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Powerful Typhoon Mangkhut Hits Northern Luzon

Powerful Typhoon Mangkhut hit northern Luzon on Friday.  At 5:00 p.m. EDT on Friday the center of Typhoon Mangkhut was located at latitude 18.2°N and longitude 121.5°W which put it about 60 miles (95 km) east of Laoag, Philippines.  Mangkhut was moving toward the west-northwest at 21 m.p.h. (35 km/h).  The maximum sustained wind speed was 165 m.p.h. (270 km/h) and there were wind gusts to 200 m.p.h. (320 km/h).  The minimum surface pressure was 908 mb.

Mangkhut is a large and dangerous typhoon.  Winds to typhoon force extend out about 110 miles (175 km) from the center of circulation.  Winds to tropical storm force extend out about 330 miles (530 km) from the center.  The outer rainbands around Typhoon Mangkhut stretch from Manila, Philippines to southern Taiwan.

The Hurricane Intensity Index (HII) is 36.8.  The Hurricane Size Index (HSI) is 38.5 and the Hurricane Wind Intensity Size Index (HWISI) is 75.3.  Typhoon Mangkhut is bigger than Hurricane Katrina was when Katrina was a Category 5 hurricane on the Saffir-Simpson Scale over the Gulf of Mexico in 2005.  Typhoon Mangkhut has the potential to cause extensive catastrophic damage over parts of Luzon.

Typhoon Mangkhut will cause extensive catastrophic wind damage over northern Luzon.  It will also drop heavy rain and there will be flash floods.  The flooding will be worse in areas of steeper slopes.  There will be a significant storm surge on the coast of extreme northeastern Luzon.

Typhoon Mangkhut will weaken while it crosses northern Luzon.  Mangkhut will then move quickly off to the west-northwest. On its anticipated track Typhoon Mangkhut could be near Hong Kong in about 30 hours.

Dangerous Typhoon Mangkhut Approaches Northern Luzon

Dangerous Typhoon Mangkhut approached northern Luzon on Thursday night.  At 11:00 p.m. EDT on Thursday the center of Typhoon Mangkhut was located at latitude 16.2°N and longitude 126.2°E which put it about 400 miles (645 km) east-northeast of Manila.  Mangkhut was moving toward the northwest at 14 m.p.h.  The maximum sustained wind speed was 170 m.p.h. (280 km/h) and there were wind gusts to 205 m.p.h. (335 km/h).  The minimum surface pressure was 905 mb.

Typhoon Mangkhut has a large powerful circulation.  There is a circular eye with a diameter of about 30 miles (50 km) at the center of circulation.  A number of bands of showers and thunderstorms are revolving around the core of the circulation.  Storms around the core were generating strong upper level divergence which was pumping mass away from the typhoon in all directions.

Winds to typhoon force extended out about 100 miles (160 km) from the center of circulation.  Winds to tropical storm force extended out about 265 miles (425 km) from the center.  The Hurricane Intensity Index (HII) for Typhoon Mangkhut was 38.5.  The Hurricane Size Index (HSI) was 33.7 and the Hurricane Wind Intensity Size Index (HWISI) was 72.2.  Those indices indicate that Typhoon Mangkhut is very similar in size and strength to what Hurricane Katrina was when Katrina was a Category 5 hurricane over the Gulf of Mexico in 2005.

Typhoon Mangkhut will move through an environment that is very favorable for strong typhoons during the next 12 to 18 hours.  Mangkhut will move over water where the Sea Surface Temperature is near 30°C.  It will move through an area where there will be little vertical wind shear.  It is difficult for a typhoon or hurricane to continue to generate enough upper level divergence to stay extremely strong for a long period of time.  However, Typhoon Mangkhut could remain the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale until it reaches northern Luzon.  Mangkhut will weaken when the center moves over northern Luzon.

