Monthly Archives: December 2017

Former Tropical Cyclone Hilda Drops Heavy Rain Over Western Australia

Former Tropical Cyclone Hilda dropped heavy rain over Western Australia on Friday.  At 11:00 a.m. EST on Friday the center of former Tropical Cyclone Hilda was located at latitude 22.7°S and longitude 123.6°E which put it about 50 miles (80 km) east-northeast of Telfer, Australia.  Hilda was moving toward the southeast at 6 m.p.h. (10 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 999 mb.

Although the center has been over land for more than a day, the circulation of former Tropical Cyclone Hilda is still well organized.  There is a well defined low level center of circulation and strong thunderstorms are occurring around the center.  Several bands of thunderstorms are revolving around the core of the circulation.  Storms near the core are generating strong upper level divergence which is pumping away mass.  The upper level divergence is preventing the surface pressure from increasing and that is allowing the surface low to maintain its intensity.

Storms near the core of former Tropical Cyclone Hilda and the rainbands are dropping heavy rain over parts of Western Australia.  That region is normally dry and the potential for flash floods exists.  The Australian Bureau of Meteorology has issued Flood Warnings for the Sandy Desert and West Kimberly District.  They have also issued Flood Watches for the De Grey River, Salt Lakes and Warburton District Catchments.  The storms generated by former Tropical Cyclone Hilda could also cause localized wind damage, but the greatest risk is posed by the heavy rain.

Tropical Cyclone Hilda Develops on Coast of Western Australia

A Tropical Low near the coast of Western Australia strengthened and the Australian Bureau of Meteorology designated the system as Tropical Cyclone Hilda. At 10:00 a.m. EST on Wednesday the center of Tropical Cyclone Hilda was located at latitude 18.0°S and longitude 122.1°E which put it about 10 miles (15 km) west-southwest of Broome, Australia.  Hilda was moving toward the south-southwest at 8 m.p.h. (12 km/h).  The maximum sustained wind speed was 50 m.p.h. (85 km/h) and there were wind gusts to 85 m.p.h. (140 km/h).  The minimum surface pressure was 985 mb.  Broome Port reported a wind gust to 86 m.p.h. (139 km/h).

The center of the Tropical Low moved off the coast of Western Australia and the core of the circulation strengthened.  Thunderstorms in the core of Tropical Cyclone Hilda generated strong upper level divergence which pumped mass away from the center of circulation.  The removal of mass allowed the surface pressure to decrease quickly and the wind speeds increased.  The strongest winds were occurring over water near the center of circulation.  Additional bands of showers and thunderstorms were revolving around the core of the circulation.  Hilda is a small tropical cyclone.  Winds to tropical storm force only extend out about 35 miles (55 km) from the center of circulation.

Tropical Cyclone Hilda will be moving through an environment that will support further intensification during the next 12 hours.  The Sea Surface Temperature of the water near the coast of Western Australia is near 30°C.  Tropical Cyclone Hilda is underneath an upper level ridge and the upper level winds are weak.  There is little vertical wind shear.  The proximity to land is the only factor preventing rapid intensification of Tropical Cyclone Hilda.  Almost half of the circulation is over land and the increased friction is reducing the wind speeds in that part of Tropical Cyclone Hilda.

Tropical Cyclone Hilda is moving around the western end of a subtropical ridge, which is steering the tropical cyclone toward the south-southwest.  A general motion toward the south-southwest is expected to continue for another 12 to 24 hours.  On its anticipated track the center of Tropical Cyclone Hilda could pass near Bidyadanga during the next 6 to 12 hours.  Hilda will bring gusty winds capable of producing localized minor wind damage.  A Warning is in effect for the portion of the coast from Beagle Bay to Pardoo Roadhouse.  The core of Tropical Cyclone Hilda will drop locally heavy rain near the coast of Western Australia and flash flooding is possible.

Tropical Low Develops Near Coast of Western Australia

A distinct low level center of circulation developed in an area of thunderstorms near the coast of Western Australia on Tuesday and the Australian Bureau of Meteorology classified the system as a Tropical Low.  At 10:00 p.m. EST on Tuesday the center of the Tropical Low as located at latitude 17.2°N and 122.3°E which put it just inland east of Coulomb Point and about 55 miles (85 km) north of Broome, Australia.  The Tropical Low was moving toward the southwest at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 998 mb.

