Typhoon Ampil strengthened to the equivalent of a major hurricane south of Tokyo on Thursday afternoon.  At 5:00 p.m. EDT on Thursday the center of Typhoon Ampil was located at latitude 33.0°N and longitude 140.9°E which put the center about 205 miles (330 km) south-southeast of Tokyo, Japan.  Ampil was moving toward the north at 12 m.p.h. (19 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 951 mb.

A large circular eye was present at the center of Typhoon Ampil.  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 Ampil’s circulation.  Storms near the core generated upper level divergence that pumped mass away from the typhoon.  The removal of mass caused the surface pressure to decrease.

The circulation around Typhoon Ampil was large.  Winds to typhoon force extended out 50 miles (80 km) from the center of Ampil’s circulation.  Winds to tropical storm force extended out 180 miles (290 km) from the center of Typhoon Ampil.

The Hurricane Intensity Index (HII) for Typhoon Ampil was 20.6.  The Hurricane Size Index (HSI) was 17.1 and the Hurricane Wind Intensity Size Index (HWISI) was 37.7.  Typhoon Ampil was similar in intensity to Hurricane Delta when Delta hit Louisiana in 2020.  Ampil is bigger than Delta was.

Typhoon Ampil will move through an environment favorable for intensification during the next 12 hours.  Ampil will move over water where the Sea Surface Temperatures are near 30°C. It will move through an area where the upper level winds are weak and there will be little vertical wind shear.  Typhoon Ampil could continue to intensify during the next 12 hours.  Ampil Will move into an area where there are stronger westerly winds in the upper level within 24 hours.  Those stronger winds will cause the vertical wind shear to increase.  Typhoon Ampil will start to weaken when the wind shear increases.

Typhoon Ampil will move around the western side of a high pressure system over the Western North Pacific Ocean.  The high pressure system will steer Ampil toward the north during the next 12 hours.  On its anticipated track, Typhoon Ampil will be near the coast of central Honshu just to the southeast of Tokyo in 12 hours.  Ampil will start to move toward the east when it reaches the westerly winds in the upper levels.

Typhoon Ampil will bring strong winds and locally heavy rain to the coast of central Honshu south and east of Tokyo.  Strong winds will be capable of causing serious damage.  Heavy rain could cause flash floods in some locations.