Tag Archives: Northern Territory

Tropical Cyclone Blanche Forms Northwest of Darwin

Tropical Cyclone Blanche formed northwest of Darwin, Australia over the Timor Sea late on Saturday.  At 10:00 p.m. EST on Saturday the center of Tropical Cyclone Blanche was located at latitude 11.9°S and longitude 130.3°E which put it about 55 miles (85 km) northwest of Darwin, Australia.  Blanche was moving toward the southwest at 7 m.p.h. (12 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 993 mb.

An area of low pressure moved north of the Northern Territory over the Arafura Sea during the past few days.  The low exhibited enough organization for the Australian Bureau of Meteorology to designate it as a tropical low.  The center of the low moved across Melville Island and Bathhurst Island earlier today.  More and stronger thunderstorms began to form closer to the center after it moved over the Beagle Gulf and into the Timor Sea.  The increased convection and organization prompted the Australian Bureau of Meteorology to name the system Tropical Cyclone Blanche.

Although the circulation of Tropical Cyclone Blanche became better organized today, it is still somewhat asymmetrical.  Many of the stronger thunderstorms are occurring in a band south and west of the center or circulation.  Bands north and east of the center contain mainly lower clouds and showers.  An upper level ridge to the east of Blanche is producing northerly winds which are blowing toward the top of the tropical cyclone.  The vertical wind shear appears to have increased during recent hours and the upper level divergence to the east of the center has been reduced.  Part of the lower level circulation appears to becoming exposed on the most recent visible satellite images.

Tropical Cyclone Blanche will be moving through an environment that contains both positive and negative factors.  Blanche will move over water where the Sea Surface Temperature is near 29°C.  So, there is sufficient energy in the upper ocean to support intensification.  However, the upper level ridge to the east of Blanche is producing moderate vertical wind shear, which appears to have stalled intensification for now.  If the wind shear remains moderate, then Blanche will not strengthen.  If the wind shear increases, it could blow the upper portion of the circulation away from the lower part and the tropical cyclone would weaken.  On the other hand if the wind shear decreases, then Tropical Cyclone Blanche could intensify a little more.  There is a great deal of uncertainty about the future intensity of Blanche.

Blanche is moving around the northwestern portion of a subtropical ridge, which is steering the tropical cyclone toward the southwest.  This general motion is expected to continue.  On its anticipated track Tropical Cyclone Blanche will move across the Timor Sea and make landfall on the coast of Western Australia between Wyndham and Kalumburu in 24 to 36 hours.  Tropical Cyclone Blanche could bring some gusty winds, but the primary risk will be locally heavy rainfall and the potential for flooding.

Tropical Cyclone Alfred Develops Over Southwest Gulf of Carpentaria

More thunderstorms developed around the center of a tropical low on Sunday and the Australian Bureau of Meteorology designated the system as Tropical Cyclone Alfred.  At 7:00 p.m. EST on Sunday the center of Tropical Cyclone Alfred was located at latitude 15.4°S and longitude 137.2°E which put it about 75 miles (120 km) northeast of Borroloola, Australia.  Alfred was moving toward the south-southeast at 5 m.p.h. (8 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.

An area of low pressure organized over the southeastern Gulf of Carpentaria a few days ago.  The Tropical Low moved across the south coast of the Gulf of Carpentaria and then it moved westward over land.  The low turned north about 36 hours ago and it crossed into the southwest Gulf of Carpentaria on Sunday.  More thunderstorms developed closer to the center of circulation after the circulation moved over water.  Downdrafts in those storms transported stronger winds to the surface.  Upper level divergence pumped out mass and the surface pressure decreased.  When the low pressure system strengthened and acquired the necessary characteristics, the Australian Bureau of Meteorology classified it as Tropical Cyclone Alfred.

The low level circulation of Tropical Cyclone Alfred is well organized but the distribution of thunderstorms is very asymmetrical.  There is a well defined center of circulation that is over the extreme southwestern portion of the Gulf of Carpentaria.  However, most of the thunderstorms are developing southwest of the center of circulation.  Those thunderstorms are where the strongest winds are occurring.  There are few thunderstorms in the other portions of the core of the circulation.  There is one band of showers and thunderstorms farther away from the center on the eastern side of the circulation.

