Tag Archives: HWISI

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.

Powerful Tropical Cyclone Debbie Makes Landfall in Queensland

Powerful Tropical Cyclone Debbie made landfall in Queensland on Monday night.  At 9:00 p.m. EDT on Monday the center of Tropical Cyclone Debbie was located at latitude 20.2°S and longitude 148.7°E which put it about 30 miles (50 km) east-southeast of Bowen, Australia.  Debbie was moving toward the southwest at 7 m.p.h. (12 km/h).  The maximum sustained wind speed was 115 m.p.h. (185 km/h) and there were wind gusts to 160 m.p.h. (260 km/h).  The minimum surface pressure was 943 mb.

Tropical Cyclone Debbie intensified rapidly on Monday into the equivalent of a major hurricane.  A symmetrical eye developed at the center of circulation and a ring of strong thunderstorms surrounded the eye.  Bands of thunderstorms were revolving around the core of Tropical Cyclone Debbie.  Winds to hurricane force extend out about 40 miles (65 km) from the center.  Winds to tropical storm force extended out about 140 miles (225 km) from the center.

The Hurricane Intensity Index (HII) for Tropical Cyclone Debbie was 20.6.  The Hurricane Size Index (HSI) was 16.0 and the Hurricane Wind Intensity Size Index (HWISI) was 36.6.  These indices indicate that Tropical Cyclone Debbie was capable of causing regional major damage.

The center of Tropical Cyclone Debbie made landfall on the coast of Queensland between Bowen and Proserpine.  Debbie will bring strong gusty winds to the portions of Queensland in the path of the tropical cyclone.  Tropical Cyclone Debbie will cause a storm surge along the coast near and to the south of where the center makes landfall.  Debbie will also produce heavy rain as it moves inland and flooding could occur in some areas.

Tropical Cyclone Debbie will weaken after the center moves inland.  The core of Debbie will move across the Clarke Range and those mountains will speed the dissipation of the tropical cyclone.