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Forecast freshness and data size

How current the weather is, and how little of it you have to download.

Forecast freshness and data size

Freshness

Every route is computed against the newest published cycle of each model, not against a cached daily snapshot.

  • GFS publishes four cycles a day, at 00, 06, 12 and 18Z.
  • HRRR publishes hourly.
  • NAM publishes four cycles a day, at 00, 06, 12 and 18Z, about two hours after each.
  • ECMWF IFS and AIFS publish twice a day on the open data release.
  • RTOFS currents publish daily.

Common corridors are fetched ahead of demand, so for most requests the current cycle is already in hand and routing starts immediately.

The top of the screen shows the forecast window the route is working inside — 0–200 h — and the reference height for wind, 10 m TWS, which is what polars are quoted against.

Data size

A global forecast field is roughly a million points per variable per time step. Downloading enough of that to route an offshore passage would be hundreds of megabytes.

You download a corridor instead: the band of ocean the route could plausibly cross, at the time steps the search needs, compressed. A coastal race is a small fraction of a megabyte. A long offshore passage at the finest resolution is still a fraction of what the raw fields would be.

That is small enough to work on marina wifi or a metered satellite connection.

Pull the forecast once and you can keep computing against it: different departure times, wind scales, and changes to the course inside the same area, with nothing further to download.

Computing again is free

Once a forecast is downloaded, computing again returns immediately and spends nothing from your allowance. Change the departure, course, or routing constraints and run it again. Forecast fidelity is selected automatically from the plan rather than chosen for each solve.