Tropical Cyclone Alfred will be moving through an environment that will be marginally favorable intensification.  It will be moving over water where the Sea Surface Temperature is near 31°C.  So, there is plenty of energy to support intensification.  An upper level ridge east of Alfred is producing northerly winds which are blowing over the top of the tropical cyclone.  Those winds are generating moderate wind shear, which is partially responsible for the asymmetrical distribution of thunderstorms.  In addition, the center is close to the coast and some of the circulation is passing over land.  Tropical Cyclone Alfred could intensify a little more before it gets to coast, but a weakening trend may be more likely.

A subtropical ridge is steering Tropical Cyclone Alfred toward the south-southeast and that general motion is expected to continue for another 12 to 24 hours.  On its anticipated track Tropical Cyclone Alfred could reach the coast near the border between the Northern Territory and Queensland in 12 to 18 hours.  Although Tropical Cyclone Alfred will bring some gusty winds, the greater hazard will be locally heavy rainfall.

Tropical Cyclone 16P Forms Over Gulf of Carpentaria

After a quiet period of several weeks in the tropics Tropical Cyclone 16P formed over the Gulf of Carpentaria on Tuesday.  At 11:00 p.m. EDT on Tuesday the center of Tropical Cyclone 16P was located at latitude 16.4°S and longitude 140.3°E which put it about 75 miles (120 km) east-northeast of Mornington Island and about 115 miles (185 km) southwest of Kowanyama, Australia.  Tropical Cyclone 16P was moving toward the east-southeast at 12 m.p.h. (18 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 996 mb.

An upper level ridge persisted over the Gulf of Carpentaria during the past few days.  The upper level ridge generated upper level divergence which enhanced rising motion and supported the development of thunderstorms.  Eventually, the upper level divergence pumped out enough mass to allow the surface pressure to decrease and the thunderstorms began to consolidate around a low level center.  The system developed enough organization on Tuesday to be classified as a tropical cyclone.

The organization of Tropical Cyclone 16P improved on Tuesday.  Spiral bands of thunderstorms wrapped around a low level center.  Strong thunderstorms near the center of circulation generated upper level divergence, especially to the east of the tropical cyclone.

The environment is favorable for intensification as long as the center of circulation remains over water.  The Sea Surface Temperatures are near 31°C in the southern Gulf of Carpentaria.  An upper level ridge to the east of the tropical cyclone is generating some vertical wind shear, but the ridge is also enhancing upper level divergence.  The primary inhibiting factor is the proximity of the center of circulation to land.  Tropical Cyclone 16P could intensify further during the next 12 hours before it makes landfall.

The upper level ridge is steering Tropical Cyclone 16P toward the southeast coast of the Gulf of Carpentaria.  On its anticipated track Tropical cyclone 16P is expected to make landfall in Queensland near the mouth of the Gilbert River in about 12 hours.  The potential track after landfall is much more uncertain.  Some guidance suggests that the tropical cyclone could move across the Cape York peninsula toward the Coral Sea.  Other guidance suggests that the tropical cyclone could turn back toward the northwest and move back out into the Gulf of Carpentaria.

Although Tropical Cyclone 16P is likely to cause minor wind damage, it could produce locally heavy rainfall and flooding when it moves over northeastern Queensland.

Tropical Low Forms Over Northern Australia

A distinct center of circulation consolidated within a broader area of low pressure near the northern coast of Australia.  The Australian Bureau of Meteorology designated the system as a Tropical Low.  At 10:00 p.m. EST on Saturday the center of the Tropical Low was located at latitude 14.7°N and longitude 132.7°E which put it about 35 miles (55 km) east-southeast of Katherine, Australia and about 135 miles (220 km) west of Ngukurr.  The Tropical Low was moving toward the east at 3 m.p.h. (5 km).  The maximum sustained wind speed was 30 m.p.h. (45 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1005 mb.

The atmospheric environment around the Tropical Low would be favorable for the development of a tropical cyclone.  The upper level winds are light and there is not much vertical wind shear.  An upper level anticyclone over the Tropical Low is providing a source of upper level divergence, which is pumping out mass.  However, the Tropical Low is over land which is preventing the development of a tropical cyclone.  As long as the Tropical Low remains over land, it will not develop into a tropical cyclone.  However, if the Tropical Low emerges over the Gulf of Carpentaria in a day or so, it could develop into a tropical cyclone.

A ridge in the middle levels of the atmosphere is steering the tropical low toward the east and that general motion is expected to continue for another 24 to 48 hours.  On its anticipated track the Tropical Low could emerge over the southwestern Gulf of Carpentaria south of Port Roper in 24 to 36 hours.

Although the Tropical Low is moving over land, it will still draw in enough moisture to be capable of producing locally heavy rain.  Flooding may be possible in some locations.