Typhoon Mangkhut is moving south of a subtropical ridge over the Western North Pacific Ocean.  The ridge is steering Mangkhut toward the northwest and that general motion is forecast to continue.  On its anticipated track Typhoon Mangkhut will reach northern Luzon east of Tuguegarao in about 18 hours.  Mangkhut is capable of causing extensive catastrophic damage.  It will produce extremely strong winds over northern Luzon.  There will be a significant storm surge at the coast.  Locally heavy rain will cause flash floods.

Hurricane Florence Moves Closer to the Carolinas

Hurricane Florence moved closer to the Carolinas on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Hurricane Florence was located at latitude 32.0°N and longitude 73.7°W which put it about 280 miles (455 km) east-southeast of Wilmington, North Carolina.  Florence was moving toward the northwest at 17 m.p.h. (28 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. (210 km/h).  The minimum surface pressure was 957 mb.

A Hurricane Warning was in effect for the portion of the coast from South Santee River, South Carolina to Duck, North Carolina including Pamlico and Albemarle Sounds.  A Hurricane Watch was in effect for the portion of the coast from Edisto Beach, South Carolina to South Santee River, South Carolina.  A Tropical Storm Warning is in effect for the portion of coast from Duck, North Carolina to the North Carolina-Virginia border.  A Tropical Storm Watch was in effect for the portion of the coast from the North Carolina-Virginia border to Cape Charles Light, Virginia and for Chesapeake Bay south of New Point Comfort.

The wind speed in Hurricane Florence decreased on Wednesday but the circulation increased in size.  It appeared that another eyewall replacement cycle could have started.  Satellite microwave images suggested that there could be two eyewalls and a reconnaissance plane reported a double wind maxima.  Both of those things could be evidence of concentric eyewalls.  In addition, counterclockwise flow around a small upper level low near Florida may have produced southerly winds that blew toward the south side of Hurricane Frances.  Those winds may have inhibited the upper level divergence to the south of Florence.  Since the hurricane was unable to pump out as much mass, the surface pressure increased and the wind speed decreased.

The circulation of Hurricane Florence increased in size on Wednesday.  Winds to hurricane force extended out about 80 miles (130 km) from the center of circulation.  Winds to tropical storm force extended out about 200 miles (320 km) from the center.  The Hurricane Intensity Index (HII) for Hurricane Florence was 19.2.  The Hurricane Size Index (HSI) was 25.5 and the Hurricane Wind Intensity Size Index (HWISI) was 44.7.  Those indices are very similar to the numbers for Hurricane Jeanne just before Jeanne made landfall in southeast Florida in 2004.

Hurricane Florence will move through an environment favorable for intensification on Thursday.  Florence will move over water where the Sea Surface Temperature is near 29°C.  Florence will move farther away from the upper low near Florida and the low should not inhibit divergence to the south of the hurricane as much.  In addition, Hurricane Florence will move over the warm water in the Gulf Stream about 6 to 12 hours before it reaches the coast.  It will be able to extract extra energy at that time.  If the inner core becomes more organized, then Hurricane Florence could intensify on Thursday.  If the inner core does not get better organized, then Florence will likely maintain its current intensity or weaken slowly.

Hurricane Florence will move near the western end of the subtropical high pressure system over the western Atlantic Ocean.  The high will steer Florence toward the northwest on Thursday.  On its anticipated track the center of Hurricane Florence will be near the coast of North Carolina on Thursday night.  A ridge over the eastern U.S. is likely to block the northward motion of Hurricane Florence when it reaches the coast.  The ridge will steer Florence slowly toward the west-southwest on Friday and Saturday.

Hurricane Florence will have the impact of a major hurricane regardless of the actual sustained wind speed.  The large circulation and slow rate of movement when Florence reaches the coast means that locations could experience strong winds for extended periods of time.  Wind damage and power outages could be extensive.  Some places in North Carolina had a rainy summer and strong winds could uproot trees.  Hurricane Florence will produce a dangerous storm surge along the coast.  The surge could exceed 10 feet (3 meters) in some locations east of where the center makes landfall.  The slow forward speed also means that Hurricane Florence could drop locally heavy rain and severe flooding could occur.

