Evolution of Drought – kwwl.com

We have another student question out of Aplington-Parkersburg this week! A student asked, “How can a drought happen in Iowa when it’s mostly humid?”. Well with the “right” parameters in place, most locations can experience a drought. Let’s take a look at the mechanisms that cause droughts to occur.


Blocking patterns can cause specific weather conditions to persist for days or even weeks. The blocking pattern pictured above is the Omega Block. The shape of it resembles the Greek letter Omega. You have high pressure in the middle of the blocking pattern and low pressure on either side. Those under high pressure experience warm and dry conditions, while those under low pressure will experience cool, cloudy, and rainy weather. Blocking patterns can be tough to move, since air has a difficult time traveling around the high pressure system.

So now that we have the basic knowledge of a blocking pattern down, it’s time to look at how a drought can occur in Iowa. The conditions we need are warm temperatures and no rain for an extended period of time.

During non-drought conditions, saturated soils will have water to evaporate into the atmosphere in the form of water vapor. Plants also undergo the process of transpiration, where water vapor is released into the atmosphere from the plant. All of the moisture in the atmosphere helps create clouds, through the process of condensation. Eventually, water droplets become