Tag Archives: HWISI

Hurricane Hilary Moves Toward Baja California

Hurricane Hilary was moving toward Baja California on Saturday morning. At 8:00 a.m. EDT on Saturday the center of Hurricane Hilary was located at latitude 21.5°N and longitude 113.4°W which put it about 490 miles (790 km) south-southeast of Punta Eugenia, Mexico. Hilary was moving toward the north-northwest at 13 m.p.h. (21 km/h). The maximum sustained wind speed was 130 m.p.h. (210 km/h) and there were wind gusts to 155 m.p.h. (250 km/h). The minimum surface pressure was 943 mb.

A Hurricane Warning was in effect for the portion of the coast from Punta Abreojos to Cabo San Quintin, Mexico. A Hurricane Watch was in effect for the portion of the coast from Cabo San Quintin to Ensenada, Mexico. A Tropical Storm Warning was in effect for the portion of the coast from Punta Abreojos to Guaymas, Mexico. The Tropical Storm Warning included Cabo San Lucas. A Tropical Storm Warning was in effect for the portion of the coast from the U.S. border with Mexico to the Point Mugu, California. The Tropical Storm Warning included San Diego. The Tropical Storm Warning also included Catalina Island. A Tropical Storm Warning was in effect for the portion of the coast from Cabo San Quintin, Mexico to the border with the U.S. A Tropical Storm Watch was in effect for the portion of the coast from Guaymas to Huatabampito, Mexico.

Hurricane Hilary was moving closer to Baja California on Saturday morning. An eye with a diameter of 30 miles (50 km) was at the center of Hilary’s circulation. The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Hurricane Hilary. Storms near the core generated upper level divergence that pumped mass away from the hurricane.

The circulation around Hurricane Hilary was large. Winds to hurricane force extended out 50 miles (80 km) from the center of Hilary’s circulation. Winds to tropical storm force extended out 265 miles (425 km) from the center of circulation. The Hurricane Intensity Index (HII) was 25.1. The Hurricane Size Index (HSI) was 19.2 and the Hurricane Wind Intensity Size Index (HWISI) was 44.3. Hurricane Hilary was capable of causing regional major damage.

Hurricane Hilary appeared to be starting to weaken on Saturday morning. Thunderstorms were weakening in bands in the western side of Hilary’s circulation. Some of the bands in the western part of Hilary consisted primarily of showers and lower clouds. Northerly winds in the western half of Hurricane Hilary were pulling cooler, drier air into that part of the hurricane.

Hurricane Hilary will be moving into an environment that will become unfavorable for a major hurricane during the next 24 hours. Hilary will move over water where the Sea Surface Temperatures are cooler than 27°C. It will move between an upper level ridge over Mexico and the south central U.S. and an upper level low west of California. The upper level ridge and upper level low will interact to produce northerly winds that will blow toward the top of Hilary’s circulation. Those winds will cause the vertical wind shear to increase. The combination of cooler water and more vertical wind shear will cause Hurricane Hilary to weaken during the next 24 hours.

The upper level ridge over the south central U.S. and the upper level low west of California will steer Hurricane Hilary toward the north-northwest during the next 24 hours. On its anticipated track, the center of Hurricane Hilary will approach Punta Eugenia on Saturday night. Hilary will bring strong, gusty winds and locally heavy rain to Baja California. Heavy rain is likely to cause flash floods in some locations.

Hilary will reach southern California on Sunday. Hilary is likely to weaken to a tropical storm before it reaches southern California. Hilary bring strong winds and locally heavy rain to parts of southern California. Heavy rain is likely to cause flash floods in some locations. Flood Watches have been issued for parts of southern California, southern Nevada, southern Utah and western Arizona. Hilary could also bring strong winds to mountains in southern Nevada, southern Utah and western Arizona.

Hilary Prompts Hurricane Warning for Baja, Tropical Storm Watch for Southern California

The potential threat from Hurricane Hilary prompted the issuance of a Hurricane Warning for part of Baja California and a Tropical Storm Watch for Southern California on Friday morning. At 11:00 a.m. EDT on Friday the center of Hurricane Hilary was located at latitude 17.9°N and longitude 111.4°W which put it about 360 miles (575 km) south-southwest of Cabo San Lucas, Mexico. Hilary was moving toward the northwest 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 170 m.p.h. (280 km/h). The minimum surface pressure was 939 mb.

