The subtropical ridge also helps form most of the world's deserts.
On May 23, it turned to the north and northeast due to a break in the subtropical ridge.
Situated to the north of a weak subtropical ridge, little movement was expected over the next two days.
Alpha was tracking along the southwest edge of a subtropical ridge.
The wet season ends during the summer when the subtropical ridge becomes strong enough to push this front north of the region.
At this time, a weakness in the subtropical ridge allowed the storm to make a turn towards the north.
Further organization occurred as the depression moved around the southern periphery of a strong subtropical ridge.
It tracked along the periphery of the subtropical ridge with slow development for the next few days.
The subtropical ridge built to its northwest, steering Ken to the west.
Alma then turned north, moving near the edge of a subtropical ridge over Mexico.