The Importance of Understanding Marine Forecasts
Posted by:GJW Direct | Apr 3, 2019
Though it’s become something of a quintessentially English tradition, there is still great value to be found within the marine shipping forecast broadcast on BBC Radio 4. Covering 31 sea areas around the British Isles, many feel that the ever-punctual broadcast simply serves as a reminder of our island status – and the geopolitical connotations that come with it.
But most significantly, the Met Office-produced shipping forecast has provided comprehensive weather reports that have guided mariners for over 90 years.
When is it broadcast?
There are four broadcasts per day on BBC Radio 4 and similar versions sent over the Navtex system. They are at the following UK times: 0048, 0520, 1201 (LW only), 1754 (LW on weekdays, both FM and LW on weekends).
The format and what each section means:
The format is always the same, limited to 350 words, with the exception of the one broadcast that extends to 380 to include Trafalgar at 0048. Once the Shipping Forecast has been introduced, the structure is as follows:
Gale warnings (winds of force 8 or more on the Beaufort scale) - for example, “There are warnings of gales in Malin, Hebrides and Fair Isle.”
The General Synopsis gives the position, pressure (in millibars) and track of pressure areas. For example, "Low, Rockall, 987, deepening rapidly, expected Fair Isle 964 by 0700 tomorrow."
Each area's forecast is then read out as follows;
- The area(s) in question (If weather conditions are similar, areas may be combined)
- Wind direction (Veering = clockwise change, backing = anti-clockwise)
- Strength on the Beaufort scale (Winds at force 8 and above described accordingly: Gale 8, Severe Gale 9, Storm 10, Violent Storm 11 & Hurricane force 12)
- Precipitation levels
- Overall visibility ("Good", meaning that the visibility is greater than 5 nautical miles (9.3 km; 5.8 mi); "Moderate", where visibility is between 2 and 5 nmi (3.7 and 9.3 km; 2.3 and 5.8 mi) nautical miles; "Poor", where visibility is between 1,000 metres and two nautical miles and "Fog", where visibility is less than 1,000 m (3,300 ft)
- Icing warnings (light, moderate or severe) will be added last during severe winter weather.
For example: "Humber, Thames. Southeast veering southwest 4 or 5, occasionally 6 later. Thundery showers. Moderate or good, occasionally poor."
The Shipping Forecast online
You can also view the latest shipping forecast and gale warnings online via the Met Office. Here, you can see if there are any gale warnings in place (colour coded in red on the map) alongside updates for wind, sea state, weather and visibility for each area.
Why should you take note of the marine forecasts?
If you’re planning on going out on the water at all, whether that’s on a motor cruiser or a paddleboard, then you need to be aware of the marine forecast. It will tell you if the conditions are safe enough to go out in and give you an understanding of what to expect if they are – allowing you to prepare in advance for particularly difficult weather.
Having a full understanding of the weather forecast and technical terminology within the shipping forecasts is essential before you even think about casting off. Wind, pressure and visibility can all have a major impact on where and how you sail; affecting your dead reckoning, piloting and celestial observation capabilities.
Should the weather be particularly bad, the safety of your vessel and crew can become a critical issue. By checking and understanding the marine forecast before you set off, you can ensure your vessel and crew or passengers are suitably prepared for any minor weather challenges.
For general weather updates, you can sign up for a free MyBoat account, which will provide you with wind, precipitation and tide times specific to your local area.
So you might know all about the marine forecast… but do you know everything there is to boat safety? Take our quiz to find out if you’ve got what it takes to be safe and in control while out on the water.