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How to Read Marine Weather Forecasts Like a Sailor

How to Read Marine Weather Forecasts Like a Sailor

You don’t need to be a sailor to understand the importance of knowing how to properly read weather forecasts. Nowadays, thanks to more accurate weather predictions, you can go about planning your time at sea more wisely.
But sophisticated data is not much use if you struggle to interpret it. Knowing how to get the most out of a complex weather report – which is often aimed at experienced mariners – is very useful, if not vital, for your safety out in the big blue.

Get acquainted with the terminology

Forecasts that are released specifically for mariners prioritise concision. For this reason, certain information might not be explicitly stated, as it tends to assume that that the reader has prior experience. It helps to be sure exactly what certain reports mean, as well as the terms associated with them.
When it comes to the visibility description, most reports would simply indicate terms such as ‘good’ or ‘poor’. This might sound vague, but each level indicates a certain distance:

 Very Poor  Visibility less than 1,000 metres
 Poor  Visibility between 1,000 metres and 2 nautical miles
 Moderate   Visibility between 2 and 5 nautical miles
 Good  Visibility more than 5 nautical miles

Similarly, when indicating the Sea State, the range used by weather forecasts is between smooth and phenomenal. This is what they actually mean:

 Smooth  Wave height less than 0.5m
 Slight  Wave height of 0.5 to 1.25m
 Moderate  Wave height of 1.25 to 2.5m
 Rough  Wave height of 2.5 to 4.0m
 Very Rough  Wave height of 4.0 to 6.0m
 High  Wave height of 6.0 to 9.0m
 Very High  Wave height of 9.0 to 14.0m
 Phenomenal  Wave height of more than 14.0m

Don’t ignore the details

Watch out for inconsistencies in the report, which might indicate uncertainty. If you sense any hesitation, you might want to rethink your voyage.

Sometimes, the report might explicitly confidence (or lack thereof) in the forecast, and in other times, the forecast may change completely in a matter of hours. In any case, it helps to compare different forecasts to get a more accurate picture, and check back often.

Use this information to conclude a safe weather window. It will help you figure the best time to go on board – and whether your passage is a sensible one to begin with.
Finally, when digesting the forecast, don’t forget to keep your destination in mind, as well as your way back.

Prepare for longer journeys

If you’re planning a long trip out at sea – such as a few days – there are extra precautions you should take. You will have to keep a close eye on the weather forecasts in the days leading to your departure, to measure consistency and reliability. 

Unfortunately, you will not get away with a simple 24-hour forecast. Think longer term and test out the waters. Speak to a forecaster personally if the prognosis seems unclear.

Think outside the forecast

Use common sense and your own local knowledge to contextualise a weather forecast report. Depending on the typography of where you are and where you’re going, the nature and direction of the wind may vary.
Before departing, take note of wind direction and strength. Re-evaluate your journey if the wind is stronger than previously predicted. Keep in mind that although forecasting has become much more sophisticated than before, it is not infallible.


The best way to read a weather forecast like a professional sailor is to find the best sources, created specifically for mainers. Adopt the terminology used in these forecasts, and research them well so that you know exactly what they mean. 

Make sure the forecasters sound confident in their delivery – and if not – take note of this possible uncertainty. Study the forecast over a period of time, check back for changes and – most importantly – use your common sense.

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