeasterly winds that will blow toward the top of Ditwah’s circulation.  Those winds will cause moderate vertical wind shear.  The vertical wind shear will inhibit intensification but the shear may not be enough to prevent some intensification.  However, the drier air being pulled into Ditwah’s circulation is likely to inhibit the formation of new thunderstorms.  Tropical Cyclone Ditwah could maintain its intensity during the next 24 hours.  However, the drier air is likely to cause Ditwah to weaken slowly during the next several days.

Tropical Cyclone Ditwah will move around the southwestern part of a high pressure system over the Bay of Bengal.  The high pressure system will steer Ditwah toward the north during the next 24 hours.  On its anticipated track, Tropical Cyclone Ditwah will move nearly parallel to the coast of southeast India.

Tropical Cyclone Ditwah will bring gusty winds and isolated heavy rain to parts of Tamil Nadu and Puducherry.

Tropical Storm Koto Meanders East of Vietnam

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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.

Tropical Cyclone Ditwah Spins Near Sri Lanka

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Tropical Cyclone Ditwah continued to spin near Sri Lanka on Friday.  At 10:00 a.m. EST on Friday the center of Tropical Cyclone Ditwah was located at latitude 8.8°N and longitude 80.8°E which put the center about 85 miles (135 km) south-southeast of Jaffna, Sri Lanka.  Ditwah was moving toward the north-northwest at 4 m.p.h. (6 km/h).  The maximum sustained wind speed was 40 m.p.h. (50 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1004 mb.

The center of Tropical Cyclone Ditwah was still over northern Sri Lanka on Friday morning.  The fact that the center of Ditwah’s circulation was still over land combined with the effects of vertical wind shear to cause the distribution of thunderstorms to be asymmetrical.  Thunderstorms were occurring in bands in the northern and western parts of Tropical Cyclone Ditwah.  Bands in the southern and eastern parts of Ditwah’s circulation consisted primarily of showers and lower clouds.

The strongest winds in Tropical Cyclone Ditwah were occurring over the southwestern Bay of Bengal.   Winds to tropical storm force extended out 110 miles (175 km) from the center of Ditwah’s circulation.  The winds were much weaker over land.

Tropical Cyclone Ditwah will move through an environment somewhat favorable for intensification when the center of its circulation moves back over the southwestern Bay of Bengal in a few hours.  Ditwah will move over water where the Sea Surface Temperatures are near 29°C.  It will move under the western part of an upper level ridge that is over Southeast Asia and the Bay of Bengal.  The upper level ridge will produce southeasterly winds that will blow toward the top of Ditwah’s circulation.  Those winds will cause moderate vertical wind shear.  The vertical wind shear will inhibit intensification but the shear may not be enough to prevent some intensification.  Tropical Cyclone Ditwah could intensify a little during the next 24 hours even with moderate vertical wind shear, when the center of its circulation moves back over water.

Tropical Cyclone Ditwah will move around the southwestern part of a high pressure system over the Bay of Bengal.  The high pressure system will steer Ditwah toward the north-northwest during the next 24 hours.  On its anticipated track, the center of Tropical Cyclone Ditwah will move north of Sri Lanka in a few hours.  Ditwah could reach the coast of Tamil Nadu during the weekend.

Tropical Cyclone Ditwah will continue to affect Sri Lanka and southern India.  Ditwah will bring strong winds and heavy rain to parts of Sri Lanka and Tamil Nadu.  Heavy rain could cause flash floods in some locations.  There were reports that flooding in Sri Lanka had already caused fatalities.

Koto Weakens Back to a Tropical Storm

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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.

Tropical Cyclone Ditwah Forms Near Sri Lanka

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Tropical Cyclone Ditwah formed over the southwestern Bay of Bengal on Thursday.  At 10:00 a.m. EST on Thursday the center of Tropical Cyclone Ditwah was located at latitude 7.8°N and longitude 81.6°E which put the center about 10 miles (15 km) northwest of Batticaloa, Sri Lanka.  Ditwah was moving toward the northwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 40 m.p.h. (50 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1002 mb.

A low pressure system over the southwestern Bay of Bengal near Sri Lanka intensified on Thursday and the India Meteorological Department designated the system as Tropical Cyclone Ditwah.

The center of Tropical Cyclone Ditwah was near the east coast of Sri Lanka.  About half of Ditwah’s circulation was over Sri Lanka.  A band of thunderstorms was wrapped around the northern and western sides of the center of Tropical Cyclone Ditwah.  Other bands of showers and thunderstorms were revolving around the center of Ditwah’s circulation.  Storms near the center of Ditwah generated upper level divergence that pumped mass away to the west of the tropical cyclone.  The removal of mass caused the surface pressure to decrease slowly.

The distribution of wind speeds in Tropical Cyclone Ditwah was asymmetrical.  Winds to tropical storm force extended out 175 miles (280 km) in the southern half of Ditwah’s circulation.  Winds to tropical storm force extended out 80 miles (130 km) in the northern side of Tropical Cyclone Ditwah.

