Monthly Archives: January 2018

Tropical Cyclone Joyce Develops Near Western Australia

Tropical Cyclone Joyce developed near Western Australia on Wednesday when a Tropical Low moved over the South Indian Ocean.  At 10:00 p.m. EST on Wednesday the center of Tropical Cyclone Joyce was located near latitude 17.0°S and longitude 121.6°E which put it about 80 miles (125 km) north-northwest of Broome, Australia.  Joyce was moving toward the south-southwest at 5 m.p.h. (7 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 990 mb.

A Tropical Low moved from Western Australia off the coast and over the warm water of the South Indian Ocean on Wednesday.  The circulation of the system organized after the center moved over water and the inner core became more well developed.  The Australian Bureau of Meteorology designated the system as Tropical Cyclone Joyce.  A Tropical Cyclone Warning was issued for the portion of the coast from Cape Leveque to De Grey including Broome and adjacent inland parts of Western Australia.  A Tropical Cyclone Watch was issued for the portion of the coast from De Grey to Dampier including Port Headland, Karratha and adjacent inland areas.

The circulation of Tropical Cyclone Joyce exhibited the classical appearance of an organizing tropical cyclone on Wednesday.  There was a well defined low level center of circulation.  Numerous bands of showers and thunderstorms were revolving around the center of circulation.  Storms in the core of Joyce were generating upper level divergence which was pumping mass away from the tropical cyclone.

Tropical Cyclone Joyce will be moving through an environment favorable for intensification during the next day or so.  Joyce will move over water where the Sea Surface Temperature is near 30°C.  The upper level winds are weak and there is little vertical wind shear.  Warm water and little vertical wind shear will allow Joyce to strengthen and it could intensify rapidly.  Tropical Cyclone Joyce is forecast to strengthen into the equivalent of a hurricane/typhoon during the next 36 hours.

Tropical Cyclone Joyce is moving around the western end of a subtropical ridge which is steering Joyce toward the south-southwest.  The ridge is forecast to steer Joyce in a general southwesterly direction during the next several days.   On its anticipated track the center of Tropical Cyclone Joyce could make landfall on the coast of western Australia between Wallal Downs and De Grey in about 36 hours.

Tropical Low Forms Over Western Australia

A Tropical Low formed over Western Australia on Monday and a Tropical Cyclone Watch was issued for a portion of the coast.  At 2:00 p.m. EST on Monday the center of the Tropical Low was located at latitude 15.9°S and longitude 126.1°E which put it about 135 miles (220 km) west-southwest of Wyndham, Australia.  It was moving toward the southwest a 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 20 m.p.h. (30 km/h) and there were wind gusts to 50 m.p.h. (85 km/h).  The minimum surface pressure was 1005 mb.  The Australia Bureau of Meteorology has issued a Tropical Cyclone Watch for the portion of the coast of Western Australia from Kuri Bay to Wallal Downs including Broome.

The circulation of the Tropical Low is still organizing.  There is a broad low level center of circulation, but there are not many showers and thunderstorms near the center.  There are numerous bands of showers and storms developing in bands on the eastern and western peripheries of the circulation.  The strongest wind gusts are occurring in those storms.  The lack of storms near the center of circulation is keeping the system from generating much upper level divergence.

The core of the Tropical Low is likely to remain over land for another 12-24 hours, which will inhibit the organization of the circulation.  When the center moves off the coast and over the South Indian Ocean, it will move into an environment favorable for intensification.  The Sea Surface Temperature of the water west of the coast of Western Australia is near 30°C.  The Tropical Low is moving north of the axis of a subtropical ridge.  The ridge is producing easterly winds which are blowing toward the top of the circulation, but there is not a lot of vertical wind shear.  The Tropical Low is likely to strengthen when it moves over water and it could intensify rapidly if a more concentrated center of circulation develops.

A subtropical ridge is current steering the Tropical Low toward the southwest, but a general motion toward the west-southwest is expected during the next 24 to 48 hours.  The Tropical Low will reach the western end of the ridge in about two days and then it will turn more toward the south.  On its anticipated track the center of the Tropical Low is expected to move off the coast between Kuri Bay and Derby on Tuesday.  The center is forecast to pass near Cape Leveque and then turn south toward Wallal Downs.

