Understanding the Quadrants: How Gradient Winds Influence the Sea Breeze

Overview of the 4 Quadrants

The basic idea of the quadrants comes from David Houghton in his book, Wind Strategy, which I do recommend as a supplement (though FYI- it is pretty basic and does not have many examples). In our SeaTactics Quadrants Masterclass, we’ll explain the basic idea of Houghton’s 4 Quadrants then expand beyond them and apply them to real on-the-water racing strategies.

For now, let’s go through a quick introduction to the 4 Quadrants. 

The 4 quadrants are an easy way to help determine how the land will affect the wind near the coast. The quadrants are always drawn the same way for a coastal racing area, no matter which direction the coast is facing. Here are the basic steps:

1.       Draw a horizontal line dividing the land and water, with the land towards the top. 

2.       Draw a vertical line perpendicular to the first line, near your racing area.

3.       Label the quadrants 1 through 4, starting from top left moving to top right, then bottom left, and lastly bottom right. 

You should end up with something that looks like this for Newport, and Miami, respectively:

and for Miami, FL:

To use the quadrants, we look at the direction of the gradient wind (big picture wind) and match it up with that quadrant. Quadrants 1 and 2 are always offshore gradient wind (which can lead to a sea breeze), and quadrants 3 and 4 are always onshore gradient winds.

Winds developing in Quadrants 1 and 2 require careful calculation of the thermal ingredients to see if sea breezes can develop. Winds from quadrants 3 and 4 can (and do) interfere with sea breeze development, even if there are strong thermal ingredients. Remember, for proper thermal sea breeze development, we need onshore gradient winds.

A “favorable” gradient wind for a sea breeze would be either no gradient wind (like the last example) or an offshore gradient wind.

Let’s look at the 3-D circulation of the sea breeze.  One often forgotten piece of this puzzle is the outflow wind above the surface flowing from land to sea, which completes the circulation.

There is a common misconception that an gradient wind that is blowing onshore will enhance the sea breeze, and it is thought to be “reinforcing the sea breeze” from the same direction. However, this is false!

When there is a gradient wind above the surface that opposes the direction of the outflow (an onshore gradient wind), it inhibits the circulation and weakens the sea breeze.

So while onshore gradient wind interferes with a thermal sea breeze, it has some unique properties of it's own when heating is involved. We call this the thermal component of the wind, which can modify the gradient wind itself. We dive into this and more in our Masterclass!

I highly recommend taking the time to learn the 4 Quadrants and apply them to your sailing venues; it has fundamentally changed many racers’ strategies afterwards (including mine!) and given them the ability to “create a playbook” for any venue worldwide!

Please join us in the Quadrants Masterclass to continue learning about how the wind develops and changes in each quadrant, and what strategies you can employ to enhance your racing! You’ll also get a step-by-step guide of how to use the quadrants at any venue around the world, and a quick guide to racing strategies for each quadrant.

Check our website and schedule to see the next time we are offering this standalone 1-hour course! 

Predict the Wind (and Your Strategy) with 2 Easy Measurements

Who would've thought all you need is a thermometer and a weather map to predict the wind?

Turns out that you can predict the wind you’ll be racing in by just 2 simple measurements, and a quick glance at a weather map.

To predict the day’s wind, you need to know two things: the prevailing wind, and the thermal ingredients.

What do I mean by “prevailing wind” and “thermal ingredients”? Let’s break each of these down further.

The prevailing wind (I also call it the “gradient” wind) is the wind that is flowing from high to low pressure. In other words, it’s the wind that is coming from the closest large-scale weather systems nearby. Contrast this to a local wind, such as winds flowing between two hills, which is more affected by local circumstances than the larger weather systems at play.

To predict the wind on your sailing course, you’ll need to know the speed and direction of the gradient wind. This can be achieved by looking at almost any weather map showing Highs and Lows, or even the first few frames of a weather model. [Still confused about how to figure out the gradient wind? Check out our Essential Weather Concepts course.]

If this gradient wind is strong enough, it can overpower some of the other local effects happening around it. However, if it’s on the lighter side, your sailing course may be highly influenced by local effects, such as a sea breeze.

Which leads us to “thermal ingredients” - what exactly are they?

Thermal ingredients are the elements necessary to produce a local thermal sea breeze. They’re called ingredients because just like baking, they’re all necessary to produce the outcome; In this case, a sea breeze.

The right sea breeze ingredients consist of two important measurements that tell us there’s proportionally more heating over land than over the sea.

The first measurement we need to know is the forecasted high temperature a few miles inland from our sailing area. The second measurement is the water temperature, ideally right around the sailing area. The high temperature for the day needs to be at least 3C or 5F warmer than the water temperature. Any less than that, and there is a much lower chance for a sea breeze. If one does develop, it will likely be extremely light.

After we have our two measurements (ingredients) and know the gradient wind, we can start to predict what we’ll see happen out on the course. If the gradient wind is very strong (say, 25 knots), then we know that will likely be our racing wind that afternoon. (Of course there are many other local effects to identify - we cover them our Coastal Racing course) But if the gradient wind is lighter, say 8 knots, and it’s also coming from a favorable direction (like offshore), then we know a sea breeze could be possible and we need to turn to our thermal ingredients for more information.

Confused? Here’s an example. We’re planning to race in Charleston tomorrow, and we’ve looked at our weather map and determined there will likely be a northerly gradient wind of around 11 knots. The gradient is offshore at moderate speeds, so we think a sea breeze is possible. Then we check the forecasted high temperature over the city of Charleston and see it is 74 F. Local water temperature sensors tell us the water temperature is 72F. With only 2 degrees difference between the temperatures, a strong sea breeze is unlikely to develop, and it is more likely that the northerly breeze will prevail.

In our Coastal Racing course, you’ll learn a step-by-step process for determining what wind you’ll be racing in, how it will change through the day, and most importantly- what you should do about it on the race course!

You’ll also learn the evolution of the 4 types of sea breezes and which strategies are your best bet for each one.

The best part is that this process works at every venue around the world.

Join us and sail like a local… anywhere!

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