A Hurricane Warning was in effect for the portion of the coast from Punta Abreojos to Punta Eugenia, Mexico. A Hurricane Watch was in effect for the portion of the coast from Punta Eugenia to Ensenada, Mexico. A Tropical Storm Warning was in effect for the portion of the coast from Punta Abreojos to Loreto, Mexico. The Tropical Storm Warning includes Cabo San Lucas. A Tropical Storm Watch was in effect for the portion of the coast from the U.S. border with Mexico to the Orange/Los Angeles County Line. The Tropical Storm Watch included Catalina Island. A Tropical Storm Watch was in effect for the portion of the coast from Ensenada, Mexico to the border with the U.S. A Tropical Storm Watch was in effect for the portion of the coast from Loreto to Huatabampito, Mexico.

Hurricane Hilary continued to intensify on Friday morning. A circular eye with a diameter of 20 miles (30 km) was at the center of Hilary’s circulation. The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Hurricane Hilary. Storms near the core generated upper level divergence that pumped mass away from the hurricane.

The circulation around Hurricane Hilary was large. Winds to hurricane force extended out 45 miles (75 km) from the center of Hilary’s circulation. Winds to tropical storm force extended out 290 miles (465 km) from the center of circulation. The Hurricane Intensity Index (HII) was 29.9. The Hurricane Size Index (HSI) was 16.9 and the Hurricane Wind Intensity Size Index (HWISI) was 46.8. Hurricane Hilary was similar in size and intensity to Hurricane Ida when Ida hit Louisiana in 2021.

Hurricane Hilary will move through an environment favorable for a major hurricane during the next 24 hours. Hilary will move over water where the Sea Surface Temperatures are near 30°C. It will move through a region where the upper level winds are weak and there will be little vertical wind shear. Hurricane Hilary could intensify during the next 24 hours. However, if the inner end of a rainband wraps around the existing eye and eyewall, then concentric eyewalls could form. If concentric eyewalls form, then an eyewall replacement cycle could cause Hilary to weaken.

Hurricane Hilary will move around the western part of a high pressure system over Mexico and the south central U.S. The high pressure system will steer Hilary toward the north-northwest during the next 24 hours. On its anticipated track Hurricane Hilary will move toward Baja California. Hilary will move more toward the north when it reaches the western end of the high pressure system during the weekend. The center of Hurricane Hilary will be near Punta Eugenia on Sunday morning. Hurricane Hilary will start to affect Baja California on Saturday. Hilary will bring strong, gusty winds and locally heavy rain to Baja California. Heavy rain is likely to cause flash floods in some locations.

The center of Hurricane Hilary is likely to approach southern California on Sunday night. There is cooler water west of the northern part of Baja California. Hilary will be weakening when it approaches southern California. Hilary bring strong winds and locally heavy rain to parts of southern California. Heavy rain is likely to cause flash floods in some locations. Flood Watches have been issued for parts of southern California, southern Nevada, southern Utah and western Arizona.

Hilary Rapidly Intensifies to a Major Hurricane

Hurricane Hilary rapidly intensified to a major hurricane over the Eastern North Pacific Ocean on Thursday evening. At 11:00 p.m. EDT on Thursday the center of Hurricane Hilary was located at latitude 16.7°N and longitude 110.0°W which put it about 430 miles (690 km) south of Cabo San Lucas, Mexico. Hilary was moving toward the west-northwest at 14 m.p.h. (22 km/h). The maximum sustained wind speed was 125 m.p.h. (200 km/h) and there were wind gusts to 150 m.p.h. (240 km/h). The minimum surface pressure was 952 mb.

A Hurricane Watch was in effect for the portion of the coast from Punta Eugenia to Punta Abreojos, Mexico. A Tropical Storm Warning was in effect for the portion of the coast from Cabo San Lazaro to Los Barriles, Mexico. The Tropical Storm Warning included Cabo San Lucas. Tropical Storm Watches were in effect for the portions of the coast from Cabo San Lazaro to Punta Eugenia, Mexico and from Los Barriles to Bahia San Juan Bautista, Mexico.

Hurricane Hilary rapidly intensified to a major hurricane on Thursday. An eye with a diameter of 23 miles (37 km) was at the center of Hilary’s circulation. The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Hurricane Hilary. Storms near the core generated upper level divergence that pumped mass away from the hurricane.

