Tag Archives: HWISI

Hurricane Fernanda Intensifies Rapidly to Category 4

Hurricane Fernanda intensified rapidly to Category 4 on the Saffir-Simpson Scale on Friday.  At 5:00 p.m. EDT on Friday the center of Hurricane Fernanda was located at latitude 10.7°N and longitude 119.7°W which put it about 1060 miles (1710 km) southwest of the southern tip of Baja California.  Fernanda was moving toward the west at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 130 m.p.h. (215 km/h) and there were wind gusts to 155 m.p.h. (250 km/h).  The minimum surface pressure was 960 mb.

A clear circular eye formed at the center of Hurricane Fernanda.  The eye is surrounded by a ring of very strong thunderstorms and the strongest winds are occurring in the eyewall.  Additional bands of showers and thunderstorms formed outside the core of Fernanda.  There are more bands in the eastern half of the hurricane, but the overall circulation is fairly symmetrical.  The thunderstorms in the core of Fernanda are generating strong upper level divergence which is pumping mass away from the hurricane.

Fernanda is a small hurricane.  Winds to hurricane force only extend out about 25 miles (40 km) from the center of circulation.  Winds to tropical storm force only extend out about 70 miles (110 km) from the center.  The Hurricane Intensity Index (HII) is 25.1.  The Hurricane Size Index (HSI) is 9.0 and the Hurricane Wind Intensity Size Index (HWISI) is 34.1.  The indices indicate that Hurricane Fernanda is somewhat similar in size and strength to Hurricane Charley in 2004 when Charley was approaching the southwest coast of Florida.

Hurricane Fernanda will remain in an environment very favorable for intensification for another 24 to 48 hours.  It will move over water where the Sea Surface Temperature (SST) is near 28.5°C.  The upper level winds are weak and there is little vertical wind shear.  Hurricane Fernanda has a chance to intensify into a Category 5 hurricane on the Saffir-Simpson Scale before it moves into a less favorable environment.  When a hurricane becomes as intense as Hurricane Fernanda is, an outer rainband can wrap around the eye and an eyewall replacement cycle can occur.  If an eyewall replacement cycle occurs in Hurricane Fernanda, then fluctuations in intensity may also happen.  Eventually Fernanda will move over cooler SSTs and the hurricane will start to weaken.

Hurricane Fernanda is moving south of a subtropical ridge and the ridge is steering the hurricane a little south of due west.  A general westward motion is forecast to continue during the next few days.  On its anticipated track Hurricane Fernanda will continue to move farther away from Mexico.  Fernanda could approach Hawaii by the end of next week.

Dora Rapidly Intensifies Into First Eastern Pacific Hurricane of 2017

Tropical Storm Dora intensified rapidly into a hurricane during the overnight hours.  Dora is the first hurricane to develop over the Eastern North Pacific during 2017.  At 11:00 a.m. EDT on Monday the center of Hurricane Dora was located at latitude 17.3°N and longitude 106.3°W which put it about 220 miles (350 km) south of Cabo Corrientes, Mexico.  Dora was moving toward the west-northwest at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 85 m.p.h. (140 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 985 mb.

The circulation of Hurricane Dora is very well organized.  A circular eye exists at the center of circulation.  A ring of strong thunderstorms surrounds the eye.  Additional bands of showers and thunderstorms are revolving around the core of the circulation.  Thunderstorms in Dora are generating well developed upper level divergence which is pumping large quantities of mass out in all directions.

Dora is a small hurricane.  Wind to hurricane force extend out about 25 miles (40 km) from the center of circulation.  Winds to tropical storm force extend out about 80 miles (130 km) from the center.  The Hurricane Intensity Index (HII) is 12.7.  The Hurricane Size Index (HSI) is 7.3.  The Hurricane Wind Intensity Size Index (HWISI) is 20.0.

