Even in these modern times of satellites and Internet, the atmospheric pressure measured with a personal barometer remains the most important indication of weather changes at your location. To evaluate present weather or forecast coming weather, we need accurate barometric pressure. Most common barometers on the market are not accurate enough to serve this purpose. They are more decorative than functional.

Barometer vs. barograph?
A barometer displays the present pressure and the change of pressure since it was last set using a marker hand on the dial. A barograph records the history of the pressure on a paper chart, wrapped around a clock-driven drum. Underway on a fully crewed vessel, the logbook serves as a detailed record of pressure changes. On overnight anchorages, a printed barograph trace is a convenient way to learn how the pressure changed overnight.

Mechanical vs. electronic instruments?
Mechanical (aneroid) barometers have been used on land and sea continuously since the mid 1800’s. By the 1960s, precision aneroid barometers were fully developed and available from selected dealers. Navies and weather-service vessels rely on these aneroid instruments worldwide today. Electronic barometers are small pressure sensors read and controlled by microprocessors with a digital and sometimes graphic display. They have been used in science laboratories for many years. Affordable models intended for public use have became popular in the past few years. As with aneroid barometers, there is a wide range of quality in electronic barometers. All barometers (aneroid and electronic) should be periodically compared with known pressures from official weather services.

Mariners have historically cared only about pressure trends (up or down, fast or slow). These are important observations (if made accurately), but the actual values of the pressure can be even more important in many modern applications. Specific pressure values are the best way to monitor the timing of a forecasted weather system, as well as to evaluate the forecast in general. Target pressures are the key to tactical weather routing, and this can only be done with accurate pressure observations.

To learn how barometric pressure can be used in weather analysis see The Barometer Handbook. The above discussion courtesy of Starpath Navigation