Tag Archives: SH02

Tropical Cyclone Ambali Rapidly Intensifies to Threshold of Cat. 5

Tropical Cyclone Ambali rapidly intensified to the threshold of a Category 5 hurricane on the Saffir-Simpson Scale on Thursday.  At 10:00 p.m. EST on Thursday the center of Tropical Cyclone Ambali was located at latitude 10.8°S and longitude 62.1°E which put it about 740 miles (1190 km) north-northeast of Port Louis, Mauritius.  Ambali was moving toward the south-southwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 155 m.p.h. (250 km/h) and there were wind gusts to 190 m.p.h. (305 km/h).  The minimum surface pressure was 932 mb.

Tropical Cyclone Ambali rapidly intensified from a minimal tropical storm to the threshold of a Cat. 5 hurricane in less than 36 hours over the Southwest Indian Ocean.  Nearly perfect environmental conditions including warm water and little vertical wind shear allowed Ambali to strengthen very rapidly.  A small circular eye formed at the center of the tropical cyclone.  The eye was surrounded by a ring of strong thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Ambali.

The circulation around Tropical Cyclone Ambali was small which also contributed to the rapid intensification.  Winds to hurricane/typhoon force extended out 25 miles (40 km) from the center of circulation.  Winds to tropical storm force extended out 100 miles (160 km) from the center.  The Hurricane Intensity Index (HII) for Tropical Cyclone Ambali was 33.3.  The Hurricane Size Index (HSI) was 7.9 and the Hurricane Wind Intensity Size Index (HWISI) was 41.2.

Tropical Cyclone Ambali may be near its maximum intensity, although it could strengthen a little more during the next six to twelve hours.  Ambali will move over water where the Sea Surface Temperature is near 28°C.  It will remain in an area where the upper level winds are weak during the next six to twelve hours and there will be little vertical wind shear during that time.  Tropical Cyclone Ambali will approach an area where there are strong upper level westerly winds during the weekend.  Ambali will weaken when the wind shear increases.

Tropical Cyclone Ambali will move around the western part of a subtropical high pressure over the South Indian Ocean.  The high will steer Ambali toward the south-southwest during the next several days.  On its anticipated track Tropical Cyclone Ambali will move toward Mauritius.

Elsewhere over the Southwest Indian Ocean, Tropical Cyclone Belna was intensifying north of Madagascar.  At 10:00 p.m. EST on Thursday the center of Tropical Cyclone Belna was located at latitude 7.5°S and longitude 49.0°E which put it about 300 miles (485 km) north of Madagsacar.  Belna was moving toward the southwest at 8 m.p.h. (13 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 982 mb.

The circulation around Tropical Cyclone Belna exhibited much greater organization on Thursday.  An eye appeared to be forming at the center of circulation on microwave satellite images.  The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving about the core of Belna.  Storms near the core were generating upper level divergence which was pumping mass away from the tropical cyclone.  Winds to tropical storm force extended out 100 miles (160 km) from the center of circulation.

Tropical Cyclone Belna will move through an environment favorable for intensification during the next 24 to 48 hours.  Belna will move over water where the Sea Surface Temperature is near 28.5°C.  It will move through a region where the upper level winds are weak and there will be little vertical wind shear.  Tropical Cyclone Belna is likely to strengthen into the equivalent of a hurricane/typhoon on Friday.  Belna could intensify rapidly once an eye and eyewall are full formed.  It could strengthen into the equivalent of a major hurricane during the weekend.

Tropical Cyclone Belna will move around the western end of a ridge of high pressure over the South Indian Ocean.  The high will steer Belna toward the south-southwest during the next few days.  On its anticipated track Tropical Cyclone Blena could approach the coast of northwestern Madagascar in three or four days.  Belna could be the equivalent of a hurricane/typhoon when it approaches Madagascar.

Two Tropical Cyclones Form over Southwest Indian Ocean

One day after a pair of tropical cyclones developed over Arabian Sea, two tropical cyclones formed over the Southwest Indian Ocean on Wednesday.  At 4:00 p.m. EST on Wednesday the center of Tropical Cyclone 02S was located at latitude 6.9°S and longitude 51.2°E which put it about 355 miles (575 km) north of Madagascar.  The tropical cyclone was moving toward the south-southwest at 4 m.p.h. (6 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.

At 4:00 p.m. EST on Wednesday the center of Tropical Cyclone 03S was located at latitude 7.5°S and longitude 64.0°E which put it about 570 miles (915 km) west of Diego Garcia.  The tropical cyclone was moving toward the southwest at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) snd there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1000 mb.

Tropical Cyclone 02S was still organizing on Wednesday afternoon and the distribution of thunderstorms was asymmetrical.  Many of the stronger thunderstorms were occurring in bands on the northern side of the circulation.  Bands on the southern side of the tropical cyclone consisted primarily of showers and lower clouds.  Storm near the center of circulation began to generate upper level divergence which was pumping mass away from the tropical cyclone.  Winds to tropical storm force extended out 30 miles (50 km) from the center.

