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Barometric pressure can raise your blood pressure

Vol. II, No. 74

A view of surface pressure forecasted in the North Atlantic last week, from's impressive collection of data.

One of our readers, Sandra Cutler, sent us this informational post about nautical barometers.  In today’s times of weather routers and sat phones, old fashioned instruments like nautical barometers have become little more than wall art to some boaters.  But to Sandra’s point, they provide a lot of critical information.  And, more importantly, they work when your iphone is out of range and your sat phone and VHF are dead.  Do you know how to interpret barometric pressure? If you don’t, look it up!  Here’s one article that I came across.

Thanks, Sandra, for the post.


5 Important Uses of Nautical Barometers

How to be Equipped for the High Seas, by Sandra Cutler

While spending time out on the open oceans can be a wonderful experience, it can also be one that is potentially hazardous. It is important for mariners to be aware of the changing weather conditions around them and to know the exact location of their vessel at all times. Without this knowledge, boaters can open themselves up to potential danger from changing tides and looming storms. In order to ensure that you are completely aware of the surrounding environment, it is critical to have the right kind of equipment on board your vessel. A Nautical Barometer is among the most important instruments to have handy. This instrument provides the captain of a boat with critical information about the surrounding environment. Below you will find five reasons for keeping this instrument on your boat at all times:

1. Atmospheric Pressure – The barometer measures the pressure in the atmosphere by housing mercury that rises and falls in relation to the external air pressure and temperature. Mercury sensors are the traditional material used in this device. Today, many instruments are being outfitted with copper-based devices or digital barometers. The sensors still work in the same basic way, enabling one to predict certain weather patterns. Weather changes correspond closely with air pressure changes. The changes in air pressure indicate a change in weather that will occur in roughly 12 to 24 hours.

2. Liquid Filled Compass – A nautical barometer is often made into a single tool setting that displays many different gages. These gages typically include a liquid compass. The liquid compass allows sailors to be aware of their orientation to magnetic north. This knowledge comes in handy when plotting a course during treacherous weather. Visual landmarks may be unavailable in conditions such as these. The liquid compass is much more steady than other forms of compasses, making it a natural choice for nautical use.

3. Time and Tide Clock – This display is another instrument typically included on a nautical barometer. The tide clock allows the captain to be aware of the depth of the water based on the progress of the changing tides. When the lowest tide peaks, the water will be at its shallowest. The boat that is caught unaware runs the risk of running the vessel aground. Tides can also be predicted by monitoring water temperatures or using anemometers.

4. Night Conditions – As was the case with extreme weather, the barometer provides valuable weather information even when there is virtually no visibility. Extreme weather can approach without warning during the night. Warning signs that are obvious during the day can often only be noticed during the night with the use of a nautical barometer. Nautical lamps do some good for increasing visibility, but they rarely provide enough light to see oncoming storms.

5. Discerning the Severity of Bad Weather – As barometer technology has been refined, mariners have gained the advantage of discerning exactly what kind of weather they will be facing. Older, simplistic mercury models gave very little indications regarding the specifics of the weather. However, advanced nautical barometers can give indications that designate “fair,” “rain,” or “stormy” weather.  Combining the readings of the barometer with the data from the other instrumentation allows mariners to have extremely accurate readings on their surroundings.