Category Archives: Western North Pacific

Western Pacific Typhoons and Tropical Storms

Typhoon Rai Rapidly Weakens to a Tropical Storm

Former Typhoon Rai rapidly weakened to a tropical storm south-southwest of Hong Kong on Monday. At 4:00 p.m. EST on Monday the center of Tropical Storm Rai was located at latitude 20.1°N and longitude 113.5°E which put it about 190 miles (305 km) south-southwest of Hong Kong. Rai was moving toward the northeast at 13 m.p.h. (20 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 997 mb.

A surface high pressure system over eastern Asia produced northeasterly winds that transported drier air which was pulled into the circulation of former Typhoon Rai. The drier air caused the thunderstorms in Rai’s circulation to dissipate and the circulation weakened. Bands revolving around the center of Tropical Storm Rai consisted almost entirely of showers and lower clouds. Winds to tropical storm force extended out 65 miles (105 km) from the center of circulation.

Since Tropical Storm Rai consists of a shallow circulation, it will be steered by the winds in the lower levels of he atmosphere. Rai will move around the northwestern part of a high pressure system over the Western North Pacific Ocean. The high pressure system will steer Tropical Storm Rai toward the east-northeast during the next 24 hours. On its anticipated track Tropical Storm Rai could be southwest of Taiwan in 24 hours.

Tropical Storm Rai will move through an environment unfavorable for a tropical cyclone. Rai will move over water where the Sea Surface Temperatures are near 27˚C. However, Rai will continue to be surrounded by drier air, which will prevent the formation of new thunderstorms. In addition, an upper level trough over eastern Asia will produce southwesterly winds that will blow across the top of Rai’s circulation. Those winds will cause strong vertical wind shear and the shear will also be unfavorable for intensification. Tropical Storm Rai will continue to weaken during the next 24 hours.

Typhoon Rai Brings Gusty Winds and Rain to Central Vietnam

Typhoon Rai brought gusty winds and rain to central Vietnam on Sunday. At 10:00 a.m. EST on Sunday the center of Typhoon Rai was located at latitude 15.5°N and longitude 110.8°E which put it about 185 miles (295 km) east-southeast of Da Nang, Vietnam. Rai was moving toward the north at 11 m.p.h. (17 km/h). The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 150 m.p.h. (240 km/h). The minimum surface pressure was 951 mb.

Bands in the western side of Typhoon Rai brought gusty winds and locally heavy rain to central Vietnam on Sunday. Although the core of Typhoon Rai was east of Vietnam, the large size of the circulation resulted in rainbands in the western side of the typhoon moving over central Vietnam. The core of Rai’s circulation where the strongest winds were located remained east of the coast of Vietnam.

Typhoon Rai was weakening over the South China Sea on Sunday. An upper level ridge over the Western North Pacific Ocean was producing southerly winds that were blowing toward the top of Rai’s circulation. A surface high pressure system over Asia was producing northeasterly winds in the lower levels of the atmosphere. The combination of southerly winds in the upper levels and northeasterly winds in the lower levels was causing moderate vertical wind shear. In addition, the northeasterly winds in the lower levels were transporting drier air toward Typhoon Rai.

Some of the drier air was wrapping around the southern side of Typhoon Rai. The strongest thunderstorms were occurring in bands in the western half of Rai’s circulation. Bands in the eastern half of the typhoon consisted primarily of showers and lower clouds. A broken ring of thunderstorms surrounded the eye of Typhoon Rai and the strongest winds were occurring in that ring of storms.

Winds to typhoon force extended out 65 miles (105 km) from the center of Typhoon Rai. Winds to tropical storm force extended out 185 miles (295 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Rai was 22.1. The Hurricane Size Index (HSI) was 20.6 and the Hurricane Wind intensity Size Index (HWISI) was 42.7. Rai was capable of causing regional major damage.

Typhoon Rai will move through an environment that will become unfavorable for intensification during the next 36 hours. Rai will move over water where the Sea Surface Temperatures are near 28˚C. However, the upper level ridge and the surface high pressure system will continue to cause moderate vertical wind shear. More dry air will be pulled into Rai’s circulation. Typhoon Rai will continue to weaken during the next 36 hours.

