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Anggrek Transitions to an Extratropical Cyclone

Former Tropical Cyclone Anggrek made a transition to an extratropical cyclone over the South Indian Ocean during Tuesday night. At 4:00 a.m. EST on Wednesday the center of former Tropical Cyclone Anggrek was located at latitude 33.3°S and longitude 84.8°E which put it about 1925 miles (3105 km) south-southeast of Diego Garcia. Anggrek was moving toward the east-southeast at 40 m.p.h. (65 km/h). The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h). The minimum surface pressure was 983 mb.

Former Tropical Cyclone Anggrek made a transition to a powerful extratropical cyclone over the South Indian Ocean. Anggrek moved over water where the Sea Surface Temperatures are near 22°C. It moved under the eastern side of an upper level trough that is east of Madagascar. The upper level trough produced northwesterly winds that caused strong vertical wind shear. The combination of colder water and strong wind shear caused formal Tropical Cyclone Anggrek to make a transition to an extratropical cyclone.

The transition to an extratropical cyclone also caused changes to the structure of former Tropical Cyclone Anggrek. The strong northwesterly winds in the upper levels of the atmosphere blew the tops off of many of the thunderstorms in Anggrek’s circulation. Thunderstorms were still occurring in bands in the southern part of former Tropical Cyclone Anggrek. Bands in the northern part of the circulation consisted primarily of showers and lower clouds. Winds to hurricane/typhoon force extended out 70 miles (110 km) in the eastern side of former Tropical Cyclone Anggrek. Winds to tropical storm force extended out 140 miles (220 km) from the center of Anggrek’s circulation.

The upper level trough east of Madagascar will steer former Tropical Cyclone Anggrek quickly toward the east-southeast. On its anticipated track, Former Tropical Cyclone Anggrek could approach southwestern Australia later this week.

Elsewhere over the South Indian Ocean, a tropical depression formed east of Rodrigues. At 10:00 a.m. EST on Wednesday the center of the tropical depression was located at latitude 19.9°S and longitude 66.2°E which put it about 175 miles (280 km) east of Port Mathurin, Rodrigues. The tropical depression was moving toward the south-southeast at 3 m.p.h. (5 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.

Tropical Cyclone Enawo Hits Madagascar

Powerful Tropical Cyclone Enawo made landfall on the coast of northeastern Madagascar near Ambohitralanana on Tuesday.  Tropical Cyclone Enawo was the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale when it made landfall.  At 10:00 p.m. EST on Tuesday the center of Tropical Cyclone Enawo was located near latitude 15.5°S and longitude 49.2°E which put it near Mandritsara, Madagascar.  Enawo was moving toward the southwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 80 m.p.h. (130 km/h).  The minimum surface pressure was 980 mb.

Even though the center has been over land for more than 12 hours the circulation of Tropical Cyclone Enawo is still very well organized.  The structure is very symmetrical and there are multiple bands of thunderstorms revolving around the center of circulation.  The strongest winds are occurring in the portions of the rainbands that are over the Indian Ocean.  The circulation of Tropical Cyclone Ewano is still very large and winds to tropical storm force extend out about 200 miles (320 km) from the center.  Thunderstorms near the core of the circulation are generating upper level divergence which is pumping out mass in all directions.

The circulation of Tropical Cyclone Enawo will continue to weaken on Wednesday because the center is over land.  However, the atmospheric environment is favorable for a tropical cyclone.  The upper level winds are weak and there is very little vertical wind shear.  The lack of wind shear will cause the circulation of Tropical Cyclone Enawo to spin down more slowly and it is likely to persist for several more days.

Tropical Cyclone Enawo is moving around the western end of a subtropical high pressure system which is steering the tropical cyclone toward the southwest.  Tropical Cyclone Enawo is likely to turn more toward the south on Wednesday as it reaches the western end of the subtropical high.  On its anticipated track Tropical Cyclone Enawo will move over the center of Madagascar and it could pass near Antananarivo in 24 to 36 hours.  Tropical Cyclone Enawo is producing very heavy rainfall and flash flooding is a serious risk in areas of steep terrain.

Powerful Tropical Cyclone Enawo Nears Madagascar

Powerful Tropical Cyclone Enawo neared Madagascar late on Monday.  At 11:00 p.m. EST on Monday the center of Tropical Cyclone Enawo was located at latitude 14.7°S and longitude 51.1°E which put it about 140 miles (225 km) northeast of Mananara, Madagascar.  Enawo was moving toward the west-southwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 145 m.p.h. (230 km/h) and there were wind gusts to 175 m.p.h. (285 km/h).  The minimum surface pressure was 931 mb.