Tropical Cyclone Nathan Weakening Over Northern Australia

The center of Tropical Cyclone Nathan moved inland between Maningrida and Goulburn Island on the northern coast of Australia on Monday.  At 11:00 p.m. EDT on Monday the center of Tropical Cyclone Nathan was located at latitude 12.2°S and longitude 133.5°E which put it about 30 miles east-northeast of Gunbalanya, about 45 miles south of Goulburn Island and about 210 miles east of Darwin, Australia.  Nathan was moving toward the southwest at 8 m.p.h.  The maximum sustained wind speed was 45 m.p.h. and there were gusts to 60 m.p.h.  The minimum surface pressure was 989 mb.

A combination of factors contributed to the weakening of Nathan.  As the center of circulation moved inland, the clockwise flow pulled in drier air from the interior of Australia.  The drier air reduced the number of thunderstorms and decreased the amount of latent energy released in the remaining thunderstorms.  Since the release of latent energy drives the circulation in a tropical cyclone, the wind speed has been decreasing as well.  In addition, northerly winds in the upper levels are creating moderate vertical wind shear over the top of Nathan.  The wind shear is displacing many of the remaining thunderstorms to the south side of the circulation.  The asymmetrical development of thunderstorms has weakened the inner core of the circulation.  As long as the center of circulation remains over land, it is likely to weaken further.

A subtropical ridge to the south of Nathan is expected to steer it in a mainly westerly direction.  The projected track would take the center of Nathan south of Darwin and keep it over land for about another 36 hours.  The circulation could be fairly weak by the time it moves back over water west of Darwin.  The water west of Darwin is warm and so, it is possible that more thunderstorms could develop, if there is a coherent circulation when the system moves back over the water.

Tropical Cyclone Nathan Moving Parallel to the Northern Coast of Australia

The center of Tropical Cyclone Nathan moved across the northeastern portion of Arnhem Land and it has emerged over the Arafura Sea.  At 10:00 p.m. EDT on Sunday the center of Tropical Cyclone Nathan was located at latitude 11.6°S and longitude 134.7°E which put it about 45 miles northeast of Maningrida, about 35 miles north-northwest of Milingimbi and about 280 miles east-northeast of Darwin, Australia.  Nathan was moving toward the west at 5 m.p.h.  The maximum sustained wind speed was 75 m.p.h. and there were gusts to 95 m.p.h.  The minimum surface pressure was 974 mb.

The core of the circulation was relatively intact when the center of Nathan moved back over water and it had an apparent eye on some satellite imagery and radar displays.  The surface temperatures are quite warm in the Arafura Sea and thunderstorms continue to develop around the southern and western sides of the circulation.  Less convection is occurring on the eastern side of Nathan.  It is possible the moving across land and proximity to the coast is allowing some drier air to be entrained into the circulation.  Light westerly winds in the upper levels may also be creating some vertical wind shear.  The intact core and warm water could allow Nathan to intensify somewhat on Monday.

Nathan is being steered toward the west by a subtropical ridge located to its south.  The ridge is expected to continue to steer Nathan in a general westerly direction for another 24 hours.  The projected track would keep the center of circulation over water.  The ridge is expected to weaken a bit in a day or so, which could allow Nathan turn southwestward and make another landfall on the north coast of Australia.  The southwesterly turn could produce a landfall between Maningrida and Croker Island.

Nathan has a relatively small circulation but it is strong enough to cause wind damage and a significant storm surge near where the center makes landfall.  It could also produce locally heavy rainfall and flooding in inland areas.

Tropical Cyclone Nathan Making Landfall in Northern Australia

The center of Tropical Cyclone Nathan is moving inland near Nhulunbuy, Australia.  At 9:00 p.m. EDT on Saturday the center of Tropical Cyclone Nathan was located at latitude 12.6°S and longitude 136.8°E which put it about 25 miles south of Nhulunbuy and about 90 miles north-northeast of Alyangula, Australia.  Nathan was moving toward the northwest at 8 m.p.h.  The maximum wind speed was 75 m.p.h. and there were gusts to 90 m.p.h.  The minimum surface pressure was 979 mb.

The atmospheric environment around Tropical Cyclone Nathan is favorable for intensification.  The upper level winds are light.  The circulation is well organized and there is upper level outflow pumping out mass.  Outflow channels extend to the northwest and southeast.  However, as the center moves over land, the circulation will weaken.  The center is expected to cross the northeastern corner of Arnhem Land and move back over water in a few hours.  The potential for re-intensification will depend on how far away from the coast the center moves.

