# It's all Greek to me. Use Deviation for sailing and other sports

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Weather forecasts might be wrong as the weather is inherently unpredictable. It seems unfair to miss all fun on weekends or spend more money on boat repairs because of the forecast errors.

According to Windy.app's in-house research, the average number of weather apps installed on our user's mobile device is four. If you also tend to hedge your risks, here is the trick: use the Deviation.

## What is the Deviation?

When you venture out, understanding of the weather is essential.

There are dozen of weather forecast sources, global and regional. Weather computer predictions are not precise, they all show different figures, and sometimes the variety is confusing, so you might want to have different tools to boost your confidence in the forecast. Use the confusion to your advantage — check Windy.app's special Deviation feature (Greek sigma sign) before or during the trip.

The feature is calculated based on the Standard Deviation of wind forecasts of the ECMWF Ensemble global weather model. Deviation represents the spread between the data and the average, it is recognized as the most useful tool forecasters have at their disposal. You can monitor the wind in real time on live wind map.

## How to use Deviation for sailing or other sport or outdoor activity?

The Deviation is composed of numbers and colors. It is measured in the same units as wind speed — for example, meters per second, or miles per hour:

• 0–2 m/s (0–4.4 mph) — green
• 2–4 m/s (4.4–8.9 mph) — amber
• >4 m/s (>8.9 mph) — red

Interpret the Deviation this way: if it's small, you may use the forecast as your guidance. If it's big, look at the parameter as a probable error, think about a wind interval and be cautious.

Background photo: David-vives / Unsplash.

## Where to find Deviation in Windy.app?

1. Open your favorite spot or the nearest one to your current location from the Wind and Precipitation map on the Home screen. For example, port of Marseille in France.

2. Click on the spot. Then you may find the Deviation feature in the Sail Weather Profile by an icon right to the weather models.

3. You can also add it manually to the weather forecast table using the Customization feature. To do so, click on the sale Weather Profiles icon.

The feature is available for all users with iOS devices from 9.8.1 version. Update your Windy.app in the App Store. Any questions? We are here to answer: [email protected].

Have a fabulous sailing season!

You can monitor the wind in real time on live wind map.

Text: Natalia Pavlova, yachting expert in Windy.app.

Cover photo: Mael-balland / Unsplash.

### You will also find useful

The basic meteorology for yachtsmen and yachtswomem

How to read wind barbs — wind speed and direction symbols

Cold fronts and warm fronts

Aerological Diagram — complex, but incredibly useful tool for weather forecasting at different heights

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01 Dec 2023

01 Dec 2023

24 Apr 2023