WEST MONROE, La. (KTVE/KARD)– From determining what to wear to how much rain is needed to grow crops for food. Different air pressures can help indicate certain weather conditions. A high pressure system and a low pressure system usually have their own recognizable weather associated with them.
The two most common units in the United States to measure pressure are Inches of Mercury and Millibars. Inches of mercury refers to the height a column of mercury measured in hundredth of inches. While a millibar is 1/1000th of a bar and is the amount of force is takes to move an object weighing a gram, one centimeter, in one second. Lower pressure will have values less than 1013 millibars and significant low pressure will be 990 millibars. However, values around 1013 millibars and higher indicate influence from a high pressure system and can possibly go as high as 1030 millibars.
When a high pressure system is viewed from above, winds spiral outward of the center in a clockwise rotation in the Northern Hemisphere. A high pressure system is also associated with sinking air, when air sinks from high in the atmosphere to the lower levels it tends warm up and dry out. Depending on how strong the high pressure system it can cause the environment to be stable. Due to that fact the air at the top of the atmosphere is less dense. The kind of conditions that a high pressure system is associated with is sunny skies and calm weather which is represented with a blue capital H.
While low pressure is the opposite, when viewed from above the winds spiral into a low pressure center in a counter-clockwise rotation in the Northern hemisphere. With a low pressure system the air is rising up in the atmosphere, and depending how strong the low pressure system is, it can causes the environment to be unstable. Within the lifting of air it mean that less pressure is exerted on the ground which is why the air pressure is low. The rising of air causes the water vapor in the air condense and form clouds and rain. The kind of weather associated with low pressure are storms and strong winds and it is represented by a red capital L.