A subtropical ridge located southwest of Nathan is steering it toward the northwest.  The ridge is expected to continue to steer the tropical cyclone in that direction for another day or so.  After that time Nathan is expected to start moving more toward the west and eventually toward the southwest and make another landfall on the northern coast of Australia,

Nathan is strong enough to cause some wind damage.  It could also produce a significant storm surge near where the center is making landfall.  Locally heavy rainfall could create possible flooding at inland locations.

Tropical Cyclone Nathan Crossing Cape York Peninsula

Tropical Cyclone Nathan made landfall in Queensland and it is now crossing the Cape York Peninsula.  At 11:00 a.m. EDT on Friday the center of Tropical Cyclone Nathan was located at latitude 14.4°N and longitude 142.2°E which put it about 75 miles west-southwest of Coen, about 80 miles north-northeast of Kowanyama and about 530 miles east-southeast of Alyangula, Australia.  Nathan was moving toward the west at 11 m.p.h.  The maximum sustained wind speed was 65 m.p.h. and there were gusts to 80 m.p.h.  The minimum surface pressure was 984 mb.

Nathan has been weakening as it moves across the Cape York Peninsula in Northern Queensland.  However, it is approaching the Gulf of Carpentaria and the center of circulation will soon be back over water.  The circulation is still mostly intact and it has well developed upper level outflow.  The water at the surface of the Gulf of Carpentaria is very warm.  In addition, the upper level winds around Nathan are very light and there is very little vertical wind shear.  So, the environment around Nathan is quite favorable for intensification and it is possible that a period of rapid re-intensification could occur.

A subtropical ridge is expected to steer Nathan in a west-northwesterly direction during the next several days.  The projected track would have Nathan making another landfall in the Northern Territory between Port Roper and Nhulunbuy in 24 to 36 hours.  If Nathan does reintensify it could bring strong winds and a storm surge to the coast.  It will also be capable of producing locally heavy rainfall and flooding in inland locations.

 

Tropical Cyclone Lam Moving Farther Inland and Weakening

Tropical Cyclone Lam made landfall earlier today just to the southwest of Elcho Island on the north coast of Australia.  Lam is continuing to move farther inland in the Northern Territory.  At 9:00 p.m. EST on Thursday the center of Lam was located at latitude 13.1°S and longitude 134.4°S which put it 40 miles north of Bulman and about 75 miles south-southwest of Milingimbi, Australia.  It was moving toward the southwest at 10 m.p.h.  The maximum sustained wind speed was 65 m.p.h. and there were gusts to 90 m.p.h.  The minimum surface pressure was 985 mb.

Lam will continue to weaken as it moves farther into the interior of Australia.  The weakening will occur slowly because the circulation is moving over relatively flat terrain.  Lam could produce locally heavy rainfall and the potential for flooding along its path.  The winds and waves along the coast should continue to lessen and the water levels should decrease.

Lam and Marcia Equivalent of Major Hurricanes As They Affect Australia

Both Severe Cyclone Lam and Severe Tropical Cyclone Marcia intensified rapidly during the past few hours and both storms are now the equivalent of major hurricanes.  Lam is making landfall on the north coast of Australia just to the southwest of Elcho Island.  The motion of Marcia has slowed, but it is approaching the coast of Queensland.

At 8:00 a.m. EST on Thursday the center of Lam was located at latitude 12.0°S and longitude 135.4°E which put it about 12 miles west-northwest of Galiwinku and about 35 miles east-northeast of Milingimbi, Australia.  Lam was moving toward the southwest at 5 m.p.h.  The maximum sustained wind speed was 115 m.p.h., which makes Lam the equivalent of a Category 3 hurricane on the Saffir-Simpson Scale.  It was estimate that there were wind gusts to 160 m.p.h. and the minimum surface pressure was 963 mb.

At 8:00 a.m. EST on Thursday the center of Marcia was located at latitude 20.8°S and longitude 150.6°S which put it about 150 miles east of Mackay and about 160 miles north of Yeppoon, Australia.  Lam was moving toward the west-southwest at 7 m.p.h.  The maximum sustained wind speed was 120 m.p.h., which makes Marcia the equivalent of a Category 3 hurricane on the Saffir-Simpson Scale.  It was estimated that there were wind gusts to 165 m.p.h. and the minimum surface pressure was 956 mb.

Both tropical cyclones are capable of causing significant wind damage.  They are also capable of generating a significant storm surge near where the center makes landfall.  Locally heavy rainfall and the potential for flooding exists, as the storms move inland.