On board sailing ships, there was always an elegant brass dial permanently fixed on the mast bulkhead. Beyond its retro and decorative aspect, the barometer remains an essential tool for forecasting the evolution of the weather on board a ship, whether it is sailing or motorized...

It is a device capable of announcing, to those who know how to observe it, the rise of the wind in the short term...

Everyone now consults a weather application during their sea escapades. These forecasts are made on the basis of calculation models, and are most often accurate. Most of the time.

A good barometer does not interpret anything, but it displays the instantaneous atmospheric pressure, and its straggler allows to measure its evolution.

When the pressure rises, the needle moves towards "fine", "fair", and conversely, when the pressure falls, the barometer points towards "bad weather", "rain".

Pressure is measured in millimeters of mercury (mmhg) or millimeters, or in fractions of a bar, millibars (mb). Both scales are usually printed on the dials.

Highs are areas of high pressure that prevent clouds from forming and generate the air currents that form some of the winds. The high pressure acts like a piston that sends cold air downward and drives out clouds.

On the contrary, depressions are born from ascending currents which reject the air masses upwards, allowing then the phenomena of evaporation, at the origin of the clouds then of the wind, to be born.

This is how a pressure of 1030 or 1040 millibars can be found in great weather and 900 millibars or even less in the eye of a cyclone.

Beyond these major phenomena, the atmospheric pressure varies continuously throughout the day.

The careful observation of the evolution of pressure gives valuable information, especially when the weather is changing. Rapid variations are always a sign of short-term change.

Thus, in summer, a rapid increase (1 millibar per hour) announces, with a blue sky, the imminent arrival of a gale. This is the pressure jump. An increase of 5 millibars in three hours is capable of generating winds of 25 to 30 knots!

This same rapid increase in pressure, in rainy weather, heralds an improvement.

In summer, a rapid decrease in pressure heralds the coming of a thunderstorm and throughout the year, more generally, bad weather. The faster the drop, the more violent the phenomenon will be.

To be aware of these phenomena, the trailing needle of the barometer allows to visualize the extent of the variation, a data easy to consult several times a day, at fixed time.

The electronic barometers often integrated into outdoor watches often offer a history function that allows you to see the trend at a glance, a function that Garmin's Quatix offers, along with interaction with the instruments on board.