Forecasts that keep themselves up to date

Weather models publish new runs several times a day, and each one corrects the last: a front a few hours late, a breeze that fills in sooner. A route computed on yesterday's run ignores all of that, and Saily WR used to need someone to press a button to fetch the new ones.

The buttons are gone. The server now watches every model and downloads each new run by itself, soon after it is published: when you compute a route, each model uses the latest run the server has fetched, with nothing to choose and nothing to refresh.

It does so for every model: GFS, ECMWF, ARPEGE, ARPEGE-EU, ICON and AROME overseas bring a new run every six hours, AROME around France, ICON-EU and ICON-D2 every three, often enough to follow a forecast that shifts during the day.

Say you plan to leave at dawn for a day along the coast, with a front forecast for the late afternoon. Computed the evening before, the routes bring you in well ahead of it. The night's runs bring it three hours earlier: compute again on the pontoon, and the routes now arrive right in it, reason enough to leave earlier, shorten the passage or stay in harbour another day. So compute again just before casting off: it costs a click, and the routes take in what the forecasters have learnt overnight.

A run is not ready at the hour it is named after: the 06z, started from the weather at six UTC, only comes out some hours later, once computed in full, so the freshest forecast is already a few hours old. A route already on the screen does not follow the new runs either: compute it again and, on a page left open since the evening, set the departure time again too, since it stays at the hour the page was opened. And a newer run is a better guess, not a certainty: where the models still disagree, the doubt remains.