Typhoon Atsani intensified over the past 24 hours and it is now the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale.  At 8:00 a.m. EDT on Wednesday the center of Typhoon Atsani was located at latitude 19.6°N and longitude 151.3°E which put it about 1340 miles (2160 km) southeast of Tokyo, Japan.  Atsani was moving toward the northwest at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 160 m.p.h. (260 km/h) and there were wind gusts to 185 m.p.h. (300 km/h).  The minimum surface pressure was 918 mb.

Atsani is in an environment that is very favorable for tropical cyclones.  The Sea Surface Temperature (SST) is near 28°C.  The upper level winds are very light and there is almost no vertical wind shear.  Upper level divergence is pumping out mass in all directions and Atsani has a very circular appearance with a large eye evident on satellite imagery.  There are more rainbands and thunderstorms in the southern half of the circulation which is probably the result of warmer, moister air in area.

Atsani could maintain its current intensity for another 24 hours or so, although an eyewall replacement cycle will cause weakening if one occurs.  In another day or two the typhoon will start to move over cooler SSTs.  In addition as Atsani moves northward, it will start to be affected by the upper level westerlies in the middle latitudes.  Those winds will increase wind shear and weaken Atsani further.

Atsani is moving around the western end of a subtropical ridge which is steering it toward the northwest.  That general motion is expected to continue for another couple of days.  When Atsani reaches the western end of the ridge it will start moving toward the north.  Eventually, the upper level westerly winds will accelerate Atsani off to the northeast.  On its anticipated track Atsani would pass north of the Marianas and northeast of Iwo To.  At the current time the center of Atsani is forecast to pass about 100 miles east of ChiChi Jima.  However, a slight deviation of the track toward the west could bring Atsani closer to Chichi JIma and Iwo To.