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How Are Clouds Formed in a Low Pressure Area?

Low pressure systems typically bring with them cloudiness, and these clouds often bring rain and unsettled weather. The physical process that generates clouds is complex and involves several layers of the atmosphere. Wind, temperature, humidity and geography all play a part in the formation of clouds within a low pressure system.

Lift
- In a low pressure environment, air rises and expands. The expansion of air causes the air to release heat. As the air cools to a particular temperature known as the dewpoint, moisture in the air condenses into clouds. Water droplets adhere to tiny dust particles in the air. Air then rises in pockets and tends to form scattered cumulus clouds and thunderstorms, typically seen in the warm, unstable air in front of a strong low pressure system.
Moisture
- Dark clouds may produce heavy rain.
  
  Without at least some moisture, clouds cannot form. In the eastern United States, moisture-laden air is often drawn in from the Gulf of Mexico or Atlantic Ocean. The moisture rises within the low pressure system and eventually condenses into clouds. Of course, higher moisture levels will speed the process of cloud production and potentially lead to heavier precipitation. In cold winter air, overall moisture content is less than in summer months.
Rotation
- In the Northern Hemisphere, low pressure systems rotate in a counterclockwise direction. The center of the low pressure is the region in the atmosphere of lowest pressure. Clouds and precipitation generally swirl around this small region. On the north and west sides of the low pressure system, clouds tend to be thick and produce steady rains. In some cases, a low pressure system passes through quickly and leaves clear skies in its wake.
Hurricanes and Tornadoes
- The condensation funnel of a tornado indicates where the winds are most violent.
  
  Extreme low pressure systems produce clouds in a process similar to ordinary systems, although the process may be greatly intensified. Hurricanes form over very warm ocean water. A huge mass of rising air creates equally massive and dense cloud cover. In tornadoes, a cloudy funnel becomes visible once the circulation reaches a certain strength. Large, powerful tornadoes may become so clogged with swirling debris that telling the difference between clouds and dust becomes impossible.

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