Complex sentence: While tracking west-northwestward, satellite imagery indicated signs of a developing low-level circulation and after significant convection developed, it was classified as Tropical Depression Eight at 1200 UTC on September 1.
Split into simpler sentences: While tracking west-northwestward, satellite imagery indicated signs of a developing low-level circulation. Because the system formed significant deep convection and a low-level circulation, it was classified as Tropical Depression Eight at 1200 UTC on September 1.