Tag Archives: Northern Territory

Tropical Low Forms North of Australia

A Tropical Low formed north of Australia late on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of the Tropical Low as located at latitude 9.2°S and longitude 130.9°E which put it about 155 miles (250 km) north of Milikapiti, Australia.  It was moving toward the east at 8 m.p.h. (13 km/h).  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 1004 mb.  The Australian Bureau of Meteorology issued a Watch for the portion of the coast from Milingimbi to Daly River Mouth including Darwin and the Tiwi Islands.

A center of circulation developed in an area of showers and thunderstorms north of Australia late on Wednesday and the Australian Bureau of Meteorology classified the system as a Tropical Low.  The circulation was still organizing.  A short band of showers and thunderstorms wrapped around the southern and western sides of the center.  Other short rainbands were developing in other parts of the circulation.  Storms near the center of circulation were just beginning to generate upper level divergence.

The Tropical Low will move through an environment somewhat favorable for intensification.  It will mover over water where the Sea Surface Temperature is near 30°C.  Westerly winds in the upper levels will cause some vertical wind shear, which will inhibit intensification.  However, the shear is not likely to be strong enough to prevent intensification.  The Tropical Low is likely to strengthen during the next 24 hours.  After that time the intensity will be influenced by how much of the circulation is over Australia.

The Tropical Low is being steered to the east by westerly winds north of Australia.  Those winds are forecast to weaken and the Tropical Low is expected to turn south toward the coast of Australia.  A subtropical ridge over Australia is expected to turn the Tropical Low toward the southwest in a day or so.  On its anticipated track the Tropical Low could be near the northern coast of Australia in 24 to 36 hours.  It could pass near the Cobourg Peninsula, Melville Island and Bathurst Island.  The Tropical Low could also bring gusty winds and heavy rain to the area near Darwin.

Tropical Cyclone Frances Develops North of Western Australia

An area of low pressure northwest of Western Australia developed into Tropical Cyclone Frances on Thursday.  At 10:00 a.m. EDT on Thursday the center of Tropical Cyclone Frances was located at latitude 11.0°S and longitude 128.3°E which put it about 255 miles (410 km) north-northeast of Kalumburu, Australia.  Frances was moving toward the west-southwest at 12 m.p.h. (19 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. (110 km/h).  The minimum surface pressure was 997 mb.

The organization of Tropical Cyclone Frances improved significantly during the past 24 hours.  A well organized center of circulation developed at the surface.  A primary rainband wrapped about two-thirds of the way around the southern and western sides of the center.  Additional bands of showers and thunderstorms formed in the outer portions of the circulation.  Thunderstorms near the core of the circulation generated upper level divergence which was pumping mass away to the south of the tropical cyclone.  Frances is a fairly small tropical cyclone and winds to tropical storm force only extend out about 100 miles (160 km) from the center.

Tropical Cyclone Frances will move through an environment that will be favorable for intensification during the next 24 to 36 hours.  Frances will move over water where the Sea Surface Temperature is near 30°C while is moves across the Timor Sea.  An upper level ridge east of Tropical Cyclone Frances is producing northeasterly winds which are blowing toward the top of the circulation.  Vertical wind shear may be the reason that the primary rainband wrapped around the southern and western sides of the center.  However, the vertical shear does not appear to be strong enough to significantly affect the upper level divergence.  Frances is likely to intensify during the next day or so.  Eventually, Tropical Cyclone Frances will move into an area where there are strong upper level northwesterly winds.  A significant increase in vertical wind shear should weaken Frances when that occurs.

A subtropical ridge to the east of Frances is steering the tropical cyclone toward the west-southwest.  A general motion toward the west-southwest is expected to continue during the next few days.  On its anticipated track the center of Tropical Cyclone Frances is forecast to stay north of the coast of Western Australia.  However, any southward deviation of the track could bring stronger winds closer to the coast.

Tropical Low Brings Wind and Rain to Northern Australia

A Tropical Low pressure system brought wind and rain to northern Australia on Tuesday.  At 11:00 a.m. EDT on Tuesday the center of the Tropical Low was located at latitude 12.1°S and 131.5°E which put it about 45 miles (75 km) east-northeast of Darwin, Australia.  The Tropical Low was moving toward the west-southwest at 8 m.p.h. (12 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.

The circulation of the Tropical Low is not very well organized.  Many of the thunderstorms are occurring in the outer portions of the circulation.  There are mostly showers, and only a few thunderstorms, near the center of circulation.  There are a few rainbands near the periphery of the circulation, but there is not a well formed core at the center.  The poor organization is preventing the Tropical Low from generating much upper level divergence and as a result the surface pressure has changed little during the past 24 hours.

A significant portion of the circulation of the Tropical Low is over land and that is inhibiting development of the system.  In addition, an upper level ridge to the east of the Tropical Low is producing northerly winds which are blowing across the top of the circulation.  Those winds are causing moderate vertical wind shear which is also inhibiting development.  The Tropical Low is moving toward the west-southwest and the center is forecast to move over the Timor Sea.  If the center of circulation moves over the Timor Sea, it will move over water where the Sea Surface Temperature is near 30°C.  More energy from the water could offset the effects of the vertical wind shear and the Tropical Low could intensify into a tropical cyclone.

A subtropical ridge east of the Tropical Low is steering the system toward the west-southwest and that general motion is expected to continue during the next several days.  On its anticipated track the center of the Tropical Low will move near the northern coast of Australia.  If the center emerges over the Timor Sea, then the system could intensify into a tropical cyclone.  If the center remains over land, then further development will not occur.  In either case the Tropical Low will bring gusty winds and heavy rains to the northern coastal regions of the Northern Territory and Western Australia.

Tropical Cyclone Blanche Strengthens Near Coast of Western Australia

Tropical Cyclone Blanche strengthened on Sunday as it moved over the Timor Sea toward the coast of Western Australia.  At 7:00 p.m. EST on Sunday the center of Tropical Cyclone Blanche was located at latitude 14.0°S and longitude 128.2°E which put it about 100 miles (165 km) north of Wyndham, Australia.  Blanche was moving toward the southwest at 11 m.p.h. (17 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 80 m.p.h. (130 km/h).  The minimum surface pressure was 988 mb.

The inner core of Tropical Cyclone Blanche became more organized on Sunday.  A band of thunderstorms wrapped about two thirds of the way around the southern and western portions of the center.  The band has the appearance of a partial eyewall.  The strongest winds are occurring in the band near the center.  The thunderstorms are generating upper level divergence which is pumping out mass to the west and southeast of the Tropical Cyclone Blanche.  The upper level divergence allowed the surface pressure to decrease and the wind speed to increase.

Tropical Cyclone Blanche will be over the Timor Sea for a few more hours.  It will be in an environment that is favorable for intensification during that time.  Blanche will move over water where the Sea Surface Temperature is near 29°C.  An upper level ridge east of Blanche is producing northerly winds which are blowing toward the tropical cyclone.  The winds are causing moderate vertical wind shear, but the shear was not strong enough to prevent intensification on Sunday.  Tropical Cyclone Blanche could intensify a little more before it makes landfall.

A subtropical ridge is steering Tropical Cyclone Blanche toward the southwest and that general motion is expected to continue.  On its anticipated track Tropical Cyclone Blanche will make landfall on the coast of Western Australia northwest of Wyndham in a few hours.  Blanche will bring gusty winds and some storm surge to the coast.  It will cause locally heavy rain and the potential for flooding as it moves inland.

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.