Tropical Cyclone Enawo intensified rapidly on Monday and it is now the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale.  The circulation of Tropical Cyclone Enawo is very well organized.  There is an circular eye with a diameter of 30 miles (50 km) at the center of the circulation.  The eye is surround by a ring of strong thunderstorms and the strongest winds are occurring in the eyewall.  The remainder of the circulation is symmetrical and additional well formed bands of thunderstorms are revolving around the core of the circulation.  Winds to hurricane force extend out about 70 miles (110 km) from the center.  Winds to tropical storm force extend out about 220 miles (350 km) from the center.

The Hurricane Intensity Index (HII) for Tropical Cyclone Enawo is 29.9.  The Hurricane Size Index (HSI) is 25.0 and the Hurricane Wind Intensity Size Index (HWISI) is 54.9.  The indices indicate that Tropical Cyclone Enawo is capable of causing significant widespread wind damage.  Tropical Cyclone Enawo is as intense as Hurricane Katrina was just before it made landfall in the coast of Mississippi in 2005.  Enawo is a little smaller than Hurricane Katrina was when Katrina was moving across the Gulf of Mexico in 2005.

Tropical Cyclone Enawo is moving through a very favorable environment.  Enawo is moving over water where the Sea Surface Temperature is near 29°C.  The upper level winds are weak and there is little vertical wind shear.  Tropical Cyclone Enawo is likely to maintain its intensity until it reaches the coast of Madagascar in a few hours.  Enawo will weaken after the center moves inland.

A subtropical ridge is steering Tropical Cyclone Enawo a little to the south of due west and that general motion is expected to continue for another 12 to 24 hours.  Tropical Cyclone Enawo will move near the western end of the subtropical ridge in another day or so and it will start to move more toward the south when it nears the end of the ridge.  On its anticipated track Tropical Cyclone Enawo will make landfall on the northeast coast of Madagascar near Ambohitralanana in a few hours.

Tropical Cyclone Enawo is a dangerous storm.  It is capable of causing widespread significant wind damage when it moves over eastern Madagascar.  The strong winds will also drive water toward the coast and Tropical Cyclone Enawo will generate a significant storm surge near where the center makes landfall.  Enawo will produce very heavy rain and significant inland flooding could occur if rainfall exceeds the capacity of rivers and streams.

Tropical Cyclone Enawo Moves Toward Madagascar and Strengthens

Tropical Cyclone Enawo moved toward Madagascar and strengthened on Sunday.  At 10:00 p.m. EST on Sunday the center of Tropical Cyclone Enawo was located at latitude 14.0°S and longitude 54.1°E which put it about 340 miles (550 km) east-northeast of Mananara, Madagascar.  Enawo was moving toward the west at 7 m.p.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 961 mb.

The circulation of Tropical Cyclone Enawo is very well organized.  A circular eye is at the center of circulation.  The eye is surrounded by a ring of thunderstorms.  Additional bands of showers and thunderstorms are revolving around the core of the circulation.  The circulation is very symmetrical although there are more thunderstorms in the northwestern quadrant of the circulation.  Thunderstorms in the core of the circulation are generating upper level divergence which is pumping mass away from the tropical cyclone.

The size of the circulation of Tropical Cyclone Enawo increased on Sunday.  Winds to hurricane force extend out about 30 miles (50 km) from the center of circulation.  Winds to tropical storm force extend out about 250 miles (400 km) from the center.  The Hurricane Intensity Index (HII) for Tropical Cyclone Enawo is 17.8.  The Hurricane Size Index (HSI) is 17.8 and the Hurricane Wind Intensity Size Index (HWISI) is 35.6.  These indices indicated that Tropical Cyclone Enawo is capable of causing serious wind damage on a regional scale.

Tropical Cyclone Enawo will continue to move through an favorable environment.  It will move over water where the Sea Surface Temperature is near 29°C.  The upper level winds are weak and there is little vertical wind shear.  Tropical Cyclone Enawo will continue to intensify during the next 24 hours and it could become the equivalent of a major hurricane.

A subtropical ridge is steering Tropical Cyclone Enawo toward the west and a general west or west-southwest motion is expected to continue during the next several days.  On its anticipated track Tropical Cyclone Enawo will approach the coast of Madagascar in about 36 hours.  Enawo will be capable of causing serious wind damage.  It will also generate a storm surge along the coast.  Tropical Cyclone Enawo will produce very heavy rain and a potential for flooding over eastern and southern Madagascar.

