Tag Archives: Tropical Low

Tropical Cyclone Riley Strengthens to Equivalent of Hurricane/Typhoon

Tropical Cyclone Riley strengthened into the equivalent of a hurricane/typhoon on Friday.  At 4:00 p.m. EST on Friday the center of Tropical Cyclone Riley was located at latitude 17.2°S and longitude 116.9°E which put it about 415 miles (675 km) north-northeast of Learmonth, Australia.  Riley was moving toward the west at 5 m.p.h. (8 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 976 mb.

Tropical Cyclone Riley strengthened, but the distribution of thunderstorms was asymmetrical.  The strongest winds were occurring in a band the curled around the northern half of the center of circulation.  Storms in the band were generating upper level divergence which was pumping mass away from the tropical cyclone.  Other bands of showers and thunderstorms were present in the western half of the circulation, but the bands in the eastern half of Tropical Cyclone Riley consisted primarily of showers and lower clouds.  Winds to hurricane/typhoon force extended out about 35 miles (55 km) from the center of circulation and they were occurring mainly north of the center of Riley.  Winds to tropical storm force extended out about 130 miles (215 km) from the center.

Tropical Cyclone Riley was moving around the northwestern part of an upper level ridge.  The ridge was producing easterly winds which were blowing toward the top of the circulation.  Those winds appeared to converge with the upper level divergence on the east side of Riley to produce sinking motion in that part of the tropical cyclone.  The sinking motion was bringing drier air to the lower levels and it appeared to suppressing convection in that region.

Tropical Cyclone Riley may be close to its peak intensity.  Riley is currently over water where the Sea Surface Temperature is near 28°C, but it will move over cooler water during the next few days.  The upper level ridge will continue to produce easterly winds which will blow toward the top of the circulation.  Those winds could strengthen which would cause more vertical wind shear.  Riley could intensify during the next 24 hours, but it is more likely to gradually weaken during the next two or three days.

The ridge will steer Tropical Cyclone Riley toward the west-southwest during the next few days.  On its anticipated track Riley will remain north of the coast of Western Australia,  However, watches and warnings are in effect for portions of the coast in case the Tropical Cyclone Riley moves more toward the south.  A Tropical Cyclone Warning is in effect for the portion of the coast from Whim Creek to Onslow including Karratha and Dampier.  A Tropical Cyclone Watch is in effect from Onslow to Exmouth.

Elsewhere around Australia, a Tropical Low was dropping heavy rain over portions of northern Queensland.  At 1:00 p.m. EST the center of the Tropical Low was located at latitude 13.8°S and longitude 141.3°E which put it about 80 miles (125 km) north-northwest of Pormpuraaw, Australia.  It was moving toward the southeast at 6 m.p.h. (10 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 1002 mb.  Locally heavy rain could cause floods in parts of northern Queensland.

Tropical Low Prompts Warning for Northern Queensland

A tropical low over the Gulf of Carpentaria prompted the issuance of warnings and watches for northern Queensland on Thursday.  A Tropical Cyclone Warning was in effect for the portion of the coast from Mapoon to Karumba.  A Tropical Cyclone Watch was in effect for the portion of the coast from Karumba to the border between Queensland and the Northern Territory including Mornington Island.

At 7:00 p.m. EST on Thursday the center of the tropical low was located at latitude 13.0°S and longitude 139.9°E which put it about 135 miles (220 km) west of Weipa, Australia.  It was moving toward the north at 5 m.p.h. (8 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 1002 mb.

The circulation around the tropical low exhibited more organization on Thursday.  A band of showers and thunderstorms wrapped around the western and northern sides of the center of circulation.  Other bands of showers and thunderstorms were developing over the Gulf of Carpentaria.  Storms near the center of circulation began to generate upper level divergence which was pumping mass away in outflow channels to the northwest and southeast of the tropical low.

The tropical low will move through an environment favorable for intensification.  It will move over water where the Sea Surface Temperature is near 30°C.  The tropical low will be in an area where the upper level winds are weaker and the vertical wind shear will be limited.  The tropical low is likely to intensify during the next 24 to 36 hours and it is forecast to become a named tropical cyclone.

The tropical low is under the northeastern portion of an upper level low.  It is in a small region where the steering winds are weaker and the tropical low meandered over the eastern Gulf of Carpentaria on Thursday.  Northerly winds blowing around the upper level low are forecast to steer the tropical low toward the south during the next day or two.  On its anticipated path the tropical low is expected to move over the eastern Gulf of Carpentaria near the coast of Queensland.  If the tropical low follow its anticipated track, it will make landfall on the south coast of the Gulf of Carpentaria in about 48 hours.  However, any eastward deviation would bring the tropical low inland over Queensland much sooner.

Elsewhere, Tropical Cyclone Riley strengthened northwest of Australia.  At 7:00 p.m. EST on Thursday the center of Tropical Cyclone Riley was located at latitude 16.5°S and longitude 118.8°E which put it about 265 miles (425 km) north of Port Hedland, Australia.  Riley was moving toward the west at 4 m.p.h. (6 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 985 mb.  A Tropical Cyclone Watch was in effect for the portion of the coast from Whim Creek to Onslow, Australia including Karratha and Dampier.