Tropical Cyclone 02S will move through an environment favorable for intensification during the next 48 to 72 hours.  The tropical cyclone will move over water where the Sea Surface Temperature is near 28.5°C.  It will move through a region where there will be weak southeasterly winds in the upper levels.  Those winds will cause some vertical wind shear and they may already have contributed to the asymmetrical distribution of thunderstorms.  The wind shear will slow the rate of intensification, but the shear will not be enough to prevent the Tropical Cyclone 02S from getting stronger. The tropical cyclone could intensify into the equivalent of a hurricane/typhoon in 48 to 72 hours.

Tropical Cyclone 02S will move near the western end of a subtropical high pressure system over the South Indian Ocean.  The high will steer the tropical cyclone toward the south-southwest.  On its anticipated track Tropical Cyclone 02S could approach northern Madagascar in three or four days.

Tropical Cyclone 03S was also still organizing on Wednesday afternoon and it too had an asymmetrical distribution of thunderstorms.  The strongest thunderstorms around Tropical Cyclone 03S were occurring in bands south and west of the center of circulation.  Bands north and east of the center consisted primarily of showers and lower clouds.  Storms near the center of circulation were generating upper level divergence which was pumping mass away from the tropical cyclone.  Winds to tropical storm force extended out 35 miles (55 km) from the center.

Tropical Cyclone 03S will move through an environment favorable for intensification during the next 24 to 48 hours.  The tropical cyclone will move over water where the Sea Surface Temperature is near 28.5°C.  It will move through a region where the upper level winds will blow from the north.  Those winds will cause some vertical wind shear and they may have already contributed to the asymmetrical distribution of thunderstorms.  The wind shear will slow the rate of intensification but it will not be strong enough to prevent Tropical Cyclone 03S from getting stronger.

Tropical Cyclone 03S will also be steered by the subtropical high pressure system over the South Indian Ocean.  The high will steer the tropical cyclone toward the south-southwest.  On its anticipated track Tropical Cyclone 03S could move toward Mauritius.

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 Cyclone Yvette Turns Toward Western Australia

Tropical Cyclone Yvette turned toward western Australia on Friday.  At 1:00 p.m. EST on Friday the center of Tropical Cyclone Yvette was located near latitude 15.1°S and longitude 117.3°E which put it about 370 miles (600 km) north-northwest of Port Headland, Australia.  Yvette was moving toward the east-southeast at 8 m.p.h. (13 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 992 mb.

An upper level ridge located to the northeast of Yvette is generating strong northeasterly winds which are blowing across the top of the tropical cyclone.  Those winds are creating strong vertical wind shear and for a time the strong upper levels winds sheared the top off of the circulation.  The upper level winds weakened slightly and new thunderstorms developed near the center of Tropical Cyclone Yvette.  The circulation of Yvette is very asymmetrical.  Most of the new thunderstorms are forming west of the center of circulation, although a few storms recently formed east of the center.  The upper level winds are also preventing upper level divergence to the east of Yvette.

Tropical Cyclone Yvette will be moving through an environment that will be only marginally favorable for intensification.  Yvette 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 strong upper level winds and vertical wind shear will inhibit intensification.  It is possible that the shear could decrease when Yvette moves east and gets closer to the core of the upper level ridge.  If the shear decreases, then some intensification may occur before Yvette reaches western Australia.

A subtropical ridge is steering Tropical Cyclone Yvette toward the east-southeast and that general motion is expected to continue.  On its anticipated track Tropical Cyclone Yvette will reach the coast of Western Australia in about 36 hours.  Landfall will likely occur between Cape Leveque and De Grey.  The highest probability is for a landfall near Bidyadanga.  Tropical Cyclone Yvette will produce locally heavy rain near where the center makes landfall.  Heavy rain could create the potential for flash floods.

Tropical Cyclone Yvette Develops Northwest of Australia

The circulation of a tropical low northwest of Australia continued to organize on Wednesday and the Australian Bureau of Meteorology named the system Tropical Cyclone Yvette.  At 7:00 a.m. EST on Wednesday the center of Tropical Cyclone Yvette was located at latitude 14.2°N and longitude 114.2°E which put it about 515 miles (830 km) northwest of Port Headland, Australia.  Yvette was making a slow clockwise loop and it was basically stationary.  The maximum sustained wind speed was 45 m.p.h. (70 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 991 mb.

The circulation of Tropical Cyclone Yvette is asymmetrical.  It has a well developed low level circulation but most of the thunderstorms are developing southwest of the center.  An upper level ridge over Australia is generating northeasterly winds which are blowing across the top of the circulation.  The moderate vertical wind shear is probably the reason why most of the thunderstorms are southwest of the center of circulation.  The upper level winds are inhibiting divergence to the east of Yvette, but they are enhancing the divergence to the west of the tropical cyclone.

The environmental factors are marginally favorable for intensification.  Tropical Cyclone Yvette will be moving over water where the Sea Surface Temperature is near 30°C.  The upper level winds are forecast to weaken and the vertical wind shear could decrease during the next several day.  As a result, Tropical Cyclone Yvette could slowly strengthen.

Winds at the steering level are currently variable around Yvette and as a result the tropical cyclone has made several clockwise loops.  The upper level ridge over Australia is forecast to extend west and the ridge is expected to steer Tropical Cyclone Yvette toward Western Australia.  On its anticipated track Tropical Cyclone Yvette is expected to approach the coast of Western Australia in three or four days.

Tropical Cyclone Yvette could bring gusty winds and locally heavy rain when it makes landfall.  Yvette could also generate a storm surge near where the center makes landfall.