The circulation around Hurricane Hilary was large. Winds to hurricane force extended out 60 miles (95 km) from the center of Hilary’s circulation. Winds to tropical storm force extended out 290 miles (465 km) from the center of circulation. The Hurricane Intensity Index (HII) was 23.6. The Hurricane Size Index (HSI) was 20.3 and the Hurricane Wind Intensity Size Index (HWISI) was 43.9.

Hurricane Hilary will move through an environment favorable for intensification during the next 24 hours. Hilary will move over water where the Sea Surface Temperatures are near 30°C. It will move through a region where the upper level winds are weak and there will be little vertical wind shear. Hurricane Hilary is likely to continue to intensify during the next 24 hours. Hilary could intensify rapidly at times on Friday.

Hurricane Hilary will move around the western part of a high pressure system over Mexico. The high pressure system will steer Hilary toward the northwest during the next 24 hours. On its anticipated track Hurricane Hilary will move toward Baja California. Hilary will move more toward the north when it reaches the western end of the high pressure system during the weekend. Hurricane Hilary will start to affect Baja California during the weekend.

Elsewhere, former Tropical Storm Greg and former Tropical Storm Fernanda both weakened to tropical depressions. At 11:00 p.m. EDT on Thursday the center of Tropical Depression Greg was located at latitude 12.0°N and longitude 158.5°W which put it about 645 miles (1035 km) south of Honolulu, Hawaii. Greg was moving toward the west at 17 m.p.h. (28 km/h). The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h). The minimum surface pressure was 1007 mb.

At 11:00 p.m. EDT on Thursday the center of Tropical Depression Fernanda was located at latitude 16.4°N and longitude 133.8°W which put it about 1615 miles (2605 km) west-southwest of the southern tip of Baja California. Fernanda was moving toward the west at 15 m.p.h. (24 km/h). The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h). The minimum surface pressure was 1005 mb.

Typhoon Lan Makes Landfall in Honshu

Typhoon Lan made landfall in Honshu on Monday. At 5:00 p.m. EDT on Monday the center of Typhoon Lan was located at latitude 33.7°N and longitude 135.9°E which put it about 15 miles (25 km) north of Shingu, Japan. Lan was moving toward the northwest at 8 m.p.h. (13 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 970 mb.

The center of Typhoon Lan made landfall in Wakayama Prefecture near Shingu on Monday. A circular eye with a diameter of 50 miles (80 km) was at the center of Lan’s circulation. A broken ring of thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Typhoon Lan.

There was still a large circulation around Typhoon Lan. Winds to typhoon force extended out 70 miles (110 km) from the center of Lan’s circulation. Winds to tropical storm force extended out 145 miles (235 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Lan was 13.9. The Hurricane Size Index (HSI) was 23.0 and the Hurricane Wind Intensity Size Index (HWISI) was 36.9. Typhoon Lan was capable of causing widespread serious damage.

Typhoon Lan will move around the western part of a high pressure system over the Western North Pacific Ocean during the next 24 hours. The high pressure system will steer Lan toward the north-northwest during the next 24 hours. On its anticipated track, Typhoon Lan will move across Honshu during the next 24 hours. The center of Lan’s circulation will pass near Osaka in a few hours. The center of circulation will also pass west of Kyoto before Lan moves over the Sea of Japan.

Although Typhoon Lan will weaken as it moves across Honshu, Lan will produce strong gusty winds and locally heavy rain over parts of Honshu. Lan will drop heavy rain over Wakayama, Nara, Osaka, Shiga, Kyoto, Hyogo, Tottori, Okayama and Fukui Prefectures. Heavy rain could cause flash floods in some locations. Wind and rain are also likely to cause loss of electricity in widespread areas.

Elsewhere over the Western North Pacific Ocean, Tropical Storm Dora continued to weaken east of Wake Island. At 5:00 p.m. EDT on Monday the center of Tropical Storm Dora was located at latitude 20.9°N and longitude 168.3°E which put it about 145 miles (235 km) east of Wake Island. Dora was moving toward the north-northwest at 11 m.p.h. (17 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 1004 mb.

