Category Archives: Indian Ocean

Tropical Cyclone Ernie Rapidly Intensifies Into the Equivalent of a Hurricane

The circulation of Tropical Cyclone Ernie rapidly intensified into the equivalent of a hurricane/typhoon late on Thursday.  At 8:00 p.m. EDT on Thursday the center of Tropical Cyclone Ernie was located at latitude 14.9°S and longitude 110.5°E which put it about 540 miles (870 km) north-northwest of Exmouth, Australia.  Ernie was moving toward the south-southwest at 8 m.p.h. (12 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 85 m.p.h. (140 km/h).  The minimum surface pressure was 987 mb.

An area of thunderstorms just west of the center of circulation quickly wrapped around the entire center.  A clear eye formed at the center of circulation.  Additional bands of storms formed and were revolving around the core of the circulation.  Thunderstorms around the eye were generating strong upper level divergence which pumped out mass and allowed the surface pressure to decrease quickly.  The circulation of Tropical Cyclone Ernie is small and winds to tropical storm force extend out only about 90 miles (150 km) from the center of circulation.

Tropical Cyclone Ernie will remain in a very favorable environment for another 12 to 24 hours.  Ernie will be over water where the Sea Surface Temperature (SST) is near 30°C.  An upper level ridge southeast of Ernie is producing northerly winds near the tropical cyclone, but those winds are not creating significant wind shear.  Tropical Cyclone Ernie could strengthen further during the next day or so.  In a day or two Ernie will move into an environment of lower SSTs and more vertical wind shear.  Tropical Cyclone Ernie will weaken at that time.

A subtropical ridge southeast of Ernie is steering the tropical cyclone slowly toward the south-southwest.  The ridge is forecast to strengthen and extend westward.  When the ridge extends toward the west it will also steer Tropical Cyclone Ernie more toward the west.  On its anticipated track Tropical Cyclone Ernie poses no current threat to land.

Tropical Cyclone Ernie Forms Northwest of Australia

Tropical Cyclone Ernie formed northwest of Australia on Thursday.  At 2:00 p.m. EDT on Thursday the center of Tropical Cyclone Ernie was located at latitude 14.1°S and longitude 110.9°E which put it about 580 miles (940 km) north-northwest of Exmouth, Australia.  Ernie was moving toward the south-southwest at 5 m.p.h. (7 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. (100 km/h).  The minimum surface pressure was 995 mb.

Thunderstorms developed around a small area of low pressure south of Indonesia during the past several days.  The storms consolidated near the center of circulation on Thursday and the Australian Bureau of Meteorology designated the system as Tropical Cyclone Ernie.  Ernie does have a well organized low level center of circulation, but many of the thunderstorms are occurring just to the west of the center of circulation.  There are also several bands of showers and thunderstorms in the southeastern quadrant of the circulation.  The thunderstorms near the center are generating upper level divergence which is pumping out mass to the south and southeast of Tropical Cyclone Ernie.

Tropical Cyclone Ernie is in an environment that is favorable for intensification.  It is moving over water where the Sea Surface Temperature (SST) is near 30°C.  An upper level ridge southeast of Ernie is generating northerly winds which are cause some vertical wind shear over the tropical cyclone.  However, the vertical wind shear is not strong enough to prevent further intensification of Tropical Cyclone Ernie.  Ernie should intensify during the next 24 hours and it could intensify rapidly during that time.  Tropical Cyclone Ernie will move into an unfavorable environment in a day or two.  Ernie will move over cooler SSTs and into a region where stronger upper level winds will produce more vertical wind shear.  The tropical cyclone will weaken at that time.

A subtropical ridge centered southeast of Ernie is steering the tropical cyclone slowly toward the south-southwest.  The ridge is forecast to strengthen and extend farther to the west.  When the ridge extends westward, it will steer Tropical Cyclone Ernie more toward the west.  On its anticipated track Tropical Cyclone Ernie currently poses no threat to land.

Tropical Cyclone Caleb Forms Over South Indian Ocean

Tropical Cyclone Caleb formed over the South Indian Ocean on Thursday.  At 8:00 a.m. EDT on Thursday the center of Tropical Cyclone Caleb was located at latitude 13.0°S and longitude 100.7°E which put it about 255 miles (410 km) east-southeast of Cocos Island.  Caleb was moving toward the south-southeast at 6 m.p.h. (9 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 995 mb.

Although there is a well defined low level circulation in Tropical Cyclone Caleb, the distribution of thunderstorms is asymmetrical.  The strongest thunderstorms are occurring in the northwestern quadrant of the circulation and they are in the primary rainband.  Those thunderstorms contain the strongest winds.  There are few thunderstorms in the other parts of the circulation, although there are some bands of lower clouds and showers in those regions.  The thunderstorms in the primary rainband are generating upper level divergence which is pumping out mass to the west of Tropical Cyclone Caleb.

