| | High and Low Pressure Systems |
 | | Low pressure systems that travel across the Northern Hemisphere (better known as mid-latitude cyclones and more loosely known as lows, cyclones or storm systems) typically develop, intensify and dissipate over periods of 3 to 4 days. |
 | | High pressure systems, on the other hand, tend to be of two types: either the semi-permanent systems that occupy the central portions of the Pacific and Atlantic Oceans, or the large systems that represent the large domes of cold (cool) air that invade southern latitudes following the passage of lows. |
 | | If a low pressure area were to move eastward along the Texas and Oklahoma border, winds over Oklahoma would be light east to northeast, would become stronger northeasterly, gradually shift to the north before becoming strong northwesterly. |
| okfirst.ocs.ou.edu /train/meteorology/HiLowSystems.html (663 words) |