Weather is a safety factor at sea – and therefore a fixed part of the SBF See theory exam. You don’t need to become a meteorologist, but you do need to understand the basics: estimating wind forces, telling a low from a high, and recognizing warning signs. This article explains the key topics concisely.
The Beaufort Scale
The Beaufort scale divides wind force into levels from 0 (calm) to 12 (hurricane). Admiral Beaufort used it to describe the effects that winds of different strengths have on the water surface – which is exactly what the exam asks: not just the number, but the effect.
A few reference points:
- 0 Bft (calm): the sea is mirror-smooth.
- 3 Bft (gentle breeze): beginnings of foam, small waves.
- 5 Bft (fresh breeze): moderate waves, whitecaps everywhere.
- 6 Bft (strong breeze): larger waves, foam crests – from here there are strong-wind warnings.
- 8 Bft (gale): from here it’s called a gale, distinctly higher waves with streaks of spray.
- 12 Bft (hurricane): the sea is completely white, the air full of foam and spray.
Note: strong-wind warning from 6 Bft, gale warning from 8 Bft. You should know these thresholds by heart.
Highs and Lows
Weather is governed by air-pressure systems:
- High-pressure area (high): mostly stable, calm weather.
- Low-pressure area (low): changeable weather, wind, precipitation.
On the weather chart, isobars connect points of equal air pressure. The closer the isobars are together, the stronger the wind.
The Baric Wind Law
In the Northern Hemisphere: if you stand with your back to the wind, the low is to your left (slightly ahead) and the high to your right (Buys-Ballot’s law). The wind does not blow directly from high to low but is deflected by the Earth’s rotation – counterclockwise around a low, clockwise around a high.
Thermal Winds: Land and Sea Breeze
On the coast, the different heating of land and water creates daily wind systems:
- Sea breeze (daytime): the land heats up faster than the water, the warm air rises, and cooler air flows in from the sea onto the land.
- Land breeze (nighttime): the land cools faster, and the air flows from the land out to sea.
These thermal winds are most pronounced in calm, settled weather.
Recognizing Weather Signs
Even without a forecast you can “read” the weather:
- Falling barometer: the pressure is dropping → a low is approaching, the weather worsens, often with freshening wind.
- Rising barometer: better, more settled weather.
- Lowering, thickening cloud: often the herald of a warm front.
- Gusts and shifting wind: can indicate a passing front.
As the responsible skipper you must not rely on the forecast alone but be able to assess the current situation yourself.
The Marine Weather Report
Before every trip, the marine weather report is part of your preparation. It gives, among other things, the expected wind direction and force (in Beaufort), visibility, sea state and any warnings. Sources include the national weather service, VHF marine radio and weather apps.
How to Learn Weather
- Memorize the Beaufort thresholds (6 = strong wind, 8 = gale).
- Understand highs/lows and isobars – close isobars = a lot of wind.
- Imprint the baric wind law and land/sea breeze with a simple sketch.
- Learn weather signs as cause-and-effect pairs (falling pressure → bad weather).
Conclusion
Weather seems vast but reduces to a few core points: the Beaufort scale with its effects and warning thresholds, the difference between high and low, the baric wind law, and the thermal land/sea breezes. Understand these building blocks and you’ll answer the exam questions confidently. In the Boatpass app you can practice the weather questions specifically with the official ELWIS question catalog – including the typical Beaufort tables.