21. Humid forests could only establish once Madagascar was north of the subtropical ridge by the Oligocene. 22. The forecast break in the subtropical ridge finally occurred on the 15th, causing a northwest motion. 23. This is attributed to a persistent subtropical ridge of high pressure located north of the cyclone. 24. Kai-tak was located along the southern periphery of a deep subtropical ridge positioned over southeast China. 25. At this time Karl began to turn sharply northward into a weakness in the subtropical ridge . 26. At this moment, Kai-tak was expected to rapidly drift eastward due to the persistent subtropical ridge . 27. Initially, the storm moved westward under the influence of a strong subtropical ridge to the south. 28. After becoming a tropical storm on August 30, the subtropical ridge caused Leslie to turn west-northwestward. 29. The system was tracking along the southwestern periphery of a deep-layered subtropical ridge to its north. 30. Lehar continued to track in a westerly direction just along the periphery of a subtropical ridge .
