Low-pressure System An area of a relative pressure minimum that has converging winds and rotates in the same direction as the earth. This is counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Also known as an cyclone, it is the opposite of an area of high pressure, or a anticyclone. See closed low, cold low, and cut-off low for further examples.
There is no set age at which all women will start to go through menopause. The average age of menopause in the United States is 51, but it is considered perfectly normal for a woman to go through it at any time between the ages of 35 and 59, says Lila Schmidt, MD, a reproductive endocrinologist in private practice in San Diego. âAnything above 35 is not premature,â she says.
1 The process of menopause does not occur overnight, but rather is a gradual process. This so-called perimenopausal transition period is a different experience for each woman.  The average age of menopause is 51 years old, but menopause may occur as early as the 30s or as late as the 60s.