Fernanda Rapidly Intensifies to a Major Hurricane

Hurricane Fernanda rapidly intensified to a major hurricane over the Eastern North Pacific Ocean during Sunday night. At 5:00 a.m. EDT on Monday the center of Hurricane Fernanda was located at latitude 15.6°N and longitude 117.7°W which put it about 715 miles (1150 km) southwest of the southern tip of Baja California. Fernanda was moving toward the west at 8 m.p.h. (13 km/h). The maximum sustained wind speed was 125 m.p.h. (200 km/h) and there were wind gusts to 150 m.p.h. (240 km/h). The minimum surface pressure was 959 mb.

Hurricane Fernanda continued to intensify rapidly during Sunday night. A small eye was at the center of Fernanda’s circulation. The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms revolved around the core of Hurricane Fernanda. Storms near the core generated upper level divergence that pumped mass away from the hurricane.

The circulation around Hurricane Fernanda was small. Winds to hurricane force extended out 25 miles (40 km) from the center of Fernanda’s circulation. Winds to tropical storm force extended out 70 miles (110 km) from the center of circulation. The Hurricane Intensity Index (HII) was 23.6. The Hurricane Size Index (HSI) was 7.8 and the Hurricane Wind Intensity Size Index (HWISI) was 31.4.

Hurricane Fernanda will move through an environment favorable for intensification during the next 12 hours. Fernanda will move over water where the Sea Surface Temperatures are near 29°C. It will move through a region where the upper level winds are weak and there will be little vertical wind shear. Hurricane Fernanda is likely to continue to intensify during the next 12 hours. Fernanda will move over slightly cooler water on Tuesday. The cooler water will cause Fernanda to start to weaken.

Hurricane Fernanda will move south of a subtropical high pressure system over the Eastern North Pacific Ocean. The high pressure system will steer Fernanda toward the west during the next 24 hours. On its anticipated track, Hurricane Fernanda will move farther away from Baja California.

Elsewhere, Tropical Storm Greg formed east-southeast of Hawaii. At 5:00 a.m. EDT on Monday the center of Tropical Storm Greg was located at latitude 11.3°N and longitude 139.8°W which put it about 1170 miles (1885 km) east-southeast of Hilo, Hawaii. Greg was moving toward the west at 13 m.p.h. (21 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 1005 mb. Tropical Storm Greg is forecast to pass south of Hawaii later this week.

Typhoon Lan Approaches Honshu

Typhoon Lan was approaching Honshu on Sunday night. At 11:00 p.m. EDT on Sunday the center of Typhoon Lan was located at latitude 32.1°N and longitude 137.2°E which put it about 120 miles (195 km) south-southeast of Shingu, Japan. Lan was moving toward the northwest at 9 m.p.h. (15 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 959 mb.

Typhoon Lan strengthened as it approached Honshu on Sunday. A large circular eye with a diameter of 60 miles (95 km) was at the center of Lan’s circulation. The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the large core of Typhoon Lan. Storms near the core generated upper level divergence that pumped mass away from the typhoon.

There was a large circulation around Typhoon Lan. Winds to typhoon force extended out 70 miles (110 km) from the center of Lan’s circulation. Winds to tropical storm force extended out 160 miles (260 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Lan was 16.5. The Hurricane Size Index (HSI) was 21.3 and the Hurricane Wind Intensity Size Index (HWISI) was 37.8. Typhoon Lan was capable of causing widespread serious damage.

Typhoon Lan will move through an environment favorable for intensification during the next 12 hours. Lan will move over water where the Sea Surface Temperatures are near 28°C. It will move through a region where the upper level winds are weak and there will be little vertical wind shear. Typhoon Lan could continue to strengthen during the next 12 hours as it approaches Honshu.

Typhoon Lan will move around the western part of a high pressure system over the Western North Pacific Ocean during the next 24 hours. The high pressure system will steer Lan toward the northwest during the next 24 hours. On its anticipated track, the center of Typhoon Lan will make landfall in Wakayama Prefecture south of Osaka in about 18 hours. Lan will produce strong gusty winds and locally heavy rain over parts of Honshu. Heavy rain is likely to cause flash floods in some locations.

Elsewhere over the Western North Pacific Ocean, former Tropical Storm Dora continue to weaken east of Wake Island. At 11:00 p.m. EDT on Sunday the center of Tropical Storm Dora was located at latitude 19.0°N and longitude 169.7°E which put it about 235 miles (380 km) east of Wake Island. Dora was moving toward the west-northwest at 15 m.p.h. (24 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 1005 mb.