Although the center of circulation was over land, the circulation of the Tropical Low became much better organized on Tuesday.  There was a well defined center of circulation and weather radar images indicated an eyelike feature at the center of the Tropical Low.  Several bands of showers and thunderstorms wrapped around the center of circulation.  Storms in the core of the Tropical Low were generating well developed upper level divergence which was pumping mass away in all directions.

The Tropical Low will move through an environment favorable for intensification during the next 24 to 36 hours.  The Sea Surface Temperature of the water off the coast of Western Australia is near 30°C.  The Tropical Low is underneath an upper level ridge and the upper level winds are not very strong.  There is little vertical wind shear.  The only factor inhibiting intensification is the fact that the center is still inland over Western Australia.  If the center moves over water as is forecast, the Tropical Low will intensify and it could intensify rapidly.

The Tropical Low is moving around the western end of a mid-level ridge which is steering it toward the southwest.  The ridge is forecast to steer the Tropical Low toward the southwest for another 12 to 24 hours.  When the Tropical Low reaches the western end of the ridge, it will move more toward the south.  On its anticipated track the center of the Tropical Low will move off the coast of Western Australia and over water during the next 6 to 12 hours.  The center of the Tropical Low is expected to pass west of Broome.  The Tropical Low could approach the coast of Western Australia between Bidyadanga and Wallal Downs in about 36 hours.

The Tropical Low will drop heavy rain along the coast of Western Australia during the next 48 hours.  It will also bring gusty winds and a Warning has been issued for the portion of the coast from Cape Leveque to De Grey.

Tropical Depression Tembin Passes Near Southern Tip of Vietnam

The center of Tropical Depression Tembin passed near the southern tip of Vietnam on Monday night.  At 10:00 p.m. EST on Monday the center of Tropical Depression Tembin was located at latitude 8.5°N and longitude 104.6°E which put it about 200 miles (320 km) southwest of Ho Chi Minh City, Vietnam.  Tembin was moving toward the west at 14 m.p.h. (22 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 1005 mb.

An upper level ridge north of Tropical Depression Tembin continued to produce strong easterly winds which were blowing across the top of the circulation.  Those winds were causing strong vertical wind shear.  The shear was strong enough to prevent thunderstorm from developing in most parts of the circulation of Tropical Depression Tembin.  A few thunderstorms formed in the extreme northwestern portion of the circulation, but most of the circulation consisted of bands of low clouds and showers.  The strong shear and lack of tall thunderstorms caused the wind speeds at the surface to decrease and Tembin weakened to a tropical depression.

Tropical Depression Tembin will remain in an environment that is unfavorable for intensification.  Tembin will move over water where the Sea Surface Temperature is near 29°C.  So, there is enough energy in the upper ocean to support intensification.  However, the upper ridge will continue to produce strong easterly winds.  The vertical wind shear is likely to cause the circulation of Tropical Depression Tembin to spin down.

The ridge north of Tembin has been steering the tropical depression toward the west and a general westerly motion is expected to continue for another day or two.  On its anticipated track Tropical Depression Tembin will move across the Gulf of Thailand.   The center of Tropical Depression Tembin could reach the coast of Thailand near Sichon in about 36 hours.

Typhoon Tembin Nears Southern Vietnam

Typhoon Tembin moved nearer to southern Vietnam on Sunday.  At 10:00 p.m. EST on Sunday the center of Typhoon Tembin was located at latitude 8.0°N and longitude 109.3°E which put it about 290 miles (470 km) southeast of Ho Chi Minh City, Vietnam.  Tembin was moving toward the west at 13 m.p.h. (21 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.

Typhoon Tembin weakened during the past 12 hours as it moved over the South China Sea.  An upper level ridge north of Tembin generated stronger easterly winds on Sunday which increased the vertical wind shear.  The strong upper level winds weakened the rainbands in the eastern half of the circulation of Typhoon Tembin.  Those winds also tilted the upper portion of the circulation toward the west.  The low level circulation of Typhoon Tembin remained well organized, but the storms around the center weakened.  The strongest thunderstorms were occurring in bands west of the core of Tembin.  Winds to typhoon force extended out about 40 miles (65 km) from the center in the northern half of the circulation and about 25 miles (40 km) in the southern half.  Winds to tropical storm force extended out about 155 miles (250 km) from the center.

