Fujiwhara effect
Weakening slightly once more Rita passed through the Ryukyu Islands of Japan on July 20, with its center passing just north of Amami Ōshima; a pressure of 968.9 mb (hPa; 28.61 inHg) was measured there. Typhoon-force winds were measured 150 km (90 mi) north of the center at this time on Gajajima. Upon moving over the East China Sea on July 21, an unusual set of conditions prompted Rita to turn southwest. The two main factors in this were the presence of a low over Manchuria which resulted in slower forward movement and Typhoon Tess located 1,480 km (920 mi) east which pulled the storm south due to the Fujiwhara effect. Over the following three and a half days, the typhoon looped along the edge of the Ryukyu Islands, fluctuating in strength all the while. The center of Rita brushed Miyako-jima as a Category 1-equivalent typhoon on July 23 and Okinawa as Category 2-equivalent the following day.