Typhoon Rai will move around the western end of a surface high pressure system over the Western North Pacific Ocean during the next 24 hours. The high pressure system will steer Rai toward the north. On its anticipated track the core of Typhoon Rai will remain east of Vietnam. Bands in the western side of Rai’s circulation will continue to produce gusty winds and locally heavy rain along the coast of Vietnam. The center of Rai could be southeast of Hainan in 18 hours.

Typhoon Rai Rapidly Intensifies Back to Equivalent of Cat. 5 Hurricane

Typhoon Rai rapidly intensified back to the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale on Saturday over the South China Sea. At 4:00 p.m. EST on Saturday the center of Typhoon Rai was located at latitude 12.8°N and longitude 111.9°E which put it about 355 miles (575 km) southeast of Da Nang, Vietnam. Rai was moving toward the west-northwest at 16 m.p.h. (26 km/h). The maximum sustained wind speed was 165 m.p.h. (265 km/h) and there were wind gusts to 200 m.p.h. (320 km/h). The minimum surface pressure was 910 mb.

Typhoon Rai rapidly intensified to the equivalent of a Category 5 hurricane as it moved over the warm water in the South China Sea on Saturday. The diameter of the eye at the center of Rai contracted to 25 miles (40 km) as the typhoon rapidly intensified. The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Typhoon Rai. Storms near the core generated upper level divergence that pumped large quantities of mass away to the west and north of the typhoon. The removal of so much mass allowed the surface pressure to decrease rapidly.

Winds to typhoon force extended out 45 miles (75 km) from the center of Typhoon Rai. Winds to tropical storm force extended out 150 miles (240 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Rai was 36.7. The Hurricane Size Index (HSI) was 19.6 and the Hurricane Wind intensity Size Index (HWISI) was 56.3. Rai was capable of causing regional catastrophic damage. Typhoon Rai was stronger than it was when it hit the southern Philippines.

Typhoon Rai will move through an environment that will become unfavorable for intensification during the next 36 hours. Rai will move over water where the Sea Surface Temperatures are near 28˚C. It will move under the western end of an upper level ridge over the Western North Pacific Ocean. The ridge will produce southerly winds that will blow toward the top of Typhoon Rai’s circulation. A surface high pressure system over Asia will produce northeasterly winds in the lower levels over the atmosphere. A combination of northeasterly winds in the lower levels and southerly winds in the upper levels will cause the vertical wind shear to increase. The northeasterly winds in the lower levels will also transport drier air toward the northwestern part of Rai’s circulation. Stronger vertical wind shear and drier air will cause Typhoon Rai to weaken during the next 36 hours. If the inner end of a rainband wraps around the existing eye and eyewall, then an eyewall replacement cycle could cause Rai to weaken more rapidly.

Typhoon Rai will move around the western end of a surface high pressure system over the Western North Pacific Ocean during the next 24 hours. The high pressure system will steer Rai toward the north during the next 24 hours. On its anticipated track Typhoon Rai is forecast to turn toward the north before the center of Rai reaches the coast of Vietnam. Rainbands on the western side of Typhoon Rai could bring gusty winds and locally heavy rain to the central coast of Vietnam within 18 hours.

Typhoon Rai Strengthens over South China Sea

Typhoon Rai strengthened to the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale over the South China Sea on Saturday morning. At 10:00 a.m. EST on Saturday the center of Typhoon Rai was located at latitude 12.2°N and longitude 113.0°E which put it about 450 miles (725 km) southeast of Da Nang, Vietnam. Rai was moving toward the west-northwest at 17 m.p.h. (28 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 942 mb.

Typhoon Rai strengthened to the equivalent of a Category 4 hurricane as it moved over the warm water in the South China Sea on Saturday morning. An eye with a diameter of 30 miles (50 km) was at the center of Rai’s circulation. The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Typhoon Rai. Storms near the core generated upper level divergence that pumped mass away to the west and north of the typhoon.