Typhoon Tembin is likely to continue to weaken on Monday.  Typhoon Tembin will move over water where the Sea Surface Temperature is near 29°C.  However, the upper level ridge is likely to continue to generate strong easterly winds and the significant vertical wind shear will make it difficult for tall thunderstorms to develop around much of the circulation.  The wind shear will probably weaken Tembin to a tropical storm on Monday.

The ridge north of Tembin is steering the typhoon toward the west and a general westerly motion is expected to continue for several more days.  On its anticipated track the center of Typhoon Tembin will pass near the southern tip of Vietnam in about 24 hours.  Tembin will likely move into the Gulf of Thailand as a tropical storm or tropical depression.

The heavy rain with Typhoon Tembin is occurring in bands west of the core of the typhoon.  So, the heavy rain will begin to fall before the center of circulation reaches places.  The heaviest rain will fall over the Mouths of the Mekong River and the part of Vietnam south of that area.  The rain could be heavy enough to cause floods in some locations.  Gusty winds could produce isolated damage as well in the southern part of Vietnam.

Tembin Strengthens to a Typhoon Over South China Sea

Tropical Storm Tembin strengthened into a typhoon on Saturday as it moved over the South China Sea.  At 10:00 p.m. EST on Saturday the center of Typhoon Tembin was located at latitude 8.2°N and longitude 113.6°E which put it about 540 miles (880 km) east of Ho Chi Minh City, Vietnam.  Tembin was moving toward the west at 18 m.p.h. (29 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. (170 km/h).  The minimum surface pressure was 976 mb.

Typhoon Tembin became much better organized on Saturday.  A primary rainband wrapped around the center of circulation and an eye became apparent on microwave satellite imagery.  Several other rainbands strengthened outside the core of Typhoon Tembin.  Storms near the core of the circulation generated strong upper level divergence which pumped mass away to the west and northeast of the typhoon.  The removal of mass allowed the surface pressure to decrease and the wind speed to increase.  Winds to typhoon force extended out about 40 miles (65 km) from the center of circulation.  Winds to tropical storm force extended out about 155 miles (250 km) from the center.

Typhoon Tembin will move through an environment favorable for intensification during the next 24 hours.  Tembin will move over water where the Sea Surface Temperature is near 29°C.  An upper level ridge north of Tempin is producing easterly winds which are blowing toward the typhoon.  However, the easterly winds are blowing at most levels of the atmosphere and there is not a lot of vertical wind shear.  Typhoon Tembin is likely to continue to intensify on Sunday.

The subtropical ridge north of Tembin is steering the typhoon quickly toward the west.  A general motion toward the west is expected to continue.  On its anticipated track Typhoon Tembin could approach the southern part of Vietnam in about 36 hours.  Tembin has the potential to bring strong winds, heavy rain and a storm surge to the southern coast of Vietnam.

Tropical Storm Tembin Strengthens Over the Sulu Sea

Tropical Storm Tembin moved west of Mindanao and it strengthened over the Sulu Sea on Friday.  At 4:00 p.m. EST on Friday the center of Tropical Storm Tembin was located at latitude 8.0°N and longitude 120.8°E which put it about 200 miles (320 km) southeast of Puerto Princesa, Philippines.  Tembin was moving toward the west at 8 m.p.h. (13 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 992 mb.

Tropical Storm Tembin weakened when the center moved across Mindanao.  The center is back over water in the Sulu Sea and the circulation of Tembin is strengthening again.  There is a distinct low level center of circulation, but the distribution of thunderstorms is asymmetrical.  Most of the strong thunderstorms are occurring in bands in the western half of the circulation.  Bands in the eastern half of the circulation consist primarily of low clouds and showers.  The storms west of the center are generating upper level divergence which is pumping mass away to the west of the tropical storm.  The removal of mass has caused the surface pressure to decrease and the wind speeds have started to increase.

Tropical Storm Tembin will be moving through an environment that is favorable for intensification.  Tembin will move over water where the Sea Surface Temperature is near 29°C.  An upper level ridge north of Tropical Storm Tembin is producing easterly winds which are blowing toward the top of the circulation.   Those winds are causing vertical wind shear, which is probably the reason for the asymmetrical distribution of thunderstorms.  However, the shear is not strong enough to prevent Tropical Storm Tembin from intensifying.  Tembin could strengthen into a typhoon during the next day or two while is moves over the South China Sea.