Elsewhere the rest of the Atlantic Ocean was also very active.  Tropical Storm Isaac was nearing the Lesser Antilles, Hurricane Helene was weakening south of the Azores and Subtropical Storm Joyce formed northwest of Helene.

At 11:00 p.m. EDT on Thursday the center of Tropical Storm Isaac was located at latitude 15.3°N and longitude 58.0°W which put it about 220 miles (355 km) east of Dominica.  Isaac was moving toward the west at 20 m.p.h. (32 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 1006 mb.  Tropical Storm Warnings were in effect for Guadeloupe, Martinique and Dominica.  Tropical Storm Watches were in effect for Antigua, Montserrat, St, Kitts and Nevis, Saba and St. Eustatius, St. Martin and St. Maarten.

At 11:00 p.m. EDT on Thursday the center of Hurricane Helene was located at latitude 22.4°N and 36.9°W which put it about 1270 mile (2045 km) south-southwest of the Azores.  Helene was moving toward the north at 13 m.p.h. (20 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 983 mb.

At 11:00 p.m. EDT on Thursday the center of Subtropical Storm Joyce was located at latitude 15.3°N and longitude 46.6°W which put it about 910 miles (1465 km) west-southwest of the Azores.  Joyce was moving toward the southwest at 6 m.p.h. (10 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 1006 mb.

Hurricane Warnings Issued for Carolinas for Hurricane Florence

Hurricane Warnings were issued for the Carolinas on Tuesday for the potential impacts of Hurricane Florence.  At 11:00 p.m. EDT on Tuesday the center of Hurricane Florence was located at latitude 28.4°N and longitude 68.7°W which put it about 670 miles (1075 km) east-southeast of Cape Fear, North Carolina.  Florence was moving toward the west-northwest at 17 m.p.h. (28 km/h).  The maximum sustained wind speed was 140 m.p.h. (220 km/h) and there were wind gusts to 165 m.p.h. (270 km/h).  The minimum surface pressure was 946 mb.

A Hurricane Warning was in effect for the portion of the coast from South Santee River, South Carolina to Duck, North Carolina.  Hurricane Watches were in effect for the portions of the coast from Edisto Beach to South Santee River, South Carolina and from Duck, North Carolina to the North Carolina-Virginia border.  Tropical Storm Watches were in effect for the portions of the coast from Duck, North Carolina to Cape Charles Light, Virginia and for Chesapeake Bay south of New Point Comfort.

Hurricane Florence completed an eyewall replacement cycle and it continues to be a powerful hurricane.  There was a circular eye with a diameter of 30 miles (48 km) at the center of Florence.  The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  The eyewall replacement cycle resulted in a larger circulation.

Winds to hurricane force extended out about 60 miles (95 km) from the center of circulation of Hurricane Florence.  Winds to tropical storm force extended out about 175 miles (280 km) from the center.  The Hurricane Intensity Index (HII) for Hurricane Florence was 28.2.  The Hurricane Size Index (HSI) was 18.9 and the Hurricane Wind Intensity Size Index (HWISI) was 47.1.  Hurricane Florence is capable of causing extensive significant damage.

Hurricane Florence will move through an environment favorable for strong hurricanes during the next 24 to 36 hours.  Florence will move over water where the Sea Surface Temperature is near 29°C.  it will move through an area where the upper level winds are weak and there will be little vertical wind shear.  Hurricane Florence is likely to maintain its intensity and it could strengthen.  If another eyewall replacement cycle occurs, then there could be fluctuations in intensity.

