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• Chelsea Carlson

## 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.