Before setting sail, it is essential to prepare your voyage. Preparing for a cruise, or even a simple day trip, begins with checking the weather forecast. Therefore, it is crucial to understand a coastal marine weather report and be able to analyze its implications for a sailing trip.
The sea is a hostile place, like the mountains. Going on a boat means leaving dry land and your certainties behind. When you set sail, whether for a day trip or a longer cruise, you take risks. Even if the sun is high in the sky, and holidays encourage carefree living, you must never forget this.
Prepare your navigation is therefore imperative for the safety of the crew. And checking the weather forecast is one of those imperatives. But beyond safety, listening to or reading a marine weather reportIt’s mainly about anticipating your navigation plan:
- Will I be able to get back easily, with a favorable wind?
- Do I need to make any stops?
- Does the weather forecast predict strong winds during my week of sailing?
- Will the navigation be comfortable?
- What clothes should I pack?
The aim of this article is not to make you meteorology experts, nor even to teach you how to read clouds like stratus and cumulonimbus. Finally, you won’t discover any miracle techniques for anticipating coastal breezes in an unfamiliar region.
In this article, you will simply learn, or relearn, to Read and understand a marine weather forecast for the coast.
What is a marine weather report?
Advances in weather knowledge and forecasting have democratized boating. Few of us still know how to read our surroundings to predict tomorrow’s weather. Today, boaters have access to five-day weather forecasts at sea. But we won’t get into the debate about the quality of weather forecasts here…
In mainland France, boaters have access to different weather forecasting servicesThe best known and most widely used are Météo-France and Météo-Consult. Météo-France offers weather forecasts for 9 coastal areas, while Météo-Consult offers around thirty.
Météo France’s coastal bulletins cover a band extending up to 20 miles from the coast French. Forecasts are updated 3 times a day:
- 6:15 AM
- 12:15
- 6:15 PM
For its part, Météo-Consult’s forecasts are updated every 3 hours.
These weather forecast They are accessible via a web browser or mobile application, and by telephone. Météo-France also broadcasts its weather forecast via VHF, SSB and Navtex transmissions all along the French coast.
Today, the weather reports The weather reports from both institutes are quite easy to read. Presented in table format, with different color schemes, they allow you to quickly visualize the current weather conditions and the short- and long-term forecasts. You will know:
- The level of sunshine
- Rainfall forecast
- Temperatures
- Wind speed (in knots) and its direction
- The height and direction of the swell
But to properly prepare for your voyage, you need to master a few terms and concepts that will help you develop good habits and anticipate your sailing ability and plan your trip. For example, who among us can tell me if, in 20 knots of wind, they are capable of carrying all their sails? No? Perhaps you’d prefer I translate that as: do you stay under full sail in Force 5? Who knows what a BMS at sea?
However, this concept is important because the Marine weather reports for coastal maritime areas are always given with the concepts below.
What is the Beaufort scale?
We must this Beaufort scale to a British admiral of the same name. It was the latter who, in 1805, conceived this scale, in order to give all sailors an identical reading of wind strength. The Beaufort scale This gives the average wind speed over a 10-minute period. It does not take gusts into account. The original idea was to determine wind speed based on visual criteria (whitecaps on the sea, sea spray, etc.). Today, the marine weather reports they indicate the wind force by referring to this scale
Beaufort force table:
| Strength | Appellation | Wind speed in knots | Sea state |
| zero | Calm | one | Sea of oil, mirror |
| one | Very light breeze | 1 to 3 | Rippled sea |
| two | Light breeze | 4 to 6 | Wavelets |
| three | Gentle breeze | 7 to 10 | Little sheep |
| four | Nice Breeze | 11 to 16 | Many sheep |
| five | Good breeze | 17 to 21 | Waves, sea spray |
| six | cool wind | 22 to 27 | Blades, crests of foam |
| seven | Great fresh | 28 to 33 | Breaking waves |
| eight | Gale | 34 to 40 | The crests of the waves erupt in swirling foam. |
| nine | Strong gust of wind | 41 to 47 | |
| ten | Storm | 48 to 55 | The sea spray obscures the view; you can’t see anything anymore. |
| eleven | Violent storm | 56 to 63 | |
| twelve | Hurricane | 65 and over |
How can we understand the state of the sea?
The state of the sea is a description of the water’s surface.It describes the sea surface based solely on wind conditions. Swell and waves should not be confused. Swell is a consequence of wind traveling over long distances. You can very well have a calm sea with a swell coming from offshore, for example. And this swell can be significant without posing major hazards to navigation.
The state of the sea is a description of its condition under the influence of the moment. I would like to point out that certain areas can exacerbate this phenomenon. This is the case in areas of shallow water or… areas of strong currents For example.
To describe the height of the waves, the weather reports use the Douglas scale.
Douglas Scale
| Strength | Description | Height in meters |
| zero | calm | zero |
| one | wrinkled | 0 to 0.1 |
| two | beautiful | 0.1 to 0.5 |
| three | little agitated | 0.5 to 1.25 |
| four | agitated | 1.25 to 2.5 |
| five | forte | 2.5 to 4 |
| six | very strong | 4 to 6 |
| seven | fat | 6 to 9 |
| eight | very big | 9 to 14 |
| nine | huge | 14 and over |
Visibility at sea
Finally, the latest information froma weather report is that of visibility at seaThose who have already navigated in thick fog They understand the importance of visibility at sea. We will distinguish four situations:
- Visibility good: greater than 5 nautical miles
- Average visibility: between 2 and 5 nautical miles
- Poor visibility: between 0.5 and 2 nautical miles
- Visibility very poor: less than 0.5 nautical miles
What if we kept in touch with the sea?