Winds to typhoon force extended out 35 miles (55 km) from the center of Typhoon Rai. Winds to tropical storm force extended out 170 miles (275 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Rai was 25.1. The Hurricane Size Index (HSI) was 14.3 and the Hurricane Wind intensity Size Index (HWISI) was 39.4. Rai was capable of causing regional severe damage.

Typhoon Rai will move through an environment that will become unfavorable for intensification during the next 48 hours. Rai will move over water where the Sea Surface Temperatures are near 28˚C. It will move under the southern side of an upper level ridge over the Western North Pacific Ocean. The ridge will produce southeasterly winds that will blow toward the top of Typhoon Rai’s circulation. A surface high pressure system over Asia will produce northeasterly winds in the lower levels over the atmosphere. A combination of northeasterly winds in the lower levels and southeasterly winds in the upper levels will cause the vertical wind shear to increase. The northeasterly winds in the lower levels will also transport drier air toward the northwestern part of Rai’s circulation. Stronger vertical wind shear and drier air will cause Typhoon Rai to weaken during the weekend.

Typhoon Rai will move around the western end of a surface high pressure system over the Western North Pacific Ocean during the next 36 hours. The high pressure system will steer Rai toward the north during the next 36 hours. On its anticipated track Typhoon Rai is forecast to turn toward the north before the center of Rai reaches the coast of Vietnam. Rainbands on the western side of Typhoon Rai could bring gusty winds and locally heavy rain to the central coast of Vietnam in 24 hours.

Typhoon Rai Moves over South China Sea

Typhoon Rai moved over the South China Sea on Friday. At 4:00 p.m. EST on Friday the center of Typhoon Rai was located at latitude 10.9°N and longitude 116.6°E which put it about 175 miles (285 km) west-northwest of Puerto Princesa, Philippines. Rai was moving toward the west-northwest at 14 m.p.h. (22 km/h). The maximum sustained wind speed was 115 m.p.h. (185 km/h) and there were wind gusts to 145 m.p.h. (230 km/h). The minimum surface pressure was 956 mb.

Typhoon Rai strengthened back to the equivalent of a major hurricane after it moved across Palawan and over the South China Sea. An eye with a diameter of 30 miles (50 km) developed at the center of Rai’s circulation. The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Typhoon Rai. Storms near the core generated upper level divergence that pumped mass away to the west and north of the typhoon.

Winds to typhoon force extended out 40 miles (65 km) from the center of Typhoon Rai. Winds to tropical storm force extended out 165 miles (270 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Rai was 20.6. The Hurricane Size Index (HSI) was 16.4 and the Hurricane Wind intensity Size Index (HWISI) was 37.0. Rai was capable of causing regional major damage.

Typhoon Rai will move through an environment favorable for intensification during the next 24 hours. Rai will move over water where the Sea Surface Temperatures are near 30˚C. It will move under the southern side of an upper level ridge over the Western North Pacific Ocean. The ridge will produce easterly winds that will blow toward the top of Typhoon Rai’s circulation. Those winds will cause some vertical wind shear but the wind shear will be too small to prevent intensification. Typhoon Rai could strengthen again during the next 24 hours.

Typhoon Rai will move south of a surface high pressure system over the Western North Pacific Ocean during the next day or so. The high pressure system will steer Rai toward the west-northwest during the next 24 hours. Rai will move more toward the northwest when it reaches the western end of the high pressure system. On its anticipated track Typhoon Rai could approach the coast of Vietnam in 36 hours.

Typhoon Rai Brings Wind and Rain to the Southern Philippines

Typhoon Rai brought wind and rain to the southern Philippines on Thursday. At 10:00 p.m. EST on Thursday the center of Typhoon Rai was located at latitude 10.0°N and longitude 120.4°E which put it about 140 miles (225 km) east of Puerto Princesa, Philippines. Rai was moving toward the west at 16 m.p.h. (26 km/h). The maximum sustained wind speed was 115 m.p.h. (185 km/h) and there were wind gusts to 145 m.p.h. (230 km/h). The minimum surface pressure was 956 mb.