Elsewhere over the South Indian Ocean, Tropical Cyclone Ava continued to swirl near southern Madagascar and stronger Tropical Cyclone Irving was passing well to the south of Diego Garcia.  At 4:00 p.m. EST on Monday the center of Tropical Storm Ava was located at latitude 27.7°S and longitude 46.8°E which put it about 180 miles (295 km) south of Farodofay, Madagascar.  Ava was moving toward the west-southwest at 17 m.p.h. (27 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 994 mb.

At 4:00 p.m. EST on Monday the center of Tropical Cyclone Irving was centered at latitude 19.6°S and longitude 76.1°E which put it about 875 miles (1415 km) south-southeast of Diego Garcia.  Irving was moving toward the west-southwest at 18 m.p.h. (29 km/h).  The maximum sustained wind speed was 105 m.p.h. (170 km/h) and there were wind gusts to 125 m.p.h. (205 km/h).  The minimum surface pressure was 960 mb.  Tropical Cyclone Irving was the equivalent of a Category 2 hurricane on the Saffir-Simpson Scale.

Tropical Cyclone Ava Drops Heavy Rain on Madagascar

Tropical Cyclone Ava dropped heavy rain over Madagascar on Saturday.  At 4:00 p.m. EST on Saturday the center of Tropical Cyclone Ava was located at latitude 21.4°S and longitude 48.2°E which put it about 70 miles (110 km) north-northwest of Mananjary, Madagascar.  Ava was moving toward the south-southeast at 11 m.p.h. (17 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 994 mb.

Tropical Cyclone Ava weakened into the equivalent of a tropical storm during the day it spent moving over Madagascar.  The strongest winds were occurring in bands of thunderstorms over the water.  The center made landfall on Friday near Toamasina.  The center then passed near Moramanga, Anosibe An’ala, and Marolambo.  There is still a distinct center of circulation and several bands of showers and thunderstorms are revolving around the center.  Some of the storms dropped heavy rain over parts of Madagascar.  There was stronger rising motion in places where the winds blew up the sides of mountains and the rainfall was heavier in those locations.  The potential for flooding exists in places that received heavy rain.

The center of Tropical Cyclone Ava is likely to move back over the water of the South Indian Ocean during the next few hours.  Tropical Cyclone Ava will move into an environment that is favorable for intensification when it moves back over water.  The Sea Surface Temperature of the water east of Madagascar is near 28°C.  Ava is moving under the axis of an upper level ridge and the upper level winds are relatively weak.  So, there is not a lot of vertical wind shear.  Tropical Cyclone Ava is likely to strengthen once the center moves back over water.

Tropical Cyclone Ava is moving around the western end of a subtropical ridge which is steering Ava toward the south-southeast.  The ridge is forecast to steer Tropical Cyclone Ava toward the south for another day or two.  When Tropical Cyclone Ava moves farther to the south in about 48 hours, an upper level trough will cause northwesterly winds, which will start to steer the tropical cyclone toward the east-southeast.  On its anticipated track the center of Tropical Cyclone Ava is expected to move off the coast of Madagascar near Mananjary in a few hours.

Elsewhere over the South Indian Ocean, Tropical Cyclone Irving was strengthening east-southeast of Diego Garcia.  At 4:00 p.m. EST on Saturday the center of Tropical Cyclone Irving was located at latitude 13.3°S and longitude 87.5°E which put it about 1145 miles (1845 km) east-southeast of Diego Garcia.  Irving was moving toward the west-southwest at 13 m.p.h. (21 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 991 mb.

Satellite imagery suggested that Tropical Cyclone Irving could be strengthening rapidly.  A primary rainband was wrapping around the center of circulation.  An eye appeared to be forming at the center of Irving.  Tropical Cyclone Irving will move through an environment favorable for intensification.  Irving is likely to intensify into the equivalent of a hurricane/typhoon while it passes well to the south of Diego Garcia during the next several days.

