You often hear us talk about the impacts of cold fronts or warm fronts as they bring changing weather conditions to our area. These fronts are associated with areas of low pressure and our signal that changes are coming. Meteorologists have been studying how low-pressure systems formed more than 100 years ago. It was at the Bergen School of Meteorology where the life cycle of these low-pressure systems was conceptualized in the 1910s and 1920s leading to the creation of the Norwegian Cyclone Model.
What is perhaps the most fascinating thing about the meteorologists who conceptualized this model is that we did not have satellite and radar capabilities available like we do today. They relied on meteorological observation data collected across Europe to create this model that has stood the test of time and is still taught in college today.
Low-pressure systems are influenced by what occurs in the upper-levels of the atmosphere which is then translated down closer to the surface as the fronts we are accustomed to seeing here in Kansas. The process begins with a wave in our jet stream high above us. At the surface, a boundary separating colder air from a warmer air mass develops, known as a stationary front. Along this front, air pressure will start to drop leading to a low-pressure center starting to form.
Winds start to rotate around this low-pressure system leading to the counterclockwise swirl in the airflow. Cooler and drier air is filtered in from the north ahead of the warm front and behind the cold front. Winds turn southerly of the warm front pumping in warmer air and a bit more moisture.
As the dip in the jet stream becomes more pronounced, it will aid in the further development of the low-pressure system closer to the surface. As the pressure lowers, the fronts become a bit stronger, well-defined and winds pick up. The lower the pressure, the stronger winds will be.
As this system becomes better organized it starts to intensify. This leads to the formation of clouds as warm and cold air masses collide forcing air particles up. Eventually, if moisture is present, this will aid in rain chances returning to the region.
Once this low-pressure system is well-organized, the cold front starts to advance as upper-level winds help to steer the pattern in a more progressive manner. As the cold front starts to accelerate, it will begin to take over the warm front.
This leads to the formation of an occluded front marked by a purple frontal boundary. When an occluded front is present, this is an indication that the storm system has reached its mature stage. It will also take on the appearance of a comma shape when looking at the clouds on satellite imagery.
Eventually, the cold front will continue to accelerate and overtake the warm front causing warm, moist air to no longer be supplied to the low-pressure system.
When ingredients lack, the system struggles to survive and begins to dissipate.
That is the start to finish life cycle of a low-pressure system. While we may not dive deep into the actual low-pressure systems themselves when describing the pattern, frontal boundaries associated with them are key in bringing us those key weather changes with regards to temperatures, humidity, wind, cloud cover, and precipitation.
— Meteorologist Erika Paige