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John Wheeler, WDAY, Published April 07 2014

Weather Talk: Forecasting temperature exactly right is impossible

Forecasting air temperature is not simple. Many different elements can affect how warm it is outside. Air of a different temperature can be blown in on a wind. Air can also be heated dynamically, when its density is changed or thermodynamically, when its humidity content is changed.

Air is not heated up very much directly by the sun, but the sun can warm the ground, which then warms the air above it. This process depends on the status of the ground. Dry, black soil is the best for heating. Snow-covered ground is the worst.

Clouds can block some of the sunlight. At night, the Earth radiates heat into space, cooling the air near the ground; more so on a clear night, less so on a cloudy night. Wind can mix up the air, minimizing the effects of radiation. Wind can also bring down air from above, mixing down whatever temperature is up there. Plus, air temperature is not uniform over an area. Small-scale pockets of cooler and warmer air can drift around at random.

All of this makes forecasting the temperature exactly right a virtual impossibility.


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