Tropical Cyclone Ditwah will move through an environment somewhat favorable for intensification during the next 24 hours.  Ditwah will move over water where the Sea Surface Temperatures are near 29°C.  It will move under the western part of an upper level ridge that is over Southeast Asia and the Bay of Bengal.  The upper level ridge will produce southeasterly winds that will blow toward the top of Ditwah’s circulation.  Those winds will cause moderate vertical wind shear.  The vertical wind shear will inhibit intensification.  The fact that almost half of Ditwah’s circulation is over Sri Lanka will also inhibit intensification.  Tropical Cyclone Ditwah could intensify during the next 24 hours even with moderate vertical wind shear, if the center of its circulation remains over water.

Tropical Cyclone Ditwah will move around the southwestern part of a high pressure system over the Bay of Bengal.  The high pressure system will steer Ditwah toward the northwest during the next 24 hours.  On its anticipated track, the center of Tropical Cyclone Ditwah will move along the coast of northeastern Sri Lanka.  Ditwah could approach the coast of India near Chennai within 72 hours.

Tropical Cyclone Ditwah will produce strong winds and heavy rain over Sri Lanka.  Heavy rain will cause flash floods in some locations.

Koto Intensifies to a Typhoon Over South China Sea

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Former Tropical Storm Koto intensified to a typhoon over the South China Sea on Wednesday.   At 4:00 p.m. EST on Wednesday the center of Typhoon Koto was located at latitude 13.2°N and longitude 114.5°E which put the center about 475 miles (765 km) east-southeast of Da Nang, Vietnam.  Koto was moving toward the northwest at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 982 mb.

Former Tropical Storm Koto intensified to a typhoon on Wednesday.  Thunderstorms continued to develop around the center of Typhoon Koto.  Bands of showers and thunderstorms were revolving around the center of Koto’s circulation.  Storms near the center of Koto 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 wind speeds around Typhoon Koto was asymmetrical.  Winds to typhoon force extended out 30 miles from the center of Koto’s circulation.  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 Typhoon Koto.

Typhoon Koto will move through an environment that will become unfavorable for intensification during the next 24 hours.  Koto will move over water where the Sea Surface Temperatures are near 30°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 easterly winds that will blow toward the top of Koto’s circulation.  Those winds will cause the vertical wind shear to increase.  In addition, Typhoon Koto will move into a region of drier air that is flowing over the western part of the South China Sea.  Some of the drier air is likely to get pulled into the western side of Koto’s circulation.  More vertical wind shear and the effects of drier air will cause Typhoon Koto to start to weaken during the next 24 hours.

Typhoon Koto will move around the southern side of a high pressure system over the Western North Pacific Ocean.  The high pressure system will steer Koto toward the west during the next 24 hours.  On its anticipated track, Typhoon Koto will move closer to Vietnam.  A second high pressure system over China and Southeast Asia that is transporting the drier air over the western part of the South China Sea will impede the progress of Koto later this week.  Koto could meander over the South China Sea for several days at the end of the week.

Tropical Cyclone Senyar Brings Wind and Rain to Northern Sumatra

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Tropical Cyclone Senyar brought wind and rain to northern Sumatra on Wednesday.  At 4:00 a.m. EST on Wednesday the center of Tropical Cyclone Senyar was located at latitude 3.8°N and longitude 98.3°E which put the center about 30 miles (50 km) northwest of Medan, Indonesia.  Senyar was moving toward the south-southeast 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 999 mb.

Tropical Cyclone Senyar was located at latitude 3.8°N which once again proves that tropical cyclones can occur near the Equator.

Tropical Cyclone Senyar continued to be in an environment characterized by strong vertical wind shear.  An upper level ridge over the Western North Pacific Ocean was causing strong easterly winds that were blowing toward the top of Senyar’s circulation.  Those winds were causing strong vertical wind shear.  The strong winds were causing the distribution of thunderstorms in Tropical Cyclone Senyar to be asymmetrical.  Thunderstorms were occurring in bands in the western side of Senyar’s circulation.  Bands in the eastern side of Tropical Cyclone Senyar consisted primarily of showers and lower clouds.

he circulation around Tropical Cyclone Senyar was small.  Winds to tropical storm force extended out 60 miles (95 km) from the center of Senyar’s circulation.

Tropical Cyclone Senyar will move through an environment that will be marginally favorable for intensification during the next 24 hours.  Senyar will move over water where the Sea Surface Temperatures are near 29°C.  However, the upper level ridge over the Western North Pacific Ocean will continue to cause strong vertical wind shear.  The strong vertical wind shear will seriously inhibit intensification, but the shear may not be enough to prevent some intensification.  In addition, the center of Senyar’s circulation will be near the coast of northeastern Sumatra.  Tropical Cyclone Senyar could maintain its intensity during the next 24 hours.

Tropical Cyclone Senyar will move through along trough of low pressure that is near the Equator. The trough of low pressure will steer Senyar toward the southeast during the next 24 hours.  On its anticipated track, Tropical Cyclone Senyar will move along the northeastern coast of Sumatra during the next 24 hours.

Tropical Cyclone Senyar will continue to bring strong winds and heavy rain to Aceh province in northern Sumatra.  Heavy rain is likely to cause floods in some locations.  There are already reports of flooding and casualties in northern Sumatra.