Pressure’s Role in Predicting Weather

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities and you. In this blog we’ll look at how pressure helps predict weather.

Pressure’s Role in Predicting Weather

With all the harsh winter weather occurring recently, knowing what to expect in your area is important knowledge for short term planning and, in some areas such as the northeast, for long term planning. Sensing barometric pressure was one of the earliest forecasting tools and continues to be important today.

One website provides the barometric pressure history from numerous major cities in the U.S. from Friday, Feb 20 to Thursday, Feb 26. The high and low readings only tell part of the story. The intensity of the weather depends on how quickly the front develops and other factors.

City Highest pressure in period (In. Hg) Lowest pressure in period (In. Hg)
Boston 30.55 29.55
Minneapolis 30.8 29.65
Denver 30.35 29.75
San Francisco 30.35 29.85
Chicago 30.7 29.7

In stormy weather, the barometric pressure tends to be lower and a lower reading is one sign of approaching inclement weather.  During fair weather, the barometric pressure is typically higher and if the pressure begins to rise, it is a sign of tranquil weather.

According to the webpage CHANGES IN ATMOSPHERIC PRESSURE, the barometric pressure is reduced through several processes:

  • The approach of a low pressure trough
  • The deepening of a low pressure trough
  • A reduction of mass caused by upper level divergence (vorticity, jet streaks)
  • Moisture advection (moist air is less dense than dry air)
  • Warm air advection (warm air is less dense than cold air)
  • Rising air (such as near a frontal boundary or any process that causes rising air)

In the U.S., the Federal government uses pressure as part of several methods available to predict weather. On Feb26, the weather in many places around the U.S. was much less severe than it had been in recent weeks with at least one exception.



  • Humidity 63%
  • Wind Speed SE 20 mph
  • Barometer 30.04 in. Hg. (1017.6 mb)
  • Dew point 17°F (-8°C)
  • Visibility 9.00 mi
  • Wind Chill 15°F (-9°C)

For weather forecasting and other sensing applications, accuracy and other factors make the measurement acceptable for reliable use. That is where the expertise of the user comes into play.

What do you think/Comments?
Do you have a pressure sensing question? Let me know and I’ll address it in an upcoming blog.
-Dan DeFalco, Marketing Manager, All Sensors Corporation (