Tag Archives: Indian Ocean

Tropical Cyclone Luban Forms Over Arabian Sea

Tropical Cyclone Luban formed over the Arabian Sea on Monday.  At 11:00 a.m. EDT on Monday the center of Tropical Cyclone Luban was located at latitude 12.3°N and longitude 61.4°E which put it about 580 miles (935 km) east-southeast of Salalah, Oman.  Luban was moving toward the west-northwest 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 993 mb.

The circulation around Tropical Cyclone Luban was still organizing.  The distribution of thunderstorms was asymmetrical.  Many of the stronger thunderstorms were occurring in bands west of the center of circulation.  Rainbands in the eastern half of Tropical Cyclone Luban consisted primarily of showers and lower clouds.  An upper level trough centered over northern India was producing easterly winds which were blowing toward the top of the circulation.  Those winds were causing moderate vertical wind shear and they were probably the reason why the stronger thunderstorms were forming on the western side of the circulation.

Tropical Cyclone Luban will move through a region that is somewhat favorable for intensification.  It will move over water where the Sea Surface Temperature is near 29°C.  The upper level ridge will continue to cause some vertical wind shear, but the winds are expected to weaken during the next day or two.  Tropical Cyclone Luban is forecast to strengthen into the equivalent of a hurricane/typhoon.

Tropical Cyclone Luban is between the upper level ridge over India and another upper level ridge over Saudi Arabia.  As a result the steering winds are weak and Luban is moving slowly toward the west-northwest.  When Tropical Cyclone Luban moves farther west, the upper ridge over Saudi Arabia will steer it in a west-northwesterly direction.  On its anticipated track Tropical Cyclone Luban could approach western Oman and eastern Yemen in four or five days.

Tropical Cyclone Ernie Very Rapidly Intensifies Into Equivalent of a Major Hurricane

Tropical Cyclone Ernie intensified very rapidly into the equivalent of a major hurricane during the past few hours.  Ernie strengthened from a tropical low to the equivalent of a major hurricane in one day which is an extremely rapid rate of intensification.  At 8:00 a.m. EDT on Friday the center of Tropical Cyclone Ernie was located at latitude 15.5°S and longitude 110.2°E which put it about 485 miles (780 km) north-northwest of Exmouth, Australia.  Ernie was moving toward the south at 6 m.p.h. (10 km/h).  The maximum sustained wind speed was 125 m.p.h. (200 km/h) and there were wind gusts to 175 m.p.h. (290 km/h).  The minimum surface pressure was 936 mb.

Tropical Cyclone Ernie is a very small well organized storm.  It has a small eye surrounded by a ring of very strong thunderstorms.  The strongest winds are occurring in the ring of storms around the eye.  Additional bands of thunderstorms are revolving around the core of Ernie.  The thunderstorms in the core of Tropical Cyclone Ernie are generating strong upper level divergence which is pumping out mass and caused the surface pressure to decrease very rapidly.  Winds to hurricane/typhoon force extend out about 18 miles (30 km) from the center of circulation.  Winds to tropical storm force extend out about 90 miles (150 km) from the center.

The Hurricane Intensity Index (HII) for Tropical Cyclone Ernie is 23.6.  The Hurricane Size Index (HSI) is 7.8 and the Hurricane Wind Intensity Size Index (HWISI) is 31.4.  Those indices indicate that Tropical Cyclone Ernie is capable of causing localized significant damage.

Tropical Cyclone Ernie is in an environment favorable for tropical cyclones.  It is moving over water where the Sea Surface Temperature (SST) is near 30°C.  An upper level ridge centered southeast of Ernie is producing northerly winds which are blowing toward the tropical cyclone but the vertical wind shear is currently having no effect on it.  Tropical Cyclone Ernie could intensify more during the next 12 hours.  Ernie will move into an area of cooler SSTs and stronger vertical winds in a day or so.  The less favorable environment will cause Tropical Cyclone Ernie to weaken.  Tropical Cyclone Ernie could weaken quickly because of its small size, if the vertical wind shear increases rapidly.

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

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.