Hurricane Florence will move around the western end of a subtropical high pressure system over the western Atlantic Ocean.  The high will steer Florence toward the west-northwest during the next 24 to 36 hours.  On its anticipated track Hurricane Florence could approach the coast of the Carolinas later on Thursday.  The steering winds are forecast to weaken when Florence nears the coast and there is great uncertainty about the track when that occurs.  Hurricane Florence will bring strong winds to coastal North Carolina and eastern South Carolina.  Wind pushing water toward the shore will cause a significant storm surge.  A slow forward speed will mean that Hurricane Florence will drop a lot of rain and there is a risk of significant flooding of rivers and streams.

Elsewhere over the Atlantic Ocean, Tropical Storm Isaac was speeding toward the Lesser Antilles and Hurricane Helene was weakening far south of the Azores.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Isaac was located at latitude 14.5°N and longitude 52.3°W which put it about 580 miles (935 km) east of Martinique.  Isaac was moving toward the west at 16 m.p.h. (26 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 999 mb.  Tropical Storm Warnings were in effect for Dominica, Martinique and Guadeloupe.  Tropical Storm Watches were in effect for Antigua, Montserrat, St. Kitts and Nevis, and Saba and St. Eustatius.

At 11:00 p.m. EDT on Tuesday the center of Hurricane Helene was located at latitude 18.0°N and longitude 35.4°W which put it about 1479 miles (2370 km) south-southwest of the Azores.  Helene was moving toward the northwest at 10 m.p.h. (16 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 973 mb.

Typhoon Mangkhut Strengthens Into Equivalent of Cat. 5 Hurricane

Typhoon Mangkhut strengthened into the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale on Tuesday.  At 11:00 a.m. EDT on Tuesday the center of Typhoon Mangkhut was located at latitude 13.7°N and longitude 138.0°E which put it about 290 miles (470 km) north of Yap.  Mangkhut was moving toward the west at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 160 m.p.h. (260 km/h) and there were wind gusts to 190 m.p.h. (305 km/h).  The minimum surface pressure was 915 mb.

Typhoon Mangkhut is strong and well organized.  It has a symmetrical circulation with a circular eye at the center.  A ring of strong thunderstorms surround the eye and the strongest winds are occurring in the ring of storms.  Several bands of showers and thunderstorms were revolving around the core of Typhoon Mangkhut.  Storms near the core were generating strong upper level divergence which was pumping large quantities of mass away from the typhoon in all directions.

Typhoon Mangkhut has a large circulation.  Winds to typhoon force extend out about 65 miles (105 km) from the center of circulation.  Winds to tropical storm force extend out about 210 miles (375 km) from the center.  The Hurricane Intensity Index (HII) for Typhoon Mangkhut is 35.0.  The Hurricane Size Index (HSI) is 22.1 and the Hurricane Wind Intensity Size Index (HWISI) is 57.1.  Typhoon Mangkhut is capable of causing extensive catastrophic damage.

Typhoon Mangkhut will be moving through an environment very favorable for powerful typhoons.  Mangkhut will be moving over water where the Sea Surface Temperature is near 30°C.  It will move through an area were the upper level winds are weak and there will be little vertical wind shear.  Typhoon Mangkhut could maintain its intensity for several more days unless eyewall replacement cycles cause fluctuations in the wind speed.

Typhoon Mangkhut is moving south a ridge of high pressure over the Western North Pacific Ocean.  The ridge will steer Mangkhut in a general west-northwesterly direction during the next few days.  On its anticipated track Typhoon Mangkhut could approach northern Luzon in about three days.  Mangkhut could be near Hong Kong in about five days.

Elsewhere over the Western North Pacific Ocean, Tropical Storm Barijat was moving southeast of Hong Kong.  At 11:00 a.m. EDT on Tuesday the center of Tropical Storm Barijat was located at latitude 20.5°N and longitude 116.5°E which put it about 215 miles (345 km) southeast of Hong Kong.  Barijat was moving toward the west-southwest at 12 m.p.h. (19 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 1000 mb.

