About Weather Visualiser

Most of us read a forecast without really understanding it. Eight metres per second, three feet of sea, two millimetres of rain – the numbers are precise but say nothing about the experience. Weather Visualiser exists to close that gap: you drag a slider and immediately see how the leaves move, how the sea builds, and how quickly the street gets wet.

How the visualisations are calculated

The scenes aren't video clips but real-time simulations drawn in the browser. The wind drives a simple physics model with mass, drag and friction, which is why an empty can, a plastic sheet and a garden chair behave differently in the same wind strength. The waves are built on Gerstner waves, the same mathematical model used in marine visualisation, with a correct dispersion relation so that long waves move faster than short ones. Rain is simulated as particles across several depth layers, with splashes and puddle formation that scale with intensity.

The goal is a convincing feel rather than scientific precision. Use the site to understand orders of magnitude – not as a basis for decisions in shipping, construction or other safety-critical assessments.

Data sources and licence

In forecast mode, current values are fetched from SMHI's open forecast API. Place search is done via Open-Meteo's open geocoding service, which translates place names into coordinates. Both services provide their data under the Creative Commons Attribution 4.0 (CC BY 4.0) licence.

Because SMHI's land forecast often lacks wave height, the wave height on this site is not taken from SMHI, but calculated by us based on wind speed. Data may also otherwise be processed and interpreted for visualisation purposes.

This site is neither affiliated with nor endorsed by SMHI or Open-Meteo. The visualisations should not be used as a basis for decisions in shipping, construction, or other safety-critical assessments. See the privacy policy for how searches are handled.

Who runs the site

Weather Visualiser is run by CADF, a one-person operation in Sweden. The background is practical rather than academic: many years of boating in the archipelago, a plot of land that needs storm-proofing every autumn, and forecasts that have to be interpreted before heading out. The guides are written from that experience, but every figure and table is checked against published scales and official definitions – the Beaufort scale, SMHI warning levels, the standard wind-chill formula, and the accepted definition of significant wave height.

The site has no sponsored articles and does not take payment to mention products or services. What appears in the guides is there because it helps the reader interpret a forecast.

How content is reviewed

Each guide goes through the same process: the figures come from a primary source, the tables are recalculated by hand, and the text is read again with the question *would I act on this?* Where a model is simplified, the text says so explicitly. Translations into English, French, German and Spanish follow the same structure and the same numbers as the Swedish original.

If you spot an error – a wrong figure, a table that doesn't add up, or a wording that could be misunderstood – get in touch. Corrections are made promptly and weigh more heavily than new content.

What the site is not

The visualisations are illustrations, not forecasting tools. They show what an order of magnitude usually looks like, not how your particular inlet, street or plot will behave. Local topography, currents, seabed, buildings and wind direction can change the outcome dramatically. Never make a maritime, construction or safety decision based on a visualisation: use SMHI warnings, the sea report and your own margin of safety.

Advertising and funding

The site is free and funded by advertising through Google AdSense. Ads are labelled and placed so they are not confused with content, and the number is deliberately kept low. Ad providers may use cookies – you choose this in the cookie banner and can change your mind on the cookies page. Read more in the privacy policy.

Contact

Questions, corrections or collaborations: Alexfrick@hotmail.se. I usually reply within a few days.

Why does the site show a different wave height from my weather app?

SMHI's land forecast rarely includes wave height. When it is missing, the site calculates a likely significant wave height from wind speed, which does not account for swell, currents or how long the wind has blown over open water. A marine forecast is always more accurate.

Can I use the visualisation to decide whether to take the boat out?

No. Use it to understand what the figures mean, and make the decision based on the sea report, warnings and your own experience of the boat. See the guide to weather warnings.

Where does the forecast data come from?

From SMHI's open forecast API for weather, and from Open-Meteo to translate place names into coordinates. Both are under CC BY 4.0.

Are my searches stored?

The place name is sent to the geocoding service to find coordinates, but the site does not keep any search history linked to you. Details are in the privacy policy.

Can I use the images or text for schoolwork?

Feel free to quote short passages with a link to the source page. If you want to use larger sections or screenshots in publications, get in touch first.