Hurricane Dora will move through an environment favorable for intensification for another 12 to 18 hours.  It is currently over water where the Sea Surface Temperature (SST) is near 28°C.  Dora will move over SSTs that will gradually be cooler, but they should be warm enough to support further intensification for another 12 to 18 hours.  Hurricane Dora is moving through an area where upper level winds are weak and there is almost no vertical wind shear.  Hurricane Dora is likely to strengthen further during the next few hours.  Dora will move over much cooler SSTs when it passes south of Baja California and it will begin to weaken on Tuesday.

A subtropical ridge to the north of Dora is steering the hurricane toward the west-northwest and that general motion is expected to continue for another 24 to 48 hours.  On its anticipated track the center of Hurricane Dora will pass south of Baja California.

Tropical Cyclone Donna Brings Wind and Rain to New Caledonia

Tropical Cyclone Donna brought wind and rain to New Caledonia as it moved over that region.  At 11:00 p.m. EDT on Monday the center of Tropical Cyclone Donna was located at latitude 19.9°S and longitude 166.8°E which put it about 185 miles (295 km) north of Noumea, New Caledonia.  Donna was moving toward the south-southeast at 11 m.p.h. (17 km/h).  The maximum sustained wind speed was 110 m.p.h. (175 km/h) and there were wind gusts to 130 m.p.h. (215 km/h).  The minimum surface pressure was 962 mb.

The inner core of Tropical Cyclone Donna remained intact despite increased vertical wind shear on Monday.  A well formed circular eye with a diameter of 30 miles (50 km) was evident on microwave satellite images.  A ring of strong thunderstorms wrapped around the eye.  Additional bands of showers and thunderstorms were revolving around the core of the circulation.  The size of the circulation of Tropical Cyclone Donna increased on Monday.  Winds to hurricane/typhoon force extend out about 80 miles (130 km) on the eastern side of the center and about 45 miles (75 km) on the western side.  Winds to tropical storm force extended out about 200 miles (320 km) from the center.

The Hurricane Intensity Index (HII) for Tropical Cyclone Donna was 19.2.  The Hurricane Size Index (HSI) was 23.3 and the Hurricane Wind Intensity Size Index was 42.5.  These indices suggest that Tropical Cyclone Donna is very similar in size and intensity to Hurricane Gustav in 2008 just before Gustav made landfall in Louisiana.

Tropical Cyclone Donna will weaken during the next several days.  An upper level trough is approaching it from the west.  The upper level trough is generating northwesterly winds which are blowing toward the top of the circulation.  The northwesterly winds are inhibiting upper level divergence to the west of Donna and moderate vertical wind shear will continue to weaken the tropical cyclone.  In addition Tropical Cyclone Donna will move over cooler SSTs when it moves farther south.

The winds in the upper level trough are pushing Tropical Cyclone Donna toward the south-southeast.  That general motion is expected to continue during the next several days.  On its anticipated track the core of Tropical Cyclone Donna will move over the Iles Loyaute (Loyalty Islands).  Donna will bring strong gusty winds winds to those islands.  In addition rainbands will bring wind and heavy rain to parts of New Caledonia.  Tropical Cyclone Donna is capable of causing widespread serious damage.

Stronger Tropical Cyclone Donna Moves North of Vanuatu

Tropical Cyclone Donna strengthened on Thursday as it moved north of Vanuatu.  The center of Donna passed near the Banks Islands and the Torres Islands and it is currently located northwest of Espiritu Santo.  At 11:00 p.m. EDT on Thursday the center of Tropical Cyclone Donna was located at latitude 13.2°S and longitude 166.0°E which put it about 350 miles (560 km) north-northwest of Port Vila, Vanuatu.  Donna was moving toward the west-southwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 100 m.p.h. (160 km/h) and there were wind gusts to 120 m.p.h. (195 km/h).  The minimum surface pressure was 967 mb.