Florence Strengthens Into a Major Hurricane

Hurricane Florence strengthened into a Major Hurricane on Monday.  At 11:00 p.m. EDT on Monday the center of Hurricane Florence was located at latitude 25.9°N and longitude 62.4°W which put it about 1085 miles (1745 km) east-southeast of Cape Fear, North Carolina.  Florence was moving toward the west-northwest at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 140 m.p.h. (220 km/h) and there were wind gusts to 165 m.p.h. (270 km/h).  The minimum surface pressure was 944 mb.

Hurricane Florence intensified rapidly on Monday morning and early afternoon.  An eye with a diameter of 18 miles (29 km) formed at the center of circulation.  A ring of strong thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms.  Several bands of showers and thunderstorms were revolving around the core of Hurricane Florence.  Storms near the core were generating strong upper level divergence which pumped mass away from the hurricane.

Hurricane Florence increased in size on Monday.  Winds to hurricane force extended out about 40 miles (65 km) from the center of circulation.  Winds to tropical storm force extended out about 150 miles (240 km) from the center.  The Hurricane Intensity Index (HII) for Hurricane Florence was 28.2.  The Hurricane Size Index (HSI) was 14.0 and the Hurricane Wind Intensity Size Index (HWISI) was 42.2.  Hurricane Florence was capable of causing extensive significant damage.

Microwave satellite imagery indicated that an inner rainband may have wrapped around the original eye and eyewall.  An eyewall replacement cycle may have begun and that may have halted the rapid intensification of Hurricane Florence.  Florence could weaken during the next few hours while the inner eyewall weakens.  Hurricane Florence will move through an area capable of supporting strong hurricanes on Tuesday and Wednesday.  Florence will move over water where the Sea Surface Temperature is near 29°C.  It will move through an area where the upper level winds are weak and there will be little vertical wind shear.  If the inner eyewall dissipates during the next day or so, then Hurricane Florence could strengthen again.

Hurricane Florence will move around the western end of the subtropical high pressure system during the next several days.  The high will steer Florence toward the west-northwest.  On its anticipated track Hurricane Florence will approach the coast of North Carolina on Thursday afternoon.  The winds steering Florence could weaken as it approaches the coast and the track forecast becomes much more uncertain at that time.

Elsewhere, Hurricane Helene and Tropical Storm Isaac were spinning over the tropical Atlantic Ocean.  At 11:00 p.m. EDT on Monday the center of Hurricane Helene was located at latitude 15.5°N and longitude 32.4°W which put it about 1590 miles (2555 km) south of the Azores.  Helen was moving toward the west-northwest at 12 m.p.h. (19 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. (210 km/h).  The minimum surface pressure was 968 mb.

At 11:00 p.m. EDT on Monday the center of Tropical Storm Isaac was located at latitude 14.5°N and longitude 46.9°W which put it about 960 miles (1550 km) east of the Lesser Antilles.  Isaac was moving toward the west at 16 m.p.h. (26 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 997 mb.

Typhoon Mangkhut Strengthens to Equivalent of a Major Hurricane

Typhoon Mangkhut strengthened into the equivalent of a major hurricane as it moved west of Guam on Monday.  At 11:00 p.m. EDT on Monday the center of Typhoon Mangkhut was located at latitude 14.0°N and longitude 140.6°E which put it about 230 miles (375 km) west of Guam.  Mangkhut was moving toward the west at 16 m.p.h. (26 km/h).  The maximum sustained wind speed was 140 m.p.h. (225 km/h) and there were wind gusts to 165 m.p.h. (270 km/h).  The minimum surface pressure was 939 mb.  Typhoon Mangkhut was the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale.

Typhoon Mangkhut intensified rapidly on Monday.  A circular eye was at the center of circulation.  A ring of strong thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms.  Several bands of showers and thunderstorms were revolving around the core of Typhoon Mangkhut.  Storms around the core were generating upper level divergence which was pumping mass away from the typhoon.

