How is cloud base calculated?

The calculation of cloud base involves understanding the relationship between air temperature and dew point. The correct method to estimate the altitude at which clouds form, or the cloud base, utilizes the difference between the air temperature at the surface and the dew point temperature. Specifically, this difference is divided by approximately 3 to give an estimation of the cloud base height in hundreds of feet.

When the air temperature is compared to the dew point, it indicates how saturated the air is: a smaller difference suggests that the air is closer to saturation, which is necessary for cloud formation. As the temperature decreases or as moisture increases, the air can eventually saturate, leading to cloud formation at or above a certain altitude. Therefore, using the temperature-dew point difference provides a practical way to predict where clouds may begin to form.

This method aligns with the general rule used in meteorology, which states that for every 1 degree Celsius of temperature difference between air temperature and dew point, cloud base is approximately 3 feet in elevation over surface temperature. This relationship helps pilots and meteorologists in estimating cloud bases for flight planning and weather analysis.