Typhoon Lan Continues to Move Toward Honshu

Typhoon Lan continued to move to Honshu on Saturday night. At 11:00 p.m. EDT on Saturday the center of Typhoon Lan was located at latitude 30.0°N and longitude 139.1°E which put it about 385 miles (625 km) south of Tokyo, Japan. Lan was moving toward the northwest at 8 m.p.h. (11 km/h). The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 100 m.p.h. (160 km/h). The minimum surface pressure was 970 mb.

Typhoon Lan completed an eyewall replacement cyclone on Saturday. The smaller, inner eye and eyewall dissipated. A circular eye with a diameter of 70 miles (110 km) was at the center of Lan’s circulation on Saturday night. The large eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the large eye. Storms around the eye generated upper level divergence that pumped mass away from the typhoon.

The area of typhoon force winds in Typhoon Lan increased during the eyewall replacement cycle. Winds to typhoon force extended out 70 miles (110 km) from the center of Lan’s circulation. Winds to tropical storm force extended out 150 miles (240 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Lan was 11.5. The Hurricane Size Index (HSI) was 21.1 and the Hurricane Wind Intensity Size Index (HWISI) was 32.6.

Typhoon Lan will move through an environment favorable for intensification during the next 24 hours. Lan will move over water where the Sea Surface Temperatures are near 28°C. It will move through a region where the upper level winds are weak and there will be little vertical wind shear. Typhoon Lan could strengthen during the next 24 hours, since the eyewall replacement cycle is complete.

Typhoon Lan will move around the western part of a high pressure system over the Western North Pacific Ocean during the next 24 hours. The high pressure system will steer Lan toward the northwest during the next 24 hours. On its anticipated track, Typhoon Lan will approach Honshu in less than 48 hours. The center of Lan could make landfall south of Osaka. Lan will be a typhoon when it reaches Honshu.

Elsewhere over the Western North Pacific Ocean, former Hurricane Dora weakened to a tropical storm East of Wake Island. At 11:00 p.m. EDT on Saturday the center of Tropical Storm Dora was located at latitude 18.2°N and longitude 174.7°E which put it about 570 miles (920 km) east of Wake Island. Dora was moving toward the west-northwest at 14 m.p.h. (22 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 996 mb.

Typhoon Lan Moves Toward Honshu

Typhoon Lan moved toward Honshu on Friday. At 11:00 p.m. EDT on Friday the center of Typhoon Lan was located at latitude 28.7°N and longitude 141.5°E which put it about 485 miles (785 km) south-southeast of Tokyo, Japan. Lan was moving toward the west-northwest 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 960 mb.

Typhoon Lan was weakening on Friday night. The inner of a rainband wrapped around the existing eye and eyewall and a larger, outer eyewall formed. The formation of concentric eyewalls was disrupting the low level convergence into the inner eyewall and the inner eyewall was weakening. Since the strongest winds were occurring in the inner eyewall, the maximum wind speed decreased when the inner eyewall weakened. Bands of showers and thunderstorms were revolving around the concentric eyewalls. Storms around the concentric eyewalls generated upper level divergence that pumped mass away from the typhoon.

Winds to typhoon force extended out 35 miles (55 km) from the center of Typhoon Lan. Winds to tropical storm force extended out 140 miles (225 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Lan was 16.5. The Hurricane Size Index (HSI) was 11.4 and the Hurricane Wind Intensity Size Index (HWISI) was 27.9.

Typhoon Lan will move through an environment favorable for intensification during the next 24 hours. Lan will move over water where the Sea Surface Temperatures are near 28°C. It will move through a region where the upper level winds are weak and there will be little vertical wind shear. However, Typhoon Lan is likely to weaken during the next 24 hours even though it will be in a favorable environment. The maximum wind speed is likely to continue to decrease as the inner eyewall dissipates.

Typhoon Lan will move around the western part of a high pressure system over the Western North Pacific Ocean. The high pressure system will steer Lan toward the northwest during the next 24 hours. On its anticipated track, Typhoon Lan will approach Honshu in less than 72 hours. Lan is likely to be a typhoon when it approaches Honshu.

Hurricane Dora Moves Across the International Date Line

Hurricane Dora moved across the International Date Line on Friday night. At 11:00 p.m. EDT on Friday the center of Hurricane Dora was located at latitude 15.9°N and longitude 179.4°E which put it about 860 miles (1390 km) south of Midway Island. Dora was moving toward the west-northwest at 18 m.p.h. (30 km/h). The maximum sustained wind speed was 105 m.p.h. (165 km/h) and there were wind gusts to 125 m.p.h. (200 km/h). The minimum surface pressure was 972 mb.