Tropical Cyclone Caleb is in an environment that is marginal for intensification.  Caleb is moving over water where the Sea Surface Temperature is near 28°C.  So, there is enough energy in the upper ocean to support intensification.  However, an upper level ridge located southeast of Caleb is producing easterly winds which are blowing across the top of the tropical cyclone.  The easterly winds are generating moderate vertical wind shear and the shear is probably the reason why most of the thunderstorms are occurring in the northwestern quadrant of the circulation.  The moderate shear will inhibit intensification, but some strengthening may be possible if the upper level winds abate.

A ridge to the east of Caleb is steering the tropical cyclone toward the south-southeast and that general motion is expected to continue for another day or two.  Eventually, a second ridge is forecast to strengthen and steer Tropical Caleb back toward the northwest.

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 Dineo Makes Landfall in Mozambique

Tropical Cyclone Dineo made landfall on the coast of Mozambique near Massinga on Wednesday.  Dineo intensified prior to landfall.  The maximum sustained wind speed at the time of landfall was 85 m.p.h. (135 km/h) and there were wind gusts to 105 m.p.h. (170 km/h).  Tropical Cyclone Dineo was capable of causing minor wind damage.  It may have produced a storm surge near and to the south of where the center made landfall.  Tropical Cyclone Dineo is producing locally heavy rain as it moves inland over Mozambique.

At 10:00 p.m. EST on Wednesday the center of Tropical Cyclone Dineo was located at latitude 23.3°N and longitude 33.6°E which put it about 125 miles (205 km) west-northwest of Inhambane, Mozambique.  Dineo was moving toward the west at 11 m.p.h. (17 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 981.

Even though it has moved inland the structure of Tropical Cyclone Dineo is still very well organized.  The remnants of the eye and the eyewall are still visible on satellite imagery.  There are several rainbands rotating around the core of Tropical Cyclone Dineo.  The strongest winds are occurring in thunderstorms in the bands that are still offshore over the Indian Ocean.  The thunderstorms near the center of Dineo are still generating upper level divergence which is pumping mass away from the core of the tropical cyclone.

Tropical Cyclone Dineo will continue to weaken slowly as it moves farther inland.  The atmospheric environment is favorable for a tropical cyclone.  The upper level winds are weak and there is little vertical wind shear.  However, now that the core of Dineo is inland, it is away from the warm water of the Indian Ocean which fueled the tropical cyclone’s intensification.  So, Tropical Cyclone Dineo will spin down, but at a slower rate than occurs with some landfalling tropical cyclones.

A subtropical ridge is steering Tropical Cyclone Dineo toward the west and that general motion is expected to continue.  On its anticipated track the center of Tropical Cyclone Dineo could pass near Dindiza, Chigubo and Mapai in Mozambique.  Dineo could produce locally heavy rain when it moves over those areas.  Tropical Cyclone Dineo or its remnants could also bring locally heavy rain to parts of northern South Africa, southern Zimbabwe and eastern Botswana.

Tropical Cyclone Dineo Intensifies As It Nears Mozambique

Tropical Cyclone Dineo intensified on Tuesday as it moved closer to Mozambique.  At 10:00 p.m. EST on Tuesday the center of Tropical Cyclone Dineo was located at latitude 22.8°S and longitude 37.5°E which put it about 160 miles (260 km) east-northeast of Inhambane, Mozambique.  Dineo was moving toward the west-southwest at 7 m.p.h. (11 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 981 mb.

Tropical Cyclone Dineo intensified on Tuesday and it was on the verge of reaching the intensity of a hurricane/typhoon.  A primary rainband wrapped most of the way around a circular eye.  There was a break on the western side of the developing eyewall.  The strongest winds were occurring in thunderstorms in the eyewall.  Several other bands of showers and thunderstorms were rotating around the core of Tropical Cyclone Dineo.  Thunderstorms around the core of Dineo were generating upper level divergence which was transporting mass away from the center of the tropical cyclone.

Tropical Cyclone Dineo will move through a favorable environment until it reaches Mozambique.  Dineo 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.  The favorable environment will allow Tropical Cyclone Dineo to continue to intensify during the next 12 to 18 hours.  It will become the equivalent of a hurricane/typhoon on Wednesday.

A subtropical ridge is steering Tropical Cyclone Dineo toward the west-southwest and that general motion is expected to continue for another 12 to 24 hours.  On its anticipated track Tropical Cyclone Dineo is expected to make landfall on the coast of Mozambique north of Inhambane in less than 24 hours.  Tropical Cyclone Dineo will be the equivalent of a hurricane/typhoon when it makes landfall.  Dineo will bring strong winds and locally heavy rain when it moves into Mozambique.  Heavy rain could create the potential for flash floods.  Tropical Cyclone Dineo will also produce a storm surge along the coast.  The highest storm surge will occur south of where the center makes landfall as the clockwise rotation pushes water toward the coast.