Question 1

The forecast says "wind NW 15-20 knots". Which direction is the wind actually blowing toward?

Accepted Answer

Roughly southeast: wind direction is always given as where it's coming FROM, not where it's headed. By international convention, wind direction is always the direction the wind is blowing FROM. "NW 15-20" means the wind is coming out of the northwest, so it's blowing toward the southeast.

Question 2

You're on deck and the sea has small wavelets with a glassy, unbroken crest, and the wind is barely felt on your face. Roughly what Beaufort force is this?

Accepted Answer

Force 1-2 (light air to light breeze, 1-6 knots). Small, glassy, unbroken wavelets with barely-felt wind is classic Force 1-2: light air to light breeze. Full calm (Force 0) has a mirror-smooth sea with no wavelets at all.

Question 3

Whitecaps are forming widely, spray is starting to lift off wave crests, and it's becoming hard to carry full sail comfortably. What Beaufort range does this describe?

Accepted Answer

Force 6 (strong breeze, 22-27 knots): many small craft head for shelter around here. Force 6, strong breeze, is where large waves form, whitecaps are everywhere, and spray becomes noticeable: a common threshold where small-craft warnings are issued and less experienced crews reef early or head in.

Question 4

On a weather chart, isobars (lines of equal pressure) are drawn very close together over an area. What does that indicate?

Accepted Answer

A strong pressure gradient, meaning stronger winds in that area. Tightly packed isobars mean pressure changes rapidly over a short distance (a steep pressure gradient), which drives stronger winds. Widely spaced isobars mean a gentler gradient and lighter wind.

Question 5

You're anchored in a Mediterranean bay on a clear, sunny day. What's a common wind pattern to expect as the afternoon goes on?

Accepted Answer

A thermal sea breeze building from the sea toward the warming land, often peaking mid-to-late afternoon. As land heats faster than the sea, warm air rises over land and draws cooler air in from the water: a thermal sea breeze that typically builds through the afternoon and fades toward evening. Very common and forecastable in the Med and similar coastlines in settled summer weather.

Question 6

The forecast wind is expected to "veer" from SW to NW over the next few hours. What does "veer" mean?

Accepted Answer

The wind direction is shifting clockwise (SW → W → NW). "Veering" means the wind is shifting clockwise (e.g. south to southwest to west). The opposite, a counter-clockwise shift, is called "backing". Both are standard forecast terms worth knowing before you plan an anchorage or a passage.

Question 7

A gale warning has been issued for your cruising area for later today. What's the most seaman-like response, if you're currently at anchor in an exposed bay?

Accepted Answer

Reassess before the gale arrives: consider moving to a more sheltered anchorage or marina, and prepare ground tackle and lines for stronger conditions. A gale warning (Force 8+) is time to act while you still have calm conditions to do it in: move to shelter if the current spot is exposed, check scope and swinging room, and secure loose gear. Waiting until the wind arrives removes your options.

Question 8

You notice building cumulus clouds developing tall, dark tops during a hot afternoon, with the air feeling increasingly humid and still beforehand. What should this prompt you to consider?

Accepted Answer

The possibility of a thunderstorm and associated squall: watch the sky and be ready to reef or reduce sail quickly. Tall, dark-based cumulonimbus developing on a hot, humid, still afternoon is a classic precursor to a thunderstorm and the squall that often arrives just ahead of it: a sudden, short burst of much stronger wind. Reef or reduce sail early rather than waiting to see how strong it gets.

Question 9

A weather system is described as a "low" (depression). What does this generally mean for conditions near its centre?

Accepted Answer

Stronger, often unsettled winds spiralling in toward the centre, frequently with cloud, rain, or worse weather. Air spirals in toward a low's centre, generally strengthening as it converges, which is exactly why forecasters and sailors pay close attention to how deep (how low the pressure) a system is.

Question 10

By contrast, what kind of weather does a "high" (anticyclone) generally bring?

Accepted Answer

Settled, often clearer and calmer conditions, though it can also mean very light or variable wind. Air sinks and spreads out from a high's centre, generally suppressing cloud formation: the flip side being that wind can drop to near nothing under a strong, stable high.

Question 11

You notice high, wispy cirrus clouds moving in from the west on an otherwise clear day. What might this be an early sign of?

Accepted Answer

An approaching frontal system: cirrus often arrives well ahead of a warm front, giving hours of advance notice before the weather actually changes. Cirrus is often the first visible sign of an approaching front, arriving well before the cloud thickens and lowers. Watching the sky ahead of a system gives you a head start a barometer alone won't.

Question 12

What's the practical difference between a wind wave and swell, and why does it matter when planning a passage?

Accepted Answer

Wind waves are generated by the current local wind and die out quickly once it drops; swell comes from distant or past weather and can persist (and arrive) even in calm local conditions. A day with no local wind can still have an uncomfortable swell rolling in from a storm hundreds of miles away days earlier: checking a swell forecast separately from the wind forecast avoids an unpleasant surprise.

Question 13

Coastal fog can form even on a day that otherwise seems unremarkable. What's a common cause of fog forming over relatively warm coastal water?

Accepted Answer

Warm, moist air moving over cooler water condenses into fog: common where warm air meets a cooler current or coastal water. This kind of advection fog can roll in with little warning wherever warm, moist air crosses noticeably cooler water: worth knowing before it becomes a restricted-visibility situation and Rule 19 procedures apply.

Question 14

The forecast says the wind will "back" from SW to S over the next few hours. What does backing mean, and how does it differ from veering?

Accepted Answer

Backing means the wind direction is shifting counter-clockwise (SW toward S toward SE); veering is the opposite: a clockwise shift. Backing (counter-clockwise) and veering (clockwise) are opposite terms for the direction a wind shift rotates: both are standard forecast vocabulary worth knowing cold.

Question 15

The old rhyme "red sky at night, sailor's delight; red sky in morning, sailor's warning": is there any real basis to it in much of the mid-latitudes?

Accepted Answer

Roughly, yes: weather systems generally move west to east, so a red sunset (clear skies to the west) can suggest fair weather arriving, while a red sunrise (clear skies already passed, cloud approaching from the west) can suggest a system on its way. It's genuine folk meteorology, not nonsense: it works because weather in the mid-latitudes generally tracks west to east, so what the sky looks like to your west is a rough preview of what's coming.

Question 16

The forecast calls for light and variable wind, under 5 knots, for most of the day. What's a practical consideration beyond "it'll be a slow sail"?

Accepted Answer

Local thermal effects like a sea breeze can dominate (and even reverse) the gradient wind when it's this light, so the actual wind you get near the coast may differ noticeably from the general forecast. A weak gradient wind is exactly when local effects take over: this is the scenario where the afternoon sea breeze can end up being most of the wind you actually sail in, regardless of what the general area forecast says.

Force	Name	Knots	What you’ll see
0-1	Calm / light air	0-3	Mirror-smooth to small ripples, barely felt
2-3	Light-gentle breeze	4-10	Small wavelets, occasional whitecap
4-5	Moderate-fresh breeze	11-21	Whitecaps common, comfortable sailing, first reef territory
6-7	Strong breeze-near gale	22-33	Large waves, spray, most crews reefed well down
8+	Gale and above	34+	Foam streaks, breaking crests, small-craft warnings in force

Weather for Sailors: Beaufort Scale and Reading a Forecast

Wind direction: always FROM, never TO

The Beaufort scale, on deck

Reading isobars

Local effects: the afternoon sea breeze

Watching the sky for squalls

Weather for Sailors: Beaufort Scale and Reading a Forecast quiz