Typhoon Rai brought strong winds and heavy rain as it moved across the southern Philippines on Thursday. The core of Typhoon Rai affected Siarago Island, Dinagat Island, northern Mindanao, southern Leyte, Bohol, Cebu, Negros and southern Panay Island. There were reports of wind damage, power outages and flash floods across the southern Philippines.

Typhoon Rai moved over the Sulu Sea on Thursday night and its structure remained well organized. A circular eye was present at the center of Rai’s circulation. The eye was surrounded by a broken 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 Rai. Storms near the core of Rai generated upper level divergence that pumped mass away to the west and north of the typhoon.

Winds to typhoon force extended out 45 miles (75 km) from the center of Typhoon Rai. Winds to tropical storm force extended out 155 miles (245 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Rai was 20.6. The Hurricane Size Index (HSI) was 13.9 and the Hurricane Wind intensity Size Index (HWISI) was 34.5. Rai was capable of causing regional major damage.

Although Typhoon Rai weakened when the center passed over the islands of the southern Philippines, it will move through an environment capable of supporting a strong typhoon as it moves over the Sulu Sea. Rai will move over water where the Sea Surface Temperatures are near 30˚C. It will move under the southern side of an upper level ridge over the Western North Pacific Ocean. The ridge will produce easterly winds that will blow toward the top of Typhoon Rai’s circulation. Those winds will cause some vertical wind shear but the wind shear will be too small to cause much weakening. Typhoon Rai is likely to maintain its intensity during the next 24 hours. Rai could strengthen when it moves over the South China Sea during the weekend.

Typhoon Rai will move south of a surface high pressure system over the Western North Pacific Ocean. The high pressure system will steer Rai toward the west during the next 24 hours. On its anticipated track the core of Typhoon Rai will move across Palawan during the next 12 hours. Rai will be capable of causing major damage. It will bring strong winds and heavy rain to Palawan on Friday. Typhoon Rai will move over the South China Sea during the weekend. Rai could approach Vietnam by the end of the weekend.

Typhoon Rai Hits the Southern Philippines

Powerful Typhoon Rai hit the southern Philippines on Thursday morning. At 4:00 a.m. EST on Thursday the center of Typhoon Rai was located at latitude 10.0°N and longitude 125.3°E which put it about 25 miles (40 km) southeast of Maasin, Philippines. Rai was moving toward the west at 17 m.p.h. (28 km/h). The maximum sustained wind speed was 150 m.p.h. (240 km/h) and there were wind gusts to 185 m.p.h. (295 km/h). The minimum surface pressure was 927 mb.

The center of powerful Typhoon Rai made landfall on Siargao Island on Thursday morning. The core of Rai’s circulation moved over Dinagat Island and northern Mindanao. The center of Typhoon Rai was over the Bohol Sea just to the south of Leyte. The inner end of a rainband wrapped around the original eye and eyewall of Typhoon Rai as it hit the southern Philippines. Microwave satellite images indicated that concentric eyewalls formed, which increased the size of the core of Rai. Winds to typhoon force extended out 60 miles (95 km) from the center of Typhoon Rai. Winds to tropical storm force extended out 185 miles (295 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Rai was 31.6. The Hurricane Size Index (HSI) was 18.9 and the Hurricane Wind intensity Size Index (HWISI) was 50.5. Rai was capable of causing regional severe damage.

Typhoon Rai will weaken when the center is over land, but it will move through an environment capable of supporting a strong typhoon as it moves over the southern Philippines. Rai will move over water where the Sea Surface Temperatures are near 30˚C. It will move under the southern side of an upper level ridge over the Western North Pacific Ocean. The ridge will produce easterly winds that will blow toward the top of Typhoon Rai’s circulation. Those winds will cause some vertical wind shear but the wind shear will be too small to cause much weakening. Typhoon Rai weaken gradually when the center passes over land.

