Meteorology 101: cold pool aloft

By Meteorologist Mike Skurko

You here this expression a lot in weather forecasts – “cold pool aloft.”  What exactly does that mean? Why is it commonly attributed to afternoon cloud development and a chance of rain showers?

A cold pool aloft is exactly as it sounds … it’s a cooler-than-normal pocket of air in the higher levels of the atmosphere.  Frequently, these cold pools are assessed at about 10,000 to 20,000 feet.  It doesn’t create a chilling effect at the surface for us, many times not having a significant impact on the day’s temperatures.  But it does aid in cloud and thunderstorm development higher up in the atmosphere.

As a parcel of air at the surface warms up during the day, it wants to rise.  This is because warmer air is less dense/more buoyant than the cooler air around it.  As it rises, the parcel of air cools off as well according to laws of thermodynamics.  Eventually, it finds an equilibrium in the atmosphere.

However, when a “cold pool aloft” exists, the parcel that began rising from the surface wants to continue rising through the cold pool.  Even though the parcel was cooling as it rises, it still remains relatively warmer than the cold pool and wants to continue its upward journey.

With these air parcels being allowed to continue rising, it induces more cloud development and rain/thunderstorm potential.  This is why cold pools aloft are often described as an unstable atmosphere.

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