The subtropical ridge north of Tembin is steering the tropical storm toward the west.  A general motion toward the west-northwest west is forecast for the next two or three days.  On its anticipated track Tropical Storm Tembin will move across Palawan in about 18 hours.  Tembin could reach the southern coast of Vietnam in about three days.  Tembin will bring gusty winds and heavy rain to Palawan.  Tembin could be a typhoon when it approaches southern Vietnam.

Elsewhere over the western North Pacific Ocean Tropical Depression Kai-tak is approaching the east coast of Malaysia.  At 4:00 p.m. EST on Friday the center of Tropical Depression Kai-tak was located at latitude 4.0°N and longitude 104.4°E which put it about 175 miles (285 km) north-northeast of Singapore.  Kai-tak was moving toward the southwest at 8 m.p.h. (13 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 1005 mb.  Tropical Depression Kai-tak will drop locally heavy rain over portions of Malaysia, which could cause floods and mudslides.

Tropical Storm Tembin Drops Heavy Rain on Mindanao

Tropical Storm Tembin dropped heavy rain on Mindanao on Thursday.  At 4:00 p.m. EST on Thursday the center of Tropical Storm Tembin was located at latitude 7.9°N and longitude 126.1°E which put it near Monkayo, Philippines.  Tembin was moving toward the west-southwest at 12 m.p.h. (19 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 Tembin intensified on Thursday before it made landfall on Mindanao.  More thunderstorms developed near the core of the circulation and those storms generated stronger upper level divergence which pumped mass away from the tropical storm.  The removal of mass allowed the surface pressure to decrease and the wind speed to increase.  Although the circulation became much better organized, the distribution of thunderstorms was still asymmetrical.  There were far fewer thunderstorms forming in the eastern half of the circulation.

The center of Tropical Storm Tembin will be moving across Mindanao for another day or so.  The mountains on the island will disrupt the lower levels of the circulation and increased friction will slow the wind speed.  Tropical Storm Tembin will weaken while the center is over Mindanao.  However, the middle and upper parts of the circulation are likely to remain intact, and Tropical Storm Tembin will move through a favorable environment when it reaches the Sulu Sea.  Tembin will move over water where the Sea Surface Temperature is near 29°C.  An upper level ridge north of Tropical Storm Tembin is producing easterly winds which are blowing toward the top of the circulation.  The winds in the middle and lower levels are also blowing from the east and the vertical wind shear will not be strong enough to prevent intensification of Tropical Storm Tembin once the center gets back over water.  Temping could strengthen into a typhoon when it reaches the South China Sea.

The ridge north of Tembin is steering the tropical storm toward the west-southwest.  A general motion toward the west is expected during the next two to three days.  On its anticipated track Tropical Storm Tembin will move east to west over Mindanao during the next 24 hours.  Afterwards, Tropical Storm Tembin will move across the Sulu Sea toward Palawan.  Tembin could be near Palawan in about 48 hours and it could be over the South China Sea shortly thereafter.

Tropical Storm Tembin represents a serious hazard for Mindanao and nearby locations in the southern Philippines.  Tembin is dropping heavy rain and it has the potential to cause serious floods.  Water levels could rise quickly and flash floods could develop.  Saturated soils could result in mudslides in areas of steeper terrain.

Farther to the west, Tropical Storm Kai-tak continued to move across the South China Sea.  At 4:00 p.m. EST on Thursday the center of Tropical Storm Kai-tak was located at latitude 5.7°N and longitude 106.9°E which put it about 250 miles (400 km) east of Kuala Terengganu, Malaysia.  Kai-tak was moving toward the west-southwest at 5 m.p.h. (8 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1000 mb.

Tropical Storm Tembin Forms East of the Philippines

Tropical Storm Tembin formed east of the Philippines on Wednesday.  At 1:00 p.m. EST on Wednesday the center of Tropical Storm Tembin was located at latitude 9.0°N and longitude 130.7°E which put it about 270 miles (435 km) east of Mindanao.  Tembin was moving toward the west at 12 m.p.h. (20 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1000 mb.

