Barometric Tides, Explained

June 26, 2025

For those who track the air pressure on a home barometer, have you ever noticed that twice each day the pressure falls and rises?

The atmospheric pressure does fluctuate twice daily across the globe. This is analogous to the ocean tides, but formed from different processes and forces. Ocean tides are caused by the gravitational pull from the moon and sun.

The daily heating and cooling cycles in the atmosphere cause the atmospheric pressure fluctuations. As the atmosphere heats up, air rises, becomes less dense, and the pressure falls. When air cools, it sinks, becomes denser, and the pressure rises. This heating and cooling at different points on the globe causes a pressure wave that moves slowly around the Earth. There are two cycles per day, with the pressure peaks near 10 a.m. and 10 p.m. local time. The two minimum pressure times are near 4 a.m. and 4 p.m. local time.

This phenomenon is called the diurnal pressure oscillation. It is strongest at the equator, where the oscillation is about 2.5 millibars. The magnitude of this oscillation is very small and equates to less than one-tenth of an inch of mercury. The oscillation decreases as we move north and is almost non-existent above 60 degrees north latitude, due to very little temperature variation at these higher latitudes. In order to view this bi-diurnal cycle, there needs to be a large area of equal pressure over a region. If a low- or high-pressure system is moving into an area, the effects from that system will mask the diurnal oscillation.

There are many other factors that can cause pressure falls and rises. As previously mentioned, low and high-pressure systems can cause some of the biggest changes. We can also see changes near a complex of thunderstorms or even patches of clouds. Before a thunderstorm arrives at your location, you will see a pressure fall, but once the wind and rain begin, the pressure rises.

Volcanoes, meteorites, and even nuclear explosions can cause pressure waves that move around the globe. The famous volcano Krakatoa created pressure waves that moved around the globe, in all directions, at about 700 mph. The great Siberian meteorite that fell on June 8, 1908, created a pressure wave that lasted about 12 minutes and traveled at about 750 mph. The 50+ megaton nuclear explosion in Russia on October 30, 1961, produced a pressure wave that circled the globe at least four times. It took about 35 hours for each lap around the globe.

The pressure oscillations are very important in our everyday weather. Have you ever noticed that during the middle of summer, when there are no cold fronts in the area, thunderstorms generally occur in the 4 p.m. to 10 p.m. time period? The daily pressure minimum around 4 p.m. helps with thunderstorm formation, while the daily maximum around 10 p.m. helps to decrease thunderstorms.

Michael Eckert

I grew up an Air Force Brat. Traveled the country and lived in Georgia, Maine, New York, Hawaii and Oklahoma.

I fell in love with the weather in Oklahoma. My father was transferred to Tinker AFB in 1973. While in Temporary housing (a mobile home, which is the standard in Oklahoma) I experienced my first severe thunderstorm with strong winds and hail the size of baseballs. The next day I was in the base library looking up books on weather. The rest is history.

I graduated from the University of Oklahoma in 1983 with a Bachelor’s Degree in Meteorology. The first two years we took Calculus, Differential equations, Physics, Chemistry and Computer science classes with the Engineering Students. It was a grind. My degree is actually from the College of Engineering. The last 2-3 year’s focus was on Meteorology including Observational networks (Satellite, Radar, Surface), Physics, Thermodynamics, Dynamics, Synoptic, Winter Weather, Severe Weather and Climatology.

My first job out of college was with a small forecasting company in Oklahoma City. I was immediately put on TV (OETA) and Radio (WKY) as their broadcast Meteorologist. After two years in broadcasting, I decided to pursue the National Weather Service route and got a position in Toledo, OH as an intern. After a couple of years, I was promoted to a forecaster position at the Cleveland Forecast office. I quickly moved into the Weather Preparedness position and was responsible for all the preparedness activities in the state of Ohio.

In 1992 I decided to pursue other forecast opportunities and moved to the Meteorological Operations Division of the National Meteorological Center in Washington, DC. This group is now called WPC (Weather Prediction Center). There I fine-tuned my forecasting of Synoptic Weather with my focus on Heavy Convective Rainfall and Winter Storms, under the supervision of Dr. Louis Uccellini. He has written several books on East Coast Winter storms. I was promoted to a Senior Branch Forecast position during my tenure at MOD. Part of my job was to teach weather classes at COMET (Cooperative Program for Operational Meteorology, Education, and Training).

In 2012 I was given the opportunity to start up a new weather support group with the FAA (Federal Aviation Administration) in Warrenton, VA at the ATCSSC (Air Traffic Control System Command Center). The ATCSCC is where the FAA identifies solutions to air traffic inefficiencies in the NAS (National Air Space) for the CONUS (Continental United State). Weather impacts are the biggest impact on Aviation with yearly losses over 20 billion dollars. My job was to help lower these inefficiencies/costs by providing weather impact briefings and forecasts in order to keep the air planes moving as safely and efficiently as possible.

I retired in 2022 and now am running Lake Anna Weather, LLC.