 Convection developed into narrow banding features far from the center, and the overall structure gradually consolidated.It is estimated that the system developed into a subtropical depression late on September 20, about 490 miles southeast of Bermuda; it was classified subtropical because of the large distance between the convection and the center, uncharacteristic of purely tropical systems.The cyclone tracked northward within the weak steering flow between an upper-level low to its south and a trough to its north.