Tropical Cyclone Enawo Intensifies Into Equivalent of a Hurricane

Tropical Cyclone Enawo intensified into the equivalent of a hurricane/typhoon on Saturday.  At 10:00 p.m. EST on Saturday the center of Tropical Cyclone Enawo was located at latitude 13.9°S and longitude 56.3°E which put it about 475 miles (765 km) north of St. Denis, La Reunion.  Enawo was moving toward the south at 2 m.p.h. (3 km/h).  The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 95 m.p.h. (155 km/h).  The minimum surface pressure was 979 mb.

A primary rainband wrapped around the center of circulation and there was evidence of an eye on microwave satellite imagery.  A broken ring of thunderstorms surrounded the eye.  Additional bands of thunderstorms were rotating around the core of the circulation.  Thunderstorms near the center of circulation were generating upper level divergence which was pumping out mass in all directions.  The circulation of Tropical Cyclone Enawo is relatively small and winds to tropical storm force only extended out about 100 miles (160 km) from the center.

Tropical Cyclone Enawo will move through an environment very favorable for intensification during the next several days.  It 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.  Tropical Cyclone Enawo will continue to intensify and it could intensify rapidly for a time.  Tropical Cyclone Enawo is likely to become the equivalent of a major hurricane within 48 hours.

Tropical Cyclone Enawo was in an area where the steering currents were weak and it did not move much on Saturday.  A subtropical ridge east of Enawo is forecast to strengthen and extend westward.  When the ridge strengthens, it is expected to steer Tropical Cyclone Enawo toward the west-southwest.  On its anticipated track Tropical Cyclone Enawo could approach the coast of northeast Madagascar in 48 to 72 hours.  It could be a strong, dangerous tropical cyclone at that time.

Tropical Cyclone Enawo Forms North of La Reunion

Tropical Cyclone Enawo formed north of La Reunion on Friday.  At 4:00 p.m. EST on Friday the center of Tropical Cyclone Enawo was located at latitude 13.2°S and longitude 56.2°E which put it about 520 miles (835 km) north of St. Denis, La Reunion.  Enawo was moving toward the southwest at 4 m.p.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 994 mb.

An area of low pressure organized slowly over the southwest Indian Ocean during the past few days.  Bands of thunderstorms formed west of the center of circulation and some of the bands began to wrap closer to the center on Friday.  The low pressure system exhibited the characteristic structure of a developing tropical cyclone and it was designated Tropical Cyclone Enawo.  Although there are more thunderstorms near the center of circulation, the distribution of the storms is still asymmetrical.  There are many more thunderstorms in the western half of the circulation.  The asymmetry probably indicates that some vertical wind shear is slowing the organization of the circulation.

Tropical Cyclone Enawo will be moving through an environment favorable for intensification during the next several days.  It will be moving over water where the Sea Surface Temperature is near 30°C.  Enawo is northwest of an upper level ridge which is generating easterly winds that are blowing toward the top of the circulation.  The upper level ridge could be the source of the vertical wind shear that is slowing the intensification of the tropical cyclone.  The upper level wind shear could decrease during the weekend and Tropical Cyclone Enawo is likely to intensify into the equivalent of a hurricane/typhoon.  Once an inner core become well established at the center of circulation, a period of rapid intensification may be possible.

A subtropical ridge located southeast of Enawo is steering the tropical cyclone toward the southwest.  Guidance from the numerical models is divergent about the future strength of the ridge.  Some of the models, like the Global Forecasting System,  are predicting a weaker ridge and turn Tropical Cyclone Enawo more toward the south.  Other models, such as the European Center for Medium Range Forecasting System model, strengthen the subtropical ridge and steer Tropical Cyclone Enawo west toward northeast Madagascar.  Given the uncertainty in both the track and intensity forecasts, interests in the southwest Indian Ocean should monitor Tropical Cyclone Enawo closely.

Tropical Cyclone Stan Brings Wind and Rain to Western Australia

Tropical Cyclone Stan brought wind and rain to the coast of Western Australia as it made landfall on Saturday.  At 2:00 p.m. EDT on Saturday the center of Tropical Cyclone Stan was located at latitude 20.0°S and longitude 119.9°E which put it about 22 miles (35 km) east-northeast of Pardoo Station, Australia.  Stan was moving toward the south-southeast at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 977 mb.

The center of Tropical Cyclone Stan made landfall just east of Pardoo Station.  The circulation of Stan is relatively small and tropical storm force winds only extend about 100 miles from the center.  Most of the heavy rain is occurring west of the center of circulation between Pardoo and Port Hedland.