Typhoon Rai will move south of a surface high pressure system over the Western North Pacific Ocean. The high pressure system will steer Rai toward the west-northwest during the next 36 hours. On its anticipated track the core of Typhoon Rai will pass over southern Leyte, northern Bohol, Cebu, northern Negros, southern Panay Island, northern Palawan, Linapacan Island, Culion Island and Busuanga Island. Typhoon Rai will weaken when the center passes over land, but it will be the equivalent of a major hurricane as it moves across the southern Philippines. Typhoon Rai will bring very strong winds and locally heavy rain to northern Mindanao, Leyte, Samar, Cebu, Negros, Bohol, Panay Island, Palawan, Linacapan Island, Culion Island and Busuanga Island. Heavy rain could cause flash floods in some locations. Rai will cause a significant storm surge along coasts where the wind blows the water toward the shore. Typhoon Rai could cause severe damage in locations that experience the inner core of the circulation.

Typhoon Rai Rapidly Intensifies to Equivalent of Cat. 5 Hurricane

Typhoon Rai rapidly intensified to the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale on Wednesday night. At 10:00 p.m. EST on Wednesday the center of Typhoon Rai was located at latitude 9.8°N and longitude 126.3°E which put it about 90 miles (145 km) east of Dinagat, Philippines. Rai was moving toward the west at 16 m.p.h. (26 km/h). The maximum sustained wind speed was 160 m.p.h. (260 km/h) and there were wind gusts to 195 m.p.h. (315 km/h). The minimum surface pressure was 915 mb.

Typhoon Rai continued to intensify very rapidly during Wednesday evening and it strengthened to the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale. A small circular eye with a diameter of 8 miles (13 km) was at the center of Rai’s circulation. The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Typhoon Rai. Storms near the core of Rai generated strong upper level divergence that pumped large quantities of mass away to the west and north of the typhoon. The continued rapid removal of mass allowed the surface pressure to decrease very rapidly.

The circulation around Typhoon Rai exhibited more symmetry as it rapidly intensified. Winds to typhoon force extended out 50 miles (80 km) from the center of Rai. Winds to tropical storm force extended out 185 miles (295 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Rai was 35.0. The Hurricane Size Index (HSI) was 17.5 and the Hurricane Wind Intensity Size Index (HWISI) was 52.5. Typhoon Rai was capable of doing regional catastrophic damage.

Typhoon Rai will move through an environment favorable for intensification during the next few hours. Rai will move over water where the Sea Surface Temperatures are near 30˚C. It will move under the southern side of an upper level ridge over the Western North Pacific Ocean. The ridge will produce easterly winds that will blow toward the top of Typhoon Rai’s circulation. Those winds will cause some vertical wind shear but the wind shear will be too small to prevent intensification. Typhoon Rai could continue to strengthen until the center makes landfall in southern Philippines in a few hours. Rai will weaken when the center passes over land.

Typhoon Rai will move south of a surface high pressure system over the Western North Pacific Ocean. The high pressure system will steer Rai toward the west-northwest during the next 36 hours. On its anticipated track the center of Typhoon Rai will pass over Siargao Island in a few hours. The core of Rai will pass over Dinagat Island, southern Leyte, northern Bohol, Cebu, northern Negros and southern Panay Island. Typhoon Rai will weaken when the center passes over land, but it will be the equivalent of a major hurricane when it moves across the southern Philippines. Typhoon Rai will bring very strong winds and locally heavy rain to northern Mindanao, Siargao Island, Dinagat Island, Samar, Leyte, Cebu, Negros, Bohol and Panay Island. Heavy rain could cause flash floods in some locations. Rai will cause a significant storm surge along coasts where the wind blows the water toward the shore. Typhoon Rai could cause catastrophic damage in locations that experience the inner core of the circulation.

Typhoon Rai Rapidly Intensifies to Equivalent of a Major Hurricane

Typhoon Rai rapidly intensified to the equivalent of a major hurricane on Wednesday. At 4:00 p.m. EST on Wednesday the center of Typhoon Rai was located at latitude 9.5°N and longitude 128.3°E which put it about 190 miles (305 km) east of Dinagat, Philippines. Rai was moving toward the west at 13 m.p.h. (20 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 942 mb.

