However, those H’s and L’s are not marking the position of high and low pressure centers, and the lines are not lines of constant pressure or isobars. So why is this different from the surface ...

High pressure brings a depression weather system. Low pressure is shown on an isobar map when the numbers are 1000mb or below. Depressions will bring rain. Winds will be calmer in a depression.

Very high or very low blood pressure can indicate ... The National Heart, Lung, and Blood Institute (NHLBI) notes that low blood pressure is normal for some people. The AHA notes that there ...