A more well organized center of circulation developed on the eastern edge of a cluster of thunderstorms east of the Philippines and the Japan Meteorological Agency classified the system as Tropical Storm Tembin.  The distribution of thunderstorms in Tembin is asymmetrical.  Most of the storms are forming in bands north and west of the center of circulation.  Those storms are generating upper level divergence which is pumping mass away from the core of Tembin.  There are a few thunderstorms in bands on the eastern periphery of the circulation, but most of the bands in the eastern half of Tropical Storm Tembin contain only low clouds and showers.

Tropical Storm Tembin will be moving through an environment favorable for intensification during the next several days.  Tembin will move over water where the Sea Surface Temperature is near 29°C.  An upper level ridge north of Tembin is producing easterly winds which are blowing toward the top of the circulation.  Those winds are causing moderate vertical wind shear and they are probably the reason why most of the thunderstorms are developing west of the center of circulation.  However, the shear has not been enough to prevent Tembin from organizing and Tembin is likely to strengthen during the next 24 hours.  The center of Tembin will move over Mindanao later on Thursday and it will weaken while the center is over land.  Tropical Storm Tembin will likely intensify once the center moves west of Mindanao.

A subtropical ridge north of Tembin is steering the tropical storm toward the west and a general westerly motion is expected to continue for several more days.  On its anticipated track the center of Tropical Storm Tembin could approach Mindanao in about 24 hours.  Tembin is then forecast to move over the Bohol Sea and Sulu Sea and on toward Palawan.  It currently looks like Tropical Storm Tembin will take a track a little to the south of the track taken by Tropical Storm Kai-tak across the Philippines last week.

Tropical Storm Tembin will drop heavy rain over parts of Mindanao, southern Leyte, Bohol, Cebu, Negros, Siargao, and Dinagat.  The heavy rain could cause floods and mudslides.  The northern part of Tropical Storm Tembin could drop heavy rain in some of the places affected by Tropical Storm Kai-tak last week.  Any additional rain in those locations would hamper efforts to recover from floods and mudslides caused by Kai-tak.

Tropical Storm Kai-Tak continue to move southwest over the South China Sea.  At 4:00 p.m. EST on Wednesday the center of Tropical Storm Kai-tak was located at latitude 6.4°N and longitude 111.1°E which put it about 440 miles (710 km) southeast of Ho Chi Minh City, Vietnam.  Kai-tak was moving toward the southwest at 7 m.p.h. (11 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 998 mb.

Tropical Storm Kai-tak Moves Over South China Sea

Tropical Storm Kai-tak moved west of the Philippines and over the South China Sea on Tuesday.  At 10:00 p.m. EST on Tuesday the center of Tropical Storm Kai-tak was located at latitude 8.2°N and longitude 112.0°E which put it about 425 miles (685 km) east-southeast of Ho Chi Minh City, Vietnam.  Kai-tak was moving toward the west-southwest 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 1000 mb.

The organization of the circulation of Tropical Storm Kai-tak improved on Tuesday.  More thunderstorms developed near the center of circulation.  The two stronger rainbands were north and west of the center.  However, thunderstorms also developed in a couple of bands southeast of the center of circulation.  These storms were the first to form in the eastern half of the circulation in several days.  The distribution of the rainbands was still asymmetrical, but storms were occurring in more quadrants of Kai-tak.  The storms in the two stronger rainbands were generating some upper level divergence which was pumping mass away to the west of the tropical storm.

Tropical Storm Kai-tak will be moving through an environment somewhat favorable for intensification during the next day or two.  Kai-tak will move over water where the Sea Surface Temperature is near 29°C.  Kai-tak is moving near the southwestern portion of a subtropical ridge.  The ridge is producing easterly winds which are blowing toward the top of the circulation.  The easterly winds are causing moderate vertical wind shear, but they have weakened somewhat during the past 24 hours.  Less wind shear has allowed Tropical Storm Kai-tak to become better organized.  Tropical Storm Kai-tak could strengthen during the next 24 to 36 hours.

The western end of the subtropical ridge is strengthening and the ridge is steering Tropical Storm Kai-tak toward the west-southwest.  A general motion toward the west-southwest is expected to continue for the next two or three days.  On its anticipated track the center of Tropical Storm Kai-tak is expected to pass south of the southern tip of Vietnam.  Kai-tak is forecast to stay north of Borneo.  The center of Tropical Storm Kai-tak could approach the region near the border between Thailand and Malaysia in about 72 hours.