Strong Tropical Cyclone Ava Makes Landfall in Madagascar

Strong Tropical Cyclone Ava made landfall on the east coast of Madagascar near Toamasina on Friday.  At 10:00 a.m. EDT on Friday the center of Tropical Cyclone Ava was located near 18.0°S and longitude 49.2°E which put it near Toamasina.  Ava was moving toward the west-southwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 105 m.p.h. (170 km/h) and there were wind gusts to 125 m.p.h. (205 km/h).  The minimum surface pressure was 959 mb.  Tropical Cyclone Ava was the equivalent of a Category 2 hurricane on the Saffir-Simpson Scale.

Tropical Cyclone Ava intensified rapidly during the past 12 hours and it was still intensifying when it made landfall on the coast of Madagascar.  There was a well defined circular eye at the center of circulation.  The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Several bands of showers and thunderstorms were revolving around the core of the circulation.  Thunderstorms in the core of Tropical Cyclone Ava were generating strong upper level divergence which was pumping away mass and allowed the surface pressure to decrease rapidly.  Winds to hurricane/typhoon force extended out about 60 miles (95 km) from the center of circulation.  Winds to tropical storm force extended out about 180 miles (290 km) from the center.

The Hurricane Intensity Index (HII) for Tropical Cyclone Ava was 17.8.  The Hurricane Size Index (HSI) was 17.6 and the Hurricane Wind Intensity Size Index (HWISI) was 35.4.  Those indices indicate that Tropical Cyclone Ava is capable of causing regional serious damage.  The core of Tropical Cyclone Ava passed over Toamasina and there is likely to be serious wind damage in that city.  Heavy rain was falling in parts of eastern Madagascar and floods could occur.  Tropical Cyclone Ava could produce a storm surge of 10 feet (3 meters) south of where the center made landfall, because the strong winds will be blowing the water toward the coast.

Tropical Cyclone Ava will weaken while the center moves over land in eastern Madagascar.  However, the rest of the environment is favorable for a tropical cyclone.  The Sea Surface Temperature off the east coast of Madagascar is near 28°C.  The upper level winds are weak and there is little vertical wind shear.  If the inner core of Tropical Cyclone Ava remains intact, then Ava could intensify again when the center moves back over the South Indian Ocean in a day or so.

Tropical Cyclone Ava is moving around the western end of a subtropical ridge which is steering the tropical cyclone toward the west-southwest.  Ava will start to move toward the south when it reaches the end of the ridge in a few hours.  On its anticipated track Tropical Cyclone Ava is forecast to move just inland of the east coast of Madagascar.  Ava is forecast to move back off the coast in 24 to 36 hours.  Tropical Cyclone Ava is capable of causing serious damage along the central east coast of Madagascar.

Tropical Cyclone Ava Strengthens East of Madagascar

Tropical Cyclone Ava intensified east of Madagascar on Thursday.  At 4:00 p.m. EST on Thursday the center of Tropical Cyclone Ava was located at latitude 17.4°S and longitude 50.8°E which put it about 125 miles (205 km) east-northeast of Toamasina, Madagascar.  Ava was moving toward the west-northwest 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 980 mb.

Tropical Cyclone Ava exhibited the classic structure of a tropical cyclone on Thursday.  A clear eye was evident at the center of circulation on microwave satellite imagery.  The eye was surrounded by a nearly complete ring of showers and thunderstorms.  Spiral bands of showers and thunderstorms were revolving around the core of Tropical Cyclone Ava.  Storms in the core of Ava were generating strong upper level divergence which was pumping mass away from the tropical cyclone.  Winds to tropical storm force extended out about 140 miles (225 km) from the center of circulation.

Tropical Cyclone Ava will move through an environment favorable for intensification on Friday.  Ava will move over water where the Sea Surface Temperature is near 28.5°C.  Tropical Cyclone Ava is moving near the western end of an upper level ridge, but the upper level winds are weak and there is not much vertical wind shear.  Warm water and little vertical wind shear will allow Tropical Cyclone Ava to intensify during the next 24 hours.  Ava should strengthen into the equivalent of a hurricane/typhoon on Friday.

Tropical Cyclone Ava is moving around the western end of a subtropical ridge, which has been steering Ava mostly toward the west.  Tropical Cyclone Ava is forecast to move more toward the southwest on Friday as it nears the western end of the ridge.  On its anticipated track the center of Tropical Cyclone Ava will move close to the east coast of Madagascar near Toamasina in 18 to 24 hours.  When Ava reaches the western end of the ridge in about 24 hours, it will start to move more toward the south.