Tropical Cyclone Stan is moving around the western end of a subtropical ridge.  A trough in the middle levels of the atmosphere is west of Stan and it is helping to steer the tropical cyclone toward the southeast.  That general motion is expected to continue during the next 24 hours.  On its anticipated track Tropical Cyclone Stan will move farther inland over Western Australia.  It could pass near Yarrie in a few hours.

Tropical Cyclone Stan will continue to weaken steadily as it moves farther inland.  It could cause localized wind damage.  Stan could also produce locally heavy rain in isolated locations.

Tropical Cyclone Stan Intensifying As It Nears Western Australia

Tropical Cyclone Stan intensified on Friday as it moved closer to the coast of Western Australia.  At 4:00 p.m. EDT on Friday the center of Tropical Cyclone Stan was located near latitude 18.6°N and longitude 118.9°E which put it about 120 miles (195 km) north of Port Hedland, Australia.  Stan was moving toward the east-southeast at 6 m.p.h. (10 km/h).  The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 80 m.p.h. (130 km/h).  The minimum surface pressure was 982 mb.

The circulation of Tropical Cyclone Stan is much more well organized than it was 24 hours ago.  A primary rainband has wrapped about two thirds of the way around a distinct center of circulation.  There are many more thunderstorms in the core of the circulation and the structure is more symmetrical.  Thunderstorms in the core of Tropical Cyclone Stan are beginning to generate more upper level divergence which is pumping out mass in all directions.

The environment surrounding Tropical Cyclone Stan is now more favorable for intensification.  Stan has moved closer to the center of an upper level ridge that is located east of the tropical cyclone.  As a result, the upper level winds are not as strong and there is less vertical wind shear.  Since Tropical Cyclone Stan is over water where the Sea Surface Temperature is near 29°C, the reduced wind shear allowed it to intensify significantly today.  The environment will be favorable for intensification until Tropical Cyclone Stan makes landfall, and it could become the equivalent of a hurricane within 12 hours.  A period of rapid intensification may be possible.

As Tropical Cyclone Stan moved into an area where the easterly winds in the middle and upper levels were not as strong, it jogged eastward on Friday.  Stan is moving around the western end of a subtropical ridge and it is expected to begin to move more toward the southeast during the next 12 to 24 hours.  The eastward jog today also moved the most likely landfall location to the east.  On its anticipated track Tropical Cyclone Stan is expected to make landfall on the coast of Western Australia in 12 to 24 hours.  The highest probability of landfall is between Broome and Port Hedland near Pardoo Station.

Tropical Cyclone Stan will likely be the equivalent of a hurricane when it makes landfall.  It will be capable of causing wind damage.  Stan will also bring locally heavy rain and a chance for flash floods.  Tropical Cyclone Stan could generate a significant storm surge along the coast near where the center makes landfall.

Tropical Cyclone Stan Heading for Western Australia

A tropical low intensified into Tropical Cyclone Stan on Thursday and it is moving toward Western Australia.  At 10:00 p.m. EST on Thursday the center of Tropical Cyclone Stan was located at latitude 17.7°N and longitude 117.8°E which put it about 190 miles (305 km) north-northwest of Port Hedland, Australia.  Stan was moving toward the south-southeast at 7 m.p.h. (11 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 995 mb.

Tropical Cyclone Stan is not particularly well organized.  A primary rainband curves around the western side of the circulation, but there are not many thunderstorms in the eastern half of the cyclone.  Upper level divergence is occurring to the west of the center, but not to the east of the center.

The environment is marginally favorable for further intensification.  Tropical Cyclone Stan is over water where the Sea Surface Temperature is near 29°C.  However, an upper level ridge east of Stan is generating easterly winds over the top of the tropical cyclone.  The resulting vertical wind shear is inhibiting upper level divergence to the east of Stan.  The tropical cyclone is extracting enough energy from the ocean to intensify but the vertical wind shear is slowing the rate of intensification.  Tropical Cyclone Stan is expected to continue to intensify until it makes landfall.

Tropical Cyclone Stan is moving around the western end of a subtropical ridge which is steering it toward the south-southeast.  The south-southeast motion is expected to continue for another 24 to 36 hours.  On its anticipated track Tropical Cyclone Stan will make landfall on the coast of Western Australia near Port Hedland in about 24 hours.

Tropical Cyclone Stan could be near hurricane intensity when it makes landfall.  It will be capable of causing some wind damage.  Stan could also produce locally heavy rain and flooding.  It will also cause some storm surge near where the center makes landfall.