What is a weather forecast and how it works

What is a weather forecast and how it works

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In this article we will discuss what is weather forecast in general and how it works. There are four important things to know about.

Point

The forecast we’re used to is a result of the complex work of lots of formulas and algorithms.

The point is the place the forecast is calculated for. Let’s take a point on the map, for instance, an alpine skiing spot. We can calculate certain parameters for it – humidity, precipitation, cloudiness etc. These are the initial conditions for a complex equation system.

 

Equations

 

It’s just a fragment of equations solved by supercomputers. They are solved for several points at once regularly.

Let’s imagine a bath of cold water. There’s a speck of dust in one corner and a glass of boiling water in another. How will it influence the particle’s movement? It’s as hard to make a weather forecast as to predict that. 

Grid

A point is the spot for which we calculate the forecast introducing the available parameters.

It’s too costly to calculate forecasts for every square meter. That’s why intervals are used, for instance, a forecast for every point with a 1km interval.

Those points make up a grid.

 

Grid

 

Model

Solving complex equations for many locations constitutes a forecast model.

According to the model, the forecast doesn’t change between the points. That’s why a smaller resolution model (1mm) will be more accurate than a 10 or 20km one.

To know the weather at a certain point the global picture is necessary first – that’s what global models do. Global models - GFS, ECMWF, ICON Global.

Regional models work on a certain territory. For example, the WRF8 covers only Europe, the global GFS27 – the whole world. Local models - AROME, OpenWRF, WRF, NEM.

Data

Models need to be “fed” constantly. The main data sources are weather stations, satellites, radars.

The Earth’s atmosphere is a very complex system, that’s why an absolutely accurate forecast is impossible. The forecast is 90% accurate for today and tomorrow, 75% - in a 7-day period, and much less – in a month. It’s better not to trust a more than 14-day forecast.

 

 

Forecast accuracy

 

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