Typhoon Rai intensified very rapidly during Wednesday afternoon and it reached the equivalent of a major hurricane. . A small circular eye with a diameter of 8 miles (13 km) was at the center of Rai’s circulation. The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Typhoon Rai. Storms near the core of Rai generated strong upper level divergence that pumped large quantities of mass away to the west and north of the typhoon. The removal of mass allowed the surface pressure to decrease rapidly.

The circulation around Typhoon Rai increased in size as it rapidly intensified. Winds to typhoon force extended out 45 miles (75 km) from the center of Rai. Winds to tropical storm force extended out 185 miles (295 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Rai was 25.1. The Hurricane Size Index (HSI) was 17.1 and the Hurricane Wind Intensity Size Index (HWISI) was 42.2. Typhoon Rai was capable of doing regional severe damage.

Typhoon Rai will move through an environment favorable for intensification during the next 12 hours. Rai will move over water where the Sea Surface Temperatures are near 30˚C. It will move under the southern side of an upper level ridge over the Western North Pacific Ocean. The ridge will produce easterly winds that will blow toward the top of Typhoon Rai’s circulation. Those winds will cause some vertical wind shear but the wind shear will be too small to prevent intensification. Typhoon Rai will continue to strengthen during the next 12 hours. Rai could continue to rapidly intensify during the next few hours.

Typhoon Rai will move south of a surface high pressure system over the Western North Pacific Ocean. The high pressure system will steer Rai toward the west-northwest during the next 48 hours. On its anticipated track the center of Typhoon Rai could approach northern Mindanao in 12 hours. Rai will be the equivalent of a major hurricane when it reaches the Philippines. Typhoon Rai will bring very strong winds and locally heavy rain to northern Mindanao, Siargao Island, Dinagat Island, Samar, Leyte, Cebu, Negros, Bohol and Panay Island. Heavy rain could cause flash floods in some locations. Rai will cause a significant storm surge along coasts where the wind blows the water toward the shore.

Typhoon Rai Strengthens East of Mindanao

Typhoon Rai strengthened east of Mindanao on Wednesday morning. At 10:00 a.m. EST on Wednesday the center of Typhoon Rai was located at latitude 9.5°N and longitude 129.3°E which put it about 260 miles (415 km) east of Dinagat, Philippines. Rai was moving toward the west at 12 m.p.h. (19 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 969 mb.

Typhoon Rai continued to intensify during Tuesday night and Wednesday morning. A small circular eye was at the center of Rai’s circulation. The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Typhoon Rai. The strongest rainbands were in the western and southern parts of the typhoon. Storms near the core of Rai generated upper level divergence that pumped mass away to the west and north of the typhoon.

The circulation around Typhoon Rai tightened as it intensified. Winds to typhoon force extended out 40 miles (65 km) from the center of Rai. Winds to tropical storm force extended out 125 miles (200 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Rai was 13.9. The Hurricane Size Index (HSI) was 10.0 and the Hurricane Wind Intensity Size Index (HWISI) was 23.9. Typhoon Rai was capable of doing regional serious damage.

Typhoon Rai will move through an environment favorable for intensification during the next 18 hours. Rai will move over water where the Sea Surface Temperatures are near 30˚C. It will move under the southern side of an upper level ridge over the Western North Pacific Ocean. The ridge will produce easterly winds that will blow toward the top of Typhoon Rai’s circulation. Those winds will cause some vertical wind shear but the wind shear will be too small to prevent intensification. Typhoon Rai will continue to strengthen during the next 18 hours. Rai could undergo a period of rapid intensification

Typhoon Rai will move south of a surface high pressure system over the Western North Pacific Ocean. The high pressure system will steer Rai toward the west-northwest during the next 48 hours. On its anticipated track the center of Typhoon Rai could approach northern Mindanao in 18 hours. Rai will be a typhoon when it reaches the Philippines. Typhoon Rai will bring strong winds and locally heavy rain to northern Mindanao, Siargao Island, Dinagat Island, Samar, Leyte, Cebu, Negros, Bohol and Panay Island. Heavy rain could cause flash floods in some locations. Rai will cause a significant storm surge along coasts where the wind blows the water toward the shore.