Hurricane Dora was weakening as it moved across the International Date Line on Friday night. Dora was moving under the western part of an upper level ridge over the Central Pacific Ocean. The ridge was producing southerly winds that were blowing toward the top of Dora’s circulation. Those winds were causing the vertical wind shear to increase and the wind shear was causing Hurricane Dora to weaken.

There still was a small eye at the center of Hurricane Dora. The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Dora’s circulation. Storms near the core generated upper level divergence that pumped mass away from the hurricane.

The circulation around Hurricane Dora was small. Winds to hurricane force extended out 25 miles (40 km) from the center of Dora. Winds to tropical storm force extended out 90 miles (145 km) from the center of circulation. The Hurricane Intensity Index (HII) was 17.8. The Hurricane Size Index (HSI) was 7.0 and the Hurricane Wind Intensity Size Index (HWISI) was 24.8.

Hurricane Dora will move through an environment that will be unfavorable for intensification during the next 24 hours. Dora will move over water where the Sea Surface Temperatures are near 28°C. However, the upper level ridge will continue to cause moderate to strong vertical wind shear. The wind shear will cause Hurricane Dora to weaken during the next 24 hours. Dora could weaken quickly even though it is over warm water, because it is such a small hurricane.

Hurricane Dora will move around the western side of a high pressure system over the Central Pacific Ocean. The high pressure system will steer Dora toward the west-northwest during the next 24 hours. On its anticipated track Hurricane Dora could be east of Wake Island in 48 hours.

Typhoon Lan Rapidly Intensifies to Equivalent of a Major Hurricane

Typhoon Lan rapidly intensified to the equivalent of a major hurricane over the Western North Pacific Ocean south of Japan on Thursday. At 11:00 p.m. EDT on Thursday the center of Typhoon Lan was located at latitude 27.1°N and longitude 142.8°E which put it about 615 miles (995 km) south-southeast of Tokyo, Japan. Lan was moving toward the north at 6 m.p.h. (10 km/h). The maximum sustained wind speed was 130 m.p.h. (210 km/h) and there were wind gusts to 160 m.p.h. (260 km/h). The minimum surface pressure was 936 mb.

Typhoon Lan intensified to the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale on Thursday. A circular eye with a diameter of 28 miles (45 km) developed at the center of Lan’s circulation. The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Typhoon Lan. Storms near the core generated upper level divergence that pumped mass away from the typhoon in all directions. The removal of large quantities of mass caused the surface pressure to decrease rapidly.

The size of the circulation around Typhoon Lan increased when Lan intensified rapidly on Thursday. Winds to typhoon force extended out 45 miles (75 km) from the center of Lan’s circulation. Winds to tropical storm force extended out 160 miles (260 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Lan was 25.1. The Hurricane Size Index (HSI) was 14.0 and the Hurricane Wind Intensity Size (HWISI) was 39.1. Typhoon Lan was similar in size and intensity to Hurricane Harvey when Harvey hit Texas in 2017.

Typhoon Lan will move through an environment favorable for intensification during the next 24 hours. Lan will move over water where the Sea Surface Temperatures are near 28°C. It will move through a region where the upper level winds are weak and there will be little vertical wind shear. Typhoon Lan is likely to intensify during the next 24 hours unless the inner end of a rainband wraps around the existing eye and eyewall. If concentric eyewalls form, then an eyewall replacement cycle could cause Typhoon Lan to weaken.

Typhoon Lan will move around the western part of a high pressure system over the Western North Pacific Ocean. The high pressure system will steer Lan toward the northwest during the next 24 hours. On its anticipated track, Typhoon Lan will bring strong, gusty winds and locally heavy rain to Chichi Jima during the next 24 hours. Typhoon Lan could approach Honshu in four days.

Elsewhere over the Western North Pacific Ocean, former Tropical Storm Khanun produced gusty winds and locally heavy rain over South Korea. At 5:00 p.m. EDT on Thursday the center of Tropical Depression Khanun was located at latitude 38.9°N and longitude 127.0°E which put it about 85 miles (135 km) north-northeast of Seoul, South Korea. Khanun was moving toward the northwest at 9 m.p.h. (15 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 994 mb.