Winds to typhoon force extended out about 50 miles (80 km) from the center of circulation.  Winds to tropical storm force extended out about 210 miles (335 km) from the center.  The Hurricane Intensity Index (HII) for Typhoon Mangkhut was 28.2.  The Hurricane Size Index (HSI) was 18.9 and the Hurricane Wind Intensity Size Index (HWISI) was 47.1.

Typhoon Mangkhut will move through an environment capable of supporting very strong typhoons during the next two or three days.  Mangkhut will move over water where the Sea Surface Temperature is near 30°C.  It will move through a region where the upper level winds are weak and there will be little vertical wind shear.  Typhoon Mangkhut is likely to remain very strong for the next few days.  Eyewall replacement cycles could cause fluctuations in intensity.

Typhoon Mangkhut will move south of a ridge over the Western North Pacific Ocean.  The ridge will steer Mangkhut to the west during the next day or two.  Typhoon Mangkhut will move more toward the west-northwest later this week.  On its anticipated track Typhoon Mangkhut could be near northern Luzon in about four days.

Typhoon Mangkhut Brings Wind and Rain to the Marianas

Typhoon Mangkhut brought wind and rain to the Marianas on Sunday night.  At 11:00 p.m. EDT on Sunday the center of Typhoon Mangkhut was located at latitude 14.4°N and longitude 146.6°E which put it about 175 miles (285 km) east-northeast of Guam.  Mangkhut was moving toward the west at 19 m.p.h. (31 km/h).  The maximum sustained wind speed was 90 m.p.h. (145 km/h) and there were wind gusts to 115 m.p.h. (185 km/h).  The minimum surface pressure was 955 mb.  Typhoon Warnings were in effect for Saipan, Tinian, Rota and Guam.  The airport on Saipan was reporting sustained winds of 41 m.p.h. (66 km/h) and wind gusts to 61 m.p.h. (98 km/h).

Typhoon Mangkhut had a well organized circulation.  There was a circular eye at the center of Mangkhut.  A ring of strong thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms.  Several bands of showers and thunderstorms were revolving around the core of Typhoon Mangkhut.  Storms near the core were generating upper level divergence which was pumping mass away from the typhoon.

Winds to typhoon force extended out about 40 miles (65 km) from the center of circulation.  Winds to tropical storm force extended out about 150 miles (240 km) from the center.  The Hurricane Intensity Index (HII) for Typhoon Mangkhut was 13.9.  The Hurricane Size Index (HSI) was 13.5 and the Hurricane Wind Intensity Size Index was 27.4.  Typhoon Mangkhut was capable of causing regional significant damage.

Typhoon Mangkhut will move through an environment favorable for intensification.  Mangkhut will move over water where the Sea Surface Temperature is near 30°C.  An upper level ridge north of Mangkhut will cause easterly winds which will blow toward the top of the circulation.  Those winds will cause some vertical wind shear, but the shear will not be strong enough to prevent intensification.  Typhoon Mangkhut could intensify into the equivalent of a major hurricane later this week.

The ridge north of Typhoon Mangkhut will steer the typhoon in a westerly direction.  The core of Typhoon Mangkhut will move over the Marianas during the next few hours.  It will bring strong winds and it will drop locally heavy rain.  On its anticipated track Typhoon Mangkhut could be east of Luzon later this week.

Florence Strengthens Into a Major Hurricane

Hurricane Florence strengthened rapidly into a major hurricane on Wednesday morning.  At 11:00 a.m. EDT on Wednesday the center of Hurricane Florence was located at latitude 22.0°N and longitude 45.7°W which put it about 1370 miles (2205 km) east-southeast of Bermuda.  Florence was moving toward the northwest at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 125 m.p.h. (205 km/h) and there were wind gusts to 145 m.p.h. (235 km/h).  The minimum surface pressure was 957 mb.