A partial eyewall continued to wrap around the center of circulation, but a well defined eye did not form.  A band of thunderstorms extended about two thirds of the way around the center.  Other bands of showers and thunderstorms were revolving around the core of the circulation.  Thunderstorms near the core of the circulation generated upper level divergence that pumped out mass to the southeast of Tropical Cyclone Donna.

Winds to hurricane/typhoon force extend out about 40 miles (65 km) from the center of circulation and winds to tropical storm force extend out about 140 miles (225 km) from the center.  The Hurricane Intensity Index (HII) is 16.5.  The Hurricane Size Index (HSI) is 13.4 and the Hurricane Wind Intensity Size Index (HWISI) is 29.9.

Tropical Cyclone Donna will move through an area that will be somewhat favorable for intensification.  Donna will move over water where the Sea Surface Temperature is near 30°C.  An upper level ridge east of Donna is producing northerly winds which are blowing toward the top of the tropical cyclone.  The upper level winds are generating moderate vertical wind shear and the shear seems to have slowed the intensification of Donna.  The strength of the upper level winds could decrease and intensification could resume on Friday.  Tropical Cyclone Donna could intensify into the equivalent of a major hurricane during the next 24 to 48 hours.

A subtropical ridge to the south of Donna is steering the tropical cyclone toward the west-southwest and that general motion is expected to continue for about another 24 hours.  Tropical Cyclone Donna will reach the western end of the ridge in about a day or so and it will turn toward the south.  On its anticipated track the center of Tropical Cyclone Donna will pass west of Espiritu Santo.  Guidance from the numerical models suggests the center of Donna could pass between Vanuatu and New Caledonia, but different models are predicting different tracks and so there is more uncertainty in the track at that time.

Stronger Tropical Cyclone Cook Nears New Caledonia

Tropical Cyclone Cook strengthened on Sunday as it neared New Caledonia.  At 8:00 p.m. EDT on Sunday the center of Tropical Cyclone Cook was located at latitude 20.3°S and longitude 165.8°E which put it about 150 miles (240 km) north-northwest of Noumea, New Caledonia.  Cook was moving toward the south-southwest at 11 m.p.h. (18 km/h).  The maximum sustained wind speed was 100 m.p.h. (160 km/h) and there were wind gusts to 120 m.p.h. (195 km/h).  The minimum surface pressure was 969 mb.

Tropical Cyclone Cook intensified on Sunday as the organization of the core improved.  A circular eye developed inside a ring of strong thunderstorms.  The fastest winds were occurring in the ring of storms around the eye.  A number of other bands of showers and thunderstorms were revolving around the core of Tropical Cyclone Cook.  Thunderstorms close to the center of circulation were generating upper level divergence which was pumping out mass to the southeast of the tropical cyclone.  Winds to tropical storm force extended out about 180 miles (290 km) from the center of circulation.

Tropical Cyclone Cook moved through an environment favorable for tropical cyclones on Sunday.  It moved over water where the Sea Surface Temperature was near 29°C.  An upper level ridge east of Cook produced northerly winds which were blowing toward the tropical cyclone, but the wind shear was not great enough to inhibit intensification.  Tropical Cyclone Cook should maintain its intensity until it makes landfall in New Caledonia.  Cook will begin to weaken after the center begins to interact with land.

A subtropical ridge east of Cook is steering the tropical cyclone toward the south-southwest.  A southerly motion is expected to bring the center of Tropical Cyclone Cook to New Caledonia on Monday.  The center of Tropical Cyclone Cook is likely to make landfall between Houailou and Thio on the central coast of New Caledonia.

The Hurricane Intensity Index (HII) for Tropical Cyclone Cook is 16.5.  The Hurricane Size Index (HSI) is 16.8 and the Hurricane Wind Intensity Size Index (HWISI) is 33.3.  The indices indicates that Tropical Cyclone Cook is capable of causing serious regional wind damage.  Tropical Cyclone Cook will also produce heavy rain and a chance for flash floods.

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.