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 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 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 Low Forms Northeast of Queensland

A Tropical Low organized quickly northeast of Queensland over the Coral Sea on Thursday.  At 11:00 p.m. EDT on Thursday the center of the Tropical Low was located at latitude 16.1°S and longitude 151.4°E which put it about 370 miles (600 km) northeast of Townsville, Australia.  The Tropical Low as moving toward the south at 9 m.p.h. (15 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.

The low level circulation of the Tropical Low organized quickly on Thursday.  Numerous bands of showers and thunderstorms formed and they began to wrap around a center of circulation.  The distribution of showers and thunderstorms was relatively symmetrical, although there are a few more storms in the eastern half of the circulation.  Storms closer to the center started to generate upper level divergence.

The Tropical Low is in an environment that is very favorable for intensification.  The low is over water where the Sea Surface Temperature is near 30°C.  The upper level winds are light and there is very little vertical wind shear.  The Tropical Low is likely to continue to organize quickly in the favorable environment and it will likely become a named tropical cyclone on Friday.  Once thunderstorms consolidate around the center of circulation, a period of rapid intensification may occur.

The Tropical Low is currently being steered to the south and that motion could continue for another 12 to 24 hours.  A strengthening subtropical ridge is forecast to turn the Tropical Low toward the west in about 24 hours.  On its anticipated track the Tropical Low could approach the coast of Queensland in about three days.

Tropical Low Forms Over Western Australia

An area of low pressure system has been moving across northern Australia during the past few days.  The low remains organized and the Australian Bureau of Meteorology classified the system as a Tropical Low on Wednesday because of the potential for it to develop into a tropical cyclone.  At 10:00 a.m. EST on Wednesday the center of the Tropical Low was located at latitude 15.9°S and longitude 127.0°E which put it about 80 miles (130 km) west-southwest of Wyndham, Australia.  The Tropical Low was moving toward the west at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) an there were wind gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 1002 mb.

There is a well defined cyclonic circulation in the lower levels of the atmosphere, but there are not many thunderstorms in the core of that circulation.  Most of the thunderstorms are developing in bands that are on the periphery of the circulation.  The strongest thunderstorms are forming in bands in the western portion of the circulation as that part of the Tropical Low begins to moves over water.  The strongest winds are also occurring in these thunderstorms that are over water.  The Tropical Low is moving underneath an upper level ridge and the ridge is causing upper level divergence which is pumping out mass.

The core of the Tropical Low is still over Western Australia and moving over land is the primary factor inhibiting intensification of the system.  The atmospheric environment is favorable for intensification.  The upper level ridge is producing light winds over the Tropical Low and there is little vertical wind shear.  The Sea Surface Temperature of the water west of Australia is near 30°C and there will be plenty of energy in the ocean to support strengthening when the core of the circulation moves west of Australia.  Some slow organization of the circulation is possible during the next 12 hours as the core of the Tropical Low moves closer to the coast of Western Australia.  Further intensification is likely during the next several days once the core of the Tropical Low moves over the warm water.  The Tropical Low could strengthen into the first named tropical cyclone of 2017 later this week.

The upper level ridge is producing light easterly winds which are slowly steering the Tropical Low toward the west.  That general motion is expected to continue for another day or so.  Eventually, the Tropical Low is forecast to move on a west-southwesterly track that would paralle, but keep it to the west of the coast of Western Australia during the next several days.

Tropical Cyclone Organizing Northwest of Australia

A tropical cyclone is organizing northwest of Australia and the Australian Bureau of Meteorology has officially designated it as a tropical low.  At 10:00 p.m. EST on Wednesday the center of the tropical low was located at latitude 15.4°S and longitude 117.7°E which put it about 345 miles (555 km) north of Port Hedland, Australia.  The tropical low was moving toward the south at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1001 mb.

The circulation around the tropical low is still in an organizational phase and there is no well defined center of circulation.  Scattered spiral bands of thunderstorms are beginning to form and rotate around a broad center of circulation.  Much of the convection is still relatively shallow and taller thunderstorms are just beginning to form.  Some upper level divergence is beginning to occur to the west of the tropical low.

The environment is favorable for intensification.  The tropical low is over water where the Sea Surface Temperature is near 30°C.  An upper level ridge east of the tropical low is generating some easterly winds over the system, but the vertical wind shear is probably not strong enough to prevent intensification.  After more thunderstorms consolidate around a center of circulation and the organization of the tropical low improves, intensification is likely.

A subtropical ridge east of the tropical low is steering the low toward the south and that general motion is expected to continue for the next several days.  On its anticipated track, the tropical low could make landfall somewhere along the coast of Western Australia between Broome and Mardie on Friday.  The highest probability is currently for a landfall near Port Hedland in about 48 hours.  However, uncertainty exists about the future track because the tropical low is still organizing and a well defined center of circulation does not yet exist.

The tropical low is likely to bring strong winds, locally heavy rain and some storm surge to parts of the coast of Western Australia.