Hurricane Florence strengthened rapidly on Wednesday morning.  A small circular eye formed at the center of circulation.  A ring of strong thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms.  Several bands of showers and thunderstorms were revolving around the core of Hurricane Florence.  Storms near the core were generating upper level divergence which was pumping mass away from the hurricane.

The circulation of Hurricane Florence is small.  Winds to hurricane force extend out about 20 miles (30 km) from the center of circulation.  Winds to tropical storm force extend out about 95 miles (155 km) from the center.  The Hurricane Intensity Index (HII) for Hurricane Florence is 23.6.  The Hurricane Size Index (HSI) is 7.0 and the Hurricane Wind Intensity Size Index (HWISI) is 30.6.

Hurricane Florence will move through an environment capable of supporting a strong hurricane.  Florence is currently over water where the Sea Surface Temperature is near 27°C and it will move over warmer water during the next several days.  An upper level trough north of Florence is producing westerly winds which are blowing toward the top of the hurricane.  However, those winds do not seem to be creating significant vertical wind shear.  Hurricane Florence could maintain its intensity and there is a chance it could get stronger when it moves over warmer water.  Because of the small circulation, if there are changes in the environment around Hurricane Florence, then the intensity could change quickly.  Also, any eyewall replacement cycles could cause the intensity to fluctuate.

Hurricane Florence will move south of a subtropical high pressure system over the Atlantic Ocean.  The high will steer Florence in a general northwesterly direction during the next few days.  On its anticipated track Hurricane Norman could be southeast of Bermuda by early next week.  The guidance from the numerical models has been variable and there is still much uncertainty about the track Hurricane Florence will take later next week.

Elsewhere, Tropical Depression Gordon was dropping rain on Alabama and Mississippi.  At 11:00 a.m. EDT on Wednesday the center of Tropical Depression Gordon was located at latitude 32.3°N and longitude 90.2°W which put it about 5 miles (10 km) west of Jackson, Mississippi.  Gordon was moving toward the northwest at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 1008 mb.

Typhoon Jebi Strengthens to Equivalent of Cat. 5 Hurricane

Powerful Typhoon Jebi strengthened into the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale on Friday.  At 11:00 a.m. EDT on Friday the center of Typhoon Jebi was located at latitude 18.8°N and longitude 141.0°E which put it about 400 miles (645 km) south of Iwo To.  Jebi was moving toward the west-northwest at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 175 m.p.h. (280 km/h) and there were wind gusts to 210 m.p.h. (335 km/h).  The minimum surface pressure was 907 mb.

The circulation of Typhoon Jebi was very well organized and symmetrical.  There was a circular eye at the center of circulation.  The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Numerous bands of showers and thunderstorms were revolving around the core of the circulation.  Storms near the core were generating strong upper level divergence which was pumping mass away from the typhoon in all directions.

Jebi is a large and powerful typhoon.  Winds to typhoon force extended out about 65 miles (105 km) from the center of circulation.  Winds to tropical storm force extended out about 195 miles (315 km) from the center.  The Hurricane Intensity Index (HII) for Typhoon Jebi was 40.4.  The Hurricane Size Index (HSI) was 21.6 and the Hurricane Wind intensity Size Index (HWISI) was 62.0.

Typhoon Jebi may have reached its maximum intensity.  Microwave satellite imagery suggested that an inner rainband may have wrapped around the existing eye and eyewall.  If that has occurred, then an eyewall replacement cycle may have begun.  An eyewall replacement cycle will cause a typhoon to weaken when the inner eyewall, where the strongest wind are, dissipates.

Typhoon Jebi will move around the western end of a subtropical ridge over the Western North Pacific Ocean.  Jebi will gradually turn toward the north as it moves around the end of the ridge.  On its anticipated track Typhoon Jebi should pass west of Iwo To.  Jebi could be approaching Japan in three days or so.