Tropical Cyclone Ava will bring strong winds and locally heavy rain to the east coast of Madagascar.  The winds will be strong enough to do damage and they could generate a storm surge at the coast.  Rain is already falling on parts of eastern Madagascar and more heavy rain will create the potential for floods.

Tropical Storm Bolaven Forms Over the South China Sea

Tropical Storm Bolaven formed over the South China Sea near the Spratly Islands on Tuesday.  At 10:00 p.m. EDT on Tuesday the center of Tropical Storm Bolaven was located at latitude 10.4°N and longitude 115.1°E which put it about 620 miles (1000 km) east of Ho Chi Minh City, Vietnam.  Bolaven was moving toward the west-northwest at 21 m.p.h. (33 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 1002 mb.

A low level center of circulation developed on the eastern side of a cluster of thunderstorms that moved across the southern Philippines on Monday.  The center exhibited greater organization on Tuesday and the Japan Meteorological Agency designated the system as Tropical Storm Bolaven.  The structure of Tropical Storm Bolaven is asymmetrical.  The strongest thunderstorms are occurring northwest of the center of circulation.  Thin bands of low clouds and showers were revolving around the center of circulation in the other quadrants of Tropical Storm Bolaven.

Tropical Storm Bolaven is moving around the southern side of an upper level ridge centered east of the Philippines.  The ridge is generating strong southeasterly winds which are blowing across the top of the circulation.  Those winds are causing moderate vertical wind shear.  The wind shear is probably the reason why most of the stronger storms are occurring northwest of the center of circulation.  Although Bolaven will move over water where the Sea Surface Temperature is near 28°C, the vertical wind shear will likely prevent intensification.  In fact if the shear increases, then Bolaven could weaken to a tropical depression.

The ridge north of Bolaven is steering the tropical storm toward the west-northwest and that general motion is expected to continue for several more days.  On its anticipated track Tropical Storm Bolaven could reach the coast of South Vietnam in 24 to 36 hours.  Bolaven will bring gusty winds and locally heavy rain to parts of southern Vietnam.

Tropical Cyclone 03S Forms East of Madagascar

Tropical Cyclone 03S formed east of Madagascar on Tuesday.  At 4:00 p.m. EST on Tuesday the center of Tropical Cyclone 03S was centered at latitude 15.5°S and longitude 53.2°E which put it about 330 miles (530 km) east-northeast of Toamasina, Madagascar.  It was moving a little south of due west at 9 m.p.h. (15 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.

A well defined center of circulation developed within a cluster of thunderstorms passing north of La Reunion on Tuesday.  A primary rainband wrapped around the center of circulation and the system exhibited the characteristics of a tropical cyclone.  The innermost end of the primary  rainband wrapped tightly around the eastern side of the center of circulation, while the rest of the band coiled around the northern and western parts of the tropical cyclone.  Additional bands of showers and thunderstorms were forming outside the core of the system.  Thunderstorms near the center of circulation were generating upper level divergence which was pumping mass away from the tropical cyclone.

Tropical Cyclone 03S will be moving through an environment favorable for intensification.  It will move over water where the Sea Surface Temperature is near 28.5°C.  Tropical Cyclone 03S is in a region where the upper level winds are weak and there is not much vertical wind shear.  Warm water and little shear will allow Tropical Cyclone 03S to intensify and it could intensify rapidly.  The system is likely to strengthen into the equivalent of a hurricane/typhoon within 36 hours.

Tropical Cyclone 03S is moving along the northwestern periphery of a subtropical ridge.  The ridge is currently steering the system toward the west.  However, Tropical Cyclone 03S is likely to move more toward the southwest when it reaches the western end of the ridge.  On its anticipated track Tropical Cyclone 03S could approach the east coast of Madagascar in 24 to 36 hours.

Tropical Cyclone 03S is likely to intensify into the equivalent of a hurricane/typhoon before it reaches Madagascar.  It will bring strong gusty winds to eastern Madagascar.  The outer rainbands on the western side of Tropical Cyclone 03S are already dropping heavy rain on parts of eastern Madagascar.  Continued heavy could create dangerous floods in some locations.