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.