windy.com is a phenomenal resource for weather forecasting. It’s less of a “will it rain at X by Y” type app but rather a data viewer for many different layers of information – you will have to draw your own conclusions. It also sports a variety of forecast models (among them the $$$ ECMWF) – for free. And it supports user-written plugins for specific purposes, which has unleashed a lot of creativity by weather-affine geeks.
For balloonists, the traj plugin is very useful – it can create tracks to answer the question “If I start at X and fly level in altitude Y at time Z, which track would I fly?”. And it can answer this according to several weather models – in Europe that’d be ECMWF, GFS and ICON-EU.
Here’s a short how-to for generating trajectories:
The traj plugin currently only works on desktop browsers – not (yet) on mobiles
The plugin must be explicitly loaded after pointing your browser to https://www.windy.com/ : click on the top left “Hamburger” (three horizontal bars) icon. In the dropdown, click “Install Windy plugin” and scroll down until you find the “Trajectory” plugin – then click on “Open”.
two windows will appear – one with explanations and one for parameters.
Select altitudes and duration in the parameter window.
Set a start time using the time selector at the bottom of the screen.
Select a model (ICON, ECMWF or GFS) in the right bottom model selector.
Choose a start location – either by clicking on the map window (the “picker”) or choosing a favorite by clicking the heart icon in the parameter window which will present a dropdown of your favorite locations
click “Start” – which changes the label on this button to “Stop”
the progress can be seen on-screen as the curves are drawn
the black bullets denote hourly intervals
Click on the lines, or the bullets for detail information (time, speed, model, model generation time etc)
when the plugin is done, you can download the trajectories as GPX files by clicking “Save”
Advanced features include:
simulation of ascent and descent – if set to zero, just level flight will be simulated
backwards trajectories – those answer the question “If I want to go to location X, where do I need to start?”
duration of the